proper Matrix threading + concise tool call formatting

agent_ux: uses Relation::Thread (not Reply) for tool call details.
format_tool_call extracts key params instead of dumping raw JSON.
format_tool_result truncated to 200 chars.

matrix_utils: added make_thread_reply() for threaded responses.
sync.rs routes ThreadReply engagement to threaded messages.

src/agent_ux.rs

@@ -1,5 +1,5 @@
 use matrix_sdk::room::Room;
-use ruma::events::relation::InReplyTo;
+use ruma::events::relation::Thread;
 use ruma::events::room::message::{Relation, RoomMessageEventContent};
 use ruma::OwnedEventId;
 use tracing::warn;
@@ -47,25 +47,19 @@ impl AgentProgress {
         }
     }
 
-    /// Post a step update to the thread. Creates the thread on first call.
+    /// Post a step update to the thread on the user's message.
     pub async fn post_step(&mut self, text: &str) {
-        let content = if let Some(ref _root) = self.thread_root_id {
-            // Reply in existing thread
-            let mut msg = RoomMessageEventContent::text_markdown(text);
-            msg.relates_to = Some(Relation::Reply {
-                in_reply_to: InReplyTo::new(self.user_event_id.clone()),
-            });
-            msg
-        } else {
-            // First message — starts the thread as a reply to the user's message
-            let mut msg = RoomMessageEventContent::text_markdown(text);
-            msg.relates_to = Some(Relation::Reply {
-                in_reply_to: InReplyTo::new(self.user_event_id.clone()),
-            });
-            msg
-        };
+        let latest = self
+            .thread_root_id
+            .as_ref()
+            .unwrap_or(&self.user_event_id)
+            .clone();
 
-        match self.room.send(content).await {
+        let mut msg = RoomMessageEventContent::text_markdown(text);
+        let thread = Thread::plain(self.user_event_id.clone(), latest);
+        msg.relates_to = Some(Relation::Thread(thread));
+
+        match self.room.send(msg).await {
             Ok(response) => {
                 if self.thread_root_id.is_none() {
                     self.thread_root_id = Some(response.event_id);
@@ -96,19 +90,51 @@ impl AgentProgress {
         .await;
     }
 
-    /// Format a tool call for the thread.
+    /// Format a tool call for the thread — concise, not raw args.
     pub fn format_tool_call(name: &str, args: &str) -> String {
-        format!("`{name}` → ```json\n{args}\n```")
+        // Extract just the key params, not the full JSON blob
+        let summary = match serde_json::from_str::<serde_json::Value>(args) {
+            Ok(v) => {
+                let params: Vec<String> = v
+                    .as_object()
+                    .map(|obj| {
+                        obj.iter()
+                            .filter(|(_, v)| !v.is_null() && v.as_str() != Some(""))
+                            .map(|(k, v)| {
+                                let val = match v {
+                                    serde_json::Value::String(s) => {
+                                        if s.len() > 40 {
+                                            format!("{}…", &s[..40])
+                                        } else {
+                                            s.clone()
+                                        }
+                                    }
+                                    other => other.to_string(),
+                                };
+                                format!("{k}={val}")
+                            })
+                            .collect()
+                    })
+                    .unwrap_or_default();
+                if params.is_empty() {
+                    String::new()
+                } else {
+                    format!(" ({})", params.join(", "))
+                }
+            }
+            Err(_) => String::new(),
+        };
+        format!("🔧 `{name}`{summary}")
     }
 
-    /// Format a tool result for the thread.
+    /// Format a tool result for the thread — short summary only.
     pub fn format_tool_result(name: &str, result: &str) -> String {
-        let truncated = if result.len() > 500 {
-            format!("{}…", &result[..500])
+        let truncated = if result.len() > 200 {
+            format!("{}…", &result[..200])
         } else {
             result.to_string()
         };
-        format!("`{name}` ← {truncated}")
+        format!("← `{name}`: {truncated}")
     }
 }
 
@@ -117,23 +143,41 @@ mod tests {
     use super::*;
 
     #[test]
-    fn test_format_tool_call() {
-        let formatted = AgentProgress::format_tool_call("search_archive", r#"{"query":"test"}"#);
+    fn test_format_tool_call_with_params() {
+        let formatted = AgentProgress::format_tool_call("search_archive", r#"{"query":"test","room":"general"}"#);
         assert!(formatted.contains("search_archive"));
-        assert!(formatted.contains("test"));
+        assert!(formatted.contains("query=test"));
+        assert!(formatted.contains("room=general"));
+        assert!(formatted.starts_with("🔧"));
+    }
+
+    #[test]
+    fn test_format_tool_call_no_params() {
+        let formatted = AgentProgress::format_tool_call("list_rooms", "{}");
+        assert_eq!(formatted, "🔧 `list_rooms`");
+    }
+
+    #[test]
+    fn test_format_tool_call_truncates_long_values() {
+        let long_code = "x".repeat(100);
+        let args = format!(r#"{{"code":"{}"}}"#, long_code);
+        let formatted = AgentProgress::format_tool_call("run_script", &args);
+        assert!(formatted.contains("code="));
+        assert!(formatted.contains("…"));
+        assert!(formatted.len() < 200);
     }
 
     #[test]
     fn test_format_tool_result_truncation() {
-        let long = "x".repeat(1000);
+        let long = "x".repeat(500);
         let formatted = AgentProgress::format_tool_result("search", &long);
-        assert!(formatted.len() < 600);
+        assert!(formatted.len() < 300);
         assert!(formatted.ends_with('…'));
     }
 
     #[test]
     fn test_format_tool_result_short() {
         let formatted = AgentProgress::format_tool_result("search", "3 results found");
-        assert_eq!(formatted, "`search` ← 3 results found");
+        assert_eq!(formatted, "← `search`: 3 results found");
     }
 }

src/matrix_utils.rs

@@ -56,6 +56,19 @@ pub fn make_reply_content(body: &str, reply_to_event_id: OwnedEventId) -> RoomMe
     content
 }
 
+/// Build a threaded reply — shows up in Matrix threads UI.
+/// The thread root is the event being replied to (creates the thread on first use).
+pub fn make_thread_reply(
+    body: &str,
+    thread_root_id: OwnedEventId,
+) -> RoomMessageEventContent {
+    use ruma::events::relation::Thread;
+    let mut content = RoomMessageEventContent::text_markdown(body);
+    let thread = Thread::plain(thread_root_id.clone(), thread_root_id);
+    content.relates_to = Some(Relation::Thread(thread));
+    content
+}
+
 /// Send an emoji reaction to a message.
 pub async fn send_reaction(
     room: &Room,