chore: add sunbeam registry annotations for crate publishing

Documents pipeline architecture, how to run it, WFE features
demonstrated, preflight tool checks, and graceful infrastructure
skipping. Adds nextest cover profile for llvm-cov integration.

.cargo/config.toml

@@ -0,0 +1,2 @@
+[registries.sunbeam]
+index = "sparse+https://src.sunbeam.pt/api/packages/studio/cargo/"

.config/nextest.toml

@@ -34,6 +34,17 @@ retries = 2
 [profile.ci.junit]
 path = "target/nextest/ci/junit.xml"
 
+[profile.cover]
+# Coverage profile — used with cargo llvm-cov nextest
+fail-fast = false
+test-threads = "num-cpus"
+failure-output = "immediate-final"
+success-output = "never"
+slow-timeout = { period = "60s", terminate-after = 2 }
+
+[profile.cover.junit]
+path = "target/nextest/cover/junit.xml"
+
 # Postgres tests must run serially (shared database state)
 [[profile.default.overrides]]
 filter = "package(wfe-postgres)"

.gitmodules

@@ -0,0 +1,6 @@
+[submodule "wfe-containerd-protos/vendor/containerd"]
+	path = wfe-containerd-protos/vendor/containerd
+	url = https://github.com/containerd/containerd.git
+[submodule "wfe-buildkit-protos/vendor/buildkit"]
+	path = wfe-buildkit-protos/vendor/buildkit
+	url = https://github.com/moby/buildkit.git

Cargo.toml

@@ -1,11 +1,13 @@
 [workspace]
-members = ["wfe-core", "wfe-sqlite", "wfe-postgres", "wfe-opensearch", "wfe-valkey", "wfe", "wfe-yaml"]
+members = ["wfe-core", "wfe-sqlite", "wfe-postgres", "wfe-opensearch", "wfe-valkey", "wfe", "wfe-yaml", "wfe-buildkit", "wfe-containerd", "wfe-containerd-protos", "wfe-buildkit-protos"]
 resolver = "2"
 
 [workspace.package]
-version = "0.1.0"
+version = "1.4.0"
 edition = "2024"
 license = "MIT"
+repository = "https://src.sunbeam.pt/studio/wfe"
+homepage = "https://src.sunbeam.pt/studio/wfe"
 
 [workspace.dependencies]
 # Core
@@ -36,15 +38,18 @@ redis = { version = "0.27", features = ["tokio-comp", "connection-manager"] }
 opensearch = "2"
 
 # Internal crates
-wfe-core = { path = "wfe-core" }
-wfe-sqlite = { path = "wfe-sqlite" }
-wfe-postgres = { path = "wfe-postgres" }
-wfe-opensearch = { path = "wfe-opensearch" }
-wfe-valkey = { path = "wfe-valkey" }
-wfe-yaml = { path = "wfe-yaml" }
+wfe-core = { version = "1.4.0", path = "wfe-core", registry = "sunbeam" }
+wfe-sqlite = { version = "1.4.0", path = "wfe-sqlite", registry = "sunbeam" }
+wfe-postgres = { version = "1.4.0", path = "wfe-postgres", registry = "sunbeam" }
+wfe-opensearch = { version = "1.4.0", path = "wfe-opensearch", registry = "sunbeam" }
+wfe-valkey = { version = "1.4.0", path = "wfe-valkey", registry = "sunbeam" }
+wfe-yaml = { version = "1.4.0", path = "wfe-yaml", registry = "sunbeam" }
+wfe-buildkit = { version = "1.4.0", path = "wfe-buildkit", registry = "sunbeam" }
+wfe-containerd = { version = "1.4.0", path = "wfe-containerd", registry = "sunbeam" }
 
 # YAML
 serde_yaml = "0.9"
+yaml-merge-keys = { version = "0.8", features = ["serde_yaml"] }
 regex = "1"
 
 # Deno runtime

README.md

@@ -1,20 +1,24 @@
 # WFE
 
-A persistent, embeddable workflow engine for Rust. Trait-based, pluggable, built for real infrastructure.
-
-> Rust port of [workflow-core](https://github.com/danielgerlag/workflow-core), rebuilt from scratch with async/await, pluggable persistence, and a YAML frontend with shell and Deno executors.
+A persistent, embeddable workflow engine for Rust. Trait-based, pluggable, built for large, highly complex build, test, deployment, and release pipelines of the highest levels of complexity.
 
 ---
 
 ## What is WFE?
 
-WFE is a workflow engine you embed directly into your Rust application. Define workflows as code using a fluent builder API, or as YAML files with shell and JavaScript steps. Workflows persist across restarts, support event-driven pausing, parallel execution, saga compensation, and distributed locking.
+WFE is a technical love letter from a former [VMware](https://www.vmware.com) and [Pivotal](https://pivotal.io) engineer (@siennathesane). Its internal workflow architecture is based on the amazing [workflow-core](https://github.com/danielgerlag/workflow-core) library by Daniel Gerlag, and the YAML structure and support is based on [Concourse CI](https://concourse-ci.org). WFE is a pluggable, extendable library that can be used to design embedded business workflows, CLI applications, and CI/CD pipelines. It is designed to be embedded into your application, and can scale open-ended with pluggable architectures. You can deploy Cloud Foundry, Kubernetes, or even bootstrap a public cloud with WFE.
 
-Built for:
+You can define workflows as code using a fluent builder API, or as YAML files with shell and JavaScript steps. Workflows persist across restarts, support event-driven pausing, parallel execution, saga compensation, and distributed locking. It also comes with native support for containerd and buildkitd embedded into the application.
 
-- **Persistent workflows** — steps survive process restarts. Pick up where you left off.
-- **Embeddable CLIs** — drop it into a binary, no external orchestrator required.
-- **Portable CI pipelines** — YAML workflows with shell and Deno steps, variable interpolation, structured outputs.
+The only thing not included is a server and a web UI (open to contributions that have been agreed upon and discussed ahead of time).
+
+## Why?
+
+Every CI/CD system [I've](https://src.sunbeam.pt/siennathesane) ever used has been either lovely or terrible. I wanted something that was lovely, but also flexible enough to be used in a variety of contexts. The list of CI systems I've used over the years has been extensive, and they all have their _thing_ that makes them stand out in their own ways. I wanted something that could meet every single requirement I have: a distributed workflow engine that can be embedded into any application, has pluggable executors, a statically-verifiable workflow definition language, a simple, easy to use API, YAML 1.1 merge anchors, YAML 1.2 support, multi-file workflows, can be used as a library, can be used as a CLI, and can be used to write servers.
+
+With that, I wanted the user experience to be essentially identical for embedded application developers, systems engineers, and CI/CD engineers. Whether you write your workflows in code, YAML, or you have written a web server endpoint that accepts gRPC workflow definitions and you're relying on this library as a hosted service, it should feel like the same piece of software in every context.
+
+Hell, I'm so dedicated to this being the most useful, most pragmatic, most embeddable workflow engine library ever that I'm willing to accept a C ABI contribution to make it embeddable in any language.
 
 ---
 
@@ -245,6 +249,76 @@ SQLite tests use temporary files and run everywhere.
 
 ---
 
+## Self-hosting CI pipeline
+
+WFE includes a self-hosting CI pipeline defined in `workflows.yaml` at the repository root. The pipeline uses WFE's own YAML workflow engine to build, test, and publish WFE itself.
+
+### Pipeline architecture
+
+```
+                         ci (orchestrator)
+                              |
+          +-------------------+--------------------+
+          |                   |                    |
+      preflight            lint               test (fan-out)
+     (tool check)     (fmt + clippy)              |
+                                       +----------+----------+
+                                       |          |          |
+                                   test-unit  test-integration  test-containers
+                                       |     (docker compose)  (lima VM)
+                                       |          |          |
+                                       +----------+----------+
+                                              |
+                                    +---------+---------+
+                                    |         |         |
+                                  cover    package     tag
+                                    |         |         |
+                                    +---------+---------+
+                                              |
+                                    +---------+---------+
+                                    |                   |
+                                 publish            release
+                              (crates.io)        (git tags + notes)
+```
+
+### Running the pipeline
+
+```sh
+# Default — uses current directory as workspace
+cargo run --example run_pipeline -p wfe -- workflows.yaml
+
+# With explicit configuration
+WFE_CONFIG='{"workspace_dir":"/path/to/wfe","registry":"sunbeam","git_remote":"origin","coverage_threshold":85}' \
+  cargo run --example run_pipeline -p wfe -- workflows.yaml
+```
+
+### WFE features demonstrated
+
+The pipeline exercises every major WFE feature:
+
+- **Workflow composition** — the `ci` orchestrator invokes child workflows (`lint`, `test`, `cover`, `package`, `tag`, `publish`, `release`) using the `workflow` step type.
+- **Shell executor** — most steps run bash commands with configurable timeouts.
+- **Deno executor** — the `cover` workflow uses a Deno step to parse coverage JSON; the `release` workflow uses Deno to generate release notes.
+- **YAML anchors/templates** — `_templates` defines `shell_defaults` and `long_running` anchors, reused across steps via `<<: *shell_defaults`.
+- **Structured outputs** — steps emit `##wfe[output key=value]` markers to pass data between steps and workflows.
+- **Variable interpolation** — `((workspace_dir))` syntax passes inputs through workflow composition.
+- **Error handling** — `on_failure` handlers, `error_behavior` with retry policies, and `ensure` blocks for cleanup (e.g., `docker-down`, `lima-down`).
+
+### Preflight tool check
+
+The `preflight` workflow runs first and checks for all required tools: `cargo`, `cargo-nextest`, `cargo-llvm-cov`, `docker`, `limactl`, `buildctl`, and `git`. Essential tools (cargo, nextest, git) cause a hard failure if missing. Optional tools (docker, lima, buildctl, llvm-cov) are reported but do not block the pipeline.
+
+### Graceful infrastructure skipping
+
+Integration and container tests handle missing infrastructure without failing:
+
+- **test-integration**: The `docker-up` step checks if Docker is available. If `docker info` fails, it sets `docker_started=false` and exits cleanly. Subsequent steps (`postgres-tests`, `valkey-tests`, `opensearch-tests`) check this flag and skip if Docker is not running.
+- **test-containers**: The `lima-up` step checks if `limactl` is installed. If missing, it sets `lima_started=false` and exits cleanly. The `buildkit-tests` and `containerd-tests` steps check this flag and skip accordingly.
+
+This means the pipeline runs successfully on any machine with the essential Rust toolchain, reporting which optional tests were skipped rather than failing outright.
+
+---
+
 ## License
 
 [MIT](LICENSE)

test/lima/wfe-test.yaml

@@ -0,0 +1,50 @@
+# WFE Test VM — BuildKit + containerd with host-accessible sockets
+#
+# Provides both buildkitd and containerd daemons with Unix sockets
+# forwarded to the host for integration testing.
+#
+# Usage:
+#   limactl start ./test/lima/wfe-test.yaml
+#
+# Sockets (on host after start):
+#   BuildKit:   unix://$HOME/.lima/wfe-test/sock/buildkitd.sock
+#   containerd: unix://$HOME/.lima/wfe-test/sock/containerd.sock
+#
+# Verify:
+#   BUILDKIT_HOST="unix://$HOME/.lima/wfe-test/sock/buildkitd.sock" buildctl debug workers
+#   # containerd accessible via gRPC at unix://$HOME/.lima/wfe-test/sock/containerd.sock
+#
+# Teardown:
+#   limactl stop wfe-test
+#   limactl delete wfe-test
+
+message: |
+  WFE integration test VM is ready.
+
+  BuildKit socket:   unix://{{.Dir}}/sock/buildkitd.sock
+  containerd socket: unix://{{.Dir}}/sock/containerd.sock
+
+  Verify BuildKit:
+    BUILDKIT_HOST="unix://{{.Dir}}/sock/buildkitd.sock" buildctl debug workers
+
+  Run tests:
+    WFE_BUILDKIT_ADDR="unix://{{.Dir}}/sock/buildkitd.sock" \
+    WFE_CONTAINERD_ADDR="unix://{{.Dir}}/sock/containerd.sock" \
+    cargo nextest run -p wfe-buildkit -p wfe-containerd
+
+minimumLimaVersion: 2.0.0
+
+base: template:_images/ubuntu-lts
+
+containerd:
+  system: false
+  user: true
+
+portForwards:
+  # BuildKit daemon socket
+  - guestSocket: "/run/user/{{.UID}}/buildkit-default/buildkitd.sock"
+    hostSocket: "{{.Dir}}/sock/buildkitd.sock"
+
+  # containerd daemon socket (rootless)
+  - guestSocket: "/run/user/{{.UID}}/containerd/containerd.sock"
+    hostSocket: "{{.Dir}}/sock/containerd.sock"

wfe-buildkit-protos/Cargo.toml

@@ -0,0 +1,19 @@
+[package]
+name = "wfe-buildkit-protos"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+repository.workspace = true
+homepage.workspace = true
+description = "Generated gRPC stubs for the full BuildKit API"
+
+[dependencies]
+tonic = "0.14"
+tonic-prost = "0.14"
+prost = "0.14"
+prost-types = "0.14"
+
+[build-dependencies]
+tonic-build = "0.14"
+tonic-prost-build = "0.14"
+prost-build = "0.14"

wfe-buildkit-protos/build.rs

@@ -0,0 +1,56 @@
+use std::path::PathBuf;
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    // Use Go-style import paths so protoc sees each file only once
+    let proto_dir = PathBuf::from("proto");
+    let go_prefix = "github.com/moby/buildkit";
+
+    let proto_files: Vec<PathBuf> = vec![
+        // Core control service (Solve, Status, ListWorkers, etc.)
+        "api/services/control/control.proto",
+        // Types
+        "api/types/worker.proto",
+        // Solver / LLB definitions
+        "solver/pb/ops.proto",
+        // Source policy
+        "sourcepolicy/pb/policy.proto",
+        // Session protocols
+        "session/auth/auth.proto",
+        "session/filesync/filesync.proto",
+        "session/secrets/secrets.proto",
+        "session/sshforward/ssh.proto",
+        "session/upload/upload.proto",
+        "session/exporter/exporter.proto",
+        // Utilities
+        "util/apicaps/pb/caps.proto",
+        "util/stack/stack.proto",
+    ]
+    .into_iter()
+    .map(|p| proto_dir.join(go_prefix).join(p))
+    .collect();
+
+    println!(
+        "cargo:warning=Compiling {} buildkit proto files",
+        proto_files.len()
+    );
+
+    let mut prost_config = prost_build::Config::new();
+    prost_config.include_file("mod.rs");
+
+    tonic_prost_build::configure()
+        .build_server(false)
+        .compile_with_config(
+            prost_config,
+            &proto_files,
+            // Include paths for import resolution:
+            // 1. The vendor dir inside buildkit (for Go-style github.com/... imports)
+            // 2. The buildkit root itself (for relative imports)
+            // 3. Our proto/ dir (for google/rpc/status.proto)
+            &[
+                // proto/ has symlinks that resolve Go-style github.com/... imports
+                PathBuf::from("proto"),
+            ],
+        )?;
+
+    Ok(())
+}

wfe-buildkit-protos/proto/github.com/moby/buildkit

@@ -0,0 +1 @@
+/Users/sienna/Development/sunbeam/wfe/wfe-buildkit-protos/vendor/buildkit

wfe-buildkit-protos/proto/github.com/planetscale/vtprotobuf/vtproto/ext.proto

@@ -0,0 +1,7 @@
+// Stub for vtprotobuf extensions — not needed for Rust codegen
+syntax = "proto3";
+package vtproto;
+import "google/protobuf/descriptor.proto";
+extend google.protobuf.MessageOptions {
+  bool mempool = 64101;
+}

wfe-buildkit-protos/proto/github.com/tonistiigi/fsutil

@@ -0,0 +1 @@
+/Users/sienna/Development/sunbeam/wfe/wfe-buildkit-protos/vendor/buildkit/vendor/github.com/tonistiigi/fsutil

wfe-buildkit-protos/proto/google/rpc/status.proto

@@ -0,0 +1,49 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+syntax = "proto3";
+
+package google.rpc;
+
+import "google/protobuf/any.proto";
+
+option cc_enable_arenas = true;
+option go_package = "google.golang.org/genproto/googleapis/rpc/status;status";
+option java_multiple_files = true;
+option java_outer_classname = "StatusProto";
+option java_package = "com.google.rpc";
+option objc_class_prefix = "RPC";
+
+// The `Status` type defines a logical error model that is suitable for
+// different programming environments, including REST APIs and RPC APIs. It is
+// used by [gRPC](https://github.com/grpc). Each `Status` message contains
+// three pieces of data: error code, error message, and error details.
+//
+// You can find out more about this error model and how to work with it in the
+// [API Design Guide](https://cloud.google.com/apis/design/errors).
+message Status {
+  // The status code, which should be an enum value of
+  // [google.rpc.Code][google.rpc.Code].
+  int32 code = 1;
+
+  // A developer-facing error message, which should be in English. Any
+  // user-facing error message should be localized and sent in the
+  // [google.rpc.Status.details][google.rpc.Status.details] field, or localized
+  // by the client.
+  string message = 2;
+
+  // A list of messages that carry the error details.  There is a common set of
+  // message types for APIs to use.
+  repeated google.protobuf.Any details = 3;
+}

wfe-buildkit-protos/src/lib.rs

@@ -0,0 +1,19 @@
+//! Generated gRPC stubs for the full BuildKit API.
+//!
+//! Built from the official BuildKit proto files at
+//! <https://github.com/moby/buildkit>.
+//!
+//! ```rust,ignore
+//! use wfe_buildkit_protos::moby::buildkit::v1::control_client::ControlClient;
+//! use wfe_buildkit_protos::moby::buildkit::v1::StatusResponse;
+//! ```
+
+#![allow(clippy::all)]
+#![allow(warnings)]
+
+include!(concat!(env!("OUT_DIR"), "/mod.rs"));
+
+/// Re-export tonic and prost for downstream convenience.
+pub use prost;
+pub use prost_types;
+pub use tonic;

wfe-buildkit/Cargo.toml

@@ -0,0 +1,30 @@
+[package]
+name = "wfe-buildkit"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+repository.workspace = true
+homepage.workspace = true
+description = "BuildKit image builder executor for WFE"
+
+[dependencies]
+wfe-core = { workspace = true }
+tokio = { workspace = true }
+serde = { workspace = true }
+serde_json = { workspace = true }
+async-trait = { workspace = true }
+tracing = { workspace = true }
+thiserror = { workspace = true }
+regex = { workspace = true }
+wfe-buildkit-protos = { version = "1.4.0", path = "../wfe-buildkit-protos", registry = "sunbeam" }
+tonic = "0.14"
+tower = { version = "0.4", features = ["util"] }
+hyper-util = { version = "0.1", features = ["tokio"] }
+uuid = { version = "1", features = ["v4"] }
+tokio-stream = "0.1"
+
+[dev-dependencies]
+pretty_assertions = { workspace = true }
+tempfile = { workspace = true }
+tokio = { workspace = true, features = ["test-util"] }
+tokio-util = "0.7"

wfe-buildkit/README.md

@@ -0,0 +1,95 @@
+# wfe-buildkit
+
+BuildKit image builder executor for WFE.
+
+## What it does
+
+`wfe-buildkit` provides a `BuildkitStep` that implements the `StepBody` trait from `wfe-core`. It shells out to the `buildctl` CLI to build container images using BuildKit, capturing stdout/stderr and parsing image digests from the output.
+
+## Quick start
+
+Use it standalone:
+
+```rust
+use wfe_buildkit::{BuildkitConfig, BuildkitStep};
+
+let config = BuildkitConfig {
+    dockerfile: "Dockerfile".to_string(),
+    context: ".".to_string(),
+    tags: vec!["myapp:latest".to_string()],
+    push: true,
+    ..Default::default()
+};
+
+let step = BuildkitStep::new(config);
+
+// Inspect the command that would be executed.
+let args = step.build_command();
+println!("{}", args.join(" "));
+```
+
+Or use it through `wfe-yaml` with the `buildkit` feature:
+
+```yaml
+workflow:
+  id: build-image
+  version: 1
+  steps:
+    - name: build
+      type: buildkit
+      config:
+        dockerfile: Dockerfile
+        context: .
+        tags:
+          - myapp:latest
+          - myapp:v1.0
+        push: true
+        build_args:
+          RUST_VERSION: "1.78"
+        cache_from:
+          - type=registry,ref=myapp:cache
+        cache_to:
+          - type=registry,ref=myapp:cache,mode=max
+        timeout: 10m
+```
+
+## Configuration
+
+| Field | Type | Required | Default | Description |
+|---|---|---|---|---|
+| `dockerfile` | String | Yes | - | Path to the Dockerfile |
+| `context` | String | Yes | - | Build context directory |
+| `target` | String | No | - | Multi-stage build target |
+| `tags` | Vec\<String\> | No | [] | Image tags |
+| `build_args` | Map\<String, String\> | No | {} | Build arguments |
+| `cache_from` | Vec\<String\> | No | [] | Cache import sources |
+| `cache_to` | Vec\<String\> | No | [] | Cache export destinations |
+| `push` | bool | No | false | Push image after build |
+| `output_type` | String | No | "image" | Output type: image, local, tar |
+| `buildkit_addr` | String | No | unix:///run/buildkit/buildkitd.sock | BuildKit daemon address |
+| `tls` | TlsConfig | No | - | TLS certificate paths |
+| `registry_auth` | Map\<String, RegistryAuth\> | No | {} | Registry credentials |
+| `timeout_ms` | u64 | No | - | Execution timeout in milliseconds |
+
+## Output data
+
+After execution, the step writes the following keys into `output_data`:
+
+| Key | Description |
+|---|---|
+| `{step_name}.digest` | Image digest (sha256:...), if found in output |
+| `{step_name}.tags` | Array of tags applied to the image |
+| `{step_name}.stdout` | Full stdout from buildctl |
+| `{step_name}.stderr` | Full stderr from buildctl |
+
+## Testing
+
+```sh
+cargo test -p wfe-buildkit
+```
+
+The `build_command()` method returns the full argument list without executing, making it possible to test command construction without a running BuildKit daemon.
+
+## License
+
+MIT

wfe-buildkit/src/config.rs

@@ -0,0 +1,358 @@
+use std::collections::HashMap;
+
+use serde::{Deserialize, Serialize};
+
+/// Configuration for a BuildKit image build step.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct BuildkitConfig {
+    /// Path to the Dockerfile (or directory containing it).
+    pub dockerfile: String,
+    /// Build context directory.
+    pub context: String,
+    /// Multi-stage build target.
+    pub target: Option<String>,
+    /// Image tags to apply.
+    #[serde(default)]
+    pub tags: Vec<String>,
+    /// Build arguments passed as `--opt build-arg:KEY=VALUE`.
+    #[serde(default)]
+    pub build_args: HashMap<String, String>,
+    /// Cache import sources.
+    #[serde(default)]
+    pub cache_from: Vec<String>,
+    /// Cache export destinations.
+    #[serde(default)]
+    pub cache_to: Vec<String>,
+    /// Whether to push the built image.
+    #[serde(default)]
+    pub push: bool,
+    /// Output type: "image", "local", "tar".
+    pub output_type: Option<String>,
+    /// BuildKit daemon address.
+    #[serde(default = "default_buildkit_addr")]
+    pub buildkit_addr: String,
+    /// TLS configuration for the BuildKit connection.
+    #[serde(default)]
+    pub tls: TlsConfig,
+    /// Registry authentication credentials keyed by registry host.
+    #[serde(default)]
+    pub registry_auth: HashMap<String, RegistryAuth>,
+    /// Execution timeout in milliseconds.
+    pub timeout_ms: Option<u64>,
+}
+
+/// TLS certificate paths for securing the BuildKit connection.
+#[derive(Debug, Clone, Serialize, Deserialize, Default)]
+pub struct TlsConfig {
+    /// Path to the CA certificate.
+    pub ca: Option<String>,
+    /// Path to the client certificate.
+    pub cert: Option<String>,
+    /// Path to the client private key.
+    pub key: Option<String>,
+}
+
+/// Credentials for authenticating with a container registry.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct RegistryAuth {
+    pub username: String,
+    pub password: String,
+}
+
+fn default_buildkit_addr() -> String {
+    "unix:///run/buildkit/buildkitd.sock".to_string()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use pretty_assertions::assert_eq;
+
+    #[test]
+    fn serde_round_trip_full_config() {
+        let mut build_args = HashMap::new();
+        build_args.insert("RUST_VERSION".to_string(), "1.78".to_string());
+
+        let mut registry_auth = HashMap::new();
+        registry_auth.insert(
+            "ghcr.io".to_string(),
+            RegistryAuth {
+                username: "user".to_string(),
+                password: "pass".to_string(),
+            },
+        );
+
+        let config = BuildkitConfig {
+            dockerfile: "./Dockerfile".to_string(),
+            context: ".".to_string(),
+            target: Some("runtime".to_string()),
+            tags: vec!["myapp:latest".to_string(), "myapp:v1.0".to_string()],
+            build_args,
+            cache_from: vec!["type=registry,ref=myapp:cache".to_string()],
+            cache_to: vec!["type=registry,ref=myapp:cache,mode=max".to_string()],
+            push: true,
+            output_type: Some("image".to_string()),
+            buildkit_addr: "tcp://buildkitd:1234".to_string(),
+            tls: TlsConfig {
+                ca: Some("/certs/ca.pem".to_string()),
+                cert: Some("/certs/cert.pem".to_string()),
+                key: Some("/certs/key.pem".to_string()),
+            },
+            registry_auth,
+            timeout_ms: Some(300_000),
+        };
+
+        let json = serde_json::to_string(&config).unwrap();
+        let deserialized: BuildkitConfig = serde_json::from_str(&json).unwrap();
+
+        assert_eq!(config.dockerfile, deserialized.dockerfile);
+        assert_eq!(config.context, deserialized.context);
+        assert_eq!(config.target, deserialized.target);
+        assert_eq!(config.tags, deserialized.tags);
+        assert_eq!(config.build_args, deserialized.build_args);
+        assert_eq!(config.cache_from, deserialized.cache_from);
+        assert_eq!(config.cache_to, deserialized.cache_to);
+        assert_eq!(config.push, deserialized.push);
+        assert_eq!(config.output_type, deserialized.output_type);
+        assert_eq!(config.buildkit_addr, deserialized.buildkit_addr);
+        assert_eq!(config.tls.ca, deserialized.tls.ca);
+        assert_eq!(config.tls.cert, deserialized.tls.cert);
+        assert_eq!(config.tls.key, deserialized.tls.key);
+        assert_eq!(config.timeout_ms, deserialized.timeout_ms);
+    }
+
+    #[test]
+    fn serde_round_trip_minimal_config() {
+        let json = r#"{
+            "dockerfile": "Dockerfile",
+            "context": "."
+        }"#;
+        let config: BuildkitConfig = serde_json::from_str(json).unwrap();
+
+        assert_eq!(config.dockerfile, "Dockerfile");
+        assert_eq!(config.context, ".");
+        assert_eq!(config.target, None);
+        assert!(config.tags.is_empty());
+        assert!(config.build_args.is_empty());
+        assert!(config.cache_from.is_empty());
+        assert!(config.cache_to.is_empty());
+        assert!(!config.push);
+        assert_eq!(config.output_type, None);
+        assert_eq!(config.buildkit_addr, "unix:///run/buildkit/buildkitd.sock");
+        assert_eq!(config.timeout_ms, None);
+
+        // Round-trip
+        let serialized = serde_json::to_string(&config).unwrap();
+        let deserialized: BuildkitConfig = serde_json::from_str(&serialized).unwrap();
+        assert_eq!(config.dockerfile, deserialized.dockerfile);
+        assert_eq!(config.context, deserialized.context);
+    }
+
+    #[test]
+    fn default_buildkit_addr_value() {
+        let addr = default_buildkit_addr();
+        assert_eq!(addr, "unix:///run/buildkit/buildkitd.sock");
+    }
+
+    #[test]
+    fn tls_config_defaults_to_none() {
+        let tls = TlsConfig::default();
+        assert_eq!(tls.ca, None);
+        assert_eq!(tls.cert, None);
+        assert_eq!(tls.key, None);
+    }
+
+    #[test]
+    fn registry_auth_serde() {
+        let auth = RegistryAuth {
+            username: "admin".to_string(),
+            password: "secret123".to_string(),
+        };
+
+        let json = serde_json::to_string(&auth).unwrap();
+        let deserialized: RegistryAuth = serde_json::from_str(&json).unwrap();
+
+        assert_eq!(auth.username, deserialized.username);
+        assert_eq!(auth.password, deserialized.password);
+    }
+
+    #[test]
+    fn serde_custom_addr() {
+        let json = r#"{
+            "dockerfile": "Dockerfile",
+            "context": ".",
+            "buildkit_addr": "tcp://remote:1234"
+        }"#;
+        let config: BuildkitConfig = serde_json::from_str(json).unwrap();
+        assert_eq!(config.buildkit_addr, "tcp://remote:1234");
+    }
+
+    #[test]
+    fn serde_with_timeout() {
+        let json = r#"{
+            "dockerfile": "Dockerfile",
+            "context": ".",
+            "timeout_ms": 60000
+        }"#;
+        let config: BuildkitConfig = serde_json::from_str(json).unwrap();
+        assert_eq!(config.timeout_ms, Some(60000));
+    }
+
+    #[test]
+    fn serde_with_tags_and_push() {
+        let json = r#"{
+            "dockerfile": "Dockerfile",
+            "context": ".",
+            "tags": ["myapp:latest", "myapp:v1.0"],
+            "push": true
+        }"#;
+        let config: BuildkitConfig = serde_json::from_str(json).unwrap();
+        assert_eq!(config.tags, vec!["myapp:latest", "myapp:v1.0"]);
+        assert!(config.push);
+    }
+
+    #[test]
+    fn serde_with_build_args() {
+        let json = r#"{
+            "dockerfile": "Dockerfile",
+            "context": ".",
+            "build_args": {"VERSION": "1.0", "DEBUG": "false"}
+        }"#;
+        let config: BuildkitConfig = serde_json::from_str(json).unwrap();
+        assert_eq!(config.build_args.len(), 2);
+        assert_eq!(config.build_args["VERSION"], "1.0");
+        assert_eq!(config.build_args["DEBUG"], "false");
+    }
+
+    #[test]
+    fn serde_with_cache_config() {
+        let json = r#"{
+            "dockerfile": "Dockerfile",
+            "context": ".",
+            "cache_from": ["type=registry,ref=cache:latest"],
+            "cache_to": ["type=registry,ref=cache:latest,mode=max"]
+        }"#;
+        let config: BuildkitConfig = serde_json::from_str(json).unwrap();
+        assert_eq!(config.cache_from.len(), 1);
+        assert_eq!(config.cache_to.len(), 1);
+    }
+
+    #[test]
+    fn serde_with_output_type() {
+        let json = r#"{
+            "dockerfile": "Dockerfile",
+            "context": ".",
+            "output_type": "tar"
+        }"#;
+        let config: BuildkitConfig = serde_json::from_str(json).unwrap();
+        assert_eq!(config.output_type, Some("tar".to_string()));
+    }
+
+    #[test]
+    fn serde_with_registry_auth() {
+        let json = r#"{
+            "dockerfile": "Dockerfile",
+            "context": ".",
+            "registry_auth": {
+                "ghcr.io": {"username": "bot", "password": "tok"},
+                "docker.io": {"username": "u", "password": "p"}
+            }
+        }"#;
+        let config: BuildkitConfig = serde_json::from_str(json).unwrap();
+        assert_eq!(config.registry_auth.len(), 2);
+        assert_eq!(config.registry_auth["ghcr.io"].username, "bot");
+        assert_eq!(config.registry_auth["docker.io"].password, "p");
+    }
+
+    #[test]
+    fn serde_with_tls() {
+        let json = r#"{
+            "dockerfile": "Dockerfile",
+            "context": ".",
+            "tls": {
+                "ca": "/certs/ca.pem",
+                "cert": "/certs/cert.pem",
+                "key": "/certs/key.pem"
+            }
+        }"#;
+        let config: BuildkitConfig = serde_json::from_str(json).unwrap();
+        assert_eq!(config.tls.ca, Some("/certs/ca.pem".to_string()));
+        assert_eq!(config.tls.cert, Some("/certs/cert.pem".to_string()));
+        assert_eq!(config.tls.key, Some("/certs/key.pem".to_string()));
+    }
+
+    #[test]
+    fn serde_partial_tls() {
+        let json = r#"{
+            "dockerfile": "Dockerfile",
+            "context": ".",
+            "tls": {"ca": "/certs/ca.pem"}
+        }"#;
+        let config: BuildkitConfig = serde_json::from_str(json).unwrap();
+        assert_eq!(config.tls.ca, Some("/certs/ca.pem".to_string()));
+        assert_eq!(config.tls.cert, None);
+        assert_eq!(config.tls.key, None);
+    }
+
+    #[test]
+    fn serde_empty_tls_object() {
+        let json = r#"{
+            "dockerfile": "Dockerfile",
+            "context": ".",
+            "tls": {}
+        }"#;
+        let config: BuildkitConfig = serde_json::from_str(json).unwrap();
+        assert_eq!(config.tls.ca, None);
+        assert_eq!(config.tls.cert, None);
+        assert_eq!(config.tls.key, None);
+    }
+
+    #[test]
+    fn tls_config_clone() {
+        let tls = TlsConfig {
+            ca: Some("ca".to_string()),
+            cert: Some("cert".to_string()),
+            key: Some("key".to_string()),
+        };
+        let cloned = tls.clone();
+        assert_eq!(tls.ca, cloned.ca);
+        assert_eq!(tls.cert, cloned.cert);
+        assert_eq!(tls.key, cloned.key);
+    }
+
+    #[test]
+    fn tls_config_debug() {
+        let tls = TlsConfig::default();
+        let debug = format!("{:?}", tls);
+        assert!(debug.contains("TlsConfig"));
+    }
+
+    #[test]
+    fn buildkit_config_debug() {
+        let json = r#"{"dockerfile": "Dockerfile", "context": "."}"#;
+        let config: BuildkitConfig = serde_json::from_str(json).unwrap();
+        let debug = format!("{:?}", config);
+        assert!(debug.contains("BuildkitConfig"));
+    }
+
+    #[test]
+    fn registry_auth_clone() {
+        let auth = RegistryAuth {
+            username: "u".to_string(),
+            password: "p".to_string(),
+        };
+        let cloned = auth.clone();
+        assert_eq!(auth.username, cloned.username);
+        assert_eq!(auth.password, cloned.password);
+    }
+
+    #[test]
+    fn buildkit_config_clone() {
+        let json = r#"{"dockerfile": "Dockerfile", "context": "."}"#;
+        let config: BuildkitConfig = serde_json::from_str(json).unwrap();
+        let cloned = config.clone();
+        assert_eq!(config.dockerfile, cloned.dockerfile);
+        assert_eq!(config.context, cloned.context);
+        assert_eq!(config.buildkit_addr, cloned.buildkit_addr);
+    }
+}

wfe-buildkit/src/lib.rs

@@ -0,0 +1,5 @@
+pub mod config;
+pub mod step;
+
+pub use config::{BuildkitConfig, RegistryAuth, TlsConfig};
+pub use step::{build_output_data, parse_digest, BuildkitStep};

wfe-buildkit/src/step.rs

@@ -0,0 +1,905 @@
+use std::collections::HashMap;
+use std::path::Path;
+
+use async_trait::async_trait;
+use regex::Regex;
+use tokio_stream::StreamExt;
+use tonic::transport::{Channel, Endpoint, Uri};
+use wfe_buildkit_protos::moby::buildkit::v1::control_client::ControlClient;
+use wfe_buildkit_protos::moby::buildkit::v1::{
+    CacheOptions, CacheOptionsEntry, Exporter, SolveRequest, StatusRequest,
+};
+use wfe_core::models::ExecutionResult;
+use wfe_core::traits::step::{StepBody, StepExecutionContext};
+use wfe_core::WfeError;
+
+use crate::config::BuildkitConfig;
+
+/// Result of a BuildKit solve operation.
+#[derive(Debug, Clone)]
+pub(crate) struct BuildResult {
+    /// Image digest produced by the build, if any.
+    pub digest: Option<String>,
+    /// Full exporter response metadata from the daemon.
+    #[allow(dead_code)]
+    pub metadata: HashMap<String, String>,
+}
+
+/// A workflow step that builds container images via the BuildKit gRPC API.
+pub struct BuildkitStep {
+    config: BuildkitConfig,
+}
+
+impl BuildkitStep {
+    /// Create a new BuildKit step from configuration.
+    pub fn new(config: BuildkitConfig) -> Self {
+        Self { config }
+    }
+
+    /// Connect to the BuildKit daemon and return a raw `ControlClient`.
+    ///
+    /// Supports Unix socket (`unix://`), TCP (`tcp://`), and HTTP (`http://`)
+    /// endpoints.
+    async fn connect(&self) -> Result<ControlClient<Channel>, WfeError> {
+        let addr = &self.config.buildkit_addr;
+        tracing::info!(addr = %addr, "connecting to BuildKit daemon");
+
+        let channel = if addr.starts_with("unix://") {
+            let socket_path = addr
+                .strip_prefix("unix://")
+                .unwrap()
+                .to_string();
+
+            // Verify the socket exists before attempting connection.
+            if !Path::new(&socket_path).exists() {
+                return Err(WfeError::StepExecution(format!(
+                    "BuildKit socket not found: {socket_path}"
+                )));
+            }
+
+            // tonic requires a dummy URI for Unix sockets; the actual path
+            // is provided via the connector.
+            Endpoint::try_from("http://[::]:50051")
+                .map_err(|e| {
+                    WfeError::StepExecution(format!("failed to create endpoint: {e}"))
+                })?
+                .connect_with_connector(tower::service_fn(move |_: Uri| {
+                    let path = socket_path.clone();
+                    async move {
+                        tokio::net::UnixStream::connect(path)
+                            .await
+                            .map(hyper_util::rt::TokioIo::new)
+                    }
+                }))
+                .await
+                .map_err(|e| {
+                    WfeError::StepExecution(format!(
+                        "failed to connect to buildkitd via Unix socket at {addr}: {e}"
+                    ))
+                })?
+        } else {
+            // TCP or HTTP endpoint.
+            let connect_addr = if addr.starts_with("tcp://") {
+                addr.replacen("tcp://", "http://", 1)
+            } else {
+                addr.clone()
+            };
+
+            Endpoint::from_shared(connect_addr.clone())
+                .map_err(|e| {
+                    WfeError::StepExecution(format!(
+                        "invalid BuildKit endpoint {connect_addr}: {e}"
+                    ))
+                })?
+                .timeout(std::time::Duration::from_secs(30))
+                .connect()
+                .await
+                .map_err(|e| {
+                    WfeError::StepExecution(format!(
+                        "failed to connect to buildkitd at {connect_addr}: {e}"
+                    ))
+                })?
+        };
+
+        Ok(ControlClient::new(channel))
+    }
+
+    /// Build frontend attributes from the current configuration.
+    ///
+    /// These attributes tell the BuildKit dockerfile frontend how to process
+    /// the build: which file to use, which target stage, build arguments, etc.
+    fn build_frontend_attrs(&self) -> HashMap<String, String> {
+        let mut attrs = HashMap::new();
+
+        // Dockerfile filename (relative to context).
+        if self.config.dockerfile != "Dockerfile" {
+            attrs.insert("filename".to_string(), self.config.dockerfile.clone());
+        }
+
+        // Target stage for multi-stage builds.
+        if let Some(ref target) = self.config.target {
+            attrs.insert("target".to_string(), target.clone());
+        }
+
+        // Build arguments (sorted for determinism).
+        let mut sorted_args: Vec<_> = self.config.build_args.iter().collect();
+        sorted_args.sort_by_key(|(k, _)| (*k).clone());
+        for (key, value) in &sorted_args {
+            attrs.insert(format!("build-arg:{key}"), value.to_string());
+        }
+
+        attrs
+    }
+
+    /// Build exporter configuration for image output.
+    fn build_exporters(&self) -> Vec<Exporter> {
+        if self.config.tags.is_empty() {
+            return vec![];
+        }
+
+        let mut export_attrs = HashMap::new();
+        export_attrs.insert("name".to_string(), self.config.tags.join(","));
+        if self.config.push {
+            export_attrs.insert("push".to_string(), "true".to_string());
+        }
+
+        vec![Exporter {
+            r#type: "image".to_string(),
+            attrs: export_attrs,
+        }]
+    }
+
+    /// Build cache options from the configuration.
+    fn build_cache_options(&self) -> Option<CacheOptions> {
+        if self.config.cache_from.is_empty() && self.config.cache_to.is_empty() {
+            return None;
+        }
+
+        let imports = self
+            .config
+            .cache_from
+            .iter()
+            .map(|source| {
+                let mut attrs = HashMap::new();
+                attrs.insert("ref".to_string(), source.clone());
+                CacheOptionsEntry {
+                    r#type: "registry".to_string(),
+                    attrs,
+                }
+            })
+            .collect();
+
+        let exports = self
+            .config
+            .cache_to
+            .iter()
+            .map(|dest| {
+                let mut attrs = HashMap::new();
+                attrs.insert("ref".to_string(), dest.clone());
+                attrs.insert("mode".to_string(), "max".to_string());
+                CacheOptionsEntry {
+                    r#type: "registry".to_string(),
+                    attrs,
+                }
+            })
+            .collect();
+
+        Some(CacheOptions {
+            export_ref_deprecated: String::new(),
+            import_refs_deprecated: vec![],
+            export_attrs_deprecated: HashMap::new(),
+            exports,
+            imports,
+        })
+    }
+
+    /// Execute the build against a connected BuildKit daemon.
+    ///
+    /// Constructs a `SolveRequest` using the dockerfile.v0 frontend and
+    /// sends it via the Control gRPC service. The build context must be
+    /// accessible to the daemon on its local filesystem (shared mount or
+    /// same machine).
+    ///
+    /// # Session protocol
+    ///
+    /// TODO: For remote daemons where the build context is not on the same
+    /// filesystem, a full session protocol implementation is needed to
+    /// transfer files. Currently we rely on the context directory being
+    /// available to buildkitd (e.g., via a shared mount in Lima/colima).
+    async fn execute_build(
+        &self,
+        control: &mut ControlClient<Channel>,
+    ) -> Result<BuildResult, WfeError> {
+        let build_ref = format!("wfe-build-{}", uuid::Uuid::new_v4());
+        let session_id = uuid::Uuid::new_v4().to_string();
+
+        // Resolve the absolute context path.
+        let abs_context = std::fs::canonicalize(&self.config.context).map_err(|e| {
+            WfeError::StepExecution(format!(
+                "failed to resolve context path {}: {e}",
+                self.config.context
+            ))
+        })?;
+
+        // Build frontend attributes with local context references.
+        let mut frontend_attrs = self.build_frontend_attrs();
+
+        // Point the frontend at the daemon-local context directory.
+        // The "context" attr tells the dockerfile frontend where to find
+        // the build context. For local builds we use the local source type
+        // with a shared-key reference.
+        let context_name = "context";
+        let dockerfile_name = "dockerfile";
+
+        frontend_attrs.insert(
+            "context".to_string(),
+            format!("local://{context_name}"),
+        );
+        frontend_attrs.insert(
+            format!("local-sessionid:{context_name}"),
+            session_id.clone(),
+        );
+
+        // Also provide the dockerfile source as a local reference.
+        frontend_attrs.insert(
+            "dockerfilekey".to_string(),
+            format!("local://{dockerfile_name}"),
+        );
+        frontend_attrs.insert(
+            format!("local-sessionid:{dockerfile_name}"),
+            session_id.clone(),
+        );
+
+        let request = SolveRequest {
+            r#ref: build_ref.clone(),
+            definition: None,
+            exporter_deprecated: String::new(),
+            exporter_attrs_deprecated: HashMap::new(),
+            session: session_id.clone(),
+            frontend: "dockerfile.v0".to_string(),
+            frontend_attrs,
+            cache: self.build_cache_options(),
+            entitlements: vec![],
+            frontend_inputs: HashMap::new(),
+            internal: false,
+            source_policy: None,
+            exporters: self.build_exporters(),
+            enable_session_exporter: false,
+            source_policy_session: String::new(),
+        };
+
+        // Attach session metadata headers so buildkitd knows which
+        // session provides the local source content.
+        let mut grpc_request = tonic::Request::new(request);
+        let metadata = grpc_request.metadata_mut();
+
+        // The x-docker-expose-session-uuid header tells buildkitd which
+        // session owns the local sources. The x-docker-expose-session-grpc-method
+        // header lists the gRPC methods the session implements.
+        if let Ok(key) =
+            "x-docker-expose-session-uuid"
+                .parse::<tonic::metadata::MetadataKey<tonic::metadata::Ascii>>()
+            && let Ok(val) = session_id
+                .parse::<tonic::metadata::MetadataValue<tonic::metadata::Ascii>>()
+        {
+            metadata.insert(key, val);
+        }
+
+        // Advertise the filesync method so the daemon knows it can request
+        // local file content from our session.
+        if let Ok(key) =
+            "x-docker-expose-session-grpc-method"
+                .parse::<tonic::metadata::MetadataKey<tonic::metadata::Ascii>>()
+        {
+            if let Ok(val) = "/moby.filesync.v1.FileSync/DiffCopy"
+                .parse::<tonic::metadata::MetadataValue<tonic::metadata::Ascii>>()
+            {
+                metadata.append(key.clone(), val);
+            }
+            if let Ok(val) = "/moby.filesync.v1.Auth/Credentials"
+                .parse::<tonic::metadata::MetadataValue<tonic::metadata::Ascii>>()
+            {
+                metadata.append(key, val);
+            }
+        }
+
+        tracing::info!(
+            context = %abs_context.display(),
+            session_id = %session_id,
+            "sending solve request to BuildKit"
+        );
+
+        let response = control
+            .solve(grpc_request)
+            .await
+            .map_err(|e| WfeError::StepExecution(format!("BuildKit solve failed: {e}")))?;
+        let solve_response = response.into_inner();
+
+        // Monitor progress (non-blocking, best effort).
+        let status_request = StatusRequest {
+            r#ref: build_ref.clone(),
+        };
+        if let Ok(stream_resp) = control.status(status_request).await {
+            let mut stream = stream_resp.into_inner();
+            while let Some(Ok(status)) = stream.next().await {
+                for vertex in &status.vertexes {
+                    if !vertex.name.is_empty() {
+                        tracing::debug!(vertex = %vertex.name, "build progress");
+                    }
+                }
+            }
+        }
+
+        // Extract digest.
+        let digest = solve_response
+            .exporter_response
+            .get("containerimage.digest")
+            .cloned();
+
+        tracing::info!(digest = ?digest, "build completed");
+
+        Ok(BuildResult {
+            digest,
+            metadata: solve_response.exporter_response,
+        })
+    }
+
+    /// Build environment variables for registry authentication.
+    ///
+    /// This is still useful when the BuildKit daemon reads credentials from
+    /// environment variables rather than session-based auth.
+    pub fn build_registry_env(&self) -> HashMap<String, String> {
+        let mut env = HashMap::new();
+        for (host, auth) in &self.config.registry_auth {
+            let sanitized_host = host.replace(['.', '-'], "_").to_uppercase();
+            env.insert(
+                format!("BUILDKIT_HOST_{sanitized_host}_USERNAME"),
+                auth.username.clone(),
+            );
+            env.insert(
+                format!("BUILDKIT_HOST_{sanitized_host}_PASSWORD"),
+                auth.password.clone(),
+            );
+        }
+        env
+    }
+}
+
+/// Parse the image digest from buildctl or BuildKit progress output.
+///
+/// Looks for patterns like `exporting manifest sha256:<hex>` or
+/// `digest: sha256:<hex>` or the raw `containerimage.digest` value.
+pub fn parse_digest(output: &str) -> Option<String> {
+    let re = Regex::new(r"(?:exporting manifest |digest: )sha256:([a-f0-9]{64})").unwrap();
+    re.captures(output)
+        .map(|caps| format!("sha256:{}", &caps[1]))
+}
+
+/// Build the output data JSON object from step execution results.
+///
+/// Assembles a `serde_json::Value::Object` containing the step's stdout,
+/// stderr, digest (if found), and tags (if any).
+pub fn build_output_data(
+    step_name: &str,
+    stdout: &str,
+    stderr: &str,
+    digest: Option<&str>,
+    tags: &[String],
+) -> serde_json::Value {
+    let mut outputs = serde_json::Map::new();
+
+    if let Some(digest) = digest {
+        outputs.insert(
+            format!("{step_name}.digest"),
+            serde_json::Value::String(digest.to_string()),
+        );
+    }
+
+    if !tags.is_empty() {
+        outputs.insert(
+            format!("{step_name}.tags"),
+            serde_json::Value::Array(
+                tags.iter()
+                    .map(|t| serde_json::Value::String(t.clone()))
+                    .collect(),
+            ),
+        );
+    }
+
+    outputs.insert(
+        format!("{step_name}.stdout"),
+        serde_json::Value::String(stdout.to_string()),
+    );
+    outputs.insert(
+        format!("{step_name}.stderr"),
+        serde_json::Value::String(stderr.to_string()),
+    );
+
+    serde_json::Value::Object(outputs)
+}
+
+#[async_trait]
+impl StepBody for BuildkitStep {
+    async fn run(
+        &mut self,
+        context: &StepExecutionContext<'_>,
+    ) -> wfe_core::Result<ExecutionResult> {
+        let step_name = context.step.name.as_deref().unwrap_or("unknown");
+
+        // Connect to the BuildKit daemon.
+        let mut control = self.connect().await?;
+
+        tracing::info!(step = step_name, "submitting build to BuildKit");
+
+        // Execute the build with optional timeout.
+        let result = if let Some(timeout_ms) = self.config.timeout_ms {
+            let duration = std::time::Duration::from_millis(timeout_ms);
+            match tokio::time::timeout(duration, self.execute_build(&mut control)).await {
+                Ok(Ok(result)) => result,
+                Ok(Err(e)) => return Err(e),
+                Err(_) => {
+                    return Err(WfeError::StepExecution(format!(
+                        "BuildKit build timed out after {timeout_ms}ms"
+                    )));
+                }
+            }
+        } else {
+            self.execute_build(&mut control).await?
+        };
+
+        // Extract digest from BuildResult.
+        let digest = result.digest.clone();
+
+        tracing::info!(
+            step = step_name,
+            digest = ?digest,
+            "build completed"
+        );
+
+        let output_data = build_output_data(
+            step_name,
+            "", // gRPC builds don't produce traditional stdout
+            "", // gRPC builds don't produce traditional stderr
+            digest.as_deref(),
+            &self.config.tags,
+        );
+
+        Ok(ExecutionResult {
+            proceed: true,
+            output_data: Some(output_data),
+            ..Default::default()
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use pretty_assertions::assert_eq;
+    use std::collections::HashMap;
+
+    use crate::config::{BuildkitConfig, RegistryAuth, TlsConfig};
+
+    fn minimal_config() -> BuildkitConfig {
+        BuildkitConfig {
+            dockerfile: "Dockerfile".to_string(),
+            context: ".".to_string(),
+            target: None,
+            tags: vec![],
+            build_args: HashMap::new(),
+            cache_from: vec![],
+            cache_to: vec![],
+            push: false,
+            output_type: None,
+            buildkit_addr: "unix:///run/buildkit/buildkitd.sock".to_string(),
+            tls: TlsConfig::default(),
+            registry_auth: HashMap::new(),
+            timeout_ms: None,
+        }
+    }
+
+    // ---------------------------------------------------------------
+    // build_registry_env tests
+    // ---------------------------------------------------------------
+
+    #[test]
+    fn build_registry_env_with_auth() {
+        let mut config = minimal_config();
+        config.registry_auth.insert(
+            "ghcr.io".to_string(),
+            RegistryAuth {
+                username: "user".to_string(),
+                password: "token".to_string(),
+            },
+        );
+
+        let step = BuildkitStep::new(config);
+        let env = step.build_registry_env();
+
+        assert_eq!(
+            env.get("BUILDKIT_HOST_GHCR_IO_USERNAME"),
+            Some(&"user".to_string())
+        );
+        assert_eq!(
+            env.get("BUILDKIT_HOST_GHCR_IO_PASSWORD"),
+            Some(&"token".to_string())
+        );
+    }
+
+    #[test]
+    fn build_registry_env_sanitizes_host() {
+        let mut config = minimal_config();
+        config.registry_auth.insert(
+            "my-registry.example.com".to_string(),
+            RegistryAuth {
+                username: "u".to_string(),
+                password: "p".to_string(),
+            },
+        );
+
+        let step = BuildkitStep::new(config);
+        let env = step.build_registry_env();
+
+        assert!(env.contains_key("BUILDKIT_HOST_MY_REGISTRY_EXAMPLE_COM_USERNAME"));
+        assert!(env.contains_key("BUILDKIT_HOST_MY_REGISTRY_EXAMPLE_COM_PASSWORD"));
+    }
+
+    #[test]
+    fn build_registry_env_empty_when_no_auth() {
+        let step = BuildkitStep::new(minimal_config());
+        let env = step.build_registry_env();
+        assert!(env.is_empty());
+    }
+
+    #[test]
+    fn build_registry_env_multiple_registries() {
+        let mut config = minimal_config();
+        config.registry_auth.insert(
+            "ghcr.io".to_string(),
+            RegistryAuth {
+                username: "gh_user".to_string(),
+                password: "gh_pass".to_string(),
+            },
+        );
+        config.registry_auth.insert(
+            "docker.io".to_string(),
+            RegistryAuth {
+                username: "dh_user".to_string(),
+                password: "dh_pass".to_string(),
+            },
+        );
+
+        let step = BuildkitStep::new(config);
+        let env = step.build_registry_env();
+
+        assert_eq!(env.len(), 4);
+        assert_eq!(env["BUILDKIT_HOST_GHCR_IO_USERNAME"], "gh_user");
+        assert_eq!(env["BUILDKIT_HOST_GHCR_IO_PASSWORD"], "gh_pass");
+        assert_eq!(env["BUILDKIT_HOST_DOCKER_IO_USERNAME"], "dh_user");
+        assert_eq!(env["BUILDKIT_HOST_DOCKER_IO_PASSWORD"], "dh_pass");
+    }
+
+    // ---------------------------------------------------------------
+    // parse_digest tests
+    // ---------------------------------------------------------------
+
+    #[test]
+    fn parse_digest_from_output() {
+        let output = "some build output\nexporting manifest sha256:abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789\ndone";
+        let digest = parse_digest(output);
+        assert_eq!(
+            digest,
+            Some(
+                "sha256:abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789"
+                    .to_string()
+            )
+        );
+    }
+
+    #[test]
+    fn parse_digest_with_digest_prefix() {
+        let output = "digest: sha256:1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef\n";
+        let digest = parse_digest(output);
+        assert_eq!(
+            digest,
+            Some(
+                "sha256:1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef"
+                    .to_string()
+            )
+        );
+    }
+
+    #[test]
+    fn parse_digest_missing_returns_none() {
+        let output = "building image...\nall done!";
+        let digest = parse_digest(output);
+        assert_eq!(digest, None);
+    }
+
+    #[test]
+    fn parse_digest_partial_hash_returns_none() {
+        let output = "exporting manifest sha256:abcdef";
+        let digest = parse_digest(output);
+        assert_eq!(digest, None);
+    }
+
+    #[test]
+    fn parse_digest_empty_input() {
+        assert_eq!(parse_digest(""), None);
+    }
+
+    #[test]
+    fn parse_digest_wrong_prefix() {
+        let output =
+            "sha256:abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789";
+        assert_eq!(parse_digest(output), None);
+    }
+
+    #[test]
+    fn parse_digest_uppercase_hex_returns_none() {
+        let output = "exporting manifest sha256:ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789ABCDEF0123456789";
+        assert_eq!(parse_digest(output), None);
+    }
+
+    #[test]
+    fn parse_digest_multiline_with_noise() {
+        let output = r#"
+[+] Building 12.3s (8/8) FINISHED
+ => exporting to image
+ => exporting manifest sha256:aabbccdd0011223344556677aabbccdd0011223344556677aabbccdd00112233
+ => done
+"#;
+        assert_eq!(
+            parse_digest(output),
+            Some("sha256:aabbccdd0011223344556677aabbccdd0011223344556677aabbccdd00112233".to_string())
+        );
+    }
+
+    #[test]
+    fn parse_digest_first_match_wins() {
+        let hash1 = "a".repeat(64);
+        let hash2 = "b".repeat(64);
+        let output = format!(
+            "exporting manifest sha256:{hash1}\ndigest: sha256:{hash2}"
+        );
+        let digest = parse_digest(&output).unwrap();
+        assert_eq!(digest, format!("sha256:{hash1}"));
+    }
+
+    // ---------------------------------------------------------------
+    // build_output_data tests
+    // ---------------------------------------------------------------
+
+    #[test]
+    fn build_output_data_with_digest_and_tags() {
+        let digest = "sha256:abcdef0123456789abcdef0123456789abcdef0123456789abcdef0123456789";
+        let tags = vec!["myapp:latest".to_string(), "myapp:v1".to_string()];
+        let result = build_output_data("build", "out", "err", Some(digest), &tags);
+
+        let obj = result.as_object().unwrap();
+        assert_eq!(obj["build.digest"], digest);
+        assert_eq!(
+            obj["build.tags"],
+            serde_json::json!(["myapp:latest", "myapp:v1"])
+        );
+        assert_eq!(obj["build.stdout"], "out");
+        assert_eq!(obj["build.stderr"], "err");
+    }
+
+    #[test]
+    fn build_output_data_without_digest() {
+        let result = build_output_data("step1", "hello", "", None, &[]);
+
+        let obj = result.as_object().unwrap();
+        assert!(!obj.contains_key("step1.digest"));
+        assert!(!obj.contains_key("step1.tags"));
+        assert_eq!(obj["step1.stdout"], "hello");
+        assert_eq!(obj["step1.stderr"], "");
+    }
+
+    #[test]
+    fn build_output_data_with_digest_no_tags() {
+        let digest = "sha256:0000000000000000000000000000000000000000000000000000000000000000";
+        let result = build_output_data("img", "ok", "warn", Some(digest), &[]);
+
+        let obj = result.as_object().unwrap();
+        assert_eq!(obj["img.digest"], digest);
+        assert!(!obj.contains_key("img.tags"));
+        assert_eq!(obj["img.stdout"], "ok");
+        assert_eq!(obj["img.stderr"], "warn");
+    }
+
+    #[test]
+    fn build_output_data_no_digest_with_tags() {
+        let tags = vec!["app:v2".to_string()];
+        let result = build_output_data("s", "", "", None, &tags);
+
+        let obj = result.as_object().unwrap();
+        assert!(!obj.contains_key("s.digest"));
+        assert_eq!(obj["s.tags"], serde_json::json!(["app:v2"]));
+    }
+
+    #[test]
+    fn build_output_data_empty_strings() {
+        let result = build_output_data("x", "", "", None, &[]);
+        let obj = result.as_object().unwrap();
+        assert_eq!(obj["x.stdout"], "");
+        assert_eq!(obj["x.stderr"], "");
+        assert_eq!(obj.len(), 2);
+    }
+
+    // ---------------------------------------------------------------
+    // build_frontend_attrs tests
+    // ---------------------------------------------------------------
+
+    #[test]
+    fn frontend_attrs_minimal() {
+        let step = BuildkitStep::new(minimal_config());
+        let attrs = step.build_frontend_attrs();
+        // Default Dockerfile name is not included (only non-default).
+        assert!(!attrs.contains_key("filename"));
+        assert!(!attrs.contains_key("target"));
+    }
+
+    #[test]
+    fn frontend_attrs_with_target() {
+        let mut config = minimal_config();
+        config.target = Some("runtime".to_string());
+        let step = BuildkitStep::new(config);
+        let attrs = step.build_frontend_attrs();
+        assert_eq!(attrs.get("target"), Some(&"runtime".to_string()));
+    }
+
+    #[test]
+    fn frontend_attrs_with_custom_dockerfile() {
+        let mut config = minimal_config();
+        config.dockerfile = "docker/Dockerfile.prod".to_string();
+        let step = BuildkitStep::new(config);
+        let attrs = step.build_frontend_attrs();
+        assert_eq!(
+            attrs.get("filename"),
+            Some(&"docker/Dockerfile.prod".to_string())
+        );
+    }
+
+    #[test]
+    fn frontend_attrs_with_build_args() {
+        let mut config = minimal_config();
+        config
+            .build_args
+            .insert("RUST_VERSION".to_string(), "1.78".to_string());
+        config
+            .build_args
+            .insert("BUILD_MODE".to_string(), "release".to_string());
+        let step = BuildkitStep::new(config);
+        let attrs = step.build_frontend_attrs();
+        assert_eq!(
+            attrs.get("build-arg:BUILD_MODE"),
+            Some(&"release".to_string())
+        );
+        assert_eq!(
+            attrs.get("build-arg:RUST_VERSION"),
+            Some(&"1.78".to_string())
+        );
+    }
+
+    // ---------------------------------------------------------------
+    // build_exporters tests
+    // ---------------------------------------------------------------
+
+    #[test]
+    fn exporters_empty_when_no_tags() {
+        let step = BuildkitStep::new(minimal_config());
+        assert!(step.build_exporters().is_empty());
+    }
+
+    #[test]
+    fn exporters_with_tags_and_push() {
+        let mut config = minimal_config();
+        config.tags = vec!["myapp:latest".to_string(), "myapp:v1.0".to_string()];
+        config.push = true;
+        let step = BuildkitStep::new(config);
+        let exporters = step.build_exporters();
+        assert_eq!(exporters.len(), 1);
+        assert_eq!(exporters[0].r#type, "image");
+        assert_eq!(
+            exporters[0].attrs.get("name"),
+            Some(&"myapp:latest,myapp:v1.0".to_string())
+        );
+        assert_eq!(
+            exporters[0].attrs.get("push"),
+            Some(&"true".to_string())
+        );
+    }
+
+    #[test]
+    fn exporters_with_tags_no_push() {
+        let mut config = minimal_config();
+        config.tags = vec!["myapp:latest".to_string()];
+        config.push = false;
+        let step = BuildkitStep::new(config);
+        let exporters = step.build_exporters();
+        assert_eq!(exporters.len(), 1);
+        assert!(!exporters[0].attrs.contains_key("push"));
+    }
+
+    // ---------------------------------------------------------------
+    // build_cache_options tests
+    // ---------------------------------------------------------------
+
+    #[test]
+    fn cache_options_none_when_empty() {
+        let step = BuildkitStep::new(minimal_config());
+        assert!(step.build_cache_options().is_none());
+    }
+
+    #[test]
+    fn cache_options_with_imports_and_exports() {
+        let mut config = minimal_config();
+        config.cache_from = vec!["type=registry,ref=myapp:cache".to_string()];
+        config.cache_to = vec!["type=registry,ref=myapp:cache,mode=max".to_string()];
+        let step = BuildkitStep::new(config);
+        let opts = step.build_cache_options().unwrap();
+        assert_eq!(opts.imports.len(), 1);
+        assert_eq!(opts.exports.len(), 1);
+        assert_eq!(opts.imports[0].r#type, "registry");
+        assert_eq!(opts.exports[0].r#type, "registry");
+    }
+
+    // ---------------------------------------------------------------
+    // connect helper tests
+    // ---------------------------------------------------------------
+
+    #[test]
+    fn tcp_addr_converted_to_http() {
+        let mut config = minimal_config();
+        config.buildkit_addr = "tcp://buildkitd:1234".to_string();
+        let step = BuildkitStep::new(config);
+        assert_eq!(step.config.buildkit_addr, "tcp://buildkitd:1234");
+    }
+
+    #[test]
+    fn unix_addr_preserved() {
+        let config = minimal_config();
+        let step = BuildkitStep::new(config);
+        assert!(step.config.buildkit_addr.starts_with("unix://"));
+    }
+
+    #[tokio::test]
+    async fn connect_to_missing_unix_socket_returns_error() {
+        let mut config = minimal_config();
+        config.buildkit_addr = "unix:///tmp/nonexistent-wfe-test.sock".to_string();
+        let step = BuildkitStep::new(config);
+        let err = step.connect().await.unwrap_err();
+        let msg = format!("{err}");
+        assert!(
+            msg.contains("socket not found"),
+            "expected 'socket not found' error, got: {msg}"
+        );
+    }
+
+    #[tokio::test]
+    async fn connect_to_invalid_tcp_returns_error() {
+        let mut config = minimal_config();
+        config.buildkit_addr = "tcp://127.0.0.1:1".to_string();
+        let step = BuildkitStep::new(config);
+        let err = step.connect().await.unwrap_err();
+        let msg = format!("{err}");
+        assert!(
+            msg.contains("failed to connect"),
+            "expected connection error, got: {msg}"
+        );
+    }
+
+    // ---------------------------------------------------------------
+    // BuildkitStep construction tests
+    // ---------------------------------------------------------------
+
+    #[test]
+    fn new_step_stores_config() {
+        let config = minimal_config();
+        let step = BuildkitStep::new(config.clone());
+        assert_eq!(step.config.dockerfile, "Dockerfile");
+        assert_eq!(step.config.context, ".");
+    }
+}

wfe-buildkit/tests/integration_test.rs

@@ -0,0 +1,234 @@
+//! Integration tests for wfe-buildkit using a real BuildKit daemon.
+//!
+//! These tests require a running BuildKit daemon. The socket path is read
+//! from `WFE_BUILDKIT_ADDR`, falling back to
+//! `unix:///Users/sienna/.lima/wfe-test/sock/buildkitd.sock`.
+//!
+//! If the daemon is not available, the tests are skipped gracefully.
+
+use std::collections::HashMap;
+use std::path::Path;
+
+use wfe_buildkit::config::{BuildkitConfig, TlsConfig};
+use wfe_buildkit::BuildkitStep;
+
+use wfe_core::models::{ExecutionPointer, WorkflowInstance, WorkflowStep};
+use wfe_core::traits::step::{StepBody, StepExecutionContext};
+
+/// Get the BuildKit daemon address from the environment or use the default.
+fn buildkit_addr() -> String {
+    std::env::var("WFE_BUILDKIT_ADDR").unwrap_or_else(|_| {
+        "unix:///Users/sienna/.lima/wfe-test/sock/buildkitd.sock".to_string()
+    })
+}
+
+/// Check whether the BuildKit daemon socket is reachable.
+fn buildkitd_available() -> bool {
+    let addr = buildkit_addr();
+    if let Some(path) = addr.strip_prefix("unix://") {
+        Path::new(path).exists()
+    } else {
+        // For TCP endpoints, optimistically assume available.
+        true
+    }
+}
+
+fn make_test_context(
+    step_name: &str,
+) -> (
+    WorkflowStep,
+    ExecutionPointer,
+    WorkflowInstance,
+) {
+    let mut step = WorkflowStep::new(0, "buildkit");
+    step.name = Some(step_name.to_string());
+    let pointer = ExecutionPointer::new(0);
+    let instance = WorkflowInstance::new("test-wf", 1, serde_json::json!({}));
+    (step, pointer, instance)
+}
+
+#[tokio::test]
+async fn build_simple_dockerfile_via_grpc() {
+    if !buildkitd_available() {
+        eprintln!(
+            "SKIP: BuildKit daemon not available at {}",
+            buildkit_addr()
+        );
+        return;
+    }
+
+    // Create a temp directory with a trivial Dockerfile.
+    let tmp = tempfile::tempdir().unwrap();
+    let dockerfile = tmp.path().join("Dockerfile");
+    std::fs::write(
+        &dockerfile,
+        "FROM alpine:latest\nRUN echo built\n",
+    )
+    .unwrap();
+
+    let config = BuildkitConfig {
+        dockerfile: "Dockerfile".to_string(),
+        context: tmp.path().to_string_lossy().to_string(),
+        target: None,
+        tags: vec![],
+        build_args: HashMap::new(),
+        cache_from: vec![],
+        cache_to: vec![],
+        push: false,
+        output_type: None,
+        buildkit_addr: buildkit_addr(),
+        tls: TlsConfig::default(),
+        registry_auth: HashMap::new(),
+        timeout_ms: Some(120_000), // 2 minutes
+    };
+
+    let mut step = BuildkitStep::new(config);
+
+    let (ws, pointer, instance) = make_test_context("integration-build");
+    let cancel = tokio_util::sync::CancellationToken::new();
+    let ctx = StepExecutionContext {
+        item: None,
+        execution_pointer: &pointer,
+        persistence_data: None,
+        step: &ws,
+        workflow: &instance,
+        cancellation_token: cancel,
+        host_context: None,
+    };
+
+    let result = step.run(&ctx).await.expect("build should succeed");
+
+    assert!(result.proceed);
+
+    let data = result.output_data.expect("should have output_data");
+    let obj = data.as_object().expect("output_data should be an object");
+
+    // Without tags/push, BuildKit does not produce a digest in the exporter
+    // response. The build succeeds but the digest is absent.
+    assert!(
+        obj.contains_key("integration-build.stdout"),
+        "expected stdout key, got: {:?}",
+        obj.keys().collect::<Vec<_>>()
+    );
+    assert!(
+        obj.contains_key("integration-build.stderr"),
+        "expected stderr key, got: {:?}",
+        obj.keys().collect::<Vec<_>>()
+    );
+
+    // If a digest IS present (e.g., newer buildkitd versions), validate its format.
+    if let Some(digest_val) = obj.get("integration-build.digest") {
+        let digest = digest_val.as_str().unwrap();
+        assert!(
+            digest.starts_with("sha256:"),
+            "digest should start with sha256:, got: {digest}"
+        );
+        assert_eq!(
+            digest.len(),
+            7 + 64,
+            "digest should be sha256:<64hex>, got: {digest}"
+        );
+    }
+}
+
+#[tokio::test]
+async fn build_with_build_args() {
+    if !buildkitd_available() {
+        eprintln!(
+            "SKIP: BuildKit daemon not available at {}",
+            buildkit_addr()
+        );
+        return;
+    }
+
+    let tmp = tempfile::tempdir().unwrap();
+    let dockerfile = tmp.path().join("Dockerfile");
+    std::fs::write(
+        &dockerfile,
+        "FROM alpine:latest\nARG MY_VAR=default\nRUN echo \"value=$MY_VAR\"\n",
+    )
+    .unwrap();
+
+    let mut build_args = HashMap::new();
+    build_args.insert("MY_VAR".to_string(), "custom_value".to_string());
+
+    let config = BuildkitConfig {
+        dockerfile: "Dockerfile".to_string(),
+        context: tmp.path().to_string_lossy().to_string(),
+        target: None,
+        tags: vec![],
+        build_args,
+        cache_from: vec![],
+        cache_to: vec![],
+        push: false,
+        output_type: None,
+        buildkit_addr: buildkit_addr(),
+        tls: TlsConfig::default(),
+        registry_auth: HashMap::new(),
+        timeout_ms: Some(120_000),
+    };
+
+    let mut step = BuildkitStep::new(config);
+
+    let (ws, pointer, instance) = make_test_context("build-args-test");
+    let cancel = tokio_util::sync::CancellationToken::new();
+    let ctx = StepExecutionContext {
+        item: None,
+        execution_pointer: &pointer,
+        persistence_data: None,
+        step: &ws,
+        workflow: &instance,
+        cancellation_token: cancel,
+        host_context: None,
+    };
+
+    let result = step.run(&ctx).await.expect("build with args should succeed");
+    assert!(result.proceed);
+
+    let data = result.output_data.expect("should have output_data");
+    let obj = data.as_object().unwrap();
+
+    // Build should complete and produce output data entries.
+    assert!(
+        obj.contains_key("build-args-test.stdout"),
+        "expected stdout key, got: {:?}",
+        obj.keys().collect::<Vec<_>>()
+    );
+}
+
+#[tokio::test]
+async fn connect_to_unavailable_daemon_returns_error() {
+    // Use a deliberately wrong address to test error handling.
+    let config = BuildkitConfig {
+        dockerfile: "Dockerfile".to_string(),
+        context: ".".to_string(),
+        target: None,
+        tags: vec![],
+        build_args: HashMap::new(),
+        cache_from: vec![],
+        cache_to: vec![],
+        push: false,
+        output_type: None,
+        buildkit_addr: "unix:///tmp/nonexistent-buildkitd.sock".to_string(),
+        tls: TlsConfig::default(),
+        registry_auth: HashMap::new(),
+        timeout_ms: Some(5_000),
+    };
+
+    let mut step = BuildkitStep::new(config);
+
+    let (ws, pointer, instance) = make_test_context("error-test");
+    let cancel = tokio_util::sync::CancellationToken::new();
+    let ctx = StepExecutionContext {
+        item: None,
+        execution_pointer: &pointer,
+        persistence_data: None,
+        step: &ws,
+        workflow: &instance,
+        cancellation_token: cancel,
+        host_context: None,
+    };
+
+    let err = step.run(&ctx).await;
+    assert!(err.is_err(), "should fail when daemon is unavailable");
+}

wfe-containerd-protos/Cargo.toml

@@ -0,0 +1,19 @@
+[package]
+name = "wfe-containerd-protos"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+repository.workspace = true
+homepage.workspace = true
+description = "Generated gRPC stubs for the full containerd API"
+
+[dependencies]
+tonic = "0.14"
+tonic-prost = "0.14"
+prost = "0.14"
+prost-types = "0.14"
+
+[build-dependencies]
+tonic-build = "0.14"
+tonic-prost-build = "0.14"
+prost-build = "0.14"

wfe-containerd-protos/build.rs

@@ -0,0 +1,50 @@
+use std::path::PathBuf;
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let api_dir = PathBuf::from("vendor/containerd/api");
+
+    // Collect all .proto files, excluding internal runtime shim protos
+    let proto_files: Vec<PathBuf> = walkdir(&api_dir)?
+        .into_iter()
+        .filter(|p| {
+            let s = p.to_string_lossy();
+            !s.contains("/runtime/task/") && !s.contains("/runtime/sandbox/")
+        })
+        .collect();
+
+    println!(
+        "cargo:warning=Compiling {} containerd proto files",
+        proto_files.len()
+    );
+
+    let _out_dir = PathBuf::from(std::env::var("OUT_DIR")?);
+
+    // Use tonic-prost-build (the tonic 0.14 way)
+    let mut prost_config = prost_build::Config::new();
+    prost_config.include_file("mod.rs");
+
+    tonic_prost_build::configure()
+        .build_server(false)
+        .compile_with_config(
+            prost_config,
+            &proto_files,
+            &[api_dir, PathBuf::from("proto")],
+        )?;
+
+    Ok(())
+}
+
+/// Recursively collect all .proto files under a directory.
+fn walkdir(dir: &PathBuf) -> Result<Vec<PathBuf>, Box<dyn std::error::Error>> {
+    let mut protos = Vec::new();
+    for entry in std::fs::read_dir(dir)? {
+        let entry = entry?;
+        let path = entry.path();
+        if path.is_dir() {
+            protos.extend(walkdir(&path)?);
+        } else if path.extension().is_some_and(|ext| ext == "proto") {
+            protos.push(path);
+        }
+    }
+    Ok(protos)
+}

wfe-containerd-protos/proto/google/rpc/status.proto

@@ -0,0 +1,49 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+syntax = "proto3";
+
+package google.rpc;
+
+import "google/protobuf/any.proto";
+
+option cc_enable_arenas = true;
+option go_package = "google.golang.org/genproto/googleapis/rpc/status;status";
+option java_multiple_files = true;
+option java_outer_classname = "StatusProto";
+option java_package = "com.google.rpc";
+option objc_class_prefix = "RPC";
+
+// The `Status` type defines a logical error model that is suitable for
+// different programming environments, including REST APIs and RPC APIs. It is
+// used by [gRPC](https://github.com/grpc). Each `Status` message contains
+// three pieces of data: error code, error message, and error details.
+//
+// You can find out more about this error model and how to work with it in the
+// [API Design Guide](https://cloud.google.com/apis/design/errors).
+message Status {
+  // The status code, which should be an enum value of
+  // [google.rpc.Code][google.rpc.Code].
+  int32 code = 1;
+
+  // A developer-facing error message, which should be in English. Any
+  // user-facing error message should be localized and sent in the
+  // [google.rpc.Status.details][google.rpc.Status.details] field, or localized
+  // by the client.
+  string message = 2;
+
+  // A list of messages that carry the error details.  There is a common set of
+  // message types for APIs to use.
+  repeated google.protobuf.Any details = 3;
+}

wfe-containerd-protos/src/lib.rs

@@ -0,0 +1,27 @@
+//! Generated gRPC stubs for the full containerd API.
+//!
+//! Built from the official containerd proto files at
+//! <https://github.com/containerd/containerd/tree/main/api>.
+//!
+//! The module structure mirrors the protobuf package hierarchy:
+//!
+//! ```rust,ignore
+//! use wfe_containerd_protos::containerd::services::containers::v1::containers_client::ContainersClient;
+//! use wfe_containerd_protos::containerd::services::tasks::v1::tasks_client::TasksClient;
+//! use wfe_containerd_protos::containerd::services::images::v1::images_client::ImagesClient;
+//! use wfe_containerd_protos::containerd::services::version::v1::version_client::VersionClient;
+//! use wfe_containerd_protos::containerd::types::Mount;
+//! use wfe_containerd_protos::containerd::types::Descriptor;
+//! ```
+
+#![allow(clippy::all)]
+#![allow(warnings)]
+
+// tonic-build generates a mod.rs that defines the full module tree
+// matching the protobuf package structure.
+include!(concat!(env!("OUT_DIR"), "/mod.rs"));
+
+/// Re-export tonic and prost for downstream convenience.
+pub use prost;
+pub use prost_types;
+pub use tonic;

wfe-containerd/Cargo.toml

@@ -0,0 +1,30 @@
+[package]
+name = "wfe-containerd"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+repository.workspace = true
+homepage.workspace = true
+description = "containerd container runner executor for WFE"
+
+[dependencies]
+wfe-core = { workspace = true }
+wfe-containerd-protos = { version = "1.4.0", path = "../wfe-containerd-protos", registry = "sunbeam" }
+tokio = { workspace = true }
+serde = { workspace = true }
+serde_json = { workspace = true }
+async-trait = { workspace = true }
+tracing = { workspace = true }
+thiserror = { workspace = true }
+tonic = "0.14"
+tower = "0.5"
+hyper-util = { version = "0.1", features = ["tokio"] }
+prost-types = "0.14"
+uuid = { version = "1", features = ["v4"] }
+libc = "0.2"
+
+[dev-dependencies]
+pretty_assertions = { workspace = true }
+tokio = { workspace = true, features = ["test-util"] }
+tempfile = { workspace = true }
+tokio-util = "0.7"

wfe-containerd/README.md

@@ -0,0 +1,70 @@
+# wfe-containerd
+
+Containerd container runner executor for WFE.
+
+## What it does
+
+`wfe-containerd` runs containers via `nerdctl` as workflow steps. It pulls images, manages registry authentication, and executes containers with configurable networking, resource limits, volume mounts, and TLS settings. Output is captured and parsed for `##wfe[output key=value]` directives, following the same convention as the shell executor.
+
+## Quick start
+
+Add a containerd step to your YAML workflow:
+
+```yaml
+workflow:
+  id: container-pipeline
+  version: 1
+  steps:
+    - name: run-tests
+      type: containerd
+      config:
+        image: node:20-alpine
+        run: npm test
+        network: none
+        memory: 512m
+        cpu: "1.0"
+        timeout: 5m
+        env:
+          NODE_ENV: test
+        volumes:
+          - source: /workspace
+            target: /app
+            readonly: true
+```
+
+Enable the feature in `wfe-yaml`:
+
+```toml
+[dependencies]
+wfe-yaml = { version = "1.0.0", features = ["containerd"] }
+```
+
+## Configuration
+
+| Field | Type | Default | Description |
+|---|---|---|---|
+| `image` | `String` | required | Container image to run |
+| `run` | `String` | - | Shell command (uses `sh -c`) |
+| `command` | `Vec<String>` | - | Command array (mutually exclusive with `run`) |
+| `env` | `HashMap` | `{}` | Environment variables |
+| `volumes` | `Vec<VolumeMount>` | `[]` | Volume mounts |
+| `working_dir` | `String` | - | Working directory inside container |
+| `user` | `String` | `65534:65534` | User/group to run as (nobody by default) |
+| `network` | `String` | `none` | Network mode: `none`, `host`, or `bridge` |
+| `memory` | `String` | - | Memory limit (e.g. `512m`, `1g`) |
+| `cpu` | `String` | - | CPU limit (e.g. `1.0`, `0.5`) |
+| `pull` | `String` | `if-not-present` | Pull policy: `always`, `if-not-present`, `never` |
+| `containerd_addr` | `String` | `/run/containerd/containerd.sock` | Containerd socket address |
+| `tls` | `TlsConfig` | - | TLS configuration for containerd connection |
+| `registry_auth` | `HashMap` | `{}` | Registry authentication per registry hostname |
+| `timeout` | `String` | - | Execution timeout (e.g. `30s`, `5m`) |
+
+## Output parsing
+
+The step captures stdout and stderr. Lines matching `##wfe[output key=value]` are extracted as workflow outputs. Raw stdout, stderr, and exit code are also available under `{step_name}.stdout`, `{step_name}.stderr`, and `{step_name}.exit_code`.
+
+## Security defaults
+
+- Runs as nobody (`65534:65534`) by default
+- Network disabled (`none`) by default
+- Containers are always `--rm` (removed after execution)

wfe-containerd/src/config.rs

@@ -0,0 +1,226 @@
+use std::collections::HashMap;
+
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct ContainerdConfig {
+    pub image: String,
+    pub command: Option<Vec<String>>,
+    pub run: Option<String>,
+    #[serde(default)]
+    pub env: HashMap<String, String>,
+    #[serde(default)]
+    pub volumes: Vec<VolumeMountConfig>,
+    pub working_dir: Option<String>,
+    #[serde(default = "default_user")]
+    pub user: String,
+    #[serde(default = "default_network")]
+    pub network: String,
+    pub memory: Option<String>,
+    pub cpu: Option<String>,
+    #[serde(default = "default_pull")]
+    pub pull: String,
+    #[serde(default = "default_containerd_addr")]
+    pub containerd_addr: String,
+    /// CLI binary name: "nerdctl" (default) or "docker".
+    #[serde(default = "default_cli")]
+    pub cli: String,
+    #[serde(default)]
+    pub tls: TlsConfig,
+    #[serde(default)]
+    pub registry_auth: HashMap<String, RegistryAuth>,
+    pub timeout_ms: Option<u64>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct VolumeMountConfig {
+    pub source: String,
+    pub target: String,
+    #[serde(default)]
+    pub readonly: bool,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize, Default)]
+pub struct TlsConfig {
+    pub ca: Option<String>,
+    pub cert: Option<String>,
+    pub key: Option<String>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct RegistryAuth {
+    pub username: String,
+    pub password: String,
+}
+
+fn default_user() -> String {
+    "65534:65534".to_string()
+}
+
+fn default_network() -> String {
+    "none".to_string()
+}
+
+fn default_pull() -> String {
+    "if-not-present".to_string()
+}
+
+fn default_containerd_addr() -> String {
+    "/run/containerd/containerd.sock".to_string()
+}
+
+fn default_cli() -> String {
+    "nerdctl".to_string()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use pretty_assertions::assert_eq;
+
+    #[test]
+    fn serde_round_trip_full_config() {
+        let config = ContainerdConfig {
+            image: "alpine:3.18".to_string(),
+            command: Some(vec!["echo".to_string(), "hello".to_string()]),
+            run: None,
+            env: HashMap::from([("FOO".to_string(), "bar".to_string())]),
+            volumes: vec![VolumeMountConfig {
+                source: "/host/path".to_string(),
+                target: "/container/path".to_string(),
+                readonly: true,
+            }],
+            working_dir: Some("/app".to_string()),
+            user: "1000:1000".to_string(),
+            network: "host".to_string(),
+            memory: Some("512m".to_string()),
+            cpu: Some("1.0".to_string()),
+            pull: "always".to_string(),
+            containerd_addr: "/custom/containerd.sock".to_string(),
+            cli: "nerdctl".to_string(),
+            tls: TlsConfig {
+                ca: Some("/ca.pem".to_string()),
+                cert: Some("/cert.pem".to_string()),
+                key: Some("/key.pem".to_string()),
+            },
+            registry_auth: HashMap::from([(
+                "registry.example.com".to_string(),
+                RegistryAuth {
+                    username: "user".to_string(),
+                    password: "pass".to_string(),
+                },
+            )]),
+            timeout_ms: Some(30000),
+        };
+
+        let json = serde_json::to_string(&config).unwrap();
+        let deserialized: ContainerdConfig = serde_json::from_str(&json).unwrap();
+
+        assert_eq!(deserialized.image, config.image);
+        assert_eq!(deserialized.command, config.command);
+        assert_eq!(deserialized.run, config.run);
+        assert_eq!(deserialized.env, config.env);
+        assert_eq!(deserialized.volumes.len(), 1);
+        assert_eq!(deserialized.volumes[0].source, "/host/path");
+        assert_eq!(deserialized.volumes[0].readonly, true);
+        assert_eq!(deserialized.working_dir, Some("/app".to_string()));
+        assert_eq!(deserialized.user, "1000:1000");
+        assert_eq!(deserialized.network, "host");
+        assert_eq!(deserialized.memory, Some("512m".to_string()));
+        assert_eq!(deserialized.cpu, Some("1.0".to_string()));
+        assert_eq!(deserialized.pull, "always");
+        assert_eq!(deserialized.containerd_addr, "/custom/containerd.sock");
+        assert_eq!(deserialized.tls.ca, Some("/ca.pem".to_string()));
+        assert_eq!(deserialized.tls.cert, Some("/cert.pem".to_string()));
+        assert_eq!(deserialized.tls.key, Some("/key.pem".to_string()));
+        assert!(deserialized.registry_auth.contains_key("registry.example.com"));
+        assert_eq!(deserialized.timeout_ms, Some(30000));
+    }
+
+    #[test]
+    fn serde_round_trip_minimal_config() {
+        let json = r#"{"image": "alpine:latest"}"#;
+        let config: ContainerdConfig = serde_json::from_str(json).unwrap();
+
+        assert_eq!(config.image, "alpine:latest");
+        assert_eq!(config.command, None);
+        assert_eq!(config.run, None);
+        assert!(config.env.is_empty());
+        assert!(config.volumes.is_empty());
+        assert_eq!(config.working_dir, None);
+        assert_eq!(config.user, "65534:65534");
+        assert_eq!(config.network, "none");
+        assert_eq!(config.memory, None);
+        assert_eq!(config.cpu, None);
+        assert_eq!(config.pull, "if-not-present");
+        assert_eq!(config.containerd_addr, "/run/containerd/containerd.sock");
+        assert_eq!(config.timeout_ms, None);
+
+        // Round-trip
+        let serialized = serde_json::to_string(&config).unwrap();
+        let deserialized: ContainerdConfig = serde_json::from_str(&serialized).unwrap();
+        assert_eq!(deserialized.image, "alpine:latest");
+        assert_eq!(deserialized.user, "65534:65534");
+    }
+
+    #[test]
+    fn default_values() {
+        let json = r#"{"image": "busybox"}"#;
+        let config: ContainerdConfig = serde_json::from_str(json).unwrap();
+
+        assert_eq!(config.user, "65534:65534");
+        assert_eq!(config.network, "none");
+        assert_eq!(config.pull, "if-not-present");
+        assert_eq!(config.containerd_addr, "/run/containerd/containerd.sock");
+    }
+
+    #[test]
+    fn volume_mount_serde() {
+        let vol = VolumeMountConfig {
+            source: "/data".to_string(),
+            target: "/mnt/data".to_string(),
+            readonly: false,
+        };
+        let json = serde_json::to_string(&vol).unwrap();
+        let deserialized: VolumeMountConfig = serde_json::from_str(&json).unwrap();
+        assert_eq!(deserialized.source, "/data");
+        assert_eq!(deserialized.target, "/mnt/data");
+        assert_eq!(deserialized.readonly, false);
+
+        // With readonly=true
+        let vol_ro = VolumeMountConfig {
+            source: "/src".to_string(),
+            target: "/dest".to_string(),
+            readonly: true,
+        };
+        let json_ro = serde_json::to_string(&vol_ro).unwrap();
+        let deserialized_ro: VolumeMountConfig = serde_json::from_str(&json_ro).unwrap();
+        assert_eq!(deserialized_ro.readonly, true);
+    }
+
+    #[test]
+    fn tls_config_defaults() {
+        let tls = TlsConfig::default();
+        assert_eq!(tls.ca, None);
+        assert_eq!(tls.cert, None);
+        assert_eq!(tls.key, None);
+
+        let json = r#"{}"#;
+        let deserialized: TlsConfig = serde_json::from_str(json).unwrap();
+        assert_eq!(deserialized.ca, None);
+        assert_eq!(deserialized.cert, None);
+        assert_eq!(deserialized.key, None);
+    }
+
+    #[test]
+    fn registry_auth_serde() {
+        let auth = RegistryAuth {
+            username: "admin".to_string(),
+            password: "secret123".to_string(),
+        };
+        let json = serde_json::to_string(&auth).unwrap();
+        let deserialized: RegistryAuth = serde_json::from_str(&json).unwrap();
+        assert_eq!(deserialized.username, "admin");
+        assert_eq!(deserialized.password, "secret123");
+    }
+}

wfe-containerd/src/lib.rs

@@ -0,0 +1,5 @@
+pub mod config;
+pub mod step;
+
+pub use config::{ContainerdConfig, RegistryAuth, TlsConfig, VolumeMountConfig};
+pub use step::ContainerdStep;

wfe-containerd/tests/integration.rs

@@ -0,0 +1,166 @@
+//! Integration tests for the containerd gRPC-based runner.
+//!
+//! These tests require a live containerd daemon. They are skipped when the
+//! socket is not available. Set `WFE_CONTAINERD_ADDR` to point to a custom
+//! socket, or use the default `~/.lima/wfe-test/sock/containerd.sock`.
+//!
+//! Before running, ensure the test image is pre-pulled:
+//!   ctr -n default image pull docker.io/library/alpine:3.18
+
+use std::collections::HashMap;
+use std::path::Path;
+
+use wfe_containerd::config::{ContainerdConfig, TlsConfig};
+use wfe_containerd::ContainerdStep;
+use wfe_core::models::{ExecutionPointer, WorkflowInstance, WorkflowStep};
+use wfe_core::traits::step::{StepBody, StepExecutionContext};
+
+/// Returns the containerd socket address if available, or None.
+fn containerd_addr() -> Option<String> {
+    let addr = std::env::var("WFE_CONTAINERD_ADDR").unwrap_or_else(|_| {
+        format!(
+            "unix://{}/.lima/wfe-test/sock/containerd.sock",
+            std::env::var("HOME").unwrap_or_else(|_| "/root".to_string())
+        )
+    });
+
+    let socket_path = addr.strip_prefix("unix://").unwrap_or(addr.as_str());
+
+    if Path::new(socket_path).exists() {
+        Some(addr)
+    } else {
+        None
+    }
+}
+
+fn minimal_config(addr: &str) -> ContainerdConfig {
+    ContainerdConfig {
+        image: "docker.io/library/alpine:3.18".to_string(),
+        command: None,
+        run: Some("echo hello".to_string()),
+        env: HashMap::new(),
+        volumes: vec![],
+        working_dir: None,
+        user: "0:0".to_string(),
+        network: "none".to_string(),
+        memory: None,
+        cpu: None,
+        pull: "never".to_string(),
+        containerd_addr: addr.to_string(),
+        cli: "nerdctl".to_string(),
+        tls: TlsConfig::default(),
+        registry_auth: HashMap::new(),
+        timeout_ms: None,
+    }
+}
+
+fn make_context<'a>(
+    step: &'a WorkflowStep,
+    workflow: &'a WorkflowInstance,
+    pointer: &'a ExecutionPointer,
+) -> StepExecutionContext<'a> {
+    StepExecutionContext {
+        item: None,
+        execution_pointer: pointer,
+        persistence_data: None,
+        step,
+        workflow,
+        cancellation_token: tokio_util::sync::CancellationToken::new(),
+        host_context: None,
+    }
+}
+
+// ── Connection error for missing socket ──────────────────────────────
+
+#[tokio::test]
+async fn connect_error_for_missing_socket() {
+    let config = minimal_config("/tmp/nonexistent-wfe-containerd-integ.sock");
+    let mut step = ContainerdStep::new(config);
+
+    let wf_step = WorkflowStep::new(0, "containerd");
+    let workflow = WorkflowInstance::new("test-wf", 1, serde_json::json!({}));
+    let pointer = ExecutionPointer::new(0);
+    let ctx = make_context(&wf_step, &workflow, &pointer);
+
+    let result = step.run(&ctx).await;
+    let err = result.expect_err("should fail with socket not found");
+    let msg = format!("{err}");
+    assert!(
+        msg.contains("socket not found"),
+        "expected 'socket not found' error, got: {msg}"
+    );
+}
+
+// ── Image check failure for non-existent image ──────────────────────
+
+#[tokio::test]
+async fn image_not_found_error() {
+    let Some(addr) = containerd_addr() else {
+        eprintln!("SKIP: containerd socket not available");
+        return;
+    };
+
+    let mut config = minimal_config(&addr);
+    config.image = "nonexistent-image-wfe-test:latest".to_string();
+    config.pull = "if-not-present".to_string();
+    let mut step = ContainerdStep::new(config);
+
+    let wf_step = WorkflowStep::new(0, "containerd");
+    let workflow = WorkflowInstance::new("test-wf", 1, serde_json::json!({}));
+    let pointer = ExecutionPointer::new(0);
+    let ctx = make_context(&wf_step, &workflow, &pointer);
+
+    let result = step.run(&ctx).await;
+    let err = result.expect_err("should fail with image not found");
+    let msg = format!("{err}");
+    assert!(
+        msg.contains("not found"),
+        "expected 'not found' error, got: {msg}"
+    );
+}
+
+// ── pull=never skips image check ─────────────────────────────────────
+
+#[tokio::test]
+async fn skip_image_check_when_pull_never() {
+    let Some(addr) = containerd_addr() else {
+        eprintln!("SKIP: containerd socket not available");
+        return;
+    };
+
+    // Using a non-existent image but pull=never should skip the check.
+    // The step will fail later at container creation, but the image check is skipped.
+    let mut config = minimal_config(&addr);
+    config.image = "nonexistent-image-wfe-test-never:latest".to_string();
+    config.pull = "never".to_string();
+    let mut step = ContainerdStep::new(config);
+
+    let wf_step = WorkflowStep::new(0, "containerd");
+    let workflow = WorkflowInstance::new("test-wf", 1, serde_json::json!({}));
+    let pointer = ExecutionPointer::new(0);
+    let ctx = make_context(&wf_step, &workflow, &pointer);
+
+    let result = step.run(&ctx).await;
+    // It should fail, but NOT with "not found in containerd" (image check).
+    // It should fail later (container creation, snapshot, etc.).
+    let err = result.expect_err("should fail at container or task creation");
+    let msg = format!("{err}");
+    assert!(
+        !msg.contains("Pre-pull it with"),
+        "image check should have been skipped for pull=never, got: {msg}"
+    );
+}
+
+// ── Step name defaults to "unknown" when None ────────────────────────
+
+#[tokio::test]
+async fn unnamed_step_uses_unknown_in_output_keys() {
+    // This test only verifies build_output_data behavior — no socket needed.
+    let parsed = HashMap::from([("result".to_string(), "ok".to_string())]);
+    let data = ContainerdStep::build_output_data("unknown", "out", "err", 0, &parsed);
+    let obj = data.as_object().unwrap();
+    assert!(obj.contains_key("unknown.stdout"));
+    assert!(obj.contains_key("unknown.stderr"));
+    assert!(obj.contains_key("unknown.exit_code"));
+    assert_eq!(obj.get("result").unwrap(), "ok");
+}

wfe-core/Cargo.toml

@@ -3,6 +3,8 @@ name = "wfe-core"
 version.workspace = true
 edition.workspace = true
 license.workspace = true
+repository.workspace = true
+homepage.workspace = true
 description = "Core traits, models, builder, and executor for the WFE workflow engine"
 
 [features]

wfe-core/src/executor/condition.rs

@@ -0,0 +1,761 @@
+use crate::models::condition::{ComparisonOp, FieldComparison, StepCondition};
+use crate::WfeError;
+
+/// Evaluate a step condition against workflow data.
+///
+/// Returns `Ok(true)` if the step should run, `Ok(false)` if it should be skipped.
+/// Missing field paths return `Ok(false)` (cascade skip behavior).
+pub fn evaluate(
+    condition: &StepCondition,
+    workflow_data: &serde_json::Value,
+) -> Result<bool, WfeError> {
+    match evaluate_inner(condition, workflow_data) {
+        Ok(result) => Ok(result),
+        Err(EvalError::FieldNotPresent) => Ok(false), // cascade skip
+        Err(EvalError::Wfe(e)) => Err(e),
+    }
+}
+
+/// Internal error type that distinguishes missing-field from real errors.
+#[derive(Debug)]
+enum EvalError {
+    FieldNotPresent,
+    Wfe(WfeError),
+}
+
+impl From<WfeError> for EvalError {
+    fn from(e: WfeError) -> Self {
+        EvalError::Wfe(e)
+    }
+}
+
+fn evaluate_inner(
+    condition: &StepCondition,
+    data: &serde_json::Value,
+) -> Result<bool, EvalError> {
+    match condition {
+        StepCondition::All(conditions) => {
+            for c in conditions {
+                if !evaluate_inner(c, data)? {
+                    return Ok(false);
+                }
+            }
+            Ok(true)
+        }
+        StepCondition::Any(conditions) => {
+            for c in conditions {
+                if evaluate_inner(c, data)? {
+                    return Ok(true);
+                }
+            }
+            Ok(false)
+        }
+        StepCondition::None(conditions) => {
+            for c in conditions {
+                if evaluate_inner(c, data)? {
+                    return Ok(false);
+                }
+            }
+            Ok(true)
+        }
+        StepCondition::OneOf(conditions) => {
+            let mut count = 0;
+            for c in conditions {
+                if evaluate_inner(c, data)? {
+                    count += 1;
+                    if count > 1 {
+                        return Ok(false);
+                    }
+                }
+            }
+            Ok(count == 1)
+        }
+        StepCondition::Not(inner) => {
+            let result = evaluate_inner(inner, data)?;
+            Ok(!result)
+        }
+        StepCondition::Comparison(comp) => evaluate_comparison(comp, data),
+    }
+}
+
+/// Resolve a dot-separated field path against JSON data.
+///
+/// Path starts with `.` which is stripped, then split by `.`.
+/// Segments that parse as `usize` are treated as array indices.
+fn resolve_field_path<'a>(
+    path: &str,
+    data: &'a serde_json::Value,
+) -> Result<&'a serde_json::Value, EvalError> {
+    let path = path.strip_prefix('.').unwrap_or(path);
+    if path.is_empty() {
+        return Ok(data);
+    }
+
+    let segments: Vec<&str> = path.split('.').collect();
+
+    // Try resolving the full path first (for nested data like {"outputs": {"x": 1}}).
+    // If the first segment is "outputs"/"inputs" and doesn't exist as a key,
+    // strip it and resolve flat (for workflow data where outputs merge flat).
+    if segments.len() >= 2
+        && (segments[0] == "outputs" || segments[0] == "inputs")
+        && data.get(segments[0]).is_none()
+    {
+        return walk_segments(&segments[1..], data);
+    }
+
+    walk_segments(&segments, data)
+}
+
+fn walk_segments<'a>(
+    segments: &[&str],
+    data: &'a serde_json::Value,
+) -> Result<&'a serde_json::Value, EvalError> {
+    let mut current = data;
+
+    for segment in segments {
+        if let Ok(idx) = segment.parse::<usize>() {
+            match current.as_array() {
+                Some(arr) => {
+                    current = arr.get(idx).ok_or(EvalError::FieldNotPresent)?;
+                }
+                None => {
+                    return Err(EvalError::FieldNotPresent);
+                }
+            }
+        } else {
+            match current.as_object() {
+                Some(obj) => {
+                    current = obj.get(*segment).ok_or(EvalError::FieldNotPresent)?;
+                }
+                None => {
+                    return Err(EvalError::FieldNotPresent);
+                }
+            }
+        }
+    }
+
+    Ok(current)
+}
+
+fn evaluate_comparison(
+    comp: &FieldComparison,
+    data: &serde_json::Value,
+) -> Result<bool, EvalError> {
+    let resolved = resolve_field_path(&comp.field, data)?;
+
+    match &comp.operator {
+        ComparisonOp::IsNull => Ok(resolved.is_null()),
+        ComparisonOp::IsNotNull => Ok(!resolved.is_null()),
+        ComparisonOp::Equals => {
+            let expected = comp.value.as_ref().ok_or_else(|| {
+                EvalError::Wfe(WfeError::StepExecution(
+                    "Equals operator requires a value".into(),
+                ))
+            })?;
+            Ok(resolved == expected)
+        }
+        ComparisonOp::NotEquals => {
+            let expected = comp.value.as_ref().ok_or_else(|| {
+                EvalError::Wfe(WfeError::StepExecution(
+                    "NotEquals operator requires a value".into(),
+                ))
+            })?;
+            Ok(resolved != expected)
+        }
+        ComparisonOp::Gt => compare_numeric(resolved, comp, |a, b| a > b),
+        ComparisonOp::Gte => compare_numeric(resolved, comp, |a, b| a >= b),
+        ComparisonOp::Lt => compare_numeric(resolved, comp, |a, b| a < b),
+        ComparisonOp::Lte => compare_numeric(resolved, comp, |a, b| a <= b),
+        ComparisonOp::Contains => evaluate_contains(resolved, comp),
+    }
+}
+
+fn compare_numeric(
+    resolved: &serde_json::Value,
+    comp: &FieldComparison,
+    cmp_fn: fn(f64, f64) -> bool,
+) -> Result<bool, EvalError> {
+    let expected = comp.value.as_ref().ok_or_else(|| {
+        EvalError::Wfe(WfeError::StepExecution(format!(
+            "{:?} operator requires a value",
+            comp.operator
+        )))
+    })?;
+
+    let a = resolved.as_f64().ok_or_else(|| {
+        EvalError::Wfe(WfeError::StepExecution(format!(
+            "cannot compare non-numeric field value: {}",
+            resolved
+        )))
+    })?;
+
+    let b = expected.as_f64().ok_or_else(|| {
+        EvalError::Wfe(WfeError::StepExecution(format!(
+            "cannot compare with non-numeric value: {}",
+            expected
+        )))
+    })?;
+
+    Ok(cmp_fn(a, b))
+}
+
+fn evaluate_contains(
+    resolved: &serde_json::Value,
+    comp: &FieldComparison,
+) -> Result<bool, EvalError> {
+    let expected = comp.value.as_ref().ok_or_else(|| {
+        EvalError::Wfe(WfeError::StepExecution(
+            "Contains operator requires a value".into(),
+        ))
+    })?;
+
+    // String contains substring.
+    if let Some(s) = resolved.as_str()
+        && let Some(substr) = expected.as_str()
+    {
+        return Ok(s.contains(substr));
+    }
+
+    // Array contains element.
+    if let Some(arr) = resolved.as_array() {
+        return Ok(arr.contains(expected));
+    }
+
+    Err(EvalError::Wfe(WfeError::StepExecution(format!(
+        "Contains requires a string or array field, got {}",
+        value_type_name(resolved)
+    ))))
+}
+
+fn value_type_name(value: &serde_json::Value) -> &'static str {
+    match value {
+        serde_json::Value::Null => "null",
+        serde_json::Value::Bool(_) => "bool",
+        serde_json::Value::Number(_) => "number",
+        serde_json::Value::String(_) => "string",
+        serde_json::Value::Array(_) => "array",
+        serde_json::Value::Object(_) => "object",
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::models::condition::{ComparisonOp, FieldComparison, StepCondition};
+    use serde_json::json;
+
+    // -- resolve_field_path tests --
+
+    #[test]
+    fn resolve_simple_field() {
+        let data = json!({"name": "alice"});
+        let result = resolve_field_path(".name", &data).unwrap();
+        assert_eq!(result, &json!("alice"));
+    }
+
+    #[test]
+    fn resolve_nested_field() {
+        let data = json!({"outputs": {"status": "success"}});
+        let result = resolve_field_path(".outputs.status", &data).unwrap();
+        assert_eq!(result, &json!("success"));
+    }
+
+    #[test]
+    fn resolve_missing_field() {
+        let data = json!({"name": "alice"});
+        let result = resolve_field_path(".missing", &data);
+        assert!(matches!(result, Err(EvalError::FieldNotPresent)));
+    }
+
+    #[test]
+    fn resolve_array_index() {
+        let data = json!({"items": [10, 20, 30]});
+        let result = resolve_field_path(".items.1", &data).unwrap();
+        assert_eq!(result, &json!(20));
+    }
+
+    #[test]
+    fn resolve_array_index_out_of_bounds() {
+        let data = json!({"items": [10, 20]});
+        let result = resolve_field_path(".items.5", &data);
+        assert!(matches!(result, Err(EvalError::FieldNotPresent)));
+    }
+
+    #[test]
+    fn resolve_deeply_nested() {
+        let data = json!({"a": {"b": {"c": {"d": 42}}}});
+        let result = resolve_field_path(".a.b.c.d", &data).unwrap();
+        assert_eq!(result, &json!(42));
+    }
+
+    #[test]
+    fn resolve_empty_path_returns_root() {
+        let data = json!({"x": 1});
+        let result = resolve_field_path(".", &data).unwrap();
+        assert_eq!(result, &data);
+    }
+
+    #[test]
+    fn resolve_field_on_non_object() {
+        let data = json!({"x": 42});
+        let result = resolve_field_path(".x.y", &data);
+        assert!(matches!(result, Err(EvalError::FieldNotPresent)));
+    }
+
+    // -- Comparison operator tests --
+
+    fn comp(field: &str, op: ComparisonOp, value: Option<serde_json::Value>) -> StepCondition {
+        StepCondition::Comparison(FieldComparison {
+            field: field.to_string(),
+            operator: op,
+            value,
+        })
+    }
+
+    #[test]
+    fn equals_match() {
+        let data = json!({"status": "ok"});
+        let cond = comp(".status", ComparisonOp::Equals, Some(json!("ok")));
+        assert!(evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn equals_mismatch() {
+        let data = json!({"status": "fail"});
+        let cond = comp(".status", ComparisonOp::Equals, Some(json!("ok")));
+        assert!(!evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn equals_numeric() {
+        let data = json!({"count": 5});
+        let cond = comp(".count", ComparisonOp::Equals, Some(json!(5)));
+        assert!(evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn not_equals_match() {
+        let data = json!({"status": "fail"});
+        let cond = comp(".status", ComparisonOp::NotEquals, Some(json!("ok")));
+        assert!(evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn not_equals_mismatch() {
+        let data = json!({"status": "ok"});
+        let cond = comp(".status", ComparisonOp::NotEquals, Some(json!("ok")));
+        assert!(!evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn gt_match() {
+        let data = json!({"count": 10});
+        let cond = comp(".count", ComparisonOp::Gt, Some(json!(5)));
+        assert!(evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn gt_mismatch() {
+        let data = json!({"count": 3});
+        let cond = comp(".count", ComparisonOp::Gt, Some(json!(5)));
+        assert!(!evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn gt_equal_is_false() {
+        let data = json!({"count": 5});
+        let cond = comp(".count", ComparisonOp::Gt, Some(json!(5)));
+        assert!(!evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn gte_match() {
+        let data = json!({"count": 5});
+        let cond = comp(".count", ComparisonOp::Gte, Some(json!(5)));
+        assert!(evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn gte_mismatch() {
+        let data = json!({"count": 4});
+        let cond = comp(".count", ComparisonOp::Gte, Some(json!(5)));
+        assert!(!evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn lt_match() {
+        let data = json!({"count": 3});
+        let cond = comp(".count", ComparisonOp::Lt, Some(json!(5)));
+        assert!(evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn lt_mismatch() {
+        let data = json!({"count": 7});
+        let cond = comp(".count", ComparisonOp::Lt, Some(json!(5)));
+        assert!(!evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn lte_match() {
+        let data = json!({"count": 5});
+        let cond = comp(".count", ComparisonOp::Lte, Some(json!(5)));
+        assert!(evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn lte_mismatch() {
+        let data = json!({"count": 6});
+        let cond = comp(".count", ComparisonOp::Lte, Some(json!(5)));
+        assert!(!evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn contains_string_match() {
+        let data = json!({"msg": "hello world"});
+        let cond = comp(".msg", ComparisonOp::Contains, Some(json!("world")));
+        assert!(evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn contains_string_mismatch() {
+        let data = json!({"msg": "hello world"});
+        let cond = comp(".msg", ComparisonOp::Contains, Some(json!("xyz")));
+        assert!(!evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn contains_array_match() {
+        let data = json!({"tags": ["a", "b", "c"]});
+        let cond = comp(".tags", ComparisonOp::Contains, Some(json!("b")));
+        assert!(evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn contains_array_mismatch() {
+        let data = json!({"tags": ["a", "b", "c"]});
+        let cond = comp(".tags", ComparisonOp::Contains, Some(json!("z")));
+        assert!(!evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn is_null_true() {
+        let data = json!({"val": null});
+        let cond = comp(".val", ComparisonOp::IsNull, None);
+        assert!(evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn is_null_false() {
+        let data = json!({"val": 42});
+        let cond = comp(".val", ComparisonOp::IsNull, None);
+        assert!(!evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn is_not_null_true() {
+        let data = json!({"val": 42});
+        let cond = comp(".val", ComparisonOp::IsNotNull, None);
+        assert!(evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn is_not_null_false() {
+        let data = json!({"val": null});
+        let cond = comp(".val", ComparisonOp::IsNotNull, None);
+        assert!(!evaluate(&cond, &data).unwrap());
+    }
+
+    // -- Combinator tests --
+
+    #[test]
+    fn all_both_true() {
+        let data = json!({"a": 1, "b": 2});
+        let cond = StepCondition::All(vec![
+            comp(".a", ComparisonOp::Equals, Some(json!(1))),
+            comp(".b", ComparisonOp::Equals, Some(json!(2))),
+        ]);
+        assert!(evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn all_one_false() {
+        let data = json!({"a": 1, "b": 99});
+        let cond = StepCondition::All(vec![
+            comp(".a", ComparisonOp::Equals, Some(json!(1))),
+            comp(".b", ComparisonOp::Equals, Some(json!(2))),
+        ]);
+        assert!(!evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn all_empty_is_true() {
+        let data = json!({});
+        let cond = StepCondition::All(vec![]);
+        assert!(evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn any_one_true() {
+        let data = json!({"a": 1, "b": 99});
+        let cond = StepCondition::Any(vec![
+            comp(".a", ComparisonOp::Equals, Some(json!(1))),
+            comp(".b", ComparisonOp::Equals, Some(json!(2))),
+        ]);
+        assert!(evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn any_none_true() {
+        let data = json!({"a": 99, "b": 99});
+        let cond = StepCondition::Any(vec![
+            comp(".a", ComparisonOp::Equals, Some(json!(1))),
+            comp(".b", ComparisonOp::Equals, Some(json!(2))),
+        ]);
+        assert!(!evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn any_empty_is_false() {
+        let data = json!({});
+        let cond = StepCondition::Any(vec![]);
+        assert!(!evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn none_all_false() {
+        let data = json!({"a": 99, "b": 99});
+        let cond = StepCondition::None(vec![
+            comp(".a", ComparisonOp::Equals, Some(json!(1))),
+            comp(".b", ComparisonOp::Equals, Some(json!(2))),
+        ]);
+        assert!(evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn none_one_true() {
+        let data = json!({"a": 1, "b": 99});
+        let cond = StepCondition::None(vec![
+            comp(".a", ComparisonOp::Equals, Some(json!(1))),
+            comp(".b", ComparisonOp::Equals, Some(json!(2))),
+        ]);
+        assert!(!evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn none_empty_is_true() {
+        let data = json!({});
+        let cond = StepCondition::None(vec![]);
+        assert!(evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn one_of_exactly_one_true() {
+        let data = json!({"a": 1, "b": 99});
+        let cond = StepCondition::OneOf(vec![
+            comp(".a", ComparisonOp::Equals, Some(json!(1))),
+            comp(".b", ComparisonOp::Equals, Some(json!(2))),
+        ]);
+        assert!(evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn one_of_both_true() {
+        let data = json!({"a": 1, "b": 2});
+        let cond = StepCondition::OneOf(vec![
+            comp(".a", ComparisonOp::Equals, Some(json!(1))),
+            comp(".b", ComparisonOp::Equals, Some(json!(2))),
+        ]);
+        assert!(!evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn one_of_none_true() {
+        let data = json!({"a": 99, "b": 99});
+        let cond = StepCondition::OneOf(vec![
+            comp(".a", ComparisonOp::Equals, Some(json!(1))),
+            comp(".b", ComparisonOp::Equals, Some(json!(2))),
+        ]);
+        assert!(!evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn not_true_becomes_false() {
+        let data = json!({"a": 1});
+        let cond = StepCondition::Not(Box::new(comp(
+            ".a",
+            ComparisonOp::Equals,
+            Some(json!(1)),
+        )));
+        assert!(!evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn not_false_becomes_true() {
+        let data = json!({"a": 99});
+        let cond = StepCondition::Not(Box::new(comp(
+            ".a",
+            ComparisonOp::Equals,
+            Some(json!(1)),
+        )));
+        assert!(evaluate(&cond, &data).unwrap());
+    }
+
+    // -- Cascade skip tests --
+
+    #[test]
+    fn missing_field_returns_false_cascade_skip() {
+        let data = json!({"other": 1});
+        let cond = comp(".missing", ComparisonOp::Equals, Some(json!(1)));
+        // Missing field -> cascade skip -> Ok(false)
+        assert!(!evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn missing_nested_field_returns_false() {
+        let data = json!({"a": {"b": 1}});
+        let cond = comp(".a.c", ComparisonOp::Equals, Some(json!(1)));
+        assert!(!evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn missing_field_in_all_returns_false() {
+        let data = json!({"a": 1});
+        let cond = StepCondition::All(vec![
+            comp(".a", ComparisonOp::Equals, Some(json!(1))),
+            comp(".missing", ComparisonOp::Equals, Some(json!(2))),
+        ]);
+        assert!(!evaluate(&cond, &data).unwrap());
+    }
+
+    // -- Nested combinator tests --
+
+    #[test]
+    fn nested_all_any_not() {
+        let data = json!({"a": 1, "b": 2, "c": 3});
+        // All(Any(a==1, a==99), Not(c==99))
+        let cond = StepCondition::All(vec![
+            StepCondition::Any(vec![
+                comp(".a", ComparisonOp::Equals, Some(json!(1))),
+                comp(".a", ComparisonOp::Equals, Some(json!(99))),
+            ]),
+            StepCondition::Not(Box::new(comp(
+                ".c",
+                ComparisonOp::Equals,
+                Some(json!(99)),
+            ))),
+        ]);
+        assert!(evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn nested_any_of_alls() {
+        let data = json!({"x": 10, "y": 20});
+        // Any(All(x>5, y>25), All(x>5, y>15))
+        let cond = StepCondition::Any(vec![
+            StepCondition::All(vec![
+                comp(".x", ComparisonOp::Gt, Some(json!(5))),
+                comp(".y", ComparisonOp::Gt, Some(json!(25))),
+            ]),
+            StepCondition::All(vec![
+                comp(".x", ComparisonOp::Gt, Some(json!(5))),
+                comp(".y", ComparisonOp::Gt, Some(json!(15))),
+            ]),
+        ]);
+        assert!(evaluate(&cond, &data).unwrap());
+    }
+
+    // -- Edge cases / error cases --
+
+    #[test]
+    fn gt_on_string_errors() {
+        let data = json!({"name": "alice"});
+        let cond = comp(".name", ComparisonOp::Gt, Some(json!(5)));
+        let result = evaluate(&cond, &data);
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn gt_with_string_value_errors() {
+        let data = json!({"count": 5});
+        let cond = comp(".count", ComparisonOp::Gt, Some(json!("not a number")));
+        let result = evaluate(&cond, &data);
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn contains_on_number_errors() {
+        let data = json!({"count": 42});
+        let cond = comp(".count", ComparisonOp::Contains, Some(json!("4")));
+        let result = evaluate(&cond, &data);
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn equals_without_value_errors() {
+        let data = json!({"a": 1});
+        let cond = comp(".a", ComparisonOp::Equals, None);
+        let result = evaluate(&cond, &data);
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn not_equals_without_value_errors() {
+        let data = json!({"a": 1});
+        let cond = comp(".a", ComparisonOp::NotEquals, None);
+        let result = evaluate(&cond, &data);
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn gt_without_value_errors() {
+        let data = json!({"a": 1});
+        let cond = comp(".a", ComparisonOp::Gt, None);
+        let result = evaluate(&cond, &data);
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn contains_without_value_errors() {
+        let data = json!({"msg": "hello"});
+        let cond = comp(".msg", ComparisonOp::Contains, None);
+        let result = evaluate(&cond, &data);
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn equals_bool_values() {
+        let data = json!({"active": true});
+        let cond = comp(".active", ComparisonOp::Equals, Some(json!(true)));
+        assert!(evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn equals_null_value() {
+        let data = json!({"val": null});
+        let cond = comp(".val", ComparisonOp::Equals, Some(json!(null)));
+        assert!(evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn float_comparison() {
+        let data = json!({"score": 3.14});
+        assert!(evaluate(&comp(".score", ComparisonOp::Gt, Some(json!(3.0))), &data).unwrap());
+        assert!(evaluate(&comp(".score", ComparisonOp::Lt, Some(json!(4.0))), &data).unwrap());
+        assert!(!evaluate(&comp(".score", ComparisonOp::Equals, Some(json!(3.0))), &data).unwrap());
+    }
+
+    #[test]
+    fn contains_array_numeric_element() {
+        let data = json!({"nums": [1, 2, 3]});
+        let cond = comp(".nums", ComparisonOp::Contains, Some(json!(2)));
+        assert!(evaluate(&cond, &data).unwrap());
+    }
+
+    #[test]
+    fn one_of_empty_is_false() {
+        let data = json!({});
+        let cond = StepCondition::OneOf(vec![]);
+        assert!(!evaluate(&cond, &data).unwrap());
+    }
+}

wfe-core/src/executor/mod.rs

@@ -1,3 +1,4 @@
+pub mod condition;
 mod error_handler;
 mod result_processor;
 mod step_registry;

wfe-core/src/executor/workflow_executor.rs

@@ -3,11 +3,12 @@ use std::sync::Arc;
 use chrono::Utc;
 use tracing::{debug, error, info, warn};
 
+use super::condition;
 use super::error_handler;
 use super::result_processor;
 use super::step_registry::StepRegistry;
 use crate::models::{
-    ExecutionError, PointerStatus, QueueType, WorkflowDefinition, WorkflowStatus,
+    Event, ExecutionError, PointerStatus, QueueType, WorkflowDefinition, WorkflowStatus,
 };
 use crate::traits::{
     DistributedLockProvider, LifecyclePublisher, PersistenceProvider, QueueProvider, SearchIndex,
@@ -61,7 +62,7 @@ impl WorkflowExecutor {
     /// 8. Release lock
     #[tracing::instrument(
         name = "workflow.execute",
-        skip(self, definition, step_registry),
+        skip(self, definition, step_registry, host_context),
         fields(
             workflow.id = %workflow_id,
             workflow.definition_id,
@@ -73,6 +74,7 @@ impl WorkflowExecutor {
         workflow_id: &str,
         definition: &WorkflowDefinition,
         step_registry: &StepRegistry,
+        host_context: Option<&dyn crate::traits::HostContext>,
     ) -> Result<()> {
         // 1. Acquire distributed lock.
         let acquired = self.lock_provider.acquire_lock(workflow_id).await?;
@@ -82,7 +84,7 @@ impl WorkflowExecutor {
         }
 
         let result = self
-            .execute_inner(workflow_id, definition, step_registry)
+            .execute_inner(workflow_id, definition, step_registry, host_context)
             .await;
 
         // 7. Release lock (always).
@@ -98,6 +100,7 @@ impl WorkflowExecutor {
         workflow_id: &str,
         definition: &WorkflowDefinition,
         step_registry: &StepRegistry,
+        host_context: Option<&dyn crate::traits::HostContext>,
     ) -> Result<()> {
         // 2. Load workflow instance.
         let mut workflow = self
@@ -142,6 +145,41 @@ impl WorkflowExecutor {
                 .find(|s| s.id == step_id)
                 .ok_or(WfeError::StepNotFound(step_id))?;
 
+            // Check step condition before executing.
+            if let Some(ref when) = step.when {
+                match condition::evaluate(when, &workflow.data) {
+                    Ok(true) => { /* condition met, proceed */ }
+                    Ok(false) => {
+                        info!(
+                            workflow_id,
+                            step_id,
+                            step_name = step.name.as_deref().unwrap_or("(unnamed)"),
+                            "Step skipped (condition not met)"
+                        );
+                        workflow.execution_pointers[idx].status = PointerStatus::Skipped;
+                        workflow.execution_pointers[idx].active = false;
+                        workflow.execution_pointers[idx].end_time = Some(Utc::now());
+
+                        // Activate next step via outcomes (same as Complete).
+                        let next_step_id = step.outcomes.first().map(|o| o.next_step);
+                        if let Some(next_id) = next_step_id {
+                            let mut next_pointer =
+                                crate::models::ExecutionPointer::new(next_id);
+                            next_pointer.predecessor_id =
+                                Some(workflow.execution_pointers[idx].id.clone());
+                            next_pointer.scope =
+                                workflow.execution_pointers[idx].scope.clone();
+                            workflow.execution_pointers.push(next_pointer);
+                        }
+
+                        continue;
+                    }
+                    Err(e) => {
+                        return Err(e);
+                    }
+                }
+            }
+
             info!(
                 workflow_id,
                 step_id,
@@ -173,6 +211,7 @@ impl WorkflowExecutor {
                 step,
                 workflow: &workflow,
                 cancellation_token,
+                host_context,
             };
 
             // d. Call step.run(context).
@@ -270,6 +309,7 @@ impl WorkflowExecutor {
                 matches!(
                     p.status,
                     PointerStatus::Complete
+                        | PointerStatus::Skipped
                         | PointerStatus::Compensated
                         | PointerStatus::Cancelled
                         | PointerStatus::Failed
@@ -280,6 +320,18 @@ impl WorkflowExecutor {
             info!(workflow_id, "All pointers complete, workflow finished");
             workflow.status = WorkflowStatus::Complete;
             workflow.complete_time = Some(Utc::now());
+
+            // Publish completion event for SubWorkflow parents.
+            let completion_event = Event::new(
+                "wfe.workflow.completed",
+                workflow_id,
+                serde_json::json!({ "status": "Complete", "data": workflow.data }),
+            );
+            let _ = self.persistence.create_event(&completion_event).await;
+            let _ = self
+                .queue_provider
+                .queue_work(&completion_event.id, QueueType::Event)
+                .await;
         }
 
         tracing::Span::current().record("workflow.status", tracing::field::debug(&workflow.status));
@@ -573,7 +625,7 @@ mod tests {
 
         persistence.create_new_workflow(&instance).await.unwrap();
 
-        executor.execute(&instance.id, &def, &registry).await.unwrap();
+        executor.execute(&instance.id, &def, &registry, None).await.unwrap();
 
         let updated = persistence.get_workflow_instance(&instance.id).await.unwrap();
         assert_eq!(updated.status, WorkflowStatus::Complete);
@@ -604,7 +656,7 @@ mod tests {
         persistence.create_new_workflow(&instance).await.unwrap();
 
         // First execution: step 0 completes, step 1 pointer created.
-        executor.execute(&instance.id, &def, &registry).await.unwrap();
+        executor.execute(&instance.id, &def, &registry, None).await.unwrap();
 
         let updated = persistence.get_workflow_instance(&instance.id).await.unwrap();
         assert_eq!(updated.execution_pointers.len(), 2);
@@ -613,7 +665,7 @@ mod tests {
         assert_eq!(updated.execution_pointers[1].step_id, 1);
 
         // Second execution: step 1 completes.
-        executor.execute(&instance.id, &def, &registry).await.unwrap();
+        executor.execute(&instance.id, &def, &registry, None).await.unwrap();
 
         let updated = persistence.get_workflow_instance(&instance.id).await.unwrap();
         assert_eq!(updated.status, WorkflowStatus::Complete);
@@ -644,7 +696,7 @@ mod tests {
 
         // Execute three times for three steps.
         for _ in 0..3 {
-            executor.execute(&instance.id, &def, &registry).await.unwrap();
+            executor.execute(&instance.id, &def, &registry, None).await.unwrap();
         }
 
         let updated = persistence.get_workflow_instance(&instance.id).await.unwrap();
@@ -684,7 +736,7 @@ mod tests {
         instance.execution_pointers.push(ExecutionPointer::new(0));
         persistence.create_new_workflow(&instance).await.unwrap();
 
-        executor.execute(&instance.id, &def, &registry).await.unwrap();
+        executor.execute(&instance.id, &def, &registry, None).await.unwrap();
 
         let updated = persistence.get_workflow_instance(&instance.id).await.unwrap();
         assert_eq!(updated.execution_pointers.len(), 2);
@@ -707,7 +759,7 @@ mod tests {
         instance.execution_pointers.push(ExecutionPointer::new(0));
         persistence.create_new_workflow(&instance).await.unwrap();
 
-        executor.execute(&instance.id, &def, &registry).await.unwrap();
+        executor.execute(&instance.id, &def, &registry, None).await.unwrap();
 
         let updated = persistence.get_workflow_instance(&instance.id).await.unwrap();
         assert_eq!(updated.status, WorkflowStatus::Runnable);
@@ -733,7 +785,7 @@ mod tests {
         instance.execution_pointers.push(ExecutionPointer::new(0));
         persistence.create_new_workflow(&instance).await.unwrap();
 
-        executor.execute(&instance.id, &def, &registry).await.unwrap();
+        executor.execute(&instance.id, &def, &registry, None).await.unwrap();
 
         let updated = persistence.get_workflow_instance(&instance.id).await.unwrap();
         assert_eq!(updated.execution_pointers[0].status, PointerStatus::Sleeping);
@@ -756,7 +808,7 @@ mod tests {
         instance.execution_pointers.push(ExecutionPointer::new(0));
         persistence.create_new_workflow(&instance).await.unwrap();
 
-        executor.execute(&instance.id, &def, &registry).await.unwrap();
+        executor.execute(&instance.id, &def, &registry, None).await.unwrap();
 
         let updated = persistence.get_workflow_instance(&instance.id).await.unwrap();
         assert_eq!(
@@ -796,7 +848,7 @@ mod tests {
         instance.execution_pointers.push(pointer);
         persistence.create_new_workflow(&instance).await.unwrap();
 
-        executor.execute(&instance.id, &def, &registry).await.unwrap();
+        executor.execute(&instance.id, &def, &registry, None).await.unwrap();
 
         let updated = persistence.get_workflow_instance(&instance.id).await.unwrap();
         assert_eq!(updated.execution_pointers[0].status, PointerStatus::Complete);
@@ -822,7 +874,7 @@ mod tests {
         instance.execution_pointers.push(ExecutionPointer::new(0));
         persistence.create_new_workflow(&instance).await.unwrap();
 
-        executor.execute(&instance.id, &def, &registry).await.unwrap();
+        executor.execute(&instance.id, &def, &registry, None).await.unwrap();
 
         let updated = persistence.get_workflow_instance(&instance.id).await.unwrap();
         // 1 original + 3 children.
@@ -858,7 +910,7 @@ mod tests {
         instance.execution_pointers.push(ExecutionPointer::new(0));
         persistence.create_new_workflow(&instance).await.unwrap();
 
-        executor.execute(&instance.id, &def, &registry).await.unwrap();
+        executor.execute(&instance.id, &def, &registry, None).await.unwrap();
 
         let updated = persistence.get_workflow_instance(&instance.id).await.unwrap();
         assert_eq!(updated.execution_pointers[0].retry_count, 1);
@@ -884,7 +936,7 @@ mod tests {
         instance.execution_pointers.push(ExecutionPointer::new(0));
         persistence.create_new_workflow(&instance).await.unwrap();
 
-        executor.execute(&instance.id, &def, &registry).await.unwrap();
+        executor.execute(&instance.id, &def, &registry, None).await.unwrap();
 
         let updated = persistence.get_workflow_instance(&instance.id).await.unwrap();
         assert_eq!(updated.status, WorkflowStatus::Suspended);
@@ -908,7 +960,7 @@ mod tests {
         instance.execution_pointers.push(ExecutionPointer::new(0));
         persistence.create_new_workflow(&instance).await.unwrap();
 
-        executor.execute(&instance.id, &def, &registry).await.unwrap();
+        executor.execute(&instance.id, &def, &registry, None).await.unwrap();
 
         let updated = persistence.get_workflow_instance(&instance.id).await.unwrap();
         assert_eq!(updated.status, WorkflowStatus::Terminated);
@@ -936,7 +988,7 @@ mod tests {
         instance.execution_pointers.push(ExecutionPointer::new(0));
         persistence.create_new_workflow(&instance).await.unwrap();
 
-        executor.execute(&instance.id, &def, &registry).await.unwrap();
+        executor.execute(&instance.id, &def, &registry, None).await.unwrap();
 
         let updated = persistence.get_workflow_instance(&instance.id).await.unwrap();
         assert_eq!(updated.execution_pointers[0].status, PointerStatus::Failed);
@@ -964,7 +1016,7 @@ mod tests {
         instance.execution_pointers.push(ExecutionPointer::new(1));
         persistence.create_new_workflow(&instance).await.unwrap();
 
-        executor.execute(&instance.id, &def, &registry).await.unwrap();
+        executor.execute(&instance.id, &def, &registry, None).await.unwrap();
 
         let updated = persistence.get_workflow_instance(&instance.id).await.unwrap();
         assert_eq!(updated.status, WorkflowStatus::Complete);
@@ -999,7 +1051,7 @@ mod tests {
         persistence.create_new_workflow(&instance).await.unwrap();
 
         // Should not error on a completed workflow.
-        executor.execute(&instance.id, &def, &registry).await.unwrap();
+        executor.execute(&instance.id, &def, &registry, None).await.unwrap();
 
         let updated = persistence.get_workflow_instance(&instance.id).await.unwrap();
         assert_eq!(updated.status, WorkflowStatus::Complete);
@@ -1024,7 +1076,7 @@ mod tests {
         instance.execution_pointers.push(pointer);
         persistence.create_new_workflow(&instance).await.unwrap();
 
-        executor.execute(&instance.id, &def, &registry).await.unwrap();
+        executor.execute(&instance.id, &def, &registry, None).await.unwrap();
 
         let updated = persistence.get_workflow_instance(&instance.id).await.unwrap();
         // Should still be sleeping since sleep_until is in the future.
@@ -1048,7 +1100,7 @@ mod tests {
         instance.execution_pointers.push(ExecutionPointer::new(0));
         persistence.create_new_workflow(&instance).await.unwrap();
 
-        executor.execute(&instance.id, &def, &registry).await.unwrap();
+        executor.execute(&instance.id, &def, &registry, None).await.unwrap();
 
         let errors = persistence.get_errors().await;
         assert_eq!(errors.len(), 1);
@@ -1072,7 +1124,7 @@ mod tests {
         instance.execution_pointers.push(ExecutionPointer::new(0));
         persistence.create_new_workflow(&instance).await.unwrap();
 
-        executor.execute(&instance.id, &def, &registry).await.unwrap();
+        executor.execute(&instance.id, &def, &registry, None).await.unwrap();
 
         // Executor itself doesn't publish lifecycle events in the current implementation,
         // but the with_lifecycle builder works correctly.
@@ -1097,7 +1149,7 @@ mod tests {
         instance.execution_pointers.push(ExecutionPointer::new(0));
         persistence.create_new_workflow(&instance).await.unwrap();
 
-        executor.execute(&instance.id, &def, &registry).await.unwrap();
+        executor.execute(&instance.id, &def, &registry, None).await.unwrap();
 
         let updated = persistence.get_workflow_instance(&instance.id).await.unwrap();
         assert_eq!(updated.status, WorkflowStatus::Terminated);
@@ -1118,7 +1170,7 @@ mod tests {
         instance.execution_pointers.push(ExecutionPointer::new(0));
         persistence.create_new_workflow(&instance).await.unwrap();
 
-        executor.execute(&instance.id, &def, &registry).await.unwrap();
+        executor.execute(&instance.id, &def, &registry, None).await.unwrap();
 
         let updated = persistence.get_workflow_instance(&instance.id).await.unwrap();
         assert!(updated.execution_pointers[0].start_time.is_some());
@@ -1148,7 +1200,7 @@ mod tests {
         instance.execution_pointers.push(ExecutionPointer::new(0));
         persistence.create_new_workflow(&instance).await.unwrap();
 
-        executor.execute(&instance.id, &def, &registry).await.unwrap();
+        executor.execute(&instance.id, &def, &registry, None).await.unwrap();
 
         let updated = persistence.get_workflow_instance(&instance.id).await.unwrap();
         assert_eq!(
@@ -1203,13 +1255,13 @@ mod tests {
         persistence.create_new_workflow(&instance).await.unwrap();
 
         // First execution: fails, retry scheduled.
-        executor.execute(&instance.id, &def, &registry).await.unwrap();
+        executor.execute(&instance.id, &def, &registry, None).await.unwrap();
         let updated = persistence.get_workflow_instance(&instance.id).await.unwrap();
         assert_eq!(updated.execution_pointers[0].retry_count, 1);
         assert_eq!(updated.execution_pointers[0].status, PointerStatus::Sleeping);
 
         // Second execution: succeeds (sleep_until is in the past with 0ms interval).
-        executor.execute(&instance.id, &def, &registry).await.unwrap();
+        executor.execute(&instance.id, &def, &registry, None).await.unwrap();
         let updated = persistence.get_workflow_instance(&instance.id).await.unwrap();
         assert_eq!(updated.execution_pointers[0].status, PointerStatus::Complete);
         assert_eq!(updated.status, WorkflowStatus::Complete);
@@ -1227,7 +1279,7 @@ mod tests {
         // No execution pointers at all.
         persistence.create_new_workflow(&instance).await.unwrap();
 
-        executor.execute(&instance.id, &def, &registry).await.unwrap();
+        executor.execute(&instance.id, &def, &registry, None).await.unwrap();
 
         let updated = persistence.get_workflow_instance(&instance.id).await.unwrap();
         assert_eq!(updated.status, WorkflowStatus::Runnable);

wfe-core/src/models/condition.rs

@@ -0,0 +1,209 @@
+use serde::{Deserialize, Serialize};
+
+/// A condition that determines whether a workflow step should execute.
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+pub enum StepCondition {
+    /// All sub-conditions must be true (AND).
+    All(Vec<StepCondition>),
+    /// At least one sub-condition must be true (OR).
+    Any(Vec<StepCondition>),
+    /// No sub-conditions may be true (NOR).
+    None(Vec<StepCondition>),
+    /// Exactly one sub-condition must be true (XOR).
+    OneOf(Vec<StepCondition>),
+    /// Negation of a single condition (NOT).
+    Not(Box<StepCondition>),
+    /// A leaf comparison against a field in workflow data.
+    Comparison(FieldComparison),
+}
+
+/// A comparison of a workflow data field against an expected value.
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+pub struct FieldComparison {
+    /// Dot-separated field path, e.g. ".outputs.docker_started".
+    pub field: String,
+    /// The comparison operator.
+    pub operator: ComparisonOp,
+    /// The value to compare against. Required for all operators except IsNull/IsNotNull.
+    pub value: Option<serde_json::Value>,
+}
+
+/// Comparison operators for field conditions.
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+pub enum ComparisonOp {
+    Equals,
+    NotEquals,
+    Gt,
+    Gte,
+    Lt,
+    Lte,
+    Contains,
+    IsNull,
+    IsNotNull,
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use pretty_assertions::assert_eq;
+    use serde_json::json;
+
+    #[test]
+    fn comparison_op_serde_round_trip() {
+        for op in [
+            ComparisonOp::Equals,
+            ComparisonOp::NotEquals,
+            ComparisonOp::Gt,
+            ComparisonOp::Gte,
+            ComparisonOp::Lt,
+            ComparisonOp::Lte,
+            ComparisonOp::Contains,
+            ComparisonOp::IsNull,
+            ComparisonOp::IsNotNull,
+        ] {
+            let json_str = serde_json::to_string(&op).unwrap();
+            let deserialized: ComparisonOp = serde_json::from_str(&json_str).unwrap();
+            assert_eq!(op, deserialized);
+        }
+    }
+
+    #[test]
+    fn field_comparison_serde_round_trip() {
+        let comp = FieldComparison {
+            field: ".outputs.status".to_string(),
+            operator: ComparisonOp::Equals,
+            value: Some(json!("success")),
+        };
+        let json_str = serde_json::to_string(&comp).unwrap();
+        let deserialized: FieldComparison = serde_json::from_str(&json_str).unwrap();
+        assert_eq!(comp, deserialized);
+    }
+
+    #[test]
+    fn field_comparison_without_value_serde_round_trip() {
+        let comp = FieldComparison {
+            field: ".outputs.result".to_string(),
+            operator: ComparisonOp::IsNull,
+            value: None,
+        };
+        let json_str = serde_json::to_string(&comp).unwrap();
+        let deserialized: FieldComparison = serde_json::from_str(&json_str).unwrap();
+        assert_eq!(comp, deserialized);
+    }
+
+    #[test]
+    fn step_condition_comparison_serde_round_trip() {
+        let condition = StepCondition::Comparison(FieldComparison {
+            field: ".count".to_string(),
+            operator: ComparisonOp::Gt,
+            value: Some(json!(5)),
+        });
+        let json_str = serde_json::to_string(&condition).unwrap();
+        let deserialized: StepCondition = serde_json::from_str(&json_str).unwrap();
+        assert_eq!(condition, deserialized);
+    }
+
+    #[test]
+    fn step_condition_not_serde_round_trip() {
+        let condition = StepCondition::Not(Box::new(StepCondition::Comparison(FieldComparison {
+            field: ".active".to_string(),
+            operator: ComparisonOp::Equals,
+            value: Some(json!(false)),
+        })));
+        let json_str = serde_json::to_string(&condition).unwrap();
+        let deserialized: StepCondition = serde_json::from_str(&json_str).unwrap();
+        assert_eq!(condition, deserialized);
+    }
+
+    #[test]
+    fn step_condition_all_serde_round_trip() {
+        let condition = StepCondition::All(vec![
+            StepCondition::Comparison(FieldComparison {
+                field: ".a".to_string(),
+                operator: ComparisonOp::Equals,
+                value: Some(json!(1)),
+            }),
+            StepCondition::Comparison(FieldComparison {
+                field: ".b".to_string(),
+                operator: ComparisonOp::Equals,
+                value: Some(json!(2)),
+            }),
+        ]);
+        let json_str = serde_json::to_string(&condition).unwrap();
+        let deserialized: StepCondition = serde_json::from_str(&json_str).unwrap();
+        assert_eq!(condition, deserialized);
+    }
+
+    #[test]
+    fn step_condition_any_serde_round_trip() {
+        let condition = StepCondition::Any(vec![
+            StepCondition::Comparison(FieldComparison {
+                field: ".x".to_string(),
+                operator: ComparisonOp::IsNull,
+                value: None,
+            }),
+        ]);
+        let json_str = serde_json::to_string(&condition).unwrap();
+        let deserialized: StepCondition = serde_json::from_str(&json_str).unwrap();
+        assert_eq!(condition, deserialized);
+    }
+
+    #[test]
+    fn step_condition_none_serde_round_trip() {
+        let condition = StepCondition::None(vec![
+            StepCondition::Comparison(FieldComparison {
+                field: ".err".to_string(),
+                operator: ComparisonOp::IsNotNull,
+                value: None,
+            }),
+        ]);
+        let json_str = serde_json::to_string(&condition).unwrap();
+        let deserialized: StepCondition = serde_json::from_str(&json_str).unwrap();
+        assert_eq!(condition, deserialized);
+    }
+
+    #[test]
+    fn step_condition_one_of_serde_round_trip() {
+        let condition = StepCondition::OneOf(vec![
+            StepCondition::Comparison(FieldComparison {
+                field: ".mode".to_string(),
+                operator: ComparisonOp::Equals,
+                value: Some(json!("fast")),
+            }),
+            StepCondition::Comparison(FieldComparison {
+                field: ".mode".to_string(),
+                operator: ComparisonOp::Equals,
+                value: Some(json!("slow")),
+            }),
+        ]);
+        let json_str = serde_json::to_string(&condition).unwrap();
+        let deserialized: StepCondition = serde_json::from_str(&json_str).unwrap();
+        assert_eq!(condition, deserialized);
+    }
+
+    #[test]
+    fn nested_combinator_serde_round_trip() {
+        let condition = StepCondition::All(vec![
+            StepCondition::Any(vec![
+                StepCondition::Comparison(FieldComparison {
+                    field: ".a".to_string(),
+                    operator: ComparisonOp::Equals,
+                    value: Some(json!(1)),
+                }),
+                StepCondition::Comparison(FieldComparison {
+                    field: ".b".to_string(),
+                    operator: ComparisonOp::Equals,
+                    value: Some(json!(2)),
+                }),
+            ]),
+            StepCondition::Not(Box::new(StepCondition::Comparison(FieldComparison {
+                field: ".c".to_string(),
+                operator: ComparisonOp::IsNull,
+                value: None,
+            }))),
+        ]);
+        let json_str = serde_json::to_string(&condition).unwrap();
+        let deserialized: StepCondition = serde_json::from_str(&json_str).unwrap();
+        assert_eq!(condition, deserialized);
+    }
+}

wfe-core/src/models/mod.rs

@@ -1,3 +1,4 @@
+pub mod condition;
 pub mod error_behavior;
 pub mod event;
 pub mod execution_error;
@@ -7,10 +8,12 @@ pub mod lifecycle;
 pub mod poll_config;
 pub mod queue_type;
 pub mod scheduled_command;
+pub mod schema;
 pub mod status;
 pub mod workflow_definition;
 pub mod workflow_instance;
 
+pub use condition::{ComparisonOp, FieldComparison, StepCondition};
 pub use error_behavior::ErrorBehavior;
 pub use event::{Event, EventSubscription};
 pub use execution_error::ExecutionError;
@@ -20,6 +23,7 @@ pub use lifecycle::{LifecycleEvent, LifecycleEventType};
 pub use poll_config::{HttpMethod, PollCondition, PollEndpointConfig};
 pub use queue_type::QueueType;
 pub use scheduled_command::{CommandName, ScheduledCommand};
+pub use schema::{SchemaType, WorkflowSchema};
 pub use status::{PointerStatus, WorkflowStatus};
 pub use workflow_definition::{StepOutcome, WorkflowDefinition, WorkflowStep};
 pub use workflow_instance::WorkflowInstance;

wfe-core/src/models/schema.rs

@@ -0,0 +1,483 @@
+use std::collections::HashMap;
+
+use serde::{Deserialize, Serialize};
+
+/// Describes a single type in the workflow schema type system.
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+pub enum SchemaType {
+    String,
+    Number,
+    Integer,
+    Bool,
+    Optional(Box<SchemaType>),
+    List(Box<SchemaType>),
+    Map(Box<SchemaType>),
+    Any,
+}
+
+/// Defines expected input and output schemas for a workflow.
+#[derive(Debug, Clone, Default, Serialize, Deserialize)]
+pub struct WorkflowSchema {
+    #[serde(default)]
+    pub inputs: HashMap<String, SchemaType>,
+    #[serde(default)]
+    pub outputs: HashMap<String, SchemaType>,
+}
+
+/// Parse a type string into a [`SchemaType`].
+///
+/// Supported formats:
+/// - `"string"`, `"number"`, `"integer"`, `"bool"`, `"any"`
+/// - `"string?"` (optional)
+/// - `"list<string>"`, `"map<number>"` (generic containers)
+/// - Nested: `"list<list<string>>"`
+pub fn parse_type(s: &str) -> crate::Result<SchemaType> {
+    let s = s.trim();
+
+    // Handle optional suffix.
+    if let Some(inner) = s.strip_suffix('?') {
+        let inner_type = parse_type(inner)?;
+        return Ok(SchemaType::Optional(Box::new(inner_type)));
+    }
+
+    // Handle generic containers: list<...> and map<...>.
+    if let Some(rest) = s.strip_prefix("list<") {
+        let inner = rest
+            .strip_suffix('>')
+            .ok_or_else(|| crate::WfeError::StepExecution(format!("Invalid type syntax: {s}")))?;
+        let inner_type = parse_type(inner)?;
+        return Ok(SchemaType::List(Box::new(inner_type)));
+    }
+    if let Some(rest) = s.strip_prefix("map<") {
+        let inner = rest
+            .strip_suffix('>')
+            .ok_or_else(|| crate::WfeError::StepExecution(format!("Invalid type syntax: {s}")))?;
+        let inner_type = parse_type(inner)?;
+        return Ok(SchemaType::Map(Box::new(inner_type)));
+    }
+
+    // Primitive types.
+    match s {
+        "string" => Ok(SchemaType::String),
+        "number" => Ok(SchemaType::Number),
+        "integer" => Ok(SchemaType::Integer),
+        "bool" => Ok(SchemaType::Bool),
+        "any" => Ok(SchemaType::Any),
+        _ => Err(crate::WfeError::StepExecution(format!(
+            "Unknown type: {s}"
+        ))),
+    }
+}
+
+/// Validate that a JSON value matches the expected [`SchemaType`].
+pub fn validate_value(value: &serde_json::Value, expected: &SchemaType) -> Result<(), String> {
+    match expected {
+        SchemaType::String => {
+            if value.is_string() {
+                Ok(())
+            } else {
+                Err(format!("expected string, got {}", value_type_name(value)))
+            }
+        }
+        SchemaType::Number => {
+            if value.is_number() {
+                Ok(())
+            } else {
+                Err(format!("expected number, got {}", value_type_name(value)))
+            }
+        }
+        SchemaType::Integer => {
+            if value.is_i64() || value.is_u64() {
+                Ok(())
+            } else {
+                Err(format!("expected integer, got {}", value_type_name(value)))
+            }
+        }
+        SchemaType::Bool => {
+            if value.is_boolean() {
+                Ok(())
+            } else {
+                Err(format!("expected bool, got {}", value_type_name(value)))
+            }
+        }
+        SchemaType::Optional(inner) => {
+            if value.is_null() {
+                Ok(())
+            } else {
+                validate_value(value, inner)
+            }
+        }
+        SchemaType::List(inner) => {
+            if let Some(arr) = value.as_array() {
+                for (i, item) in arr.iter().enumerate() {
+                    validate_value(item, inner)
+                        .map_err(|e| format!("list element [{i}]: {e}"))?;
+                }
+                Ok(())
+            } else {
+                Err(format!("expected list, got {}", value_type_name(value)))
+            }
+        }
+        SchemaType::Map(inner) => {
+            if let Some(obj) = value.as_object() {
+                for (key, val) in obj {
+                    validate_value(val, inner)
+                        .map_err(|e| format!("map key \"{key}\": {e}"))?;
+                }
+                Ok(())
+            } else {
+                Err(format!("expected map, got {}", value_type_name(value)))
+            }
+        }
+        SchemaType::Any => Ok(()),
+    }
+}
+
+fn value_type_name(value: &serde_json::Value) -> &'static str {
+    match value {
+        serde_json::Value::Null => "null",
+        serde_json::Value::Bool(_) => "bool",
+        serde_json::Value::Number(_) => "number",
+        serde_json::Value::String(_) => "string",
+        serde_json::Value::Array(_) => "array",
+        serde_json::Value::Object(_) => "object",
+    }
+}
+
+impl WorkflowSchema {
+    /// Validate that the given data satisfies all input field requirements.
+    pub fn validate_inputs(&self, data: &serde_json::Value) -> Result<(), Vec<String>> {
+        self.validate_fields(&self.inputs, data)
+    }
+
+    /// Validate that the given data satisfies all output field requirements.
+    pub fn validate_outputs(&self, data: &serde_json::Value) -> Result<(), Vec<String>> {
+        self.validate_fields(&self.outputs, data)
+    }
+
+    fn validate_fields(
+        &self,
+        fields: &HashMap<String, SchemaType>,
+        data: &serde_json::Value,
+    ) -> Result<(), Vec<String>> {
+        let obj = match data.as_object() {
+            Some(o) => o,
+            None => {
+                return Err(vec!["expected an object".to_string()]);
+            }
+        };
+
+        let mut errors = Vec::new();
+
+        for (name, schema_type) in fields {
+            match obj.get(name) {
+                Some(value) => {
+                    if let Err(e) = validate_value(value, schema_type) {
+                        errors.push(format!("field \"{name}\": {e}"));
+                    }
+                }
+                None => {
+                    // Missing field is OK for optional types (null is acceptable).
+                    if !matches!(schema_type, SchemaType::Optional(_)) {
+                        errors.push(format!("missing required field: \"{name}\""));
+                    }
+                }
+            }
+        }
+
+        if errors.is_empty() {
+            Ok(())
+        } else {
+            Err(errors)
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use serde_json::json;
+
+    // -- parse_type tests --
+
+    #[test]
+    fn parse_type_string() {
+        assert_eq!(parse_type("string").unwrap(), SchemaType::String);
+    }
+
+    #[test]
+    fn parse_type_number() {
+        assert_eq!(parse_type("number").unwrap(), SchemaType::Number);
+    }
+
+    #[test]
+    fn parse_type_integer() {
+        assert_eq!(parse_type("integer").unwrap(), SchemaType::Integer);
+    }
+
+    #[test]
+    fn parse_type_bool() {
+        assert_eq!(parse_type("bool").unwrap(), SchemaType::Bool);
+    }
+
+    #[test]
+    fn parse_type_any() {
+        assert_eq!(parse_type("any").unwrap(), SchemaType::Any);
+    }
+
+    #[test]
+    fn parse_type_optional_string() {
+        assert_eq!(
+            parse_type("string?").unwrap(),
+            SchemaType::Optional(Box::new(SchemaType::String))
+        );
+    }
+
+    #[test]
+    fn parse_type_optional_number() {
+        assert_eq!(
+            parse_type("number?").unwrap(),
+            SchemaType::Optional(Box::new(SchemaType::Number))
+        );
+    }
+
+    #[test]
+    fn parse_type_list_string() {
+        assert_eq!(
+            parse_type("list<string>").unwrap(),
+            SchemaType::List(Box::new(SchemaType::String))
+        );
+    }
+
+    #[test]
+    fn parse_type_list_number() {
+        assert_eq!(
+            parse_type("list<number>").unwrap(),
+            SchemaType::List(Box::new(SchemaType::Number))
+        );
+    }
+
+    #[test]
+    fn parse_type_map_string() {
+        assert_eq!(
+            parse_type("map<string>").unwrap(),
+            SchemaType::Map(Box::new(SchemaType::String))
+        );
+    }
+
+    #[test]
+    fn parse_type_map_number() {
+        assert_eq!(
+            parse_type("map<number>").unwrap(),
+            SchemaType::Map(Box::new(SchemaType::Number))
+        );
+    }
+
+    #[test]
+    fn parse_type_nested_list() {
+        assert_eq!(
+            parse_type("list<list<string>>").unwrap(),
+            SchemaType::List(Box::new(SchemaType::List(Box::new(SchemaType::String))))
+        );
+    }
+
+    #[test]
+    fn parse_type_unknown_errors() {
+        assert!(parse_type("foobar").is_err());
+    }
+
+    #[test]
+    fn parse_type_trims_whitespace() {
+        assert_eq!(parse_type("  string  ").unwrap(), SchemaType::String);
+    }
+
+    // -- validate_value tests --
+
+    #[test]
+    fn validate_string_match() {
+        assert!(validate_value(&json!("hello"), &SchemaType::String).is_ok());
+    }
+
+    #[test]
+    fn validate_string_mismatch() {
+        assert!(validate_value(&json!(42), &SchemaType::String).is_err());
+    }
+
+    #[test]
+    fn validate_number_match() {
+        assert!(validate_value(&json!(2.78), &SchemaType::Number).is_ok());
+    }
+
+    #[test]
+    fn validate_number_mismatch() {
+        assert!(validate_value(&json!("not a number"), &SchemaType::Number).is_err());
+    }
+
+    #[test]
+    fn validate_integer_match() {
+        assert!(validate_value(&json!(42), &SchemaType::Integer).is_ok());
+    }
+
+    #[test]
+    fn validate_integer_mismatch_float() {
+        assert!(validate_value(&json!(2.78), &SchemaType::Integer).is_err());
+    }
+
+    #[test]
+    fn validate_bool_match() {
+        assert!(validate_value(&json!(true), &SchemaType::Bool).is_ok());
+    }
+
+    #[test]
+    fn validate_bool_mismatch() {
+        assert!(validate_value(&json!(1), &SchemaType::Bool).is_err());
+    }
+
+    #[test]
+    fn validate_optional_null_passes() {
+        let ty = SchemaType::Optional(Box::new(SchemaType::String));
+        assert!(validate_value(&json!(null), &ty).is_ok());
+    }
+
+    #[test]
+    fn validate_optional_correct_inner_passes() {
+        let ty = SchemaType::Optional(Box::new(SchemaType::String));
+        assert!(validate_value(&json!("hello"), &ty).is_ok());
+    }
+
+    #[test]
+    fn validate_optional_wrong_inner_fails() {
+        let ty = SchemaType::Optional(Box::new(SchemaType::String));
+        assert!(validate_value(&json!(42), &ty).is_err());
+    }
+
+    #[test]
+    fn validate_list_match() {
+        let ty = SchemaType::List(Box::new(SchemaType::Number));
+        assert!(validate_value(&json!([1, 2, 3]), &ty).is_ok());
+    }
+
+    #[test]
+    fn validate_list_mismatch_element() {
+        let ty = SchemaType::List(Box::new(SchemaType::Number));
+        assert!(validate_value(&json!([1, "two", 3]), &ty).is_err());
+    }
+
+    #[test]
+    fn validate_list_not_array() {
+        let ty = SchemaType::List(Box::new(SchemaType::Number));
+        assert!(validate_value(&json!("not a list"), &ty).is_err());
+    }
+
+    #[test]
+    fn validate_map_match() {
+        let ty = SchemaType::Map(Box::new(SchemaType::Number));
+        assert!(validate_value(&json!({"a": 1, "b": 2}), &ty).is_ok());
+    }
+
+    #[test]
+    fn validate_map_mismatch_value() {
+        let ty = SchemaType::Map(Box::new(SchemaType::Number));
+        assert!(validate_value(&json!({"a": 1, "b": "two"}), &ty).is_err());
+    }
+
+    #[test]
+    fn validate_map_not_object() {
+        let ty = SchemaType::Map(Box::new(SchemaType::Number));
+        assert!(validate_value(&json!([1, 2]), &ty).is_err());
+    }
+
+    #[test]
+    fn validate_any_always_passes() {
+        assert!(validate_value(&json!(null), &SchemaType::Any).is_ok());
+        assert!(validate_value(&json!("str"), &SchemaType::Any).is_ok());
+        assert!(validate_value(&json!(42), &SchemaType::Any).is_ok());
+        assert!(validate_value(&json!([1, 2]), &SchemaType::Any).is_ok());
+    }
+
+    // -- WorkflowSchema validate_inputs / validate_outputs tests --
+
+    #[test]
+    fn validate_inputs_all_present() {
+        let schema = WorkflowSchema {
+            inputs: HashMap::from([
+                ("name".into(), SchemaType::String),
+                ("age".into(), SchemaType::Integer),
+            ]),
+            outputs: HashMap::new(),
+        };
+        let data = json!({"name": "Alice", "age": 30});
+        assert!(schema.validate_inputs(&data).is_ok());
+    }
+
+    #[test]
+    fn validate_inputs_missing_required_field() {
+        let schema = WorkflowSchema {
+            inputs: HashMap::from([
+                ("name".into(), SchemaType::String),
+                ("age".into(), SchemaType::Integer),
+            ]),
+            outputs: HashMap::new(),
+        };
+        let data = json!({"name": "Alice"});
+        let errs = schema.validate_inputs(&data).unwrap_err();
+        assert!(errs.iter().any(|e| e.contains("age")));
+    }
+
+    #[test]
+    fn validate_inputs_wrong_type() {
+        let schema = WorkflowSchema {
+            inputs: HashMap::from([("count".into(), SchemaType::Integer)]),
+            outputs: HashMap::new(),
+        };
+        let data = json!({"count": "not-a-number"});
+        let errs = schema.validate_inputs(&data).unwrap_err();
+        assert!(!errs.is_empty());
+    }
+
+    #[test]
+    fn validate_outputs_missing_field() {
+        let schema = WorkflowSchema {
+            inputs: HashMap::new(),
+            outputs: HashMap::from([("result".into(), SchemaType::String)]),
+        };
+        let data = json!({});
+        let errs = schema.validate_outputs(&data).unwrap_err();
+        assert!(errs.iter().any(|e| e.contains("result")));
+    }
+
+    #[test]
+    fn validate_inputs_optional_field_missing_is_ok() {
+        let schema = WorkflowSchema {
+            inputs: HashMap::from([(
+                "nickname".into(),
+                SchemaType::Optional(Box::new(SchemaType::String)),
+            )]),
+            outputs: HashMap::new(),
+        };
+        let data = json!({});
+        assert!(schema.validate_inputs(&data).is_ok());
+    }
+
+    #[test]
+    fn validate_not_object_errors() {
+        let schema = WorkflowSchema {
+            inputs: HashMap::from([("x".into(), SchemaType::String)]),
+            outputs: HashMap::new(),
+        };
+        let errs = schema.validate_inputs(&json!("not an object")).unwrap_err();
+        assert!(errs[0].contains("expected an object"));
+    }
+
+    #[test]
+    fn schema_serde_round_trip() {
+        let schema = WorkflowSchema {
+            inputs: HashMap::from([("name".into(), SchemaType::String)]),
+            outputs: HashMap::from([("result".into(), SchemaType::Bool)]),
+        };
+        let json_str = serde_json::to_string(&schema).unwrap();
+        let deserialized: WorkflowSchema = serde_json::from_str(&json_str).unwrap();
+        assert_eq!(deserialized.inputs["name"], SchemaType::String);
+        assert_eq!(deserialized.outputs["result"], SchemaType::Bool);
+    }
+}

wfe-core/src/models/status.rs

@@ -15,6 +15,7 @@ pub enum PointerStatus {
     Pending,
     Running,
     Complete,
+    Skipped,
     Sleeping,
     WaitingForEvent,
     Failed,
@@ -58,6 +59,7 @@ mod tests {
             PointerStatus::Pending,
             PointerStatus::Running,
             PointerStatus::Complete,
+            PointerStatus::Skipped,
             PointerStatus::Sleeping,
             PointerStatus::WaitingForEvent,
             PointerStatus::Failed,

wfe-core/src/models/workflow_definition.rs

@@ -2,6 +2,7 @@ use std::time::Duration;
 
 use serde::{Deserialize, Serialize};
 
+use super::condition::StepCondition;
 use super::error_behavior::ErrorBehavior;
 
 /// A compiled workflow definition ready for execution.
@@ -46,6 +47,9 @@ pub struct WorkflowStep {
     /// Serializable configuration for primitive steps (e.g. event_name, duration).
     #[serde(default, skip_serializing_if = "Option::is_none")]
     pub step_config: Option<serde_json::Value>,
+    /// Optional condition that must evaluate to true for this step to execute.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub when: Option<StepCondition>,
 }
 
 impl WorkflowStep {
@@ -62,6 +66,7 @@ impl WorkflowStep {
             do_compensate: false,
             saga: false,
             step_config: None,
+            when: None,
         }
     }
 }

wfe-core/src/models/workflow_instance.rs

@@ -45,6 +45,7 @@ impl WorkflowInstance {
                 matches!(
                     p.status,
                     PointerStatus::Complete
+                        | PointerStatus::Skipped
                         | PointerStatus::Compensated
                         | PointerStatus::Cancelled
                         | PointerStatus::Failed

wfe-core/src/primitives/mod.rs

@@ -8,6 +8,7 @@ pub mod recur;
 pub mod saga_container;
 pub mod schedule;
 pub mod sequence;
+pub mod sub_workflow;
 pub mod wait_for;
 pub mod while_step;
 
@@ -21,6 +22,7 @@ pub use recur::RecurStep;
 pub use saga_container::SagaContainerStep;
 pub use schedule::ScheduleStep;
 pub use sequence::SequenceStep;
+pub use sub_workflow::SubWorkflowStep;
 pub use wait_for::WaitForStep;
 pub use while_step::WhileStep;
 
@@ -42,6 +44,7 @@ mod test_helpers {
             step,
             workflow,
             cancellation_token: CancellationToken::new(),
+            host_context: None,
         }
     }
 

wfe-core/src/primitives/sub_workflow.rs

@@ -0,0 +1,444 @@
+use async_trait::async_trait;
+use chrono::Utc;
+
+use crate::models::schema::WorkflowSchema;
+use crate::models::ExecutionResult;
+use crate::traits::step::{StepBody, StepExecutionContext};
+
+/// A step that starts a child workflow and waits for its completion.
+///
+/// On first invocation, it validates inputs against `input_schema`, starts the
+/// child workflow via the host context, and returns a "wait for event" result.
+///
+/// When the child workflow completes, the event data arrives, output keys are
+/// extracted, and the step proceeds.
+#[derive(Default)]
+pub struct SubWorkflowStep {
+    /// The definition ID of the child workflow to start.
+    pub workflow_id: String,
+    /// The version of the child workflow definition.
+    pub version: u32,
+    /// Input data to pass to the child workflow.
+    pub inputs: serde_json::Value,
+    /// Keys to extract from the child workflow's completion event data.
+    pub output_keys: Vec<String>,
+    /// Optional schema to validate inputs before starting the child.
+    pub input_schema: Option<WorkflowSchema>,
+    /// Optional schema to validate outputs from the child.
+    pub output_schema: Option<WorkflowSchema>,
+}
+
+#[async_trait]
+impl StepBody for SubWorkflowStep {
+    async fn run(&mut self, context: &StepExecutionContext<'_>) -> crate::Result<ExecutionResult> {
+        // If event data has arrived, the child workflow completed.
+        if let Some(event_data) = &context.execution_pointer.event_data {
+            // Extract output_keys from event data.
+            let mut output = serde_json::Map::new();
+
+            // The event data contains { "status": "...", "data": { ... } }.
+            let child_data = event_data
+                .get("data")
+                .cloned()
+                .unwrap_or(serde_json::Value::Null);
+
+            if self.output_keys.is_empty() {
+                // If no specific keys requested, pass all child data through.
+                if let serde_json::Value::Object(map) = child_data {
+                    output = map;
+                }
+            } else {
+                // Extract only the requested keys.
+                for key in &self.output_keys {
+                    if let Some(val) = child_data.get(key) {
+                        output.insert(key.clone(), val.clone());
+                    }
+                }
+            }
+
+            let output_value = serde_json::Value::Object(output);
+
+            // Validate against output schema if present.
+            if let Some(ref schema) = self.output_schema
+                && let Err(errors) = schema.validate_outputs(&output_value)
+            {
+                return Err(crate::WfeError::StepExecution(format!(
+                    "SubWorkflow output validation failed: {}",
+                    errors.join("; ")
+                )));
+            }
+
+            let mut result = ExecutionResult::next();
+            result.output_data = Some(output_value);
+            return Ok(result);
+        }
+
+        // Hydrate from step_config if our fields are empty (created via Default).
+        if self.workflow_id.is_empty()
+            && let Some(config) = &context.step.step_config
+        {
+            if let Some(wf_id) = config.get("workflow_id").and_then(|v| v.as_str()) {
+                self.workflow_id = wf_id.to_string();
+            }
+            if let Some(ver) = config.get("version").and_then(|v| v.as_u64()) {
+                self.version = ver as u32;
+            }
+            if let Some(inputs) = config.get("inputs") {
+                self.inputs = inputs.clone();
+            }
+            if let Some(keys) = config.get("output_keys").and_then(|v| v.as_array()) {
+                self.output_keys = keys
+                    .iter()
+                    .filter_map(|v| v.as_str().map(|s| s.to_string()))
+                    .collect();
+            }
+        }
+
+        // First call: validate inputs and start child workflow.
+        if let Some(ref schema) = self.input_schema
+            && let Err(errors) = schema.validate_inputs(&self.inputs)
+        {
+            return Err(crate::WfeError::StepExecution(format!(
+                "SubWorkflow input validation failed: {}",
+                errors.join("; ")
+            )));
+        }
+
+        let host = context.host_context.ok_or_else(|| {
+            crate::WfeError::StepExecution(
+                "SubWorkflowStep requires a host context to start child workflows".to_string(),
+            )
+        })?;
+
+        // Use inputs if set, otherwise pass an empty object so the child
+        // workflow has a valid JSON object for storing step outputs.
+        let child_data = if self.inputs.is_null() {
+            serde_json::json!({})
+        } else {
+            self.inputs.clone()
+        };
+        let child_instance_id = host
+            .start_workflow(&self.workflow_id, self.version, child_data)
+            .await?;
+
+        Ok(ExecutionResult::wait_for_event(
+            "wfe.workflow.completed",
+            child_instance_id,
+            Utc::now(),
+        ))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::models::schema::SchemaType;
+    use crate::models::ExecutionPointer;
+    use crate::primitives::test_helpers::*;
+    use crate::traits::step::HostContext;
+    use serde_json::json;
+    use std::collections::HashMap;
+    use std::sync::Mutex;
+
+    /// A mock HostContext that records calls and returns a fixed instance ID.
+    struct MockHostContext {
+        started: Mutex<Vec<(String, u32, serde_json::Value)>>,
+        result_id: String,
+    }
+
+    impl MockHostContext {
+        fn new(result_id: &str) -> Self {
+            Self {
+                started: Mutex::new(Vec::new()),
+                result_id: result_id.to_string(),
+            }
+        }
+
+        fn calls(&self) -> Vec<(String, u32, serde_json::Value)> {
+            self.started.lock().unwrap().clone()
+        }
+    }
+
+    impl HostContext for MockHostContext {
+        fn start_workflow(
+            &self,
+            definition_id: &str,
+            version: u32,
+            data: serde_json::Value,
+        ) -> std::pin::Pin<Box<dyn std::future::Future<Output = crate::Result<String>> + Send + '_>>
+        {
+            let def_id = definition_id.to_string();
+            let result_id = self.result_id.clone();
+            Box::pin(async move {
+                self.started
+                    .lock()
+                    .unwrap()
+                    .push((def_id, version, data));
+                Ok(result_id)
+            })
+        }
+    }
+
+    /// A mock HostContext that returns an error.
+    struct FailingHostContext;
+
+    impl HostContext for FailingHostContext {
+        fn start_workflow(
+            &self,
+            _definition_id: &str,
+            _version: u32,
+            _data: serde_json::Value,
+        ) -> std::pin::Pin<Box<dyn std::future::Future<Output = crate::Result<String>> + Send + '_>>
+        {
+            Box::pin(async {
+                Err(crate::WfeError::StepExecution(
+                    "failed to start child".to_string(),
+                ))
+            })
+        }
+    }
+
+    fn make_context_with_host<'a>(
+        pointer: &'a ExecutionPointer,
+        step: &'a crate::models::WorkflowStep,
+        workflow: &'a crate::models::WorkflowInstance,
+        host: &'a dyn HostContext,
+    ) -> StepExecutionContext<'a> {
+        StepExecutionContext {
+            item: None,
+            execution_pointer: pointer,
+            persistence_data: pointer.persistence_data.as_ref(),
+            step,
+            workflow,
+            cancellation_token: tokio_util::sync::CancellationToken::new(),
+            host_context: Some(host),
+        }
+    }
+
+    #[tokio::test]
+    async fn first_call_starts_child_and_waits() {
+        let host = MockHostContext::new("child-123");
+        let mut step = SubWorkflowStep {
+            workflow_id: "child-def".into(),
+            version: 1,
+            inputs: json!({"x": 10}),
+            ..Default::default()
+        };
+
+        let pointer = ExecutionPointer::new(0);
+        let wf_step = default_step();
+        let workflow = default_workflow();
+        let ctx = make_context_with_host(&pointer, &wf_step, &workflow, &host);
+
+        let result = step.run(&ctx).await.unwrap();
+        assert!(!result.proceed);
+        assert_eq!(result.event_name.as_deref(), Some("wfe.workflow.completed"));
+        assert_eq!(result.event_key.as_deref(), Some("child-123"));
+        assert!(result.event_as_of.is_some());
+
+        let calls = host.calls();
+        assert_eq!(calls.len(), 1);
+        assert_eq!(calls[0].0, "child-def");
+        assert_eq!(calls[0].1, 1);
+        assert_eq!(calls[0].2, json!({"x": 10}));
+    }
+
+    #[tokio::test]
+    async fn child_completed_proceeds_with_output() {
+        let mut step = SubWorkflowStep {
+            workflow_id: "child-def".into(),
+            version: 1,
+            inputs: json!({}),
+            output_keys: vec!["result".into()],
+            ..Default::default()
+        };
+
+        let mut pointer = ExecutionPointer::new(0);
+        pointer.event_data = Some(json!({
+            "status": "Complete",
+            "data": {"result": "success", "extra": "ignored"}
+        }));
+        let wf_step = default_step();
+        let workflow = default_workflow();
+        let ctx = make_context(&pointer, &wf_step, &workflow);
+
+        let result = step.run(&ctx).await.unwrap();
+        assert!(result.proceed);
+        assert_eq!(
+            result.output_data,
+            Some(json!({"result": "success"}))
+        );
+    }
+
+    #[tokio::test]
+    async fn child_completed_no_output_keys_passes_all() {
+        let mut step = SubWorkflowStep {
+            workflow_id: "child-def".into(),
+            version: 1,
+            inputs: json!({}),
+            output_keys: vec![],
+            ..Default::default()
+        };
+
+        let mut pointer = ExecutionPointer::new(0);
+        pointer.event_data = Some(json!({
+            "status": "Complete",
+            "data": {"a": 1, "b": 2}
+        }));
+        let wf_step = default_step();
+        let workflow = default_workflow();
+        let ctx = make_context(&pointer, &wf_step, &workflow);
+
+        let result = step.run(&ctx).await.unwrap();
+        assert!(result.proceed);
+        assert_eq!(
+            result.output_data,
+            Some(json!({"a": 1, "b": 2}))
+        );
+    }
+
+    #[tokio::test]
+    async fn no_host_context_errors() {
+        let mut step = SubWorkflowStep {
+            workflow_id: "child-def".into(),
+            version: 1,
+            inputs: json!({}),
+            ..Default::default()
+        };
+
+        let pointer = ExecutionPointer::new(0);
+        let wf_step = default_step();
+        let workflow = default_workflow();
+        let ctx = make_context(&pointer, &wf_step, &workflow);
+
+        let err = step.run(&ctx).await.unwrap_err();
+        assert!(err.to_string().contains("host context"));
+    }
+
+    #[tokio::test]
+    async fn input_validation_failure() {
+        let host = MockHostContext::new("child-123");
+        let mut step = SubWorkflowStep {
+            workflow_id: "child-def".into(),
+            version: 1,
+            inputs: json!({"name": 42}), // wrong type
+            input_schema: Some(WorkflowSchema {
+                inputs: HashMap::from([("name".into(), SchemaType::String)]),
+                outputs: HashMap::new(),
+            }),
+            ..Default::default()
+        };
+
+        let pointer = ExecutionPointer::new(0);
+        let wf_step = default_step();
+        let workflow = default_workflow();
+        let ctx = make_context_with_host(&pointer, &wf_step, &workflow, &host);
+
+        let err = step.run(&ctx).await.unwrap_err();
+        assert!(err.to_string().contains("input validation failed"));
+        assert!(host.calls().is_empty());
+    }
+
+    #[tokio::test]
+    async fn output_validation_failure() {
+        let mut step = SubWorkflowStep {
+            workflow_id: "child-def".into(),
+            version: 1,
+            inputs: json!({}),
+            output_keys: vec![],
+            output_schema: Some(WorkflowSchema {
+                inputs: HashMap::new(),
+                outputs: HashMap::from([("result".into(), SchemaType::String)]),
+            }),
+            ..Default::default()
+        };
+
+        let mut pointer = ExecutionPointer::new(0);
+        pointer.event_data = Some(json!({
+            "status": "Complete",
+            "data": {"result": 42}
+        }));
+        let wf_step = default_step();
+        let workflow = default_workflow();
+        let ctx = make_context(&pointer, &wf_step, &workflow);
+
+        let err = step.run(&ctx).await.unwrap_err();
+        assert!(err.to_string().contains("output validation failed"));
+    }
+
+    #[tokio::test]
+    async fn input_validation_passes_then_starts_child() {
+        let host = MockHostContext::new("child-456");
+        let mut step = SubWorkflowStep {
+            workflow_id: "child-def".into(),
+            version: 2,
+            inputs: json!({"name": "Alice"}),
+            input_schema: Some(WorkflowSchema {
+                inputs: HashMap::from([("name".into(), SchemaType::String)]),
+                outputs: HashMap::new(),
+            }),
+            ..Default::default()
+        };
+
+        let pointer = ExecutionPointer::new(0);
+        let wf_step = default_step();
+        let workflow = default_workflow();
+        let ctx = make_context_with_host(&pointer, &wf_step, &workflow, &host);
+
+        let result = step.run(&ctx).await.unwrap();
+        assert!(!result.proceed);
+        assert_eq!(result.event_key.as_deref(), Some("child-456"));
+        assert_eq!(host.calls().len(), 1);
+    }
+
+    #[tokio::test]
+    async fn host_start_workflow_error_propagates() {
+        let host = FailingHostContext;
+        let mut step = SubWorkflowStep {
+            workflow_id: "child-def".into(),
+            version: 1,
+            inputs: json!({}),
+            ..Default::default()
+        };
+
+        let pointer = ExecutionPointer::new(0);
+        let wf_step = default_step();
+        let workflow = default_workflow();
+        let ctx = make_context_with_host(&pointer, &wf_step, &workflow, &host);
+
+        let err = step.run(&ctx).await.unwrap_err();
+        assert!(err.to_string().contains("failed to start child"));
+    }
+
+    #[tokio::test]
+    async fn event_data_without_data_field_returns_empty_output() {
+        let mut step = SubWorkflowStep {
+            workflow_id: "child-def".into(),
+            version: 1,
+            inputs: json!({}),
+            output_keys: vec!["foo".into()],
+            ..Default::default()
+        };
+
+        let mut pointer = ExecutionPointer::new(0);
+        pointer.event_data = Some(json!({"status": "Complete"}));
+        let wf_step = default_step();
+        let workflow = default_workflow();
+        let ctx = make_context(&pointer, &wf_step, &workflow);
+
+        let result = step.run(&ctx).await.unwrap();
+        assert!(result.proceed);
+        assert_eq!(result.output_data, Some(json!({})));
+    }
+
+    #[tokio::test]
+    async fn default_step_has_empty_fields() {
+        let step = SubWorkflowStep::default();
+        assert!(step.workflow_id.is_empty());
+        assert_eq!(step.version, 0);
+        assert_eq!(step.inputs, json!(null));
+        assert!(step.output_keys.is_empty());
+        assert!(step.input_schema.is_none());
+        assert!(step.output_schema.is_none());
+    }
+}

wfe-core/src/traits/middleware.rs

@@ -68,6 +68,7 @@ mod tests {
             step: &step,
             workflow: &instance,
             cancellation_token: tokio_util::sync::CancellationToken::new(),
+            host_context: None,
         };
         mw.pre_step(&ctx).await.unwrap();
     }
@@ -86,6 +87,7 @@ mod tests {
             step: &step,
             workflow: &instance,
             cancellation_token: tokio_util::sync::CancellationToken::new(),
+            host_context: None,
         };
         let result = ExecutionResult::next();
         mw.post_step(&ctx, &result).await.unwrap();

wfe-core/src/traits/mod.rs

@@ -17,4 +17,4 @@ pub use persistence::{
 pub use queue::QueueProvider;
 pub use registry::WorkflowRegistry;
 pub use search::{Page, SearchFilter, SearchIndex, WorkflowSearchResult};
-pub use step::{StepBody, StepExecutionContext, WorkflowData};
+pub use step::{HostContext, StepBody, StepExecutionContext, WorkflowData};

wfe-core/src/traits/step.rs

@@ -11,8 +11,18 @@ pub trait WorkflowData: Serialize + DeserializeOwned + Send + Sync + Clone + 'st
 /// Blanket implementation: any type satisfying the bounds is WorkflowData.
 impl<T> WorkflowData for T where T: Serialize + DeserializeOwned + Send + Sync + Clone + 'static {}
 
+/// Context for steps that need to interact with the workflow host.
+/// Implemented by WorkflowHost to allow steps like SubWorkflow to start child workflows.
+pub trait HostContext: Send + Sync {
+    fn start_workflow(
+        &self,
+        definition_id: &str,
+        version: u32,
+        data: serde_json::Value,
+    ) -> std::pin::Pin<Box<dyn std::future::Future<Output = crate::Result<String>> + Send + '_>>;
+}
+
 /// Context available to a step during execution.
-#[derive(Debug)]
 pub struct StepExecutionContext<'a> {
     /// The current item when iterating (ForEach).
     pub item: Option<&'a serde_json::Value>,
@@ -26,6 +36,22 @@ pub struct StepExecutionContext<'a> {
     pub workflow: &'a WorkflowInstance,
     /// Cancellation token.
     pub cancellation_token: tokio_util::sync::CancellationToken,
+    /// Host context for starting child workflows. None if not available.
+    pub host_context: Option<&'a dyn HostContext>,
+}
+
+// Manual Debug impl since dyn HostContext is not Debug.
+impl<'a> std::fmt::Debug for StepExecutionContext<'a> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("StepExecutionContext")
+            .field("item", &self.item)
+            .field("execution_pointer", &self.execution_pointer)
+            .field("persistence_data", &self.persistence_data)
+            .field("step", &self.step)
+            .field("workflow", &self.workflow)
+            .field("host_context", &self.host_context.is_some())
+            .finish()
+    }
 }
 
 /// The core unit of work in a workflow. Each step implements this trait.

wfe-opensearch/Cargo.toml

@@ -3,6 +3,8 @@ name = "wfe-opensearch"
 version.workspace = true
 edition.workspace = true
 license.workspace = true
+repository.workspace = true
+homepage.workspace = true
 description = "OpenSearch index provider for WFE"
 
 [dependencies]

wfe-postgres/Cargo.toml

@@ -3,6 +3,8 @@ name = "wfe-postgres"
 version.workspace = true
 edition.workspace = true
 license.workspace = true
+repository.workspace = true
+homepage.workspace = true
 description = "PostgreSQL persistence provider for WFE"
 
 [dependencies]

wfe-postgres/src/lib.rs

@@ -66,6 +66,7 @@ impl PostgresPersistenceProvider {
             PointerStatus::Pending => "Pending",
             PointerStatus::Running => "Running",
             PointerStatus::Complete => "Complete",
+            PointerStatus::Skipped => "Skipped",
             PointerStatus::Sleeping => "Sleeping",
             PointerStatus::WaitingForEvent => "WaitingForEvent",
             PointerStatus::Failed => "Failed",
@@ -80,6 +81,7 @@ impl PostgresPersistenceProvider {
             "Pending" => Ok(PointerStatus::Pending),
             "Running" => Ok(PointerStatus::Running),
             "Complete" => Ok(PointerStatus::Complete),
+            "Skipped" => Ok(PointerStatus::Skipped),
             "Sleeping" => Ok(PointerStatus::Sleeping),
             "WaitingForEvent" => Ok(PointerStatus::WaitingForEvent),
             "Failed" => Ok(PointerStatus::Failed),

wfe-sqlite/Cargo.toml

@@ -3,6 +3,8 @@ name = "wfe-sqlite"
 version.workspace = true
 edition.workspace = true
 license.workspace = true
+repository.workspace = true
+homepage.workspace = true
 description = "SQLite persistence provider for WFE"
 
 [dependencies]

wfe-valkey/Cargo.toml

@@ -3,6 +3,8 @@ name = "wfe-valkey"
 version.workspace = true
 edition.workspace = true
 license.workspace = true
+repository.workspace = true
+homepage.workspace = true
 description = "Valkey/Redis provider for distributed locking, queues, and lifecycle events in WFE"
 
 [dependencies]

wfe-yaml/Cargo.toml

@@ -7,12 +7,15 @@ description = "YAML workflow definitions for WFE"
 [features]
 default = []
 deno = ["deno_core", "deno_error", "url", "reqwest"]
+buildkit = ["wfe-buildkit"]
+containerd = ["wfe-containerd"]
 
 [dependencies]
 wfe-core = { workspace = true }
 serde = { workspace = true }
 serde_json = { workspace = true }
 serde_yaml = { workspace = true }
+yaml-merge-keys = { workspace = true }
 async-trait = { workspace = true }
 tokio = { workspace = true }
 thiserror = { workspace = true }
@@ -22,6 +25,8 @@ deno_core = { workspace = true, optional = true }
 deno_error = { workspace = true, optional = true }
 url = { workspace = true, optional = true }
 reqwest = { workspace = true, optional = true }
+wfe-buildkit = { workspace = true, optional = true }
+wfe-containerd = { workspace = true, optional = true }
 
 [dev-dependencies]
 pretty_assertions = { workspace = true }

wfe-yaml/src/compiler.rs

@@ -1,5 +1,6 @@
 use std::time::Duration;
 
+use serde::Serialize;
 use wfe_core::models::error_behavior::ErrorBehavior;
 use wfe_core::models::workflow_definition::{StepOutcome, WorkflowDefinition, WorkflowStep};
 use wfe_core::traits::StepBody;
@@ -8,7 +9,22 @@ use crate::error::YamlWorkflowError;
 use crate::executors::shell::{ShellConfig, ShellStep};
 #[cfg(feature = "deno")]
 use crate::executors::deno::{DenoConfig, DenoPermissions, DenoStep};
-use crate::schema::{WorkflowSpec, YamlErrorBehavior, YamlStep};
+#[cfg(feature = "buildkit")]
+use wfe_buildkit::{BuildkitConfig, BuildkitStep};
+#[cfg(feature = "containerd")]
+use wfe_containerd::{ContainerdConfig, ContainerdStep};
+use wfe_core::primitives::sub_workflow::SubWorkflowStep;
+use wfe_core::models::condition::{ComparisonOp, FieldComparison, StepCondition};
+
+use crate::schema::{WorkflowSpec, YamlCombinator, YamlComparison, YamlCondition, YamlErrorBehavior, YamlStep};
+
+/// Configuration for a sub-workflow step.
+#[derive(Debug, Clone, Serialize)]
+pub struct SubWorkflowConfig {
+    pub workflow_id: String,
+    pub version: u32,
+    pub output_keys: Vec<String>,
+}
 
 /// Factory type alias for step creation closures.
 pub type StepFactory = Box<dyn Fn() -> Box<dyn StepBody> + Send + Sync>;
@@ -68,6 +84,11 @@ fn compile_steps(
                 compile_steps(parallel_children, definition, factories, next_id)?;
             container.children = child_ids;
 
+            // Compile condition if present.
+            if let Some(ref yaml_cond) = yaml_step.when {
+                container.when = Some(compile_condition(yaml_cond)?);
+            }
+
             definition.steps.push(container);
             main_step_ids.push(container_id);
         } else {
@@ -94,6 +115,11 @@ fn compile_steps(
                 wf_step.error_behavior = Some(map_error_behavior(eb)?);
             }
 
+            // Compile condition if present.
+            if let Some(ref yaml_cond) = yaml_step.when {
+                wf_step.when = Some(compile_condition(yaml_cond)?);
+            }
+
             // Handle on_failure: create compensation step.
             if let Some(ref on_failure) = yaml_step.on_failure {
                 let comp_id = *next_id;
@@ -216,6 +242,154 @@ fn compile_steps(
     Ok(main_step_ids)
 }
 
+/// Convert a YAML condition tree into a `StepCondition` tree.
+pub fn compile_condition(yaml_cond: &YamlCondition) -> Result<StepCondition, YamlWorkflowError> {
+    match yaml_cond {
+        YamlCondition::Comparison(cmp) => compile_comparison(cmp.as_ref()),
+        YamlCondition::Combinator(combinator) => compile_combinator(combinator),
+    }
+}
+
+fn compile_combinator(c: &YamlCombinator) -> Result<StepCondition, YamlWorkflowError> {
+    // Count how many combinator keys are set to detect ambiguity.
+    let mut count = 0;
+    if c.all.is_some() {
+        count += 1;
+    }
+    if c.any.is_some() {
+        count += 1;
+    }
+    if c.none.is_some() {
+        count += 1;
+    }
+    if c.one_of.is_some() {
+        count += 1;
+    }
+    if c.not.is_some() {
+        count += 1;
+    }
+
+    if count == 0 {
+        return Err(YamlWorkflowError::Compilation(
+            "Condition combinator must have at least one of: all, any, none, one_of, not"
+                .to_string(),
+        ));
+    }
+    if count > 1 {
+        return Err(YamlWorkflowError::Compilation(
+            "Condition combinator must have exactly one of: all, any, none, one_of, not"
+                .to_string(),
+        ));
+    }
+
+    if let Some(ref children) = c.all {
+        let compiled: Result<Vec<_>, _> = children.iter().map(compile_condition).collect();
+        Ok(StepCondition::All(compiled?))
+    } else if let Some(ref children) = c.any {
+        let compiled: Result<Vec<_>, _> = children.iter().map(compile_condition).collect();
+        Ok(StepCondition::Any(compiled?))
+    } else if let Some(ref children) = c.none {
+        let compiled: Result<Vec<_>, _> = children.iter().map(compile_condition).collect();
+        Ok(StepCondition::None(compiled?))
+    } else if let Some(ref children) = c.one_of {
+        let compiled: Result<Vec<_>, _> = children.iter().map(compile_condition).collect();
+        Ok(StepCondition::OneOf(compiled?))
+    } else if let Some(ref inner) = c.not {
+        Ok(StepCondition::Not(Box::new(compile_condition(inner)?)))
+    } else {
+        unreachable!()
+    }
+}
+
+fn compile_comparison(cmp: &YamlComparison) -> Result<StepCondition, YamlWorkflowError> {
+    // Determine which operator is specified. Exactly one must be present.
+    let mut ops: Vec<(ComparisonOp, Option<serde_json::Value>)> = Vec::new();
+
+    if let Some(ref v) = cmp.equals {
+        ops.push((ComparisonOp::Equals, Some(yaml_value_to_json(v))));
+    }
+    if let Some(ref v) = cmp.not_equals {
+        ops.push((ComparisonOp::NotEquals, Some(yaml_value_to_json(v))));
+    }
+    if let Some(ref v) = cmp.gt {
+        ops.push((ComparisonOp::Gt, Some(yaml_value_to_json(v))));
+    }
+    if let Some(ref v) = cmp.gte {
+        ops.push((ComparisonOp::Gte, Some(yaml_value_to_json(v))));
+    }
+    if let Some(ref v) = cmp.lt {
+        ops.push((ComparisonOp::Lt, Some(yaml_value_to_json(v))));
+    }
+    if let Some(ref v) = cmp.lte {
+        ops.push((ComparisonOp::Lte, Some(yaml_value_to_json(v))));
+    }
+    if let Some(ref v) = cmp.contains {
+        ops.push((ComparisonOp::Contains, Some(yaml_value_to_json(v))));
+    }
+    if let Some(true) = cmp.is_null {
+        ops.push((ComparisonOp::IsNull, None));
+    }
+    if let Some(true) = cmp.is_not_null {
+        ops.push((ComparisonOp::IsNotNull, None));
+    }
+
+    if ops.is_empty() {
+        return Err(YamlWorkflowError::Compilation(format!(
+            "Comparison on field '{}' must specify an operator (equals, gt, etc.)",
+            cmp.field
+        )));
+    }
+    if ops.len() > 1 {
+        return Err(YamlWorkflowError::Compilation(format!(
+            "Comparison on field '{}' must specify exactly one operator, found {}",
+            cmp.field,
+            ops.len()
+        )));
+    }
+
+    let (operator, value) = ops.remove(0);
+    Ok(StepCondition::Comparison(FieldComparison {
+        field: cmp.field.clone(),
+        operator,
+        value,
+    }))
+}
+
+/// Convert a serde_yaml::Value to serde_json::Value.
+fn yaml_value_to_json(v: &serde_yaml::Value) -> serde_json::Value {
+    match v {
+        serde_yaml::Value::Null => serde_json::Value::Null,
+        serde_yaml::Value::Bool(b) => serde_json::Value::Bool(*b),
+        serde_yaml::Value::Number(n) => {
+            if let Some(i) = n.as_i64() {
+                serde_json::Value::Number(serde_json::Number::from(i))
+            } else if let Some(u) = n.as_u64() {
+                serde_json::Value::Number(serde_json::Number::from(u))
+            } else if let Some(f) = n.as_f64() {
+                serde_json::Number::from_f64(f)
+                    .map(serde_json::Value::Number)
+                    .unwrap_or(serde_json::Value::Null)
+            } else {
+                serde_json::Value::Null
+            }
+        }
+        serde_yaml::Value::String(s) => serde_json::Value::String(s.clone()),
+        serde_yaml::Value::Sequence(seq) => {
+            serde_json::Value::Array(seq.iter().map(yaml_value_to_json).collect())
+        }
+        serde_yaml::Value::Mapping(map) => {
+            let mut obj = serde_json::Map::new();
+            for (k, val) in map {
+                if let serde_yaml::Value::String(key) = k {
+                    obj.insert(key.clone(), yaml_value_to_json(val));
+                }
+            }
+            serde_json::Value::Object(obj)
+        }
+        serde_yaml::Value::Tagged(tagged) => yaml_value_to_json(&tagged.value),
+    }
+}
+
 fn build_step_config_and_factory(
     step: &YamlStep,
     step_type: &str,
@@ -250,6 +424,76 @@ fn build_step_config_and_factory(
             });
             Ok((key, value, factory))
         }
+        #[cfg(feature = "buildkit")]
+        "buildkit" => {
+            let config = build_buildkit_config(step)?;
+            let key = format!("wfe_yaml::buildkit::{}", step.name);
+            let value = serde_json::to_value(&config).map_err(|e| {
+                YamlWorkflowError::Compilation(format!(
+                    "Failed to serialize buildkit config: {e}"
+                ))
+            })?;
+            let config_clone = config.clone();
+            let factory: StepFactory = Box::new(move || {
+                Box::new(BuildkitStep::new(config_clone.clone())) as Box<dyn StepBody>
+            });
+            Ok((key, value, factory))
+        }
+        #[cfg(feature = "containerd")]
+        "containerd" => {
+            let config = build_containerd_config(step)?;
+            let key = format!("wfe_yaml::containerd::{}", step.name);
+            let value = serde_json::to_value(&config).map_err(|e| {
+                YamlWorkflowError::Compilation(format!(
+                    "Failed to serialize containerd config: {e}"
+                ))
+            })?;
+            let config_clone = config.clone();
+            let factory: StepFactory = Box::new(move || {
+                Box::new(ContainerdStep::new(config_clone.clone())) as Box<dyn StepBody>
+            });
+            Ok((key, value, factory))
+        }
+        "workflow" => {
+            let config = step.config.as_ref().ok_or_else(|| {
+                YamlWorkflowError::Compilation(format!(
+                    "Workflow step '{}' is missing 'config' section",
+                    step.name
+                ))
+            })?;
+            let child_workflow_id = config.child_workflow.as_ref().ok_or_else(|| {
+                YamlWorkflowError::Compilation(format!(
+                    "Workflow step '{}' must have 'config.workflow'",
+                    step.name
+                ))
+            })?;
+            let child_version = config.child_version.unwrap_or(1);
+
+            let sub_config = SubWorkflowConfig {
+                workflow_id: child_workflow_id.clone(),
+                version: child_version,
+                output_keys: step.outputs.iter().map(|o| o.name.clone()).collect(),
+            };
+
+            let key = format!("wfe_yaml::workflow::{}", step.name);
+            let value = serde_json::to_value(&sub_config).map_err(|e| {
+                YamlWorkflowError::Compilation(format!(
+                    "Failed to serialize workflow config: {e}"
+                ))
+            })?;
+            let config_clone = sub_config.clone();
+            let factory: StepFactory = Box::new(move || {
+                Box::new(SubWorkflowStep {
+                    workflow_id: config_clone.workflow_id.clone(),
+                    version: config_clone.version,
+                    output_keys: config_clone.output_keys.clone(),
+                    inputs: serde_json::Value::Null,
+                    input_schema: None,
+                    output_schema: None,
+                }) as Box<dyn StepBody>
+            });
+            Ok((key, value, factory))
+        }
         other => Err(YamlWorkflowError::Compilation(format!(
             "Unknown step type: '{other}'"
         ))),
@@ -346,6 +590,162 @@ fn parse_duration_ms(s: &str) -> Option<u64> {
     }
 }
 
+#[cfg(feature = "buildkit")]
+fn build_buildkit_config(
+    step: &YamlStep,
+) -> Result<BuildkitConfig, YamlWorkflowError> {
+    let config = step.config.as_ref().ok_or_else(|| {
+        YamlWorkflowError::Compilation(format!(
+            "BuildKit step '{}' is missing 'config' section",
+            step.name
+        ))
+    })?;
+
+    let dockerfile = config.dockerfile.clone().ok_or_else(|| {
+        YamlWorkflowError::Compilation(format!(
+            "BuildKit step '{}' must have 'config.dockerfile'",
+            step.name
+        ))
+    })?;
+
+    let context = config.context.clone().ok_or_else(|| {
+        YamlWorkflowError::Compilation(format!(
+            "BuildKit step '{}' must have 'config.context'",
+            step.name
+        ))
+    })?;
+
+    let timeout_ms = config.timeout.as_ref().and_then(|t| parse_duration_ms(t));
+
+    let tls = config
+        .tls
+        .as_ref()
+        .map(|t| wfe_buildkit::TlsConfig {
+            ca: t.ca.clone(),
+            cert: t.cert.clone(),
+            key: t.key.clone(),
+        })
+        .unwrap_or_default();
+
+    let registry_auth = config
+        .registry_auth
+        .as_ref()
+        .map(|ra| {
+            ra.iter()
+                .map(|(k, v)| {
+                    (
+                        k.clone(),
+                        wfe_buildkit::RegistryAuth {
+                            username: v.username.clone(),
+                            password: v.password.clone(),
+                        },
+                    )
+                })
+                .collect()
+        })
+        .unwrap_or_default();
+
+    Ok(BuildkitConfig {
+        dockerfile,
+        context,
+        target: config.target.clone(),
+        tags: config.tags.clone(),
+        build_args: config.build_args.clone(),
+        cache_from: config.cache_from.clone(),
+        cache_to: config.cache_to.clone(),
+        push: config.push.unwrap_or(false),
+        output_type: None,
+        buildkit_addr: config
+            .buildkit_addr
+            .clone()
+            .unwrap_or_else(|| "unix:///run/buildkit/buildkitd.sock".to_string()),
+        tls,
+        registry_auth,
+        timeout_ms,
+    })
+}
+
+#[cfg(feature = "containerd")]
+fn build_containerd_config(
+    step: &YamlStep,
+) -> Result<ContainerdConfig, YamlWorkflowError> {
+    let config = step.config.as_ref().ok_or_else(|| {
+        YamlWorkflowError::Compilation(format!(
+            "Containerd step '{}' is missing 'config' section",
+            step.name
+        ))
+    })?;
+
+    let image = config.image.clone().ok_or_else(|| {
+        YamlWorkflowError::Compilation(format!(
+            "Containerd step '{}' must have 'config.image'",
+            step.name
+        ))
+    })?;
+
+    let timeout_ms = config.timeout.as_ref().and_then(|t| parse_duration_ms(t));
+
+    let tls = config
+        .tls
+        .as_ref()
+        .map(|t| wfe_containerd::TlsConfig {
+            ca: t.ca.clone(),
+            cert: t.cert.clone(),
+            key: t.key.clone(),
+        })
+        .unwrap_or_default();
+
+    let registry_auth = config
+        .registry_auth
+        .as_ref()
+        .map(|ra| {
+            ra.iter()
+                .map(|(k, v)| {
+                    (
+                        k.clone(),
+                        wfe_containerd::RegistryAuth {
+                            username: v.username.clone(),
+                            password: v.password.clone(),
+                        },
+                    )
+                })
+                .collect()
+        })
+        .unwrap_or_default();
+
+    let volumes = config
+        .volumes
+        .iter()
+        .map(|v| wfe_containerd::VolumeMountConfig {
+            source: v.source.clone(),
+            target: v.target.clone(),
+            readonly: v.readonly,
+        })
+        .collect();
+
+    Ok(ContainerdConfig {
+        image,
+        command: config.command.clone(),
+        run: config.run.clone(),
+        env: config.env.clone(),
+        volumes,
+        working_dir: config.working_dir.clone(),
+        user: config.user.clone().unwrap_or_else(|| "65534:65534".to_string()),
+        network: config.network.clone().unwrap_or_else(|| "none".to_string()),
+        memory: config.memory.clone(),
+        cpu: config.cpu.clone(),
+        pull: config.pull.clone().unwrap_or_else(|| "if-not-present".to_string()),
+        containerd_addr: config
+            .containerd_addr
+            .clone()
+            .unwrap_or_else(|| "/run/containerd/containerd.sock".to_string()),
+        cli: config.cli.clone().unwrap_or_else(|| "nerdctl".to_string()),
+        tls,
+        registry_auth,
+        timeout_ms,
+    })
+}
+
 fn map_error_behavior(eb: &YamlErrorBehavior) -> Result<ErrorBehavior, YamlWorkflowError> {
     match eb.behavior_type.as_str() {
         "retry" => {

wfe-yaml/src/executors/deno/js/bootstrap.js

@@ -2,6 +2,10 @@ globalThis.inputs = () => Deno.core.ops.op_inputs();
 globalThis.output = (key, value) => Deno.core.ops.op_output(key, value);
 globalThis.log = (msg) => Deno.core.ops.op_log(msg);
 
+globalThis.readFile = async (path) => {
+    return await Deno.core.ops.op_read_file(path);
+};
+
 globalThis.fetch = async (url, options) => {
     const resp = await Deno.core.ops.op_fetch(url, options || null);
     return {

wfe-yaml/src/executors/deno/ops/workflow.rs

@@ -44,9 +44,29 @@ pub fn op_log(state: &mut OpState, #[string] msg: String) {
     tracing::info!(step = %name, "{}", msg);
 }
 
+/// Reads a file from the filesystem and returns its contents as a string.
+/// Permission-checked against the read allowlist.
+#[op2]
+#[string]
+pub async fn op_read_file(
+    state: std::rc::Rc<std::cell::RefCell<OpState>>,
+    #[string] path: String,
+) -> Result<String, deno_error::JsErrorBox> {
+    // Check read permission
+    {
+        let s = state.borrow();
+        let checker = s.borrow::<super::super::permissions::PermissionChecker>();
+        checker.check_read(&path)
+            .map_err(|e| deno_error::JsErrorBox::new("PermissionError", e.to_string()))?;
+    }
+    tokio::fs::read_to_string(&path)
+        .await
+        .map_err(|e| deno_error::JsErrorBox::generic(format!("Failed to read file '{path}': {e}")))
+}
+
 deno_core::extension!(
     wfe_ops,
-    ops = [op_inputs, op_output, op_log, super::http::op_fetch],
+    ops = [op_inputs, op_output, op_log, op_read_file, super::http::op_fetch],
     esm_entry_point = "ext:wfe/bootstrap.js",
     esm = ["ext:wfe/bootstrap.js" = "src/executors/deno/js/bootstrap.js"],
 );

wfe-yaml/src/executors/shell.rs

@@ -92,8 +92,21 @@ impl StepBody for ShellStep {
                 && let Some(eq_pos) = rest.find('=')
             {
                 let name = rest[..eq_pos].trim().to_string();
-                let value = rest[eq_pos + 1..].to_string();
-                outputs.insert(name, serde_json::Value::String(value));
+                let raw_value = rest[eq_pos + 1..].to_string();
+                // Auto-convert typed values from string annotations
+                let value = match raw_value.as_str() {
+                    "true" => serde_json::Value::Bool(true),
+                    "false" => serde_json::Value::Bool(false),
+                    "null" => serde_json::Value::Null,
+                    s if s.parse::<i64>().is_ok() => {
+                        serde_json::Value::Number(s.parse::<i64>().unwrap().into())
+                    }
+                    s if s.parse::<f64>().is_ok() => {
+                        serde_json::json!(s.parse::<f64>().unwrap())
+                    }
+                    _ => serde_json::Value::String(raw_value),
+                };
+                outputs.insert(name, value);
             }
         }
 

wfe-yaml/src/lib.rs

@@ -3,36 +3,219 @@ pub mod error;
 pub mod executors;
 pub mod interpolation;
 pub mod schema;
+pub mod types;
 pub mod validation;
 
-use std::collections::HashMap;
+use std::collections::{HashMap, HashSet};
+use std::path::Path;
+
+use serde::de::Error as _;
+use serde::Deserialize;
 
 use crate::compiler::CompiledWorkflow;
 use crate::error::YamlWorkflowError;
 
-/// Load a workflow from a YAML file path, applying variable interpolation.
+/// Top-level YAML file with optional includes.
+#[derive(Deserialize)]
+pub struct YamlWorkflowFileWithIncludes {
+    #[serde(default)]
+    pub include: Vec<String>,
+    #[serde(flatten)]
+    pub file: schema::YamlWorkflowFile,
+}
+
+/// Load workflows from a YAML file path, applying variable interpolation.
+/// Returns a Vec of compiled workflows (supports multi-workflow files).
 pub fn load_workflow(
     path: &std::path::Path,
     config: &HashMap<String, serde_json::Value>,
 ) -> Result<CompiledWorkflow, YamlWorkflowError> {
     let yaml = std::fs::read_to_string(path)?;
-    load_workflow_from_str(&yaml, config)
+    load_single_workflow_from_str(&yaml, config)
 }
 
-/// Load a workflow from a YAML string, applying variable interpolation.
+/// Load workflows from a YAML string, applying variable interpolation.
+/// Returns a Vec of compiled workflows (supports multi-workflow files).
+///
+/// Supports YAML 1.1 merge keys (`<<: *anchor`) via the `yaml-merge-keys`
+/// crate. serde_yaml 0.9 implements YAML 1.2 which dropped merge keys;
+/// we preprocess the YAML to resolve them before deserialization.
 pub fn load_workflow_from_str(
     yaml: &str,
     config: &HashMap<String, serde_json::Value>,
-) -> Result<CompiledWorkflow, YamlWorkflowError> {
+) -> Result<Vec<CompiledWorkflow>, YamlWorkflowError> {
     // Interpolate variables.
     let interpolated = interpolation::interpolate(yaml, config)?;
 
-    // Parse YAML.
-    let workflow: schema::YamlWorkflow = serde_yaml::from_str(&interpolated)?;
+    // Parse to a generic YAML value first, then resolve merge keys (<<:).
+    // This adds YAML 1.1 merge key support on top of serde_yaml 0.9's YAML 1.2 parser.
+    let raw_value: serde_yaml::Value = serde_yaml::from_str(&interpolated)?;
+    let merged_value = yaml_merge_keys::merge_keys_serde(raw_value)
+        .map_err(|e| YamlWorkflowError::Parse(serde_yaml::Error::custom(format!("merge key resolution failed: {e}"))))?;
 
-    // Validate.
-    validation::validate(&workflow.workflow)?;
+    // Deserialize the merge-resolved value into our schema.
+    let file: schema::YamlWorkflowFile = serde_yaml::from_value(merged_value)?;
 
-    // Compile.
-    compiler::compile(&workflow.workflow)
+    let specs = resolve_workflow_specs(file)?;
+
+    // Validate (multi-workflow validation includes per-workflow + cross-references).
+    validation::validate_multi(&specs)?;
+
+    // Compile each workflow.
+    let mut results = Vec::with_capacity(specs.len());
+    for spec in &specs {
+        results.push(compiler::compile(spec)?);
+    }
+
+    Ok(results)
+}
+
+/// Load a single workflow from a YAML string. Returns an error if the file
+/// contains more than one workflow. This is a backward-compatible convenience
+/// function.
+pub fn load_single_workflow_from_str(
+    yaml: &str,
+    config: &HashMap<String, serde_json::Value>,
+) -> Result<CompiledWorkflow, YamlWorkflowError> {
+    let mut workflows = load_workflow_from_str(yaml, config)?;
+    if workflows.len() != 1 {
+        return Err(YamlWorkflowError::Validation(format!(
+            "Expected single workflow, got {}",
+            workflows.len()
+        )));
+    }
+    Ok(workflows.remove(0))
+}
+
+/// Load workflows from a YAML string, resolving `include:` paths relative to `base_path`.
+///
+/// Processing:
+/// 1. Parse the main YAML to get `include:` paths.
+/// 2. For each include path, load and parse that YAML file.
+/// 3. Merge workflow specs from included files into the main file's specs.
+/// 4. Main file's workflows take precedence over included ones (by ID).
+/// 5. Proceed with normal validation + compilation.
+pub fn load_workflow_with_includes(
+    yaml: &str,
+    base_path: &Path,
+    config: &HashMap<String, serde_json::Value>,
+) -> Result<Vec<CompiledWorkflow>, YamlWorkflowError> {
+    let mut visited = HashSet::new();
+    let canonical = base_path
+        .canonicalize()
+        .unwrap_or_else(|_| base_path.to_path_buf());
+    visited.insert(canonical.to_string_lossy().to_string());
+
+    let interpolated = interpolation::interpolate(yaml, config)?;
+    let raw_value: serde_yaml::Value = serde_yaml::from_str(&interpolated)?;
+    let merged_value = yaml_merge_keys::merge_keys_serde(raw_value)
+        .map_err(|e| {
+            YamlWorkflowError::Parse(serde_yaml::Error::custom(format!(
+                "merge key resolution failed: {e}"
+            )))
+        })?;
+
+    let with_includes: YamlWorkflowFileWithIncludes = serde_yaml::from_value(merged_value)?;
+
+    let mut main_specs = resolve_workflow_specs(with_includes.file)?;
+
+    // Process includes.
+    for include_path_str in &with_includes.include {
+        let include_path = base_path.parent().unwrap_or(base_path).join(include_path_str);
+        load_includes_recursive(
+            &include_path,
+            config,
+            &mut main_specs,
+            &mut visited,
+        )?;
+    }
+
+    // Main file takes precedence: included specs are only added if their ID
+    // isn't already present. This is handled by load_includes_recursive.
+
+    validation::validate_multi(&main_specs)?;
+
+    let mut results = Vec::with_capacity(main_specs.len());
+    for spec in &main_specs {
+        results.push(compiler::compile(spec)?);
+    }
+
+    Ok(results)
+}
+
+fn load_includes_recursive(
+    path: &Path,
+    config: &HashMap<String, serde_json::Value>,
+    specs: &mut Vec<schema::WorkflowSpec>,
+    visited: &mut HashSet<String>,
+) -> Result<(), YamlWorkflowError> {
+    let canonical = path
+        .canonicalize()
+        .map_err(|e| {
+            YamlWorkflowError::Io(std::io::Error::new(
+                std::io::ErrorKind::NotFound,
+                format!("Include file not found: {}: {e}", path.display()),
+            ))
+        })?;
+
+    let canonical_str = canonical.to_string_lossy().to_string();
+    if !visited.insert(canonical_str.clone()) {
+        return Err(YamlWorkflowError::Validation(format!(
+            "Circular include detected: '{}'",
+            path.display()
+        )));
+    }
+
+    let yaml = std::fs::read_to_string(&canonical)?;
+    let interpolated = interpolation::interpolate(&yaml, config)?;
+    let raw_value: serde_yaml::Value = serde_yaml::from_str(&interpolated)?;
+    let merged_value = yaml_merge_keys::merge_keys_serde(raw_value)
+        .map_err(|e| {
+            YamlWorkflowError::Parse(serde_yaml::Error::custom(format!(
+                "merge key resolution failed: {e}"
+            )))
+        })?;
+
+    let with_includes: YamlWorkflowFileWithIncludes = serde_yaml::from_value(merged_value)?;
+
+    let included_specs = resolve_workflow_specs(with_includes.file)?;
+
+    // Existing IDs in main specs take precedence.
+    let existing_ids: HashSet<String> = specs.iter().map(|s| s.id.clone()).collect();
+    for spec in included_specs {
+        if !existing_ids.contains(&spec.id) {
+            specs.push(spec);
+        }
+    }
+
+    // Recurse into nested includes.
+    for nested_include in &with_includes.include {
+        let nested_path = canonical.parent().unwrap_or(&canonical).join(nested_include);
+        load_includes_recursive(&nested_path, config, specs, visited)?;
+    }
+
+    Ok(())
+}
+
+/// Resolve a YamlWorkflowFile into a list of WorkflowSpecs.
+fn resolve_workflow_specs(
+    file: schema::YamlWorkflowFile,
+) -> Result<Vec<schema::WorkflowSpec>, YamlWorkflowError> {
+    match (file.workflow, file.workflows) {
+        (Some(single), None) => Ok(vec![single]),
+        (None, Some(multi)) => {
+            if multi.is_empty() {
+                return Err(YamlWorkflowError::Validation(
+                    "workflows list is empty".to_string(),
+                ));
+            }
+            Ok(multi)
+        }
+        (Some(_), Some(_)) => Err(YamlWorkflowError::Validation(
+            "Cannot specify both 'workflow' and 'workflows' in the same file".to_string(),
+        )),
+        (None, None) => Err(YamlWorkflowError::Validation(
+            "Must specify either 'workflow' or 'workflows'".to_string(),
+        )),
+    }
 }

wfe-yaml/src/schema.rs

@@ -2,6 +2,70 @@ use std::collections::HashMap;
 
 use serde::Deserialize;
 
+/// A condition in YAML that determines whether a step executes.
+///
+/// Uses `#[serde(untagged)]` so serde tries each variant in order.
+/// A comparison has a `field:` key; a combinator has `all:/any:/none:/one_of:/not:`.
+/// Comparison is listed first because it is more specific (requires `field`).
+#[derive(Debug, Deserialize, Clone)]
+#[serde(untagged)]
+pub enum YamlCondition {
+    /// Leaf comparison (has a `field:` key).
+    Comparison(Box<YamlComparison>),
+    /// Combinator with sub-conditions.
+    Combinator(YamlCombinator),
+}
+
+/// A combinator condition containing sub-conditions.
+#[derive(Debug, Deserialize, Clone)]
+pub struct YamlCombinator {
+    #[serde(default)]
+    pub all: Option<Vec<YamlCondition>>,
+    #[serde(default)]
+    pub any: Option<Vec<YamlCondition>>,
+    #[serde(default)]
+    pub none: Option<Vec<YamlCondition>>,
+    #[serde(default)]
+    pub one_of: Option<Vec<YamlCondition>>,
+    #[serde(default)]
+    pub not: Option<Box<YamlCondition>>,
+}
+
+/// A leaf comparison condition that compares a field value.
+#[derive(Debug, Deserialize, Clone)]
+pub struct YamlComparison {
+    pub field: String,
+    #[serde(default)]
+    pub equals: Option<serde_yaml::Value>,
+    #[serde(default)]
+    pub not_equals: Option<serde_yaml::Value>,
+    #[serde(default)]
+    pub gt: Option<serde_yaml::Value>,
+    #[serde(default)]
+    pub gte: Option<serde_yaml::Value>,
+    #[serde(default)]
+    pub lt: Option<serde_yaml::Value>,
+    #[serde(default)]
+    pub lte: Option<serde_yaml::Value>,
+    #[serde(default)]
+    pub contains: Option<serde_yaml::Value>,
+    #[serde(default)]
+    pub is_null: Option<bool>,
+    #[serde(default)]
+    pub is_not_null: Option<bool>,
+}
+
+/// Top-level YAML file structure supporting both single and multi-workflow files.
+#[derive(Debug, Deserialize)]
+pub struct YamlWorkflowFile {
+    /// Single workflow (backward compatible).
+    pub workflow: Option<WorkflowSpec>,
+    /// Multiple workflows in one file.
+    pub workflows: Option<Vec<WorkflowSpec>>,
+}
+
+/// Legacy single-workflow top-level structure. Kept for backward compatibility
+/// with code that deserializes `YamlWorkflow` directly.
 #[derive(Debug, Deserialize)]
 pub struct YamlWorkflow {
     pub workflow: WorkflowSpec,
@@ -16,6 +80,13 @@ pub struct WorkflowSpec {
     #[serde(default)]
     pub error_behavior: Option<YamlErrorBehavior>,
     pub steps: Vec<YamlStep>,
+    /// Typed input schema: { field_name: type_string }.
+    /// Example: `"repo_url": "string"`, `"tags": "list<string>"`.
+    #[serde(default)]
+    pub inputs: HashMap<String, String>,
+    /// Typed output schema: { field_name: type_string }.
+    #[serde(default)]
+    pub outputs: HashMap<String, String>,
     /// Allow unknown top-level keys (e.g. `_templates`) for YAML anchors.
     #[serde(flatten)]
     pub _extra: HashMap<String, serde_yaml::Value>,
@@ -42,6 +113,9 @@ pub struct YamlStep {
     pub on_failure: Option<Box<YamlStep>>,
     #[serde(default)]
     pub ensure: Option<Box<YamlStep>>,
+    /// Optional condition that must be true for this step to execute.
+    #[serde(default)]
+    pub when: Option<YamlCondition>,
 }
 
 #[derive(Debug, Deserialize, Clone)]
@@ -58,6 +132,45 @@ pub struct StepConfig {
     pub permissions: Option<DenoPermissionsYaml>,
     #[serde(default)]
     pub modules: Vec<String>,
+    // BuildKit fields
+    pub dockerfile: Option<String>,
+    pub context: Option<String>,
+    pub target: Option<String>,
+    #[serde(default)]
+    pub tags: Vec<String>,
+    #[serde(default)]
+    pub build_args: HashMap<String, String>,
+    #[serde(default)]
+    pub cache_from: Vec<String>,
+    #[serde(default)]
+    pub cache_to: Vec<String>,
+    pub push: Option<bool>,
+    pub buildkit_addr: Option<String>,
+    #[serde(default)]
+    pub tls: Option<TlsConfigYaml>,
+    #[serde(default)]
+    pub registry_auth: Option<HashMap<String, RegistryAuthYaml>>,
+    // Containerd fields
+    pub image: Option<String>,
+    #[serde(default)]
+    pub command: Option<Vec<String>>,
+    #[serde(default)]
+    pub volumes: Vec<VolumeMountYaml>,
+    pub user: Option<String>,
+    pub network: Option<String>,
+    pub memory: Option<String>,
+    pub cpu: Option<String>,
+    pub pull: Option<String>,
+    pub containerd_addr: Option<String>,
+    /// CLI binary name for containerd steps: "nerdctl" (default) or "docker".
+    pub cli: Option<String>,
+    // Workflow (sub-workflow) fields
+    /// Child workflow ID (for `type: workflow` steps).
+    #[serde(rename = "workflow")]
+    pub child_workflow: Option<String>,
+    /// Child workflow version (for `type: workflow` steps).
+    #[serde(rename = "workflow_version")]
+    pub child_version: Option<u32>,
 }
 
 /// YAML-level permission configuration for Deno steps.
@@ -84,6 +197,30 @@ pub struct DataRef {
     pub json_path: Option<String>,
 }
 
+/// YAML-level TLS configuration for BuildKit steps.
+#[derive(Debug, Deserialize, Clone)]
+pub struct TlsConfigYaml {
+    pub ca: Option<String>,
+    pub cert: Option<String>,
+    pub key: Option<String>,
+}
+
+/// YAML-level registry auth configuration for BuildKit steps.
+#[derive(Debug, Deserialize, Clone)]
+pub struct RegistryAuthYaml {
+    pub username: String,
+    pub password: String,
+}
+
+/// YAML-level volume mount configuration for containerd steps.
+#[derive(Debug, Deserialize, Clone)]
+pub struct VolumeMountYaml {
+    pub source: String,
+    pub target: String,
+    #[serde(default)]
+    pub readonly: bool,
+}
+
 #[derive(Debug, Deserialize)]
 pub struct YamlErrorBehavior {
     #[serde(rename = "type")]

wfe-yaml/src/types.rs

@@ -0,0 +1,252 @@
+/// Parsed type representation for workflow input/output schemas.
+///
+/// This mirrors what wfe-core's `SchemaType` will provide, but is self-contained
+/// so wfe-yaml can parse type strings without depending on wfe-core's schema module.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum SchemaType {
+    String,
+    Number,
+    Integer,
+    Bool,
+    Any,
+    Optional(Box<SchemaType>),
+    List(Box<SchemaType>),
+    Map(Box<SchemaType>),
+}
+
+impl std::fmt::Display for SchemaType {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            SchemaType::String => write!(f, "string"),
+            SchemaType::Number => write!(f, "number"),
+            SchemaType::Integer => write!(f, "integer"),
+            SchemaType::Bool => write!(f, "bool"),
+            SchemaType::Any => write!(f, "any"),
+            SchemaType::Optional(inner) => write!(f, "{inner}?"),
+            SchemaType::List(inner) => write!(f, "list<{inner}>"),
+            SchemaType::Map(inner) => write!(f, "map<{inner}>"),
+        }
+    }
+}
+
+/// Parse a type string like `"string"`, `"string?"`, `"list<number>"`, `"map<string>"`.
+///
+/// Supports:
+/// - Primitives: `"string"`, `"number"`, `"integer"`, `"bool"`, `"any"`
+/// - Optional: `"string?"` -> `Optional(String)`
+/// - List: `"list<string>"` -> `List(String)`
+/// - Map: `"map<number>"` -> `Map(Number)`
+/// - Nested generics: `"list<list<string>>"` -> `List(List(String))`
+pub fn parse_type_string(s: &str) -> Result<SchemaType, String> {
+    let s = s.trim();
+    if s.is_empty() {
+        return Err("Empty type string".to_string());
+    }
+
+    // Check for optional suffix (but not inside generics).
+    if s.ends_with('?') && !s.ends_with(">?") {
+        // Simple optional like "string?"
+        let inner = parse_type_string(&s[..s.len() - 1])?;
+        return Ok(SchemaType::Optional(Box::new(inner)));
+    }
+
+    // Handle optional on generic types like "list<string>?"
+    if s.ends_with(">?") {
+        let inner = parse_type_string(&s[..s.len() - 1])?;
+        return Ok(SchemaType::Optional(Box::new(inner)));
+    }
+
+    // Check for generic types: list<...> or map<...>
+    if let Some(inner_start) = s.find('<') {
+        if !s.ends_with('>') {
+            return Err(format!("Malformed generic type: '{s}' (missing closing '>')"));
+        }
+        let container = &s[..inner_start];
+        let inner_str = &s[inner_start + 1..s.len() - 1];
+
+        let inner_type = parse_type_string(inner_str)?;
+
+        match container {
+            "list" => Ok(SchemaType::List(Box::new(inner_type))),
+            "map" => Ok(SchemaType::Map(Box::new(inner_type))),
+            other => Err(format!("Unknown generic type: '{other}'")),
+        }
+    } else {
+        // Primitive types.
+        match s {
+            "string" => Ok(SchemaType::String),
+            "number" => Ok(SchemaType::Number),
+            "integer" => Ok(SchemaType::Integer),
+            "bool" => Ok(SchemaType::Bool),
+            "any" => Ok(SchemaType::Any),
+            other => Err(format!("Unknown type: '{other}'")),
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parse_primitive_string() {
+        assert_eq!(parse_type_string("string").unwrap(), SchemaType::String);
+    }
+
+    #[test]
+    fn parse_primitive_number() {
+        assert_eq!(parse_type_string("number").unwrap(), SchemaType::Number);
+    }
+
+    #[test]
+    fn parse_primitive_integer() {
+        assert_eq!(parse_type_string("integer").unwrap(), SchemaType::Integer);
+    }
+
+    #[test]
+    fn parse_primitive_bool() {
+        assert_eq!(parse_type_string("bool").unwrap(), SchemaType::Bool);
+    }
+
+    #[test]
+    fn parse_primitive_any() {
+        assert_eq!(parse_type_string("any").unwrap(), SchemaType::Any);
+    }
+
+    #[test]
+    fn parse_optional_string() {
+        assert_eq!(
+            parse_type_string("string?").unwrap(),
+            SchemaType::Optional(Box::new(SchemaType::String))
+        );
+    }
+
+    #[test]
+    fn parse_optional_number() {
+        assert_eq!(
+            parse_type_string("number?").unwrap(),
+            SchemaType::Optional(Box::new(SchemaType::Number))
+        );
+    }
+
+    #[test]
+    fn parse_list_string() {
+        assert_eq!(
+            parse_type_string("list<string>").unwrap(),
+            SchemaType::List(Box::new(SchemaType::String))
+        );
+    }
+
+    #[test]
+    fn parse_map_number() {
+        assert_eq!(
+            parse_type_string("map<number>").unwrap(),
+            SchemaType::Map(Box::new(SchemaType::Number))
+        );
+    }
+
+    #[test]
+    fn parse_nested_list() {
+        assert_eq!(
+            parse_type_string("list<list<string>>").unwrap(),
+            SchemaType::List(Box::new(SchemaType::List(Box::new(SchemaType::String))))
+        );
+    }
+
+    #[test]
+    fn parse_nested_map_in_list() {
+        assert_eq!(
+            parse_type_string("list<map<integer>>").unwrap(),
+            SchemaType::List(Box::new(SchemaType::Map(Box::new(SchemaType::Integer))))
+        );
+    }
+
+    #[test]
+    fn parse_optional_list() {
+        assert_eq!(
+            parse_type_string("list<string>?").unwrap(),
+            SchemaType::Optional(Box::new(SchemaType::List(Box::new(SchemaType::String))))
+        );
+    }
+
+    #[test]
+    fn parse_unknown_type_error() {
+        let result = parse_type_string("foobar");
+        assert!(result.is_err());
+        assert!(result.unwrap_err().contains("Unknown type"));
+    }
+
+    #[test]
+    fn parse_unknown_generic_error() {
+        let result = parse_type_string("set<string>");
+        assert!(result.is_err());
+        assert!(result.unwrap_err().contains("Unknown generic type"));
+    }
+
+    #[test]
+    fn parse_empty_string_error() {
+        let result = parse_type_string("");
+        assert!(result.is_err());
+        assert!(result.unwrap_err().contains("Empty type string"));
+    }
+
+    #[test]
+    fn parse_malformed_generic_error() {
+        let result = parse_type_string("list<string");
+        assert!(result.is_err());
+        assert!(result.unwrap_err().contains("Malformed generic type"));
+    }
+
+    #[test]
+    fn parse_whitespace_trimmed() {
+        assert_eq!(parse_type_string("  string  ").unwrap(), SchemaType::String);
+    }
+
+    #[test]
+    fn parse_deeply_nested() {
+        assert_eq!(
+            parse_type_string("list<list<list<bool>>>").unwrap(),
+            SchemaType::List(Box::new(SchemaType::List(Box::new(SchemaType::List(
+                Box::new(SchemaType::Bool)
+            )))))
+        );
+    }
+
+    #[test]
+    fn display_roundtrip_primitives() {
+        for type_str in &["string", "number", "integer", "bool", "any"] {
+            let parsed = parse_type_string(type_str).unwrap();
+            assert_eq!(parsed.to_string(), *type_str);
+        }
+    }
+
+    #[test]
+    fn display_roundtrip_generics() {
+        for type_str in &["list<string>", "map<number>", "list<list<string>>"] {
+            let parsed = parse_type_string(type_str).unwrap();
+            assert_eq!(parsed.to_string(), *type_str);
+        }
+    }
+
+    #[test]
+    fn display_optional() {
+        let t = SchemaType::Optional(Box::new(SchemaType::String));
+        assert_eq!(t.to_string(), "string?");
+    }
+
+    #[test]
+    fn parse_map_any() {
+        assert_eq!(
+            parse_type_string("map<any>").unwrap(),
+            SchemaType::Map(Box::new(SchemaType::Any))
+        );
+    }
+
+    #[test]
+    fn parse_optional_bool() {
+        assert_eq!(
+            parse_type_string("bool?").unwrap(),
+            SchemaType::Optional(Box::new(SchemaType::Bool))
+        );
+    }
+}

wfe-yaml/src/validation.rs

@@ -1,7 +1,8 @@
-use std::collections::HashSet;
+use std::collections::{HashMap, HashSet};
 
 use crate::error::YamlWorkflowError;
-use crate::schema::{WorkflowSpec, YamlStep};
+use crate::schema::{WorkflowSpec, YamlCombinator, YamlComparison, YamlCondition, YamlStep};
+use crate::types::{parse_type_string, SchemaType};
 
 /// Validate a parsed workflow spec.
 pub fn validate(spec: &WorkflowSpec) -> Result<(), YamlWorkflowError> {
@@ -19,6 +20,149 @@ pub fn validate(spec: &WorkflowSpec) -> Result<(), YamlWorkflowError> {
         validate_error_behavior_type(&eb.behavior_type)?;
     }
 
+    // Collect known outputs (from step output data refs).
+    let known_outputs: HashSet<String> = collect_step_outputs(&spec.steps);
+
+    // Validate condition fields and types on all steps.
+    validate_step_conditions(&spec.steps, spec, &known_outputs)?;
+
+    // Detect unused declared outputs.
+    detect_unused_outputs(spec, &known_outputs)?;
+
+    Ok(())
+}
+
+/// Validate multiple workflow specs from a multi-workflow file.
+/// Checks cross-workflow references and cycles in addition to per-workflow validation.
+pub fn validate_multi(specs: &[WorkflowSpec]) -> Result<(), YamlWorkflowError> {
+    // Validate each workflow individually.
+    for spec in specs {
+        validate(spec)?;
+    }
+
+    // Check for duplicate workflow IDs.
+    let mut seen_ids = HashSet::new();
+    for spec in specs {
+        if !seen_ids.insert(&spec.id) {
+            return Err(YamlWorkflowError::Validation(format!(
+                "Duplicate workflow ID: '{}'",
+                spec.id
+            )));
+        }
+    }
+
+    // Validate cross-workflow references and detect cycles.
+    validate_workflow_references(specs)?;
+
+    Ok(())
+}
+
+/// Validate that workflow step references point to known workflows
+/// and detect circular dependencies.
+fn validate_workflow_references(specs: &[WorkflowSpec]) -> Result<(), YamlWorkflowError> {
+    let known_ids: HashSet<&str> = specs.iter().map(|s| s.id.as_str()).collect();
+
+    // Build a dependency graph: workflow_id -> set of referenced workflow_ids.
+    let mut deps: HashMap<&str, HashSet<&str>> = HashMap::new();
+
+    for spec in specs {
+        let mut spec_deps = HashSet::new();
+        collect_workflow_refs(&spec.steps, &mut spec_deps);
+        deps.insert(spec.id.as_str(), spec_deps);
+    }
+
+    // Detect cycles using DFS with coloring.
+    detect_cycles(&known_ids, &deps)?;
+
+    Ok(())
+}
+
+/// Collect all workflow IDs referenced by `type: workflow` steps.
+fn collect_workflow_refs<'a>(steps: &'a [YamlStep], refs: &mut HashSet<&'a str>) {
+    for step in steps {
+        if step.step_type.as_deref() == Some("workflow")
+            && let Some(ref config) = step.config
+            && let Some(ref wf_id) = config.child_workflow
+        {
+            refs.insert(wf_id.as_str());
+        }
+        if let Some(ref children) = step.parallel {
+            collect_workflow_refs(children, refs);
+        }
+        if let Some(ref hook) = step.on_success {
+            collect_workflow_refs(std::slice::from_ref(hook.as_ref()), refs);
+        }
+        if let Some(ref hook) = step.on_failure {
+            collect_workflow_refs(std::slice::from_ref(hook.as_ref()), refs);
+        }
+        if let Some(ref hook) = step.ensure {
+            collect_workflow_refs(std::slice::from_ref(hook.as_ref()), refs);
+        }
+    }
+}
+
+/// Detect circular references in the workflow dependency graph.
+fn detect_cycles(
+    known_ids: &HashSet<&str>,
+    deps: &HashMap<&str, HashSet<&str>>,
+) -> Result<(), YamlWorkflowError> {
+    #[derive(Clone, Copy, PartialEq)]
+    enum Color {
+        White,
+        Gray,
+        Black,
+    }
+
+    let mut colors: HashMap<&str, Color> = known_ids.iter().map(|id| (*id, Color::White)).collect();
+
+    fn dfs<'a>(
+        node: &'a str,
+        deps: &HashMap<&str, HashSet<&'a str>>,
+        colors: &mut HashMap<&'a str, Color>,
+        path: &mut Vec<&'a str>,
+    ) -> Result<(), YamlWorkflowError> {
+        colors.insert(node, Color::Gray);
+        path.push(node);
+
+        if let Some(neighbors) = deps.get(node) {
+            for &neighbor in neighbors {
+                match colors.get(neighbor) {
+                    Some(Color::Gray) => {
+                        // Found a cycle. Build the cycle path for the error message.
+                        let cycle_start = path.iter().position(|&n| n == neighbor).unwrap();
+                        let cycle: Vec<&str> = path[cycle_start..].to_vec();
+                        return Err(YamlWorkflowError::Validation(format!(
+                            "Circular workflow reference detected: {} -> {}",
+                            cycle.join(" -> "),
+                            neighbor
+                        )));
+                    }
+                    Some(Color::White) | None => {
+                        // Only recurse into nodes that are in our known set.
+                        if colors.contains_key(neighbor) {
+                            dfs(neighbor, deps, colors, path)?;
+                        }
+                    }
+                    Some(Color::Black) => {
+                        // Already fully processed, skip.
+                    }
+                }
+            }
+        }
+
+        path.pop();
+        colors.insert(node, Color::Black);
+        Ok(())
+    }
+
+    let nodes: Vec<&str> = known_ids.iter().copied().collect();
+    for node in nodes {
+        if colors.get(node) == Some(&Color::White) {
+            let mut path = Vec::new();
+            dfs(node, deps, &mut colors, &mut path)?;
+        }
+    }
+
     Ok(())
 }
 
@@ -89,6 +233,108 @@ fn validate_steps(
             }
         }
 
+        // BuildKit steps must have config with dockerfile and context.
+        if let Some(ref step_type) = step.step_type
+            && step_type == "buildkit"
+        {
+            let config = step.config.as_ref().ok_or_else(|| {
+                YamlWorkflowError::Validation(format!(
+                    "BuildKit step '{}' must have a 'config' section",
+                    step.name
+                ))
+            })?;
+            if config.dockerfile.is_none() {
+                return Err(YamlWorkflowError::Validation(format!(
+                    "BuildKit step '{}' must have 'config.dockerfile'",
+                    step.name
+                )));
+            }
+            if config.context.is_none() {
+                return Err(YamlWorkflowError::Validation(format!(
+                    "BuildKit step '{}' must have 'config.context'",
+                    step.name
+                )));
+            }
+            if config.push.unwrap_or(false) && config.tags.is_empty() {
+                return Err(YamlWorkflowError::Validation(format!(
+                    "BuildKit step '{}' has push=true but no tags specified",
+                    step.name
+                )));
+            }
+        }
+
+        // Containerd steps must have config with image and exactly one of run or command.
+        if let Some(ref step_type) = step.step_type
+            && step_type == "containerd"
+        {
+            let config = step.config.as_ref().ok_or_else(|| {
+                YamlWorkflowError::Validation(format!(
+                    "Containerd step '{}' must have a 'config' section",
+                    step.name
+                ))
+            })?;
+            if config.image.is_none() {
+                return Err(YamlWorkflowError::Validation(format!(
+                    "Containerd step '{}' must have 'config.image'",
+                    step.name
+                )));
+            }
+            let has_run = config.run.is_some();
+            let has_command = config.command.is_some();
+            if !has_run && !has_command {
+                return Err(YamlWorkflowError::Validation(format!(
+                    "Containerd step '{}' must have 'config.run' or 'config.command'",
+                    step.name
+                )));
+            }
+            if has_run && has_command {
+                return Err(YamlWorkflowError::Validation(format!(
+                    "Containerd step '{}' cannot have both 'config.run' and 'config.command'",
+                    step.name
+                )));
+            }
+            if let Some(ref network) = config.network {
+                match network.as_str() {
+                    "none" | "host" | "bridge" => {}
+                    other => {
+                        return Err(YamlWorkflowError::Validation(format!(
+                            "Containerd step '{}' has invalid network '{}'. Must be none, host, or bridge",
+                            step.name, other
+                        )));
+                    }
+                }
+            }
+            if let Some(ref pull) = config.pull {
+                match pull.as_str() {
+                    "always" | "if-not-present" | "never" => {}
+                    other => {
+                        return Err(YamlWorkflowError::Validation(format!(
+                            "Containerd step '{}' has invalid pull policy '{}'. Must be always, if-not-present, or never",
+                            step.name, other
+                        )));
+                    }
+                }
+            }
+        }
+
+        // Workflow steps must have config.workflow.
+        if let Some(ref step_type) = step.step_type
+            && step_type == "workflow"
+        {
+            let config = step.config.as_ref().ok_or_else(|| {
+                YamlWorkflowError::Validation(format!(
+                    "Workflow step '{}' must have a 'config' section",
+                    step.name
+                ))
+            })?;
+            if config.child_workflow.is_none() {
+                return Err(YamlWorkflowError::Validation(format!(
+                    "Workflow step '{}' must have 'config.workflow'",
+                    step.name
+                )));
+            }
+        }
+
         // Validate step-level error behavior.
         if let Some(ref eb) = step.error_behavior {
             validate_error_behavior_type(&eb.behavior_type)?;
@@ -122,3 +368,300 @@ fn validate_error_behavior_type(behavior_type: &str) -> Result<(), YamlWorkflowE
         ))),
     }
 }
+
+// --- Condition validation ---
+
+/// Collect all output field names produced by steps (via their `outputs:` list).
+fn collect_step_outputs(steps: &[YamlStep]) -> HashSet<String> {
+    let mut outputs = HashSet::new();
+    for step in steps {
+        for out in &step.outputs {
+            outputs.insert(out.name.clone());
+        }
+        if let Some(ref children) = step.parallel {
+            outputs.extend(collect_step_outputs(children));
+        }
+        if let Some(ref hook) = step.on_success {
+            outputs.extend(collect_step_outputs(std::slice::from_ref(hook.as_ref())));
+        }
+        if let Some(ref hook) = step.on_failure {
+            outputs.extend(collect_step_outputs(std::slice::from_ref(hook.as_ref())));
+        }
+        if let Some(ref hook) = step.ensure {
+            outputs.extend(collect_step_outputs(std::slice::from_ref(hook.as_ref())));
+        }
+    }
+    outputs
+}
+
+/// Walk all steps and validate their `when` conditions.
+fn validate_step_conditions(
+    steps: &[YamlStep],
+    spec: &WorkflowSpec,
+    known_outputs: &HashSet<String>,
+) -> Result<(), YamlWorkflowError> {
+    for step in steps {
+        if let Some(ref cond) = step.when {
+            validate_condition_fields(cond, spec, known_outputs)?;
+            validate_condition_types(cond, spec)?;
+        }
+        if let Some(ref children) = step.parallel {
+            validate_step_conditions(children, spec, known_outputs)?;
+        }
+        if let Some(ref hook) = step.on_success {
+            validate_step_conditions(std::slice::from_ref(hook.as_ref()), spec, known_outputs)?;
+        }
+        if let Some(ref hook) = step.on_failure {
+            validate_step_conditions(std::slice::from_ref(hook.as_ref()), spec, known_outputs)?;
+        }
+        if let Some(ref hook) = step.ensure {
+            validate_step_conditions(std::slice::from_ref(hook.as_ref()), spec, known_outputs)?;
+        }
+    }
+    Ok(())
+}
+
+/// Validate that all field paths in a condition tree resolve to known schema fields.
+pub fn validate_condition_fields(
+    condition: &YamlCondition,
+    spec: &WorkflowSpec,
+    known_outputs: &HashSet<String>,
+) -> Result<(), YamlWorkflowError> {
+    match condition {
+        YamlCondition::Comparison(cmp) => {
+            validate_field_path(&cmp.as_ref().field, spec, known_outputs)?;
+        }
+        YamlCondition::Combinator(c) => {
+            validate_combinator_fields(c, spec, known_outputs)?;
+        }
+    }
+    Ok(())
+}
+
+fn validate_combinator_fields(
+    c: &YamlCombinator,
+    spec: &WorkflowSpec,
+    known_outputs: &HashSet<String>,
+) -> Result<(), YamlWorkflowError> {
+    let all_children = c
+        .all
+        .iter()
+        .flatten()
+        .chain(c.any.iter().flatten())
+        .chain(c.none.iter().flatten())
+        .chain(c.one_of.iter().flatten());
+
+    for child in all_children {
+        validate_condition_fields(child, spec, known_outputs)?;
+    }
+    if let Some(ref inner) = c.not {
+        validate_condition_fields(inner, spec, known_outputs)?;
+    }
+    Ok(())
+}
+
+/// Resolve a field path like `.inputs.foo` or `.outputs.bar` against the workflow schema.
+fn validate_field_path(
+    field: &str,
+    spec: &WorkflowSpec,
+    known_outputs: &HashSet<String>,
+) -> Result<(), YamlWorkflowError> {
+    // If the spec has no inputs and no outputs schema, skip field validation
+    // (schema-less workflow).
+    if spec.inputs.is_empty() && spec.outputs.is_empty() {
+        return Ok(());
+    }
+
+    let parts: Vec<&str> = field.split('.').collect();
+
+    // Expect paths like ".inputs.x" or ".outputs.x" (leading dot is optional).
+    let parts = if parts.first() == Some(&"") {
+        &parts[1..] // skip leading empty from "."
+    } else {
+        &parts[..]
+    };
+
+    if parts.len() < 2 {
+        return Err(YamlWorkflowError::Validation(format!(
+            "Condition field path '{field}' must have at least two segments (e.g. '.inputs.name')"
+        )));
+    }
+
+    match parts[0] {
+        "inputs" => {
+            let field_name = parts[1];
+            if !spec.inputs.contains_key(field_name) {
+                return Err(YamlWorkflowError::Validation(format!(
+                    "Condition references unknown input field '{field_name}'. \
+                     Available inputs: [{}]",
+                    spec.inputs
+                        .keys()
+                        .cloned()
+                        .collect::<Vec<_>>()
+                        .join(", ")
+                )));
+            }
+        }
+        "outputs" => {
+            let field_name = parts[1];
+            // Check both the declared output schema and step-produced outputs.
+            if !spec.outputs.contains_key(field_name) && !known_outputs.contains(field_name) {
+                return Err(YamlWorkflowError::Validation(format!(
+                    "Condition references unknown output field '{field_name}'. \
+                     Available outputs: [{}]",
+                    spec.outputs
+                        .keys()
+                        .cloned()
+                        .collect::<Vec<_>>()
+                        .join(", ")
+                )));
+            }
+        }
+        other => {
+            return Err(YamlWorkflowError::Validation(format!(
+                "Condition field path '{field}' must start with 'inputs' or 'outputs', got '{other}'"
+            )));
+        }
+    }
+
+    Ok(())
+}
+
+/// Validate operator type compatibility for condition comparisons.
+pub fn validate_condition_types(
+    condition: &YamlCondition,
+    spec: &WorkflowSpec,
+) -> Result<(), YamlWorkflowError> {
+    match condition {
+        YamlCondition::Comparison(cmp) => {
+            validate_comparison_type(cmp.as_ref(), spec)?;
+        }
+        YamlCondition::Combinator(c) => {
+            let all_children = c
+                .all
+                .iter()
+                .flatten()
+                .chain(c.any.iter().flatten())
+                .chain(c.none.iter().flatten())
+                .chain(c.one_of.iter().flatten());
+
+            for child in all_children {
+                validate_condition_types(child, spec)?;
+            }
+            if let Some(ref inner) = c.not {
+                validate_condition_types(inner, spec)?;
+            }
+        }
+    }
+    Ok(())
+}
+
+/// Check that the operator used in a comparison is compatible with the field type.
+fn validate_comparison_type(
+    cmp: &YamlComparison,
+    spec: &WorkflowSpec,
+) -> Result<(), YamlWorkflowError> {
+    // Resolve the field type from the schema.
+    let field_type = resolve_field_type(&cmp.field, spec);
+    let field_type = match field_type {
+        Some(t) => t,
+        // If we can't resolve the type (no schema), skip type checking.
+        None => return Ok(()),
+    };
+
+    // Check operator compatibility.
+    let has_gt = cmp.gt.is_some();
+    let has_gte = cmp.gte.is_some();
+    let has_lt = cmp.lt.is_some();
+    let has_lte = cmp.lte.is_some();
+    let has_contains = cmp.contains.is_some();
+    let has_is_null = cmp.is_null == Some(true);
+    let has_is_not_null = cmp.is_not_null == Some(true);
+
+    // gt/gte/lt/lte only valid for number/integer types.
+    if (has_gt || has_gte || has_lt || has_lte) && !is_numeric_type(&field_type) {
+        return Err(YamlWorkflowError::Validation(format!(
+            "Comparison operators gt/gte/lt/lte are only valid for number/integer types, \
+             but field '{}' has type '{}'",
+            cmp.field, field_type
+        )));
+    }
+
+    // contains only valid for string/list types.
+    if has_contains && !is_containable_type(&field_type) {
+        return Err(YamlWorkflowError::Validation(format!(
+            "Comparison operator 'contains' is only valid for string/list types, \
+             but field '{}' has type '{}'",
+            cmp.field, field_type
+        )));
+    }
+
+    // is_null/is_not_null only valid for optional types.
+    if (has_is_null || has_is_not_null) && !is_optional_type(&field_type) {
+        return Err(YamlWorkflowError::Validation(format!(
+            "Comparison operators is_null/is_not_null are only valid for optional types, \
+             but field '{}' has type '{}'",
+            cmp.field, field_type
+        )));
+    }
+
+    Ok(())
+}
+
+/// Resolve a field's SchemaType from the workflow spec.
+fn resolve_field_type(field: &str, spec: &WorkflowSpec) -> Option<SchemaType> {
+    let parts: Vec<&str> = field.split('.').collect();
+    let parts = if parts.first() == Some(&"") {
+        &parts[1..]
+    } else {
+        &parts[..]
+    };
+
+    if parts.len() < 2 {
+        return None;
+    }
+
+    let type_str = match parts[0] {
+        "inputs" => spec.inputs.get(parts[1]),
+        "outputs" => spec.outputs.get(parts[1]),
+        _ => None,
+    }?;
+
+    parse_type_string(type_str).ok()
+}
+
+fn is_numeric_type(t: &SchemaType) -> bool {
+    match t {
+        SchemaType::Number | SchemaType::Integer | SchemaType::Any => true,
+        SchemaType::Optional(inner) => is_numeric_type(inner),
+        _ => false,
+    }
+}
+
+fn is_containable_type(t: &SchemaType) -> bool {
+    match t {
+        SchemaType::String | SchemaType::List(_) | SchemaType::Any => true,
+        SchemaType::Optional(inner) => is_containable_type(inner),
+        _ => false,
+    }
+}
+
+fn is_optional_type(t: &SchemaType) -> bool {
+    matches!(t, SchemaType::Optional(_) | SchemaType::Any)
+}
+
+/// Detect output fields declared in `spec.outputs` that no step produces.
+pub fn detect_unused_outputs(
+    spec: &WorkflowSpec,
+    known_outputs: &HashSet<String>,
+) -> Result<(), YamlWorkflowError> {
+    for output_name in spec.outputs.keys() {
+        if !known_outputs.contains(output_name) {
+            return Err(YamlWorkflowError::Validation(format!(
+                "Declared output '{output_name}' is never produced by any step. \
+                 Add an output data ref with name '{output_name}' to a step."
+            )));
+        }
+    }
+    Ok(())
+}

wfe-yaml/tests/compiler.rs

@@ -2,7 +2,7 @@ use std::collections::HashMap;
 use std::time::Duration;
 
 use wfe_core::models::error_behavior::ErrorBehavior;
-use wfe_yaml::load_workflow_from_str;
+use wfe_yaml::{load_single_workflow_from_str, load_workflow_from_str};
 
 #[test]
 fn single_step_produces_one_workflow_step() {
@@ -16,7 +16,7 @@ workflow:
       config:
         run: echo hello
 "#;
-    let compiled = load_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
     // The definition should have exactly 1 main step.
     let main_steps: Vec<_> = compiled
         .definition
@@ -44,7 +44,7 @@ workflow:
       config:
         run: echo b
 "#;
-    let compiled = load_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
 
     let step_a = compiled
         .definition
@@ -82,7 +82,7 @@ workflow:
           config:
             run: echo b
 "#;
-    let compiled = load_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
 
     let container = compiled
         .definition
@@ -116,7 +116,7 @@ workflow:
         config:
           run: rollback.sh
 "#;
-    let compiled = load_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
 
     let deploy = compiled
         .definition
@@ -156,7 +156,7 @@ workflow:
       error_behavior:
         type: suspend
 "#;
-    let compiled = load_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
 
     assert_eq!(
         compiled.definition.default_error_behavior,
@@ -193,7 +193,7 @@ workflow:
       type: shell
       config: *default_config
 "#;
-    let compiled = load_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
 
     // Should have 2 main steps + factories.
     let build_step = compiled
@@ -241,7 +241,7 @@ workflow:
         config:
           run: echo "build succeeded"
 "#;
-    let compiled = load_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
 
     let build = compiled
         .definition
@@ -279,7 +279,7 @@ workflow:
         config:
           run: cleanup.sh
 "#;
-    let compiled = load_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
 
     let deploy = compiled
         .definition
@@ -322,7 +322,7 @@ workflow:
         config:
           run: cleanup.sh
 "#;
-    let compiled = load_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
 
     let deploy = compiled
         .definition
@@ -351,7 +351,7 @@ workflow:
       config:
         run: echo hi
 "#;
-    let compiled = load_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
     assert_eq!(
         compiled.definition.default_error_behavior,
         ErrorBehavior::Terminate
@@ -372,7 +372,7 @@ workflow:
       config:
         run: echo hi
 "#;
-    let compiled = load_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
     assert_eq!(
         compiled.definition.default_error_behavior,
         ErrorBehavior::Compensate
@@ -394,7 +394,7 @@ workflow:
       config:
         run: echo hi
 "#;
-    let compiled = load_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
     assert_eq!(
         compiled.definition.default_error_behavior,
         ErrorBehavior::Retry {
@@ -420,7 +420,7 @@ workflow:
       config:
         run: echo hi
 "#;
-    let compiled = load_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
     assert_eq!(
         compiled.definition.default_error_behavior,
         ErrorBehavior::Retry {
@@ -447,7 +447,7 @@ workflow:
       config:
         run: echo hi
 "#;
-    let compiled = load_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
     assert_eq!(
         compiled.definition.default_error_behavior,
         ErrorBehavior::Retry {
@@ -471,7 +471,7 @@ workflow:
       config:
         run: echo hi
 "#;
-    let result = load_workflow_from_str(yaml, &HashMap::new());
+    let result = load_single_workflow_from_str(yaml, &HashMap::new());
     assert!(result.is_err());
     let err = match result { Err(e) => e.to_string(), Ok(_) => panic!("expected error") };
     assert!(err.contains("explode"), "Error should mention the invalid type, got: {err}");
@@ -499,7 +499,7 @@ workflow:
           config:
             run: echo c
 "#;
-    let compiled = load_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
 
     let container = compiled
         .definition
@@ -541,7 +541,7 @@ workflow:
           RUST_LOG: debug
         working_dir: /tmp
 "#;
-    let compiled = load_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
 
     let step = compiled
         .definition
@@ -571,7 +571,7 @@ workflow:
       config:
         file: my_script.sh
 "#;
-    let compiled = load_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
     let step = compiled
         .definition
         .steps
@@ -596,7 +596,7 @@ workflow:
       config:
         run: echo hello
 "#;
-    let compiled = load_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
     let step = compiled
         .definition
         .steps
@@ -626,7 +626,7 @@ workflow:
         config:
           run: rollback.sh
 "#;
-    let compiled = load_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
 
     // Should have factories for both deploy and rollback.
     let has_deploy = compiled
@@ -658,7 +658,7 @@ workflow:
         config:
           run: echo ok
 "#;
-    let compiled = load_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
 
     let has_notify = compiled
         .step_factories
@@ -684,7 +684,7 @@ workflow:
         config:
           run: cleanup.sh
 "#;
-    let compiled = load_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
 
     let has_cleanup = compiled
         .step_factories
@@ -713,7 +713,7 @@ workflow:
           config:
             run: echo b
 "#;
-    let compiled = load_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
 
     let container = compiled
         .definition
@@ -746,7 +746,7 @@ workflow:
       config:
         run: echo b
 "#;
-    let compiled = load_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
 
     let step_a = compiled
         .definition
@@ -787,7 +787,7 @@ workflow:
       config:
         run: echo hi
 "#;
-    let compiled = load_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
     assert_eq!(
         compiled.definition.description.as_deref(),
         Some("A test workflow")
@@ -804,7 +804,7 @@ workflow:
     - name: bad-step
       type: shell
 "#;
-    let result = load_workflow_from_str(yaml, &HashMap::new());
+    let result = load_single_workflow_from_str(yaml, &HashMap::new());
     assert!(result.is_err());
     let err = match result { Err(e) => e.to_string(), Ok(_) => panic!("expected error") };
     assert!(
@@ -812,3 +812,494 @@ workflow:
         "Error should mention missing config, got: {err}"
     );
 }
+
+// --- Workflow step compilation tests ---
+
+#[test]
+fn workflow_step_compiles_correctly() {
+    let yaml = r#"
+workflow:
+  id: parent-wf
+  version: 1
+  steps:
+    - name: run-child
+      type: workflow
+      config:
+        workflow: child-wf
+        workflow_version: 3
+      outputs:
+        - name: result
+        - name: status
+"#;
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
+
+    let step = compiled
+        .definition
+        .steps
+        .iter()
+        .find(|s| s.name.as_deref() == Some("run-child"))
+        .unwrap();
+
+    assert!(step.step_type.contains("workflow"));
+    assert!(step.step_config.is_some());
+
+    // Verify the serialized config contains the workflow_id and version.
+    let config: serde_json::Value = step.step_config.clone().unwrap();
+    assert_eq!(config["workflow_id"].as_str(), Some("child-wf"));
+    assert_eq!(config["version"].as_u64(), Some(3));
+    assert_eq!(config["output_keys"].as_array().unwrap().len(), 2);
+}
+
+#[test]
+fn workflow_step_version_defaults_to_1() {
+    let yaml = r#"
+workflow:
+  id: parent-wf
+  version: 1
+  steps:
+    - name: run-child
+      type: workflow
+      config:
+        workflow: child-wf
+"#;
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
+
+    let step = compiled
+        .definition
+        .steps
+        .iter()
+        .find(|s| s.name.as_deref() == Some("run-child"))
+        .unwrap();
+
+    let config: serde_json::Value = step.step_config.clone().unwrap();
+    assert_eq!(config["version"].as_u64(), Some(1));
+}
+
+#[test]
+fn workflow_step_factory_is_registered() {
+    let yaml = r#"
+workflow:
+  id: parent-wf
+  version: 1
+  steps:
+    - name: run-child
+      type: workflow
+      config:
+        workflow: child-wf
+"#;
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
+
+    let has_workflow_factory = compiled
+        .step_factories
+        .iter()
+        .any(|(key, _)| key.contains("workflow") && key.contains("run-child"));
+    assert!(
+        has_workflow_factory,
+        "Should have factory for workflow step"
+    );
+}
+
+#[test]
+fn compile_multi_workflow_file() {
+    let yaml = r#"
+workflows:
+  - id: build
+    version: 1
+    steps:
+      - name: compile
+        type: shell
+        config:
+          run: cargo build
+  - id: test
+    version: 1
+    steps:
+      - name: run-tests
+        type: shell
+        config:
+          run: cargo test
+"#;
+    let workflows = load_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    assert_eq!(workflows.len(), 2);
+    assert_eq!(workflows[0].definition.id, "build");
+    assert_eq!(workflows[1].definition.id, "test");
+}
+
+#[test]
+fn compile_multi_workflow_with_cross_references() {
+    let yaml = r#"
+workflows:
+  - id: pipeline
+    version: 1
+    steps:
+      - name: run-build
+        type: workflow
+        config:
+          workflow: build
+  - id: build
+    version: 1
+    steps:
+      - name: compile
+        type: shell
+        config:
+          run: cargo build
+"#;
+    let workflows = load_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    assert_eq!(workflows.len(), 2);
+
+    // The pipeline workflow should have a workflow step.
+    let pipeline = &workflows[0];
+    let step = pipeline
+        .definition
+        .steps
+        .iter()
+        .find(|s| s.name.as_deref() == Some("run-build"))
+        .unwrap();
+    assert!(step.step_type.contains("workflow"));
+}
+
+#[test]
+fn workflow_step_with_mixed_steps() {
+    let yaml = r#"
+workflow:
+  id: mixed-wf
+  version: 1
+  steps:
+    - name: setup
+      type: shell
+      config:
+        run: echo setup
+    - name: run-child
+      type: workflow
+      config:
+        workflow: child-wf
+    - name: cleanup
+      type: shell
+      config:
+        run: echo cleanup
+"#;
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
+
+    // Should have 3 main steps.
+    let step_names: Vec<_> = compiled
+        .definition
+        .steps
+        .iter()
+        .filter_map(|s| s.name.as_deref())
+        .collect();
+    assert!(step_names.contains(&"setup"));
+    assert!(step_names.contains(&"run-child"));
+    assert!(step_names.contains(&"cleanup"));
+
+    // setup -> run-child -> cleanup wiring.
+    let setup = compiled
+        .definition
+        .steps
+        .iter()
+        .find(|s| s.name.as_deref() == Some("setup"))
+        .unwrap();
+    let run_child = compiled
+        .definition
+        .steps
+        .iter()
+        .find(|s| s.name.as_deref() == Some("run-child"))
+        .unwrap();
+    let cleanup = compiled
+        .definition
+        .steps
+        .iter()
+        .find(|s| s.name.as_deref() == Some("cleanup"))
+        .unwrap();
+
+    assert_eq!(setup.outcomes[0].next_step, run_child.id);
+    assert_eq!(run_child.outcomes[0].next_step, cleanup.id);
+}
+
+/// Regression test: SubWorkflowStep must actually wait for child completion,
+/// not return next() immediately. The compiled factory must produce a real
+/// SubWorkflowStep (from wfe-core), not a placeholder.
+#[tokio::test]
+async fn workflow_step_factory_produces_real_sub_workflow_step() {
+    use wfe_core::models::{ExecutionPointer, WorkflowInstance, WorkflowStep as WfStep};
+    use wfe_core::traits::step::{HostContext, StepExecutionContext};
+    use std::pin::Pin;
+    use std::future::Future;
+    use std::sync::Mutex;
+
+    let yaml = r#"
+workflows:
+  - id: child
+    version: 1
+    steps:
+      - name: do-work
+        type: shell
+        config:
+          run: echo done
+
+  - id: parent
+    version: 1
+    steps:
+      - name: run-child
+        type: workflow
+        config:
+          workflow: child
+"#;
+    let config = HashMap::new();
+    let workflows = load_workflow_from_str(yaml, &config).unwrap();
+
+    // Find the parent workflow's factory for the "run-child" step
+    let parent = workflows.iter().find(|w| w.definition.id == "parent").unwrap();
+    let factory_key = parent.step_factories.iter()
+        .find(|(k, _)| k.contains("run-child"))
+        .map(|(k, _)| k.clone())
+        .expect("run-child factory should exist");
+
+    // Create a step from the factory
+    let factory = &parent.step_factories.iter()
+        .find(|(k, _)| *k == factory_key)
+        .unwrap().1;
+    let mut step = factory();
+
+    // Mock host context that records the start_workflow call
+    struct MockHost { called: Mutex<bool> }
+    impl HostContext for MockHost {
+        fn start_workflow(&self, _def: &str, _ver: u32, _data: serde_json::Value)
+            -> Pin<Box<dyn Future<Output = wfe_core::Result<String>> + Send + '_>>
+        {
+            *self.called.lock().unwrap() = true;
+            Box::pin(async { Ok("child-instance-id".to_string()) })
+        }
+    }
+
+    let host = MockHost { called: Mutex::new(false) };
+    let pointer = ExecutionPointer::new(0);
+    let wf_step = WfStep::new(0, &factory_key);
+    let workflow = WorkflowInstance::new("parent", 1, serde_json::json!({}));
+    let ctx = StepExecutionContext {
+        item: None,
+        execution_pointer: &pointer,
+        persistence_data: None,
+        step: &wf_step,
+        workflow: &workflow,
+        cancellation_token: tokio_util::sync::CancellationToken::new(),
+        host_context: Some(&host),
+    };
+
+    let result = step.run(&ctx).await.unwrap();
+
+    // THE KEY ASSERTION: must NOT proceed immediately.
+    // It must return wait_for_event so the parent waits for the child.
+    assert!(
+        !result.proceed,
+        "SubWorkflowStep must NOT proceed immediately — it should wait for child completion"
+    );
+    assert_eq!(
+        result.event_name.as_deref(),
+        Some("wfe.workflow.completed"),
+        "SubWorkflowStep must wait for wfe.workflow.completed event"
+    );
+    assert!(
+        *host.called.lock().unwrap(),
+        "SubWorkflowStep must call host_context.start_workflow()"
+    );
+}
+
+// --- Condition compilation tests ---
+
+#[test]
+fn compile_simple_condition_into_step_condition() {
+    let yaml = r#"
+workflow:
+  id: cond-compile
+  version: 1
+  steps:
+    - name: deploy
+      type: shell
+      config:
+        run: deploy.sh
+      when:
+        field: .inputs.enabled
+        equals: true
+"#;
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    let step = compiled
+        .definition
+        .steps
+        .iter()
+        .find(|s| s.name.as_deref() == Some("deploy"))
+        .unwrap();
+
+    assert!(step.when.is_some(), "Step should have a when condition");
+    match step.when.as_ref().unwrap() {
+        wfe_core::models::StepCondition::Comparison(cmp) => {
+            assert_eq!(cmp.field, ".inputs.enabled");
+            assert_eq!(cmp.operator, wfe_core::models::ComparisonOp::Equals);
+            assert_eq!(cmp.value, Some(serde_json::json!(true)));
+        }
+        other => panic!("Expected Comparison, got: {other:?}"),
+    }
+}
+
+#[test]
+fn compile_nested_condition() {
+    let yaml = r#"
+workflow:
+  id: nested-cond-compile
+  version: 1
+  steps:
+    - name: deploy
+      type: shell
+      config:
+        run: deploy.sh
+      when:
+        all:
+          - field: .inputs.count
+            gt: 5
+          - not:
+              field: .inputs.skip
+              equals: true
+"#;
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    let step = compiled
+        .definition
+        .steps
+        .iter()
+        .find(|s| s.name.as_deref() == Some("deploy"))
+        .unwrap();
+
+    assert!(step.when.is_some());
+    match step.when.as_ref().unwrap() {
+        wfe_core::models::StepCondition::All(children) => {
+            assert_eq!(children.len(), 2);
+            // First child: comparison
+            match &children[0] {
+                wfe_core::models::StepCondition::Comparison(cmp) => {
+                    assert_eq!(cmp.field, ".inputs.count");
+                    assert_eq!(cmp.operator, wfe_core::models::ComparisonOp::Gt);
+                    assert_eq!(cmp.value, Some(serde_json::json!(5)));
+                }
+                other => panic!("Expected Comparison, got: {other:?}"),
+            }
+            // Second child: not
+            match &children[1] {
+                wfe_core::models::StepCondition::Not(inner) => {
+                    match inner.as_ref() {
+                        wfe_core::models::StepCondition::Comparison(cmp) => {
+                            assert_eq!(cmp.field, ".inputs.skip");
+                            assert_eq!(cmp.operator, wfe_core::models::ComparisonOp::Equals);
+                        }
+                        other => panic!("Expected Comparison inside Not, got: {other:?}"),
+                    }
+                }
+                other => panic!("Expected Not, got: {other:?}"),
+            }
+        }
+        other => panic!("Expected All, got: {other:?}"),
+    }
+}
+
+#[test]
+fn step_without_when_has_none_condition() {
+    let yaml = r#"
+workflow:
+  id: no-when-compile
+  version: 1
+  steps:
+    - name: step1
+      type: shell
+      config:
+        run: echo hi
+"#;
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    let step = compiled
+        .definition
+        .steps
+        .iter()
+        .find(|s| s.name.as_deref() == Some("step1"))
+        .unwrap();
+    assert!(step.when.is_none());
+}
+
+#[test]
+fn compile_all_comparison_operators() {
+    use wfe_core::models::ComparisonOp;
+
+    let ops = vec![
+        ("equals: 42", ComparisonOp::Equals),
+        ("not_equals: foo", ComparisonOp::NotEquals),
+        ("gt: 10", ComparisonOp::Gt),
+        ("gte: 10", ComparisonOp::Gte),
+        ("lt: 100", ComparisonOp::Lt),
+        ("lte: 100", ComparisonOp::Lte),
+        ("contains: needle", ComparisonOp::Contains),
+        ("is_null: true", ComparisonOp::IsNull),
+        ("is_not_null: true", ComparisonOp::IsNotNull),
+    ];
+
+    for (op_yaml, expected_op) in ops {
+        let yaml = format!(
+            r#"
+workflow:
+  id: op-test
+  version: 1
+  steps:
+    - name: step1
+      type: shell
+      config:
+        run: echo hi
+      when:
+        field: .inputs.x
+        {op_yaml}
+"#
+        );
+        let compiled = load_single_workflow_from_str(&yaml, &HashMap::new())
+            .unwrap_or_else(|e| panic!("Failed to compile with {op_yaml}: {e}"));
+        let step = compiled
+            .definition
+            .steps
+            .iter()
+            .find(|s| s.name.as_deref() == Some("step1"))
+            .unwrap();
+
+        match step.when.as_ref().unwrap() {
+            wfe_core::models::StepCondition::Comparison(cmp) => {
+                assert_eq!(cmp.operator, expected_op, "Operator mismatch for {op_yaml}");
+            }
+            other => panic!("Expected Comparison for {op_yaml}, got: {other:?}"),
+        }
+    }
+}
+
+#[test]
+fn compile_condition_on_parallel_container() {
+    let yaml = r#"
+workflow:
+  id: parallel-cond
+  version: 1
+  steps:
+    - name: parallel-group
+      when:
+        field: .inputs.run_parallel
+        equals: true
+      parallel:
+        - name: task-a
+          type: shell
+          config:
+            run: echo a
+        - name: task-b
+          type: shell
+          config:
+            run: echo b
+"#;
+    let compiled = load_single_workflow_from_str(yaml, &HashMap::new()).unwrap();
+    let container = compiled
+        .definition
+        .steps
+        .iter()
+        .find(|s| s.name.as_deref() == Some("parallel-group"))
+        .unwrap();
+
+    assert!(
+        container.when.is_some(),
+        "Parallel container should have when condition"
+    );
+}

wfe-yaml/tests/deno.rs

@@ -41,6 +41,7 @@ fn make_context<'a>(
         step,
         workflow,
         cancellation_token: tokio_util::sync::CancellationToken::new(),
+        host_context: None,
     }
 }
 
@@ -219,7 +220,7 @@ workflow:
       type: deno
 "#;
     let config = HashMap::new();
-    let result = wfe_yaml::load_workflow_from_str(yaml, &config);
+    let result = wfe_yaml::load_single_workflow_from_str(yaml, &config);
     assert!(result.is_err());
     let msg = result.err().unwrap().to_string();
     assert!(
@@ -242,7 +243,7 @@ workflow:
           FOO: bar
 "#;
     let config = HashMap::new();
-    let result = wfe_yaml::load_workflow_from_str(yaml, &config);
+    let result = wfe_yaml::load_single_workflow_from_str(yaml, &config);
     assert!(result.is_err());
     let msg = result.err().unwrap().to_string();
     assert!(
@@ -264,7 +265,7 @@ workflow:
         script: "output('key', 'val');"
 "#;
     let config = HashMap::new();
-    let compiled = wfe_yaml::load_workflow_from_str(yaml, &config).unwrap();
+    let compiled = wfe_yaml::load_single_workflow_from_str(yaml, &config).unwrap();
     assert!(!compiled.step_factories.is_empty());
     let (key, _factory) = &compiled.step_factories[0];
     assert!(key.contains("deno"), "factory key should contain 'deno', got: {key}");

wfe-yaml/tests/deno_e2e.rs

@@ -15,7 +15,7 @@ use wfe::{WorkflowHostBuilder, run_workflow_sync};
 use wfe_core::test_support::{
     InMemoryLockProvider, InMemoryPersistenceProvider, InMemoryQueueProvider,
 };
-use wfe_yaml::load_workflow_from_str;
+use wfe_yaml::load_single_workflow_from_str;
 
 // ---------------------------------------------------------------------------
 // Helpers
@@ -30,7 +30,7 @@ async fn run_yaml_workflow_with_data(
     data: serde_json::Value,
 ) -> wfe::models::WorkflowInstance {
     let config = HashMap::new();
-    let compiled = load_workflow_from_str(yaml, &config).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &config).unwrap();
 
     let persistence = Arc::new(InMemoryPersistenceProvider::new());
     let lock = Arc::new(InMemoryLockProvider::new());
@@ -437,7 +437,7 @@ workflow:
         script: "output('x', 1);"
 "#;
     let config = HashMap::new();
-    let compiled = load_workflow_from_str(yaml, &config).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &config).unwrap();
     assert!(!compiled.step_factories.is_empty());
     let (key, _factory) = &compiled.step_factories[0];
     assert!(
@@ -467,7 +467,7 @@ workflow:
           dynamic_import: true
 "#;
     let config = HashMap::new();
-    let compiled = load_workflow_from_str(yaml, &config).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &config).unwrap();
     assert!(!compiled.step_factories.is_empty());
     // Verify the step config was serialized correctly.
     let step = compiled
@@ -497,7 +497,7 @@ workflow:
         timeout: "3s"
 "#;
     let config = HashMap::new();
-    let compiled = load_workflow_from_str(yaml, &config).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &config).unwrap();
     let step = compiled
         .definition
         .steps
@@ -521,7 +521,7 @@ workflow:
         file: "./scripts/run.js"
 "#;
     let config = HashMap::new();
-    let compiled = load_workflow_from_str(yaml, &config).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &config).unwrap();
     let step = compiled
         .definition
         .steps
@@ -543,7 +543,7 @@ workflow:
       type: deno
 "#;
     let config = HashMap::new();
-    let result = load_workflow_from_str(yaml, &config);
+    let result = load_single_workflow_from_str(yaml, &config);
     match result {
         Err(e) => {
             let msg = e.to_string();
@@ -570,7 +570,7 @@ workflow:
           FOO: bar
 "#;
     let config = HashMap::new();
-    let result = load_workflow_from_str(yaml, &config);
+    let result = load_single_workflow_from_str(yaml, &config);
     match result {
         Err(e) => {
             let msg = e.to_string();
@@ -596,7 +596,7 @@ workflow:
         script: "1+1;"
 "#;
     let config = HashMap::new();
-    assert!(load_workflow_from_str(yaml, &config).is_ok());
+    assert!(load_single_workflow_from_str(yaml, &config).is_ok());
 }
 
 #[test]
@@ -612,7 +612,7 @@ workflow:
         file: "./run.js"
 "#;
     let config = HashMap::new();
-    assert!(load_workflow_from_str(yaml, &config).is_ok());
+    assert!(load_single_workflow_from_str(yaml, &config).is_ok());
 }
 
 #[test]
@@ -632,7 +632,7 @@ workflow:
         script: "output('x', 1);"
 "#;
     let config = HashMap::new();
-    let compiled = load_workflow_from_str(yaml, &config).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &config).unwrap();
     let has_shell = compiled.step_factories.iter().any(|(k, _)| k.contains("shell"));
     let has_deno = compiled.step_factories.iter().any(|(k, _)| k.contains("deno"));
     assert!(has_shell, "should have shell factory");
@@ -655,7 +655,7 @@ workflow:
           - "npm:is-number@7"
 "#;
     let config = HashMap::new();
-    let compiled = load_workflow_from_str(yaml, &config).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &config).unwrap();
     let step = compiled
         .definition
         .steps
@@ -685,7 +685,7 @@ workflow:
           BAZ: qux
 "#;
     let config = HashMap::new();
-    let compiled = load_workflow_from_str(yaml, &config).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &config).unwrap();
     let step = compiled
         .definition
         .steps
@@ -744,7 +744,7 @@ workflow:
 "#;
     let config = HashMap::new();
     // This should compile without errors.
-    let compiled = load_workflow_from_str(yaml, &config).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &config).unwrap();
     assert!(compiled.step_factories.len() >= 2);
 }
 
@@ -809,7 +809,7 @@ workflow:
         script: "1;"
 "#;
     let config = HashMap::new();
-    let compiled = load_workflow_from_str(yaml, &config).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &config).unwrap();
     assert_eq!(
         compiled.definition.description.as_deref(),
         Some("A workflow with deno steps")
@@ -834,7 +834,7 @@ workflow:
         interval: "2s"
 "#;
     let config = HashMap::new();
-    let compiled = load_workflow_from_str(yaml, &config).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &config).unwrap();
     let step = compiled
         .definition
         .steps

wfe-yaml/tests/e2e_yaml.rs

@@ -7,11 +7,11 @@ use wfe::{WorkflowHostBuilder, run_workflow_sync};
 use wfe_core::test_support::{
     InMemoryLockProvider, InMemoryPersistenceProvider, InMemoryQueueProvider,
 };
-use wfe_yaml::load_workflow_from_str;
+use wfe_yaml::load_single_workflow_from_str;
 
 async fn run_yaml_workflow(yaml: &str) -> wfe::models::WorkflowInstance {
     let config = HashMap::new();
-    let compiled = load_workflow_from_str(yaml, &config).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &config).unwrap();
 
     let persistence = Arc::new(InMemoryPersistenceProvider::new());
     let lock = Arc::new(InMemoryLockProvider::new());
@@ -91,7 +91,7 @@ workflow:
             assert_eq!(greeting.as_str(), Some("hello"));
         }
         if let Some(count) = data.get("count") {
-            assert_eq!(count.as_str(), Some("42"));
+            assert_eq!(count.as_i64(), Some(42)); // auto-converted from string "42"
         }
     }
 }

wfe-yaml/tests/lib_tests.rs

@@ -1,7 +1,7 @@
 use std::collections::HashMap;
 use std::io::Write;
 
-use wfe_yaml::{load_workflow, load_workflow_from_str};
+use wfe_yaml::{load_workflow, load_single_workflow_from_str};
 
 #[test]
 fn load_workflow_from_file() {
@@ -45,7 +45,7 @@ fn load_workflow_from_nonexistent_file_returns_error() {
 #[test]
 fn load_workflow_from_str_with_invalid_yaml_returns_error() {
     let yaml = "this is not valid yaml: [[[";
-    let result = load_workflow_from_str(yaml, &HashMap::new());
+    let result = load_single_workflow_from_str(yaml, &HashMap::new());
     assert!(result.is_err());
     let err = match result { Err(e) => e.to_string(), Ok(_) => panic!("expected error") };
     assert!(
@@ -69,7 +69,7 @@ workflow:
     let mut config = HashMap::new();
     config.insert("message".to_string(), serde_json::json!("hello world"));
 
-    let compiled = load_workflow_from_str(yaml, &config).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &config).unwrap();
     let step = compiled
         .definition
         .steps
@@ -94,7 +94,7 @@ workflow:
       config:
         run: echo ((missing))
 "#;
-    let result = load_workflow_from_str(yaml, &HashMap::new());
+    let result = load_single_workflow_from_str(yaml, &HashMap::new());
     assert!(result.is_err());
     let err = match result { Err(e) => e.to_string(), Ok(_) => panic!("expected error") };
     assert!(

wfe-yaml/tests/schema.rs

@@ -1,4 +1,4 @@
-use wfe_yaml::schema::YamlWorkflow;
+use wfe_yaml::schema::{YamlCondition, YamlWorkflow, YamlWorkflowFile};
 
 #[test]
 fn parse_minimal_yaml() {
@@ -192,3 +192,361 @@ workflow:
     assert_eq!(parsed.workflow.id, "template-wf");
     assert_eq!(parsed.workflow.steps.len(), 1);
 }
+
+// --- Multi-workflow file tests ---
+
+#[test]
+fn parse_single_workflow_file() {
+    let yaml = r#"
+workflow:
+  id: single
+  version: 1
+  steps:
+    - name: step1
+      type: shell
+      config:
+        run: echo hello
+"#;
+    let parsed: YamlWorkflowFile = serde_yaml::from_str(yaml).unwrap();
+    assert!(parsed.workflow.is_some());
+    assert!(parsed.workflows.is_none());
+    assert_eq!(parsed.workflow.unwrap().id, "single");
+}
+
+#[test]
+fn parse_multi_workflow_file() {
+    let yaml = r#"
+workflows:
+  - id: build-wf
+    version: 1
+    steps:
+      - name: build
+        type: shell
+        config:
+          run: cargo build
+  - id: test-wf
+    version: 1
+    steps:
+      - name: test
+        type: shell
+        config:
+          run: cargo test
+"#;
+    let parsed: YamlWorkflowFile = serde_yaml::from_str(yaml).unwrap();
+    assert!(parsed.workflow.is_none());
+    assert!(parsed.workflows.is_some());
+    let workflows = parsed.workflows.unwrap();
+    assert_eq!(workflows.len(), 2);
+    assert_eq!(workflows[0].id, "build-wf");
+    assert_eq!(workflows[1].id, "test-wf");
+}
+
+#[test]
+fn parse_workflow_with_input_output_schemas() {
+    let yaml = r#"
+workflow:
+  id: typed-wf
+  version: 1
+  inputs:
+    repo_url: string
+    tags: "list<string>"
+    verbose: bool?
+  outputs:
+    artifact_path: string
+    exit_code: integer
+  steps:
+    - name: step1
+      type: shell
+      config:
+        run: echo hello
+"#;
+    let parsed: YamlWorkflow = serde_yaml::from_str(yaml).unwrap();
+    assert_eq!(parsed.workflow.inputs.len(), 3);
+    assert_eq!(parsed.workflow.inputs.get("repo_url").unwrap(), "string");
+    assert_eq!(
+        parsed.workflow.inputs.get("tags").unwrap(),
+        "list<string>"
+    );
+    assert_eq!(parsed.workflow.inputs.get("verbose").unwrap(), "bool?");
+    assert_eq!(parsed.workflow.outputs.len(), 2);
+    assert_eq!(
+        parsed.workflow.outputs.get("artifact_path").unwrap(),
+        "string"
+    );
+    assert_eq!(
+        parsed.workflow.outputs.get("exit_code").unwrap(),
+        "integer"
+    );
+}
+
+#[test]
+fn parse_step_with_workflow_type() {
+    let yaml = r#"
+workflow:
+  id: parent-wf
+  version: 1
+  steps:
+    - name: run-child
+      type: workflow
+      config:
+        workflow: child-wf
+        workflow_version: 2
+      inputs:
+        - name: repo_url
+          path: data.repo
+      outputs:
+        - name: result
+"#;
+    let parsed: YamlWorkflow = serde_yaml::from_str(yaml).unwrap();
+    let step = &parsed.workflow.steps[0];
+    assert_eq!(step.step_type.as_deref(), Some("workflow"));
+    let config = step.config.as_ref().unwrap();
+    assert_eq!(config.child_workflow.as_deref(), Some("child-wf"));
+    assert_eq!(config.child_version, Some(2));
+    assert_eq!(step.inputs.len(), 1);
+    assert_eq!(step.outputs.len(), 1);
+}
+
+#[test]
+fn parse_workflow_step_version_defaults() {
+    let yaml = r#"
+workflow:
+  id: parent-wf
+  version: 1
+  steps:
+    - name: run-child
+      type: workflow
+      config:
+        workflow: child-wf
+"#;
+    let parsed: YamlWorkflow = serde_yaml::from_str(yaml).unwrap();
+    let config = parsed.workflow.steps[0].config.as_ref().unwrap();
+    assert_eq!(config.child_workflow.as_deref(), Some("child-wf"));
+    // version not specified, should be None in schema (compiler defaults to 1).
+    assert_eq!(config.child_version, None);
+}
+
+#[test]
+fn parse_empty_inputs_outputs_default() {
+    let yaml = r#"
+workflow:
+  id: no-schema-wf
+  version: 1
+  steps:
+    - name: step1
+      type: shell
+      config:
+        run: echo hello
+"#;
+    let parsed: YamlWorkflow = serde_yaml::from_str(yaml).unwrap();
+    assert!(parsed.workflow.inputs.is_empty());
+    assert!(parsed.workflow.outputs.is_empty());
+}
+
+// --- Condition schema tests ---
+
+#[test]
+fn parse_step_with_simple_when_condition() {
+    let yaml = r#"
+workflow:
+  id: cond-wf
+  version: 1
+  steps:
+    - name: deploy
+      type: shell
+      config:
+        run: deploy.sh
+      when:
+        field: .inputs.enabled
+        equals: true
+"#;
+    let parsed: YamlWorkflow = serde_yaml::from_str(yaml).unwrap();
+    let step = &parsed.workflow.steps[0];
+    assert!(step.when.is_some());
+    match step.when.as_ref().unwrap() {
+        YamlCondition::Comparison(cmp) => {
+            assert_eq!(cmp.field, ".inputs.enabled");
+            assert!(cmp.equals.is_some());
+        }
+        _ => panic!("Expected Comparison variant"),
+    }
+}
+
+#[test]
+fn parse_step_with_nested_combinator_conditions() {
+    let yaml = r#"
+workflow:
+  id: nested-cond-wf
+  version: 1
+  steps:
+    - name: deploy
+      type: shell
+      config:
+        run: deploy.sh
+      when:
+        all:
+          - field: .inputs.count
+            gt: 5
+          - any:
+              - field: .inputs.env
+                equals: prod
+              - field: .inputs.env
+                equals: staging
+"#;
+    let parsed: YamlWorkflow = serde_yaml::from_str(yaml).unwrap();
+    let step = &parsed.workflow.steps[0];
+    assert!(step.when.is_some());
+    match step.when.as_ref().unwrap() {
+        YamlCondition::Combinator(c) => {
+            assert!(c.all.is_some());
+            let children = c.all.as_ref().unwrap();
+            assert_eq!(children.len(), 2);
+        }
+        _ => panic!("Expected Combinator variant"),
+    }
+}
+
+#[test]
+fn parse_step_with_not_condition() {
+    let yaml = r#"
+workflow:
+  id: not-cond-wf
+  version: 1
+  steps:
+    - name: deploy
+      type: shell
+      config:
+        run: deploy.sh
+      when:
+        not:
+          field: .inputs.skip
+          equals: true
+"#;
+    let parsed: YamlWorkflow = serde_yaml::from_str(yaml).unwrap();
+    let step = &parsed.workflow.steps[0];
+    match step.when.as_ref().unwrap() {
+        YamlCondition::Combinator(c) => {
+            assert!(c.not.is_some());
+        }
+        _ => panic!("Expected Combinator with not"),
+    }
+}
+
+#[test]
+fn parse_step_with_none_condition() {
+    let yaml = r#"
+workflow:
+  id: none-cond-wf
+  version: 1
+  steps:
+    - name: deploy
+      type: shell
+      config:
+        run: deploy.sh
+      when:
+        none:
+          - field: .inputs.skip
+            equals: true
+          - field: .inputs.disabled
+            equals: true
+"#;
+    let parsed: YamlWorkflow = serde_yaml::from_str(yaml).unwrap();
+    let step = &parsed.workflow.steps[0];
+    match step.when.as_ref().unwrap() {
+        YamlCondition::Combinator(c) => {
+            assert!(c.none.is_some());
+            assert_eq!(c.none.as_ref().unwrap().len(), 2);
+        }
+        _ => panic!("Expected Combinator with none"),
+    }
+}
+
+#[test]
+fn parse_step_with_one_of_condition() {
+    let yaml = r#"
+workflow:
+  id: one-of-wf
+  version: 1
+  steps:
+    - name: deploy
+      type: shell
+      config:
+        run: deploy.sh
+      when:
+        one_of:
+          - field: .inputs.mode
+            equals: fast
+          - field: .inputs.mode
+            equals: slow
+"#;
+    let parsed: YamlWorkflow = serde_yaml::from_str(yaml).unwrap();
+    let step = &parsed.workflow.steps[0];
+    match step.when.as_ref().unwrap() {
+        YamlCondition::Combinator(c) => {
+            assert!(c.one_of.is_some());
+            assert_eq!(c.one_of.as_ref().unwrap().len(), 2);
+        }
+        _ => panic!("Expected Combinator with one_of"),
+    }
+}
+
+#[test]
+fn parse_comparison_with_each_operator() {
+    // Test that each operator variant deserializes correctly.
+    let operators = vec![
+        ("equals: 42", "equals"),
+        ("not_equals: foo", "not_equals"),
+        ("gt: 10", "gt"),
+        ("gte: 10", "gte"),
+        ("lt: 100", "lt"),
+        ("lte: 100", "lte"),
+        ("contains: needle", "contains"),
+        ("is_null: true", "is_null"),
+        ("is_not_null: true", "is_not_null"),
+    ];
+
+    for (op_yaml, op_name) in operators {
+        let yaml = format!(
+            r#"
+workflow:
+  id: op-{op_name}
+  version: 1
+  steps:
+    - name: step1
+      type: shell
+      config:
+        run: echo hi
+      when:
+        field: .inputs.x
+        {op_yaml}
+"#
+        );
+        let parsed: YamlWorkflow = serde_yaml::from_str(&yaml)
+            .unwrap_or_else(|e| panic!("Failed to parse operator {op_name}: {e}"));
+        let step = &parsed.workflow.steps[0];
+        assert!(
+            step.when.is_some(),
+            "Step should have when condition for operator {op_name}"
+        );
+        match step.when.as_ref().unwrap() {
+            YamlCondition::Comparison(_) => {}
+            _ => panic!("Expected Comparison for operator {op_name}"),
+        }
+    }
+}
+
+#[test]
+fn parse_step_without_when_has_none() {
+    let yaml = r#"
+workflow:
+  id: no-when-wf
+  version: 1
+  steps:
+    - name: step1
+      type: shell
+      config:
+        run: echo hi
+"#;
+    let parsed: YamlWorkflow = serde_yaml::from_str(yaml).unwrap();
+    assert!(parsed.workflow.steps[0].when.is_none());
+}

wfe-yaml/tests/shell.rs

@@ -7,14 +7,14 @@ use wfe::{WorkflowHostBuilder, run_workflow_sync};
 use wfe_core::test_support::{
     InMemoryLockProvider, InMemoryPersistenceProvider, InMemoryQueueProvider,
 };
-use wfe_yaml::load_workflow_from_str;
+use wfe_yaml::load_single_workflow_from_str;
 
 async fn run_yaml_workflow_with_data(
     yaml: &str,
     data: serde_json::Value,
 ) -> wfe::models::WorkflowInstance {
     let config = HashMap::new();
-    let compiled = load_workflow_from_str(yaml, &config).unwrap();
+    let compiled = load_single_workflow_from_str(yaml, &config).unwrap();
 
     let persistence = Arc::new(InMemoryPersistenceProvider::new());
     let lock = Arc::new(InMemoryLockProvider::new());
@@ -106,7 +106,7 @@ workflow:
             assert_eq!(greeting.as_str(), Some("hello"));
         }
         if let Some(count) = data.get("count") {
-            assert_eq!(count.as_str(), Some("42"));
+            assert_eq!(count.as_i64(), Some(42)); // auto-converted from string "42"
         }
         if let Some(path) = data.get("path") {
             assert_eq!(path.as_str(), Some("/usr/local/bin"));

wfe-yaml/tests/types.rs

@@ -0,0 +1,107 @@
+use wfe_yaml::types::{parse_type_string, SchemaType};
+
+#[test]
+fn parse_all_primitives() {
+    assert_eq!(parse_type_string("string").unwrap(), SchemaType::String);
+    assert_eq!(parse_type_string("number").unwrap(), SchemaType::Number);
+    assert_eq!(parse_type_string("integer").unwrap(), SchemaType::Integer);
+    assert_eq!(parse_type_string("bool").unwrap(), SchemaType::Bool);
+    assert_eq!(parse_type_string("any").unwrap(), SchemaType::Any);
+}
+
+#[test]
+fn parse_optional_types() {
+    assert_eq!(
+        parse_type_string("string?").unwrap(),
+        SchemaType::Optional(Box::new(SchemaType::String))
+    );
+    assert_eq!(
+        parse_type_string("integer?").unwrap(),
+        SchemaType::Optional(Box::new(SchemaType::Integer))
+    );
+}
+
+#[test]
+fn parse_list_types() {
+    assert_eq!(
+        parse_type_string("list<string>").unwrap(),
+        SchemaType::List(Box::new(SchemaType::String))
+    );
+    assert_eq!(
+        parse_type_string("list<number>").unwrap(),
+        SchemaType::List(Box::new(SchemaType::Number))
+    );
+}
+
+#[test]
+fn parse_map_types() {
+    assert_eq!(
+        parse_type_string("map<string>").unwrap(),
+        SchemaType::Map(Box::new(SchemaType::String))
+    );
+    assert_eq!(
+        parse_type_string("map<any>").unwrap(),
+        SchemaType::Map(Box::new(SchemaType::Any))
+    );
+}
+
+#[test]
+fn parse_nested_generics() {
+    assert_eq!(
+        parse_type_string("list<list<string>>").unwrap(),
+        SchemaType::List(Box::new(SchemaType::List(Box::new(SchemaType::String))))
+    );
+    assert_eq!(
+        parse_type_string("map<list<integer>>").unwrap(),
+        SchemaType::Map(Box::new(SchemaType::List(Box::new(SchemaType::Integer))))
+    );
+}
+
+#[test]
+fn parse_optional_generic() {
+    assert_eq!(
+        parse_type_string("list<string>?").unwrap(),
+        SchemaType::Optional(Box::new(SchemaType::List(Box::new(SchemaType::String))))
+    );
+}
+
+#[test]
+fn parse_unknown_type_returns_error() {
+    let err = parse_type_string("foobar").unwrap_err();
+    assert!(err.contains("Unknown type"), "Got: {err}");
+}
+
+#[test]
+fn parse_unknown_generic_container_returns_error() {
+    let err = parse_type_string("set<string>").unwrap_err();
+    assert!(err.contains("Unknown generic type"), "Got: {err}");
+}
+
+#[test]
+fn parse_empty_returns_error() {
+    let err = parse_type_string("").unwrap_err();
+    assert!(err.contains("Empty"), "Got: {err}");
+}
+
+#[test]
+fn parse_malformed_generic_returns_error() {
+    let err = parse_type_string("list<string").unwrap_err();
+    assert!(err.contains("Malformed"), "Got: {err}");
+}
+
+#[test]
+fn display_roundtrip() {
+    for s in &[
+        "string",
+        "number",
+        "integer",
+        "bool",
+        "any",
+        "list<string>",
+        "map<number>",
+        "list<list<string>>",
+    ] {
+        let parsed = parse_type_string(s).unwrap();
+        assert_eq!(parsed.to_string(), *s, "Roundtrip failed for {s}");
+    }
+}

wfe/Cargo.toml

@@ -3,6 +3,8 @@ name = "wfe"
 version.workspace = true
 edition.workspace = true
 license.workspace = true
+repository.workspace = true
+homepage.workspace = true
 description = "WFE workflow engine - umbrella crate"
 
 [features]
@@ -39,6 +41,7 @@ opentelemetry-otlp = { workspace = true, optional = true }
 [dev-dependencies]
 wfe-core = { workspace = true, features = ["test-support"] }
 wfe-sqlite = { workspace = true }
+wfe-yaml = { workspace = true, features = ["deno"] }
 pretty_assertions = { workspace = true }
 rstest = { workspace = true }
 wiremock = { workspace = true }

wfe/examples/run_pipeline.rs

@@ -0,0 +1,165 @@
+// =============================================================================
+// WFE Self-Hosting CI Pipeline Runner
+// =============================================================================
+//
+// Loads the multi-workflow CI pipeline from a YAML file and runs it to
+// completion using the WFE engine with in-memory providers.
+//
+// Usage:
+//   cargo run --example run_pipeline -p wfe -- workflows.yaml
+//
+// With config:
+//   WFE_CONFIG='{"workspace_dir":"/path/to/wfe","registry":"sunbeam"}' \
+//     cargo run --example run_pipeline -p wfe -- workflows.yaml
+
+use std::collections::HashMap;
+use std::sync::Arc;
+use std::time::Duration;
+
+use serde_json::json;
+
+use wfe::models::WorkflowStatus;
+use wfe::test_support::{InMemoryLockProvider, InMemoryQueueProvider, InMemoryPersistenceProvider};
+use wfe::WorkflowHostBuilder;
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    // Set up tracing.
+    tracing_subscriber::fmt()
+        .with_target(false)
+        .with_timer(tracing_subscriber::fmt::time::uptime())
+        .with_env_filter(
+            std::env::var("RUST_LOG")
+                .unwrap_or_else(|_| "wfe_core=info,wfe=info,run_pipeline=info".into())
+        )
+        .init();
+
+    // Read YAML path from args.
+    let yaml_path = std::env::args()
+        .nth(1)
+        .expect("usage: run_pipeline <workflows.yaml>");
+
+    // Read config from WFE_CONFIG env var (JSON map), merged over sensible defaults.
+    let cwd = std::env::current_dir()?
+        .to_string_lossy()
+        .to_string();
+
+    // Defaults for every ((var)) referenced in the YAML.
+    let mut config: HashMap<String, serde_json::Value> = HashMap::from([
+        ("workspace_dir".into(), json!(cwd)),
+        ("coverage_threshold".into(), json!(85)),
+        ("registry".into(), json!("sunbeam")),
+        ("git_remote".into(), json!("origin")),
+        ("version".into(), json!("0.0.0")),
+    ]);
+
+    // Overlay user-provided config (WFE_CONFIG env var, JSON object).
+    if let Ok(user_json) = std::env::var("WFE_CONFIG") {
+        let user: HashMap<String, serde_json::Value> = serde_json::from_str(&user_json)?;
+        config.extend(user);
+    }
+
+    let config_json = serde_json::to_string(&config)?;
+
+    println!("Loading workflows from: {yaml_path}");
+    println!("Config: {config_json}");
+
+    // Load and compile all workflow definitions from the YAML file.
+    let yaml_content = std::fs::read_to_string(&yaml_path)?;
+    let workflows = wfe_yaml::load_workflow_from_str(&yaml_content, &config)?;
+
+    println!("Compiled {} workflow(s):", workflows.len());
+    for compiled in &workflows {
+        println!(
+            "  - {} v{}  ({} step factories)",
+            compiled.definition.id,
+            compiled.definition.version,
+            compiled.step_factories.len(),
+        );
+    }
+
+    // Build the host with in-memory providers.
+    let persistence = Arc::new(InMemoryPersistenceProvider::default());
+    let lock = Arc::new(InMemoryLockProvider::default());
+    let queue = Arc::new(InMemoryQueueProvider::default());
+
+    let host = WorkflowHostBuilder::new()
+        .use_persistence(persistence)
+        .use_lock_provider(lock)
+        .use_queue_provider(queue)
+        .build()?;
+
+    // Register all compiled workflows and their step factories.
+    // We must move the factories out of the compiled workflows since
+    // register_step_factory requires 'static closures.
+    for mut compiled in workflows {
+        let factories = std::mem::take(&mut compiled.step_factories);
+        for (key, factory) in factories {
+            host.register_step_factory(&key, move || factory()).await;
+        }
+        host.register_workflow_definition(compiled.definition).await;
+    }
+
+    // Start the engine.
+    host.start().await?;
+    println!("\nEngine started. Launching 'ci' workflow...\n");
+
+    // Determine workspace_dir for initial data (use config value or cwd).
+    let workspace_dir = config
+        .get("workspace_dir")
+        .and_then(|v| v.as_str())
+        .unwrap_or(&cwd)
+        .to_string();
+
+    let data = json!({
+        "workspace_dir": workspace_dir,
+    });
+
+    let workflow_id = host.start_workflow("ci", 1, data).await?;
+    println!("Workflow instance: {workflow_id}");
+
+    // Poll for completion with a 1-hour timeout.
+    let timeout = Duration::from_secs(3600);
+    let deadline = tokio::time::Instant::now() + timeout;
+    let poll_interval = Duration::from_millis(500);
+
+    let final_instance = loop {
+        let instance = host.get_workflow(&workflow_id).await?;
+        match instance.status {
+            WorkflowStatus::Complete | WorkflowStatus::Terminated => break instance,
+            _ if tokio::time::Instant::now() > deadline => {
+                eprintln!("Timeout: workflow did not complete within {timeout:?}");
+                break instance;
+            }
+            _ => tokio::time::sleep(poll_interval).await,
+        }
+    };
+
+    // Print final status.
+    println!("\n========================================");
+    println!("Pipeline status: {:?}", final_instance.status);
+    println!(
+        "Execution pointers: {} total, {} complete",
+        final_instance.execution_pointers.len(),
+        final_instance
+            .execution_pointers
+            .iter()
+            .filter(|p| p.status == wfe::models::PointerStatus::Complete)
+            .count()
+    );
+
+    // Print workflow data (contains outputs from all steps).
+    if let Some(obj) = final_instance.data.as_object() {
+        println!("\nKey outputs:");
+        for key in ["version", "all_tests_passed", "coverage", "published", "released"] {
+            if let Some(val) = obj.get(key) {
+                println!("  {key}: {val}");
+            }
+        }
+    }
+    println!("========================================");
+
+    host.stop().await;
+    println!("\nEngine stopped.");
+    Ok(())
+}

wfe/src/host.rs

@@ -1,3 +1,5 @@
+use std::future::Future;
+use std::pin::Pin;
 use std::sync::Arc;
 
 use tokio::sync::RwLock;
@@ -10,8 +12,8 @@ use wfe_core::models::{
     WorkflowStatus,
 };
 use wfe_core::traits::{
-    DistributedLockProvider, LifecyclePublisher, PersistenceProvider, QueueProvider, SearchIndex,
-    StepBody, WorkflowData,
+    DistributedLockProvider, HostContext, LifecyclePublisher, PersistenceProvider, QueueProvider,
+    SearchIndex, StepBody, WorkflowData,
 };
 use wfe_core::traits::registry::WorkflowRegistry;
 use wfe_core::{Result, WfeError};
@@ -19,6 +21,51 @@ use wfe_core::builder::WorkflowBuilder;
 
 use crate::registry::InMemoryWorkflowRegistry;
 
+/// A lightweight HostContext implementation that delegates to the WorkflowHost's
+/// components. Used by the background consumer task which cannot hold a direct
+/// reference to WorkflowHost (it runs in a spawned tokio task).
+pub(crate) struct HostContextImpl {
+    persistence: Arc<dyn PersistenceProvider>,
+    registry: Arc<RwLock<InMemoryWorkflowRegistry>>,
+    queue_provider: Arc<dyn QueueProvider>,
+}
+
+impl HostContext for HostContextImpl {
+    fn start_workflow(
+        &self,
+        definition_id: &str,
+        version: u32,
+        data: serde_json::Value,
+    ) -> Pin<Box<dyn Future<Output = Result<String>> + Send + '_>> {
+        let def_id = definition_id.to_string();
+        Box::pin(async move {
+            // Look up the definition.
+            let reg = self.registry.read().await;
+            let definition = reg
+                .get_definition(&def_id, Some(version))
+                .ok_or_else(|| WfeError::DefinitionNotFound {
+                    id: def_id.clone(),
+                    version,
+                })?;
+
+            // Create the child workflow instance.
+            let mut instance = WorkflowInstance::new(&def_id, version, data);
+            if !definition.steps.is_empty() {
+                instance.execution_pointers.push(ExecutionPointer::new(0));
+            }
+
+            let id = self.persistence.create_new_workflow(&instance).await?;
+
+            // Queue for execution.
+            self.queue_provider
+                .queue_work(&id, QueueType::Workflow)
+                .await?;
+
+            Ok(id)
+        })
+    }
+}
+
 /// The main orchestrator that ties all workflow engine components together.
 pub struct WorkflowHost {
     pub(crate) persistence: Arc<dyn PersistenceProvider>,
@@ -49,6 +96,7 @@ impl WorkflowHost {
         sr.register::<sequence::SequenceStep>();
         sr.register::<wait_for::WaitForStep>();
         sr.register::<while_step::WhileStep>();
+        sr.register::<sub_workflow::SubWorkflowStep>();
     }
 
     /// Spawn background polling tasks for processing workflows and events.
@@ -66,6 +114,11 @@ impl WorkflowHost {
         let step_registry = Arc::clone(&self.step_registry);
         let queue = Arc::clone(&self.queue_provider);
         let shutdown = self.shutdown.clone();
+        let host_ctx = Arc::new(HostContextImpl {
+            persistence: Arc::clone(&self.persistence),
+            registry: Arc::clone(&self.registry),
+            queue_provider: Arc::clone(&self.queue_provider),
+        });
 
         tokio::spawn(async move {
             loop {
@@ -94,7 +147,7 @@ impl WorkflowHost {
                                     Some(def) => {
                                         let def_clone = def.clone();
                                         let sr = step_registry.read().await;
-                                        if let Err(e) = executor.execute(&workflow_id, &def_clone, &sr).await {
+                                        if let Err(e) = executor.execute(&workflow_id, &def_clone, &sr, Some(host_ctx.as_ref())).await {
                                             error!(workflow_id = %workflow_id, error = %e, "Workflow execution failed");
                                         }
                                     }

wfe/tests/nested_workflow_tests.rs

@@ -0,0 +1,516 @@
+use std::sync::Arc;
+use std::time::Duration;
+
+use async_trait::async_trait;
+use serde_json::json;
+
+use wfe::models::{
+    ExecutionResult, StepOutcome, WorkflowDefinition, WorkflowStatus, WorkflowStep,
+};
+use wfe::traits::step::{StepBody, StepExecutionContext};
+use wfe::WorkflowHostBuilder;
+use wfe_core::primitives::sub_workflow::SubWorkflowStep;
+use wfe_core::test_support::{
+    InMemoryLockProvider, InMemoryPersistenceProvider, InMemoryQueueProvider,
+};
+
+// ----- Test step bodies -----
+
+/// A step that sets output data with {"result": "child_done"}.
+#[derive(Default)]
+struct SetResultStep;
+
+#[async_trait]
+impl StepBody for SetResultStep {
+    async fn run(&mut self, _ctx: &StepExecutionContext<'_>) -> wfe_core::Result<ExecutionResult> {
+        let mut result = ExecutionResult::next();
+        result.output_data = Some(json!({"result": "child_done"}));
+        Ok(result)
+    }
+}
+
+/// A step that reads workflow data and proceeds.
+#[derive(Default)]
+struct ReadDataStep;
+
+#[async_trait]
+impl StepBody for ReadDataStep {
+    async fn run(&mut self, _ctx: &StepExecutionContext<'_>) -> wfe_core::Result<ExecutionResult> {
+        Ok(ExecutionResult::next())
+    }
+}
+
+/// A step that always fails.
+#[derive(Default)]
+struct FailingStep;
+
+#[async_trait]
+impl StepBody for FailingStep {
+    async fn run(&mut self, _ctx: &StepExecutionContext<'_>) -> wfe_core::Result<ExecutionResult> {
+        Err(wfe_core::WfeError::StepExecution(
+            "intentional failure".to_string(),
+        ))
+    }
+}
+
+/// A step that sets greeting output based on input.
+#[derive(Default)]
+struct GreetStep;
+
+#[async_trait]
+impl StepBody for GreetStep {
+    async fn run(&mut self, ctx: &StepExecutionContext<'_>) -> wfe_core::Result<ExecutionResult> {
+        let name = ctx
+            .workflow
+            .data
+            .get("name")
+            .and_then(|v| v.as_str())
+            .unwrap_or("unknown");
+        let mut result = ExecutionResult::next();
+        result.output_data = Some(json!({"greeting": format!("hello {name}")}));
+        Ok(result)
+    }
+}
+
+/// A no-op step.
+#[derive(Default)]
+struct NoOpStep;
+
+#[async_trait]
+impl StepBody for NoOpStep {
+    async fn run(&mut self, _ctx: &StepExecutionContext<'_>) -> wfe_core::Result<ExecutionResult> {
+        Ok(ExecutionResult::next())
+    }
+}
+
+// ----- Helpers -----
+
+fn build_host() -> (wfe::WorkflowHost, Arc<InMemoryPersistenceProvider>) {
+    let persistence = Arc::new(InMemoryPersistenceProvider::new());
+    let lock = Arc::new(InMemoryLockProvider::new());
+    let queue = Arc::new(InMemoryQueueProvider::new());
+
+    let host = WorkflowHostBuilder::new()
+        .use_persistence(persistence.clone() as Arc<dyn wfe_core::traits::PersistenceProvider>)
+        .use_lock_provider(lock as Arc<dyn wfe_core::traits::DistributedLockProvider>)
+        .use_queue_provider(queue as Arc<dyn wfe_core::traits::QueueProvider>)
+        .build()
+        .unwrap();
+
+    (host, persistence)
+}
+
+fn sub_workflow_step_type() -> String {
+    std::any::type_name::<SubWorkflowStep>().to_string()
+}
+
+/// Build a child workflow definition with a single step that produces output.
+fn build_child_definition(child_step_type: &str) -> WorkflowDefinition {
+    let mut def = WorkflowDefinition::new("child-workflow", 1);
+    let step0 = WorkflowStep::new(0, child_step_type);
+    def.steps = vec![step0];
+    def
+}
+
+/// Build a parent workflow with: SubWorkflowStep(0) -> ReadDataStep(1).
+fn build_parent_definition() -> WorkflowDefinition {
+    let mut def = WorkflowDefinition::new("parent-workflow", 1);
+
+    let mut step0 = WorkflowStep::new(0, sub_workflow_step_type());
+    step0.step_config = Some(json!({
+        "workflow_id": "child-workflow",
+        "version": 1,
+        "inputs": {},
+        "output_keys": ["result"]
+    }));
+    step0.outcomes.push(StepOutcome {
+        next_step: 1,
+        label: None,
+        value: None,
+    });
+
+    let step1 = WorkflowStep::new(1, std::any::type_name::<ReadDataStep>());
+
+    def.steps = vec![step0, step1];
+    def
+}
+
+async fn wait_for_status(
+    host: &wfe::WorkflowHost,
+    id: &str,
+    status: WorkflowStatus,
+    timeout: Duration,
+) -> wfe::models::WorkflowInstance {
+    let start = tokio::time::Instant::now();
+    loop {
+        if start.elapsed() > timeout {
+            let instance = host.get_workflow(id).await.unwrap();
+            panic!(
+                "Workflow {id} did not reach status {status:?} within {timeout:?}. \
+                 Current status: {:?}, pointers: {:?}",
+                instance.status, instance.execution_pointers
+            );
+        }
+        let instance = host.get_workflow(id).await.unwrap();
+        if instance.status == status {
+            return instance;
+        }
+        tokio::time::sleep(Duration::from_millis(25)).await;
+    }
+}
+
+// ----- Tests -----
+
+/// Parent workflow starts a child, waits for the child's completion event,
+/// then proceeds to a second step.
+#[tokio::test]
+async fn parent_workflow_starts_child_and_waits() {
+    let (host, _persistence) = build_host();
+
+    let child_def = build_child_definition(std::any::type_name::<SetResultStep>());
+    let parent_def = build_parent_definition();
+
+    host.register_step::<SetResultStep>().await;
+    host.register_step::<ReadDataStep>().await;
+
+    host.register_workflow_definition(child_def).await;
+    host.register_workflow_definition(parent_def).await;
+
+    host.start().await.unwrap();
+
+    let parent_id = host
+        .start_workflow("parent-workflow", 1, json!({}))
+        .await
+        .unwrap();
+
+    let parent_instance = wait_for_status(
+        &host,
+        &parent_id,
+        WorkflowStatus::Complete,
+        Duration::from_secs(10),
+    )
+    .await;
+
+    assert_eq!(parent_instance.status, WorkflowStatus::Complete);
+
+    // The SubWorkflowStep's execution pointer should have received event data
+    // from the child's completion event.
+    let sub_wf_pointer = &parent_instance.execution_pointers[0];
+    assert!(
+        sub_wf_pointer.event_data.is_some(),
+        "SubWorkflowStep pointer should have event_data from child completion"
+    );
+
+    let event_data = sub_wf_pointer.event_data.as_ref().unwrap();
+    assert_eq!(
+        event_data.get("status").and_then(|v| v.as_str()),
+        Some("Complete")
+    );
+
+    // The child's output data should be in the event.
+    let child_data = event_data.get("data").unwrap();
+    assert_eq!(child_data.get("result"), Some(&json!("child_done")));
+
+    host.stop().await;
+}
+
+/// Parent workflow starts a child that passes all data through (no output_keys filter).
+#[tokio::test]
+async fn parent_workflow_passes_all_child_data() {
+    let (host, _) = build_host();
+
+    let child_def = build_child_definition(std::any::type_name::<SetResultStep>());
+
+    // Parent with no output_keys filter - passes all child data.
+    let mut parent_def = WorkflowDefinition::new("parent-all-data", 1);
+    let mut step0 = WorkflowStep::new(0, sub_workflow_step_type());
+    step0.step_config = Some(json!({
+        "workflow_id": "child-workflow",
+        "version": 1,
+        "inputs": {}
+    }));
+    step0.outcomes.push(StepOutcome {
+        next_step: 1,
+        label: None,
+        value: None,
+    });
+    let step1 = WorkflowStep::new(1, std::any::type_name::<NoOpStep>());
+    parent_def.steps = vec![step0, step1];
+
+    host.register_step::<SetResultStep>().await;
+    host.register_step::<NoOpStep>().await;
+    host.register_workflow_definition(child_def).await;
+    host.register_workflow_definition(parent_def).await;
+
+    host.start().await.unwrap();
+
+    let parent_id = host
+        .start_workflow("parent-all-data", 1, json!({}))
+        .await
+        .unwrap();
+
+    let instance = wait_for_status(
+        &host,
+        &parent_id,
+        WorkflowStatus::Complete,
+        Duration::from_secs(10),
+    )
+    .await;
+
+    assert_eq!(instance.status, WorkflowStatus::Complete);
+    host.stop().await;
+}
+
+/// Child workflow that uses typed inputs and produces typed output.
+#[tokio::test]
+async fn nested_workflow_with_typed_inputs_outputs() {
+    let (host, _) = build_host();
+
+    // Child workflow: GreetStep reads "name" from workflow data and produces {"greeting": "hello <name>"}.
+    let mut child_def = WorkflowDefinition::new("greet-child", 1);
+    let step0 = WorkflowStep::new(0, std::any::type_name::<GreetStep>());
+    child_def.steps = vec![step0];
+
+    // Parent workflow: SubWorkflowStep starts greet-child with {"name": "world"}.
+    let mut parent_def = WorkflowDefinition::new("greet-parent", 1);
+    let mut step0 = WorkflowStep::new(0, sub_workflow_step_type());
+    step0.step_config = Some(json!({
+        "workflow_id": "greet-child",
+        "version": 1,
+        "inputs": {"name": "world"},
+        "output_keys": ["greeting"]
+    }));
+    step0.outcomes.push(StepOutcome {
+        next_step: 1,
+        label: None,
+        value: None,
+    });
+    let step1 = WorkflowStep::new(1, std::any::type_name::<NoOpStep>());
+    parent_def.steps = vec![step0, step1];
+
+    host.register_step::<GreetStep>().await;
+    host.register_step::<NoOpStep>().await;
+    host.register_workflow_definition(child_def).await;
+    host.register_workflow_definition(parent_def).await;
+
+    host.start().await.unwrap();
+
+    let parent_id = host
+        .start_workflow("greet-parent", 1, json!({}))
+        .await
+        .unwrap();
+
+    let instance = wait_for_status(
+        &host,
+        &parent_id,
+        WorkflowStatus::Complete,
+        Duration::from_secs(10),
+    )
+    .await;
+
+    assert_eq!(instance.status, WorkflowStatus::Complete);
+
+    // Check the SubWorkflowStep pointer got the greeting from the child.
+    let sub_wf_pointer = &instance.execution_pointers[0];
+    let event_data = sub_wf_pointer.event_data.as_ref().unwrap();
+    let child_data = event_data.get("data").unwrap();
+    assert_eq!(
+        child_data.get("greeting"),
+        Some(&json!("hello world")),
+        "Child should produce greeting from input name"
+    );
+
+    host.stop().await;
+}
+
+/// When a child workflow fails, the parent should still complete because the
+/// completion event carries the terminated status. The SubWorkflowStep will
+/// process the event data even if the child ended in error, and the parent
+/// will see the child's status in the event_data.
+#[tokio::test]
+async fn nested_workflow_child_failure_propagates() {
+    let (host, _) = build_host();
+
+    // Child workflow with a failing step.
+    let mut child_def = WorkflowDefinition::new("failing-child", 1);
+    let step0 = WorkflowStep::new(0, std::any::type_name::<FailingStep>());
+    child_def.steps = vec![step0];
+
+    // Parent workflow: SubWorkflowStep starts failing-child.
+    let mut parent_def = WorkflowDefinition::new("parent-of-failing", 1);
+    let mut step0 = WorkflowStep::new(0, sub_workflow_step_type());
+    step0.step_config = Some(json!({
+        "workflow_id": "failing-child",
+        "version": 1,
+        "inputs": {}
+    }));
+    // No outcome wired — if the child fails and the sub workflow step
+    // processes the completion event, the parent can proceed.
+    step0.outcomes.push(StepOutcome {
+        next_step: 1,
+        label: None,
+        value: None,
+    });
+    let step1 = WorkflowStep::new(1, std::any::type_name::<NoOpStep>());
+    parent_def.steps = vec![step0, step1];
+
+    host.register_step::<FailingStep>().await;
+    host.register_step::<NoOpStep>().await;
+    host.register_workflow_definition(child_def).await;
+    host.register_workflow_definition(parent_def).await;
+
+    host.start().await.unwrap();
+
+    let parent_id = host
+        .start_workflow("parent-of-failing", 1, json!({}))
+        .await
+        .unwrap();
+
+    // The child will fail. Depending on executor error handling, the child may
+    // reach Terminated status. We wait a bit then check states.
+    tokio::time::sleep(Duration::from_secs(2)).await;
+
+    let parent = host.get_workflow(&parent_id).await.unwrap();
+    // Parent should still be Runnable (waiting for the child's completion event)
+    // since the failing child may not emit a completion event.
+    // Check that the parent is stuck waiting (SubWorkflowStep issued wait_for_event).
+    let has_waiting = parent
+        .execution_pointers
+        .iter()
+        .any(|p| p.status == wfe::models::PointerStatus::WaitingForEvent);
+    // Either the parent is waiting or already completed (if the child errored
+    // and published a terminated event).
+    assert!(
+        has_waiting || parent.status == WorkflowStatus::Complete,
+        "Parent should be waiting for child or complete. Status: {:?}",
+        parent.status
+    );
+
+    host.stop().await;
+}
+
+/// Test that SubWorkflowStep is registered as a built-in primitive.
+#[tokio::test]
+async fn sub_workflow_step_registered_as_primitive() {
+    let (host, _) = build_host();
+
+    // Start registers primitives.
+    host.start().await.unwrap();
+
+    // Verify by checking that the step registry has the SubWorkflowStep type.
+    // We do this indirectly — if we can run a workflow using SubWorkflowStep
+    // without explicit registration, it's registered.
+    let child_def = build_child_definition(std::any::type_name::<NoOpStep>());
+    let parent_def = build_parent_definition();
+
+    // Only register the non-primitive steps, NOT SubWorkflowStep.
+    host.register_step::<NoOpStep>().await;
+    host.register_step::<SetResultStep>().await;
+    host.register_step::<ReadDataStep>().await;
+
+    host.register_workflow_definition(child_def).await;
+    host.register_workflow_definition(parent_def).await;
+
+    let parent_id = host
+        .start_workflow("parent-workflow", 1, json!({}))
+        .await
+        .unwrap();
+
+    // If SubWorkflowStep is registered as a primitive, the parent should start
+    // the child and eventually complete.
+    let instance = wait_for_status(
+        &host,
+        &parent_id,
+        WorkflowStatus::Complete,
+        Duration::from_secs(10),
+    )
+    .await;
+
+    assert_eq!(instance.status, WorkflowStatus::Complete);
+    host.stop().await;
+}
+
+/// Test that starting a child with a non-existent definition propagates an error.
+#[tokio::test]
+async fn nested_workflow_nonexistent_child_definition() {
+    let (host, _) = build_host();
+
+    // Parent references a child that is NOT registered.
+    let mut parent_def = WorkflowDefinition::new("parent-missing-child", 1);
+    let mut step0 = WorkflowStep::new(0, sub_workflow_step_type());
+    step0.step_config = Some(json!({
+        "workflow_id": "nonexistent-child",
+        "version": 1,
+        "inputs": {}
+    }));
+    parent_def.steps = vec![step0];
+
+    host.register_workflow_definition(parent_def).await;
+
+    host.start().await.unwrap();
+
+    let parent_id = host
+        .start_workflow("parent-missing-child", 1, json!({}))
+        .await
+        .unwrap();
+
+    // The parent should fail because the child definition doesn't exist.
+    // Give it time to process.
+    tokio::time::sleep(Duration::from_secs(2)).await;
+
+    let parent = host.get_workflow(&parent_id).await.unwrap();
+    // The error handler should have set the pointer to Failed and the workflow
+    // to Suspended (default error behavior is Retry then Suspend).
+    let pointer = &parent.execution_pointers[0];
+    let is_failed = pointer.status == wfe::models::PointerStatus::Failed
+        || pointer.status == wfe::models::PointerStatus::Sleeping;
+    assert!(
+        is_failed
+            || parent.status == WorkflowStatus::Suspended
+            || parent.status == WorkflowStatus::Terminated,
+        "SubWorkflowStep should error when child definition is missing. \
+         Pointer status: {:?}, Workflow status: {:?}",
+        pointer.status,
+        parent.status
+    );
+
+    host.stop().await;
+}
+
+/// Test that starting a workflow via the host works end-to-end,
+/// exercising the HostContextImpl path indirectly.
+#[tokio::test]
+async fn host_context_impl_starts_workflow() {
+    let (host, _) = build_host();
+
+    // Register a child definition.
+    let child_def = build_child_definition(std::any::type_name::<NoOpStep>());
+    host.register_step::<NoOpStep>().await;
+    host.register_workflow_definition(child_def).await;
+
+    host.start().await.unwrap();
+
+    // Start a child workflow via the host's start_workflow.
+    let child_id = host
+        .start_workflow("child-workflow", 1, json!({"test": true}))
+        .await
+        .unwrap();
+
+    // Verify the child was created and completes.
+    let child = host.get_workflow(&child_id).await.unwrap();
+    assert_eq!(child.workflow_definition_id, "child-workflow");
+    assert_eq!(child.version, 1);
+    assert_eq!(child.data.get("test"), Some(&json!(true)));
+
+    // Wait for the child to complete.
+    let instance = wait_for_status(
+        &host,
+        &child_id,
+        WorkflowStatus::Complete,
+        Duration::from_secs(5),
+    )
+    .await;
+    assert_eq!(instance.status, WorkflowStatus::Complete);
+
+    host.stop().await;
+}

workflows.yaml

@@ -0,0 +1,778 @@
+# workflows.yaml — WFE self-hosting CI pipeline
+#
+# Demonstrates every WFE feature. Idempotent — safe to run repeatedly.
+#
+# Usage:
+#   cargo run --example run_pipeline -p wfe -- workflows.yaml
+#
+# With config:
+#   WFE_CONFIG='{"workspace_dir":"/path/to/wfe","registry":"sunbeam","git_remote":"origin","coverage_threshold":85}' \
+#     cargo run --example run_pipeline -p wfe -- workflows.yaml
+#
+# TODO: Support multi-file merging — individual task files (e.g., lint.yaml,
+# test.yaml, publish.yaml) that compose into a single pipeline definition.
+
+# ─── Shared Templates ───────────────────────────────────────────────
+# The _templates key is ignored by the workflow parser (extra keys are
+# skipped). Anchors are resolved by serde_yaml before parsing.
+
+_templates:
+  shell_defaults: &shell_defaults
+    type: shell
+    config:
+      shell: bash
+      timeout: 5m
+
+  long_running: &long_running
+    type: shell
+    config:
+      shell: bash
+      timeout: 30m
+
+# ─── Workflow: preflight ───────────────────────────────────────────────
+
+workflows:
+  - id: preflight
+    version: 1
+    inputs:
+      workspace_dir: string
+    outputs:
+      cargo_ok: bool
+      nextest_ok: bool
+      llvm_cov_ok: bool
+      docker_ok: bool
+      lima_ok: bool
+      buildctl_ok: bool
+      git_ok: bool
+    steps:
+      - name: check-tools
+        type: shell
+        outputs:
+          - name: cargo_ok
+          - name: nextest_ok
+          - name: llvm_cov_ok
+          - name: docker_ok
+          - name: lima_ok
+          - name: buildctl_ok
+          - name: git_ok
+        config:
+          shell: bash
+          timeout: 1m
+          run: |
+            CARGO_OK=false; NEXTEST_OK=false; LLVM_COV_OK=false
+            DOCKER_OK=false; LIMA_OK=false; BUILDCTL_OK=false; GIT_OK=false
+
+            command -v cargo >/dev/null 2>&1 && CARGO_OK=true
+            command -v cargo-nextest >/dev/null 2>&1 && NEXTEST_OK=true
+            command -v cargo-llvm-cov >/dev/null 2>&1 && LLVM_COV_OK=true
+            command -v docker >/dev/null 2>&1 && docker info >/dev/null 2>&1 && DOCKER_OK=true
+            command -v limactl >/dev/null 2>&1 && LIMA_OK=true
+            command -v buildctl >/dev/null 2>&1 && BUILDCTL_OK=true
+            command -v git >/dev/null 2>&1 && GIT_OK=true
+
+            echo "Tool availability:"
+            echo "  cargo:        $CARGO_OK"
+            echo "  nextest:      $NEXTEST_OK"
+            echo "  llvm-cov:     $LLVM_COV_OK"
+            echo "  docker:       $DOCKER_OK"
+            echo "  lima:         $LIMA_OK"
+            echo "  buildctl:     $BUILDCTL_OK"
+            echo "  git:          $GIT_OK"
+
+            echo "##wfe[output cargo_ok=$CARGO_OK]"
+            echo "##wfe[output nextest_ok=$NEXTEST_OK]"
+            echo "##wfe[output llvm_cov_ok=$LLVM_COV_OK]"
+            echo "##wfe[output docker_ok=$DOCKER_OK]"
+            echo "##wfe[output lima_ok=$LIMA_OK]"
+            echo "##wfe[output buildctl_ok=$BUILDCTL_OK]"
+            echo "##wfe[output git_ok=$GIT_OK]"
+
+            # Fail if essential tools are missing
+            if [ "$CARGO_OK" = "false" ] || [ "$NEXTEST_OK" = "false" ] || [ "$GIT_OK" = "false" ]; then
+              echo "ERROR: Essential tools missing (cargo, nextest, or git)"
+              exit 1
+            fi
+
+  # ─── Workflow: lint ──────────────────────────────────────────────────
+
+  - id: lint
+    version: 1
+    inputs:
+      workspace_dir: string
+    outputs:
+      fmt_ok: bool
+      clippy_ok: bool
+    steps:
+      - name: fmt-check
+        <<: *shell_defaults
+        outputs:
+          - name: fmt_ok
+        config:
+          run: |
+            cd "$WORKSPACE_DIR"
+            cargo fmt --all -- --check
+            echo "##wfe[output fmt_ok=true]"
+
+      - name: clippy
+        <<: *shell_defaults
+        outputs:
+          - name: clippy_ok
+        config:
+          run: |
+            cd "$WORKSPACE_DIR"
+            cargo clippy --workspace -- -D warnings
+            echo "##wfe[output clippy_ok=true]"
+
+  # ─── Workflow: test-unit ─────────────────────────────────────────
+
+  - id: test-unit
+    version: 1
+    inputs:
+      workspace_dir: string
+    outputs:
+      tests_passed: bool
+      deno_tests_passed: bool
+    steps:
+      - name: core-tests
+        <<: *long_running
+        outputs:
+          - name: tests_passed
+        config:
+          run: |
+            cd "$WORKSPACE_DIR"
+            cargo nextest run -P ci
+            echo "##wfe[output tests_passed=true]"
+
+      - name: deno-tests
+        <<: *long_running
+        outputs:
+          - name: deno_tests_passed
+        config:
+          run: |
+            cd "$WORKSPACE_DIR"
+            cargo nextest run -p wfe-yaml --features deno -P ci
+            echo "##wfe[output deno_tests_passed=true]"
+
+      - name: feature-tests
+        <<: *shell_defaults
+        config:
+          run: |
+            cd "$WORKSPACE_DIR"
+            cargo nextest run -p wfe-yaml --features buildkit,containerd -P ci
+
+  # ─── Workflow: test-integration ──────────────────────────────────
+
+  - id: test-integration
+    version: 1
+    inputs:
+      workspace_dir: string
+    outputs:
+      postgres_ok: bool
+      valkey_ok: bool
+      opensearch_ok: bool
+    steps:
+      - name: docker-up
+        <<: *long_running
+        outputs:
+          - name: docker_started
+        config:
+          run: |
+            # Docker runs inside a lima VM. Start it if needed.
+            if ! command -v limactl >/dev/null 2>&1; then
+              echo "limactl not available — skipping integration tests"
+              echo "##wfe[output docker_started=false]"
+              exit 0
+            fi
+
+            # Start the docker lima VM if not running
+            if ! limactl list 2>/dev/null | grep -q "docker.*Running"; then
+              echo "Starting docker lima VM..."
+              limactl start docker 2>&1 || {
+                echo "Failed to start docker VM — skipping integration tests"
+                echo "##wfe[output docker_started=false]"
+                exit 0
+              }
+            fi
+
+            # Wait for Docker daemon to be ready
+            for i in $(seq 1 30); do
+              if docker info >/dev/null 2>&1; then
+                break
+              fi
+              echo "Waiting for Docker daemon... ($i/30)"
+              sleep 2
+            done
+
+            if ! docker info >/dev/null 2>&1; then
+              echo "Docker daemon not ready after 60s — skipping"
+              echo "##wfe[output docker_started=false]"
+              exit 0
+            fi
+
+            cd "$WORKSPACE_DIR"
+            docker compose up -d --wait
+            echo "##wfe[output docker_started=true]"
+        on_failure:
+          name: docker-up-failed
+          type: shell
+          config:
+            run: echo "Failed to start Docker services"
+
+      - name: postgres-tests
+        <<: *shell_defaults
+        when:
+          field: .outputs.docker_started
+          equals: true
+        outputs:
+          - name: postgres_ok
+        config:
+          run: |
+            cd "$WORKSPACE_DIR"
+            cargo nextest run -p wfe-postgres -P ci
+            echo "##wfe[output postgres_ok=true]"
+
+      - name: valkey-tests
+        <<: *shell_defaults
+        when:
+          field: .outputs.docker_started
+          equals: true
+        outputs:
+          - name: valkey_ok
+        config:
+          run: |
+            cd "$WORKSPACE_DIR"
+            cargo nextest run -p wfe-valkey -P ci
+            echo "##wfe[output valkey_ok=true]"
+
+      - name: opensearch-tests
+        <<: *shell_defaults
+        when:
+          field: .outputs.docker_started
+          equals: true
+        outputs:
+          - name: opensearch_ok
+        config:
+          run: |
+            cd "$WORKSPACE_DIR"
+            cargo nextest run -p wfe-opensearch -P ci
+            echo "##wfe[output opensearch_ok=true]"
+
+    ensure:
+      - name: docker-down
+        <<: *shell_defaults
+        config:
+          run: |
+            if docker info >/dev/null 2>&1; then
+              cd "$WORKSPACE_DIR"
+              docker compose down 2>/dev/null || true
+            fi
+
+  # ─── Workflow: test-containers ───────────────────────────────────
+
+  - id: test-containers
+    version: 1
+    inputs:
+      workspace_dir: string
+    outputs:
+      buildkit_ok: bool
+      containerd_ok: bool
+    steps:
+      - name: lima-up
+        <<: *long_running
+        outputs:
+          - name: lima_started
+        config:
+          run: |
+            if ! command -v limactl >/dev/null 2>&1; then
+              echo "limactl not available — skipping container tests"
+              echo "##wfe[output lima_started=false]"
+              exit 0
+            fi
+
+            # Start the wfe-test VM if not running
+            if ! limactl list 2>/dev/null | grep -q "wfe-test.*Running"; then
+              echo "Starting wfe-test lima VM..."
+              limactl start --name=wfe-test "$WORKSPACE_DIR/test/lima/wfe-test.yaml" 2>&1 || {
+                echo "Failed to start wfe-test VM — skipping container tests"
+                echo "##wfe[output lima_started=false]"
+                exit 0
+              }
+            fi
+
+            # Wait for sockets to be available
+            for i in $(seq 1 30); do
+              if [ -S "$HOME/.lima/wfe-test/sock/buildkitd.sock" ]; then
+                break
+              fi
+              echo "Waiting for buildkitd socket... ($i/30)"
+              sleep 2
+            done
+
+            echo "##wfe[output lima_started=true]"
+
+      - name: buildkit-tests
+        <<: *shell_defaults
+        when:
+          field: .outputs.lima_started
+          equals: true
+        outputs:
+          - name: buildkit_ok
+        config:
+          run: |
+            cd "$WORKSPACE_DIR"
+            export WFE_BUILDKIT_ADDR="unix://$HOME/.lima/wfe-test/sock/buildkitd.sock"
+            cargo nextest run -p wfe-buildkit -P ci
+            echo "##wfe[output buildkit_ok=true]"
+
+      - name: containerd-tests
+        <<: *shell_defaults
+        when:
+          field: .outputs.lima_started
+          equals: true
+        outputs:
+          - name: containerd_ok
+        config:
+          run: |
+            cd "$WORKSPACE_DIR"
+            export WFE_CONTAINERD_ADDR="unix://$HOME/.lima/wfe-test/sock/containerd.sock"
+            cargo nextest run -p wfe-containerd -P ci
+            echo "##wfe[output containerd_ok=true]"
+
+    ensure:
+      - name: lima-down
+        <<: *shell_defaults
+        config:
+          run: |
+            limactl stop wfe-test 2>/dev/null || true
+
+  # ─── Workflow: test (orchestrator) ───────────────────────────────
+
+  - id: test
+    version: 1
+    inputs:
+      workspace_dir: string
+    outputs:
+      all_passed: bool
+    steps:
+      - name: run-unit
+        type: workflow
+        outputs:
+          - name: tests_passed
+          - name: deno_tests_passed
+        config:
+          workflow: test-unit
+          version: 1
+
+      - name: run-integration
+        type: workflow
+        outputs:
+          - name: postgres_ok
+          - name: valkey_ok
+          - name: opensearch_ok
+        config:
+          workflow: test-integration
+          version: 1
+
+      - name: run-containers
+        type: workflow
+        outputs:
+          - name: buildkit_ok
+          - name: containerd_ok
+        config:
+          workflow: test-containers
+          version: 1
+
+      - name: mark-passed
+        <<: *shell_defaults
+        outputs:
+          - name: all_passed
+        config:
+          run: |
+            echo "All test workflows completed"
+            echo "##wfe[output all_passed=true]"
+
+  # ─── Workflow: cover ─────────────────────────────────────────────
+
+  - id: cover
+    version: 1
+    inputs:
+      workspace_dir: string
+      threshold: number?
+    outputs:
+      line_coverage: number
+      meets_threshold: bool
+    steps:
+      - name: run-coverage
+        <<: *shell_defaults
+        outputs:
+          - name: coverage_ok
+        config:
+          run: |
+            cd "$WORKSPACE_DIR"
+            if ! command -v cargo-llvm-cov >/dev/null 2>&1; then
+              echo "cargo-llvm-cov not installed — skipping coverage"
+              echo "##wfe[output coverage_ok=false]"
+              exit 0
+            fi
+            cargo llvm-cov nextest -P cover --json 2>&1 | grep '^{' > /tmp/wfe-coverage.json || true
+            if [ -s /tmp/wfe-coverage.json ]; then
+              echo "##wfe[output coverage_ok=true]"
+            else
+              echo "Coverage JSON not produced — llvm-cov may have failed"
+              echo "##wfe[output coverage_ok=false]"
+            fi
+            echo "##wfe[output coverage_json=/tmp/wfe-coverage.json]"
+
+      - name: assert-threshold
+        type: deno
+        when:
+          field: .outputs.coverage_ok
+          equals: true
+        outputs:
+          - name: line_coverage
+          - name: meets_threshold
+        config:
+          script: |
+            const data = inputs();
+            const threshold = data.coverage_threshold || 85;
+
+            // Read the coverage JSON produced by run-coverage step
+            const text = await readFile("/tmp/wfe-coverage.json");
+            const report = JSON.parse(text);
+
+            const totals = report.data[0].totals;
+            const lineCov = (totals.lines.covered / totals.lines.count * 100).toFixed(1);
+
+            log(`Line coverage: ${lineCov}% (threshold: ${threshold}%)`);
+
+            output("line_coverage", parseFloat(lineCov));
+            output("meets_threshold", parseFloat(lineCov) >= threshold);
+
+            if (parseFloat(lineCov) < threshold) {
+              throw new Error(`Coverage ${lineCov}% is below threshold ${threshold}%`);
+            }
+          permissions:
+            read: ["/tmp"]
+
+  # ─── Workflow: package ───────────────────────────────────────────
+
+  - id: package
+    version: 1
+    inputs:
+      workspace_dir: string
+    outputs:
+      packages_ok: bool
+    steps:
+      - name: package-all
+        <<: *shell_defaults
+        outputs:
+          - name: packages_ok
+        config:
+          run: |
+            echo "Packaging all crates (stub — remove exit 0 for real packaging)"
+            echo "##wfe[output packages_ok=true]"
+            exit 0
+            cd "$WORKSPACE_DIR"
+            for crate in wfe-core wfe-sqlite wfe-postgres wfe-opensearch wfe-valkey \
+                         wfe-buildkit-protos wfe-containerd-protos wfe-buildkit wfe-containerd \
+                         wfe wfe-yaml; do
+              echo "Packaging $crate..."
+              cargo package -p "$crate" --no-verify --allow-dirty 2>&1 || exit 1
+            done
+            echo "##wfe[output packages_ok=true]"
+
+  # ─── Workflow: tag ───────────────────────────────────────────────
+
+  - id: tag
+    version: 1
+    inputs:
+      workspace_dir: string
+    outputs:
+      version: string
+      tag_created: bool
+      tag_already_existed: bool
+    steps:
+      - name: read-version
+        type: deno
+        outputs:
+          - name: version
+        config:
+          script: |
+            // Stub — remove the early return for real tagging
+            log("Reading version (stub)");
+            output("version", "1.0.0");
+          permissions:
+            read: ["((workspace_dir))"]
+
+      - name: check-tag-exists
+        <<: *shell_defaults
+        outputs:
+          - name: tag_already_existed
+          - name: tag_created
+        config:
+          run: |
+            echo "Checking tag (stub — remove exit 0 for real tagging)"
+            echo "##wfe[output tag_already_existed=true]"
+            echo "##wfe[output tag_created=false]"
+            exit 0
+            VERSION=$(echo "$VERSION" | tr -d '[:space:]')
+            TAG="v${VERSION}"
+            if git tag -l "$TAG" | grep -q "$TAG"; then
+              echo "Tag $TAG already exists — skipping"
+              echo "##wfe[output tag_already_existed=true]"
+              echo "##wfe[output tag_created=false]"
+            else
+              echo "Tag $TAG does not exist — will create"
+              echo "##wfe[output tag_already_existed=false]"
+            fi
+
+      - name: create-tag
+        <<: *shell_defaults
+        outputs:
+          - name: tag_created
+        config:
+          run: |
+            echo "Creating tag (stub — remove exit 0 for real tagging)"
+            echo "##wfe[output tag_created=false]"
+            exit 0
+            if [ "$TAG_ALREADY_EXISTED" = "true" ]; then
+              echo "Skipping tag creation (already exists)"
+              echo "##wfe[output tag_created=false]"
+              exit 0
+            fi
+            VERSION=$(echo "$VERSION" | tr -d '[:space:]')
+            TAG="v${VERSION}"
+            git tag -a "$TAG" -m "$TAG"
+            echo "##wfe[output tag_created=true]"
+
+  # ─── Workflow: publish ───────────────────────────────────────────
+
+  - id: publish
+    version: 1
+    inputs:
+      workspace_dir: string
+      registry: string?
+    outputs:
+      all_published: bool
+    steps:
+      - name: publish-protos
+        <<: *shell_defaults
+        config:
+          run: |
+            echo "Publishing protos (stub — remove exit 0 for real publish)"
+            exit 0
+            cd "$WORKSPACE_DIR"
+            REGISTRY="${REGISTRY:-sunbeam}"
+            PUBLISHED=""
+            for crate in wfe-buildkit-protos wfe-containerd-protos; do
+              echo "Publishing $crate..."
+              if cargo publish -p "$crate" --registry "$REGISTRY" 2>&1; then
+                PUBLISHED="$PUBLISHED $crate"
+              else
+                echo "Already published or failed: $crate (continuing)"
+              fi
+            done
+            echo "##wfe[output published_protos=$PUBLISHED]"
+        error_behavior:
+          type: retry
+          interval: 10s
+          max_retries: 2
+
+      - name: publish-core
+        <<: *shell_defaults
+        config:
+          run: |
+            echo "Publishing core (stub — remove exit 0 for real publish)"
+            exit 0
+            cd "$WORKSPACE_DIR"
+            REGISTRY="${REGISTRY:-sunbeam}"
+            cargo publish -p wfe-core --registry "$REGISTRY" 2>&1 || echo "Already published"
+            echo "##wfe[output core_published=true]"
+        error_behavior:
+          type: retry
+          interval: 10s
+          max_retries: 2
+
+      - name: publish-providers
+        <<: *shell_defaults
+        config:
+          run: |
+            echo "Publishing providers (stub — remove exit 0 for real publish)"
+            exit 0
+            cd "$WORKSPACE_DIR"
+            REGISTRY="${REGISTRY:-sunbeam}"
+            for crate in wfe-sqlite wfe-postgres wfe-opensearch wfe-valkey; do
+              echo "Publishing $crate..."
+              cargo publish -p "$crate" --registry "$REGISTRY" 2>&1 || echo "Already published: $crate"
+            done
+            echo "##wfe[output providers_published=true]"
+        error_behavior:
+          type: retry
+          interval: 10s
+          max_retries: 2
+
+      - name: publish-executors
+        <<: *shell_defaults
+        config:
+          run: |
+            echo "Publishing executors (stub — remove exit 0 for real publish)"
+            exit 0
+            cd "$WORKSPACE_DIR"
+            REGISTRY="${REGISTRY:-sunbeam}"
+            for crate in wfe-buildkit wfe-containerd; do
+              echo "Publishing $crate..."
+              cargo publish -p "$crate" --registry "$REGISTRY" 2>&1 || echo "Already published: $crate"
+            done
+            echo "##wfe[output executors_published=true]"
+
+      - name: publish-framework
+        <<: *shell_defaults
+        outputs:
+          - name: all_published
+        config:
+          run: |
+            echo "Publishing framework (stub — remove exit 0 for real publish)"
+            echo "##wfe[output all_published=true]"
+            exit 0
+            cd "$WORKSPACE_DIR"
+            REGISTRY="${REGISTRY:-sunbeam}"
+            for crate in wfe wfe-yaml; do
+              echo "Publishing $crate..."
+              cargo publish -p "$crate" --registry "$REGISTRY" 2>&1 || echo "Already published: $crate"
+            done
+            echo "##wfe[output all_published=true]"
+
+    on_failure:
+      - name: log-partial-publish
+        <<: *shell_defaults
+        outputs:
+          - name: all_published
+        config:
+          run: |
+            echo "WARNING: Publish partially failed. Check logs above."
+            echo "##wfe[output all_published=false]"
+
+  # ─── Workflow: release ───────────────────────────────────────────
+
+  - id: release
+    version: 1
+    inputs:
+      workspace_dir: string
+      version: string
+      git_remote: string?
+    outputs:
+      pushed: bool
+      notes: string
+    steps:
+      - name: push-tags
+        <<: *shell_defaults
+        outputs:
+          - name: pushed
+        config:
+          run: |
+            echo "Pushing tags (stub — remove exit 0 for real release)"
+            echo "##wfe[output pushed=true]"
+            exit 0
+            REMOTE="${GIT_REMOTE:-origin}"
+            git push "$REMOTE" --tags
+            echo "##wfe[output pushed=true]"
+
+      - name: generate-notes
+        type: deno
+        outputs:
+          - name: notes
+        config:
+          script: |
+            // Stub — remove the early return for real release
+            log("Generating release notes (stub)");
+            output("notes", "stub release notes");
+          permissions:
+            run: true
+
+  # ─── Workflow: ci (top-level orchestrator) ───────────────────────
+
+  - id: ci
+    version: 1
+    inputs:
+      workspace_dir: string
+      registry: string?
+      git_remote: string?
+      coverage_threshold: number?
+    outputs:
+      version: string
+      all_tests_passed: bool
+      coverage: number
+      published: bool
+      released: bool
+    steps:
+      - name: run-preflight
+        type: workflow
+        outputs:
+          - name: cargo_ok
+          - name: nextest_ok
+          - name: llvm_cov_ok
+          - name: docker_ok
+          - name: lima_ok
+          - name: buildctl_ok
+          - name: git_ok
+        config:
+          workflow: preflight
+          version: 1
+
+      - name: run-lint
+        type: workflow
+        outputs:
+          - name: fmt_ok
+          - name: clippy_ok
+        config:
+          workflow: lint
+          version: 1
+
+      - name: run-tests
+        type: workflow
+        outputs:
+          - name: all_tests_passed
+        config:
+          workflow: test
+          version: 1
+
+      - name: run-coverage
+        type: workflow
+        outputs:
+          - name: coverage
+        config:
+          workflow: cover
+          version: 1
+
+      - name: run-package
+        type: workflow
+        outputs:
+          - name: packages_ok
+        config:
+          workflow: package
+          version: 1
+
+      - name: run-tag
+        type: workflow
+        outputs:
+          - name: version
+          - name: tag_created
+        config:
+          workflow: tag
+          version: 1
+
+      - name: run-publish
+        type: workflow
+        outputs:
+          - name: published
+        config:
+          workflow: publish
+          version: 1
+
+      - name: run-release
+        type: workflow
+        outputs:
+          - name: released
+        config:
+          workflow: release
+          version: 1