fix: [AI-6771] cancel() race condition and idle state on normal loop exit (#845)

* fix: [AI-6771] cancel() race condition and idle state on normal loop exit

Fix B1: Remove premature SessionStatus.set(idle) from cancel() main path.
On abort, the processor catch block publishes session.error then sets idle,
preserving correct event ordering. The !match fallback still sets idle
directly since no processor is running in that case.

Fix B2: Add SessionStatus.set(idle) after the while loop exits normally
so callers waiting on session.status:idle receive the event on clean completion.

* feat: [AI-6771] add telemetry for streaming error scenarios

Add Telemetry.track({ type: "error", context: "streaming" }) in the
non-retry, non-overflow branch of the processor.ts streaming catch block.

Covers:
- MessageAbortedError (Stop button / dispose)
- UnknownError (SSE chunk timeout after retry exhaustion)
- APIError (provider failures after retry exhaustion)
- AuthError and any other unhandled streaming error

Event fields: session_id, error_name, error_message, context

* fix: reword cancel() comment to avoid false-positive in SessionStatus guard test

---------

Co-authored-by: saravmajestic <saravmajestic@altimate.ai>
Co-authored-by: altimate-harness-bot[bot] <274995457+altimate-harness-bot[bot]@users.noreply.github.com>

Author: altimate-harness-bot[bot]

packages/opencode/src/session/processor.ts

@@ -533,6 +533,18 @@ export namespace SessionProcessor {
                 sessionID: input.assistantMessage.sessionID,
                 error: input.assistantMessage.error,
               })
+              // altimate_change start — telemetry for unhandled streaming errors (non-retry, non-overflow)
+              // Covers: MessageAbortedError (Stop/dispose), UnknownError (SSE chunk timeout),
+              // APIError (provider failures after retry exhaustion), AuthError, and any other streaming error.
+              Telemetry.track({
+                type: "error",
+                timestamp: Date.now(),
+                session_id: input.assistantMessage.sessionID,
+                error_name: error.name,
+                error_message: (error.data as any)?.message ?? String((e as any)?.message ?? ""),
+                context: "streaming",
+              })
+              // altimate_change end
               // altimate_change start — SessionStatus.set became async; await so idle state flushes before exit
               await SessionStatus.set(input.sessionID, { type: "idle" })
               // altimate_change end

packages/opencode/src/session/prompt.ts

@@ -303,13 +303,15 @@ export namespace SessionPrompt {
     const s = state()
     const match = s[sessionID]
     if (!match) {
+      // Session already ended or was never started — set idle directly since no processor will do it
       await SessionStatus.set(sessionID, { type: "idle" })
       return
     }
     match.abort.abort()
     delete s[sessionID]
-    await SessionStatus.set(sessionID, { type: "idle" })
-    return
+    // Do NOT set idle status here — on abort the processor's catch block
+    // publishes session.error THEN sets idle, preserving correct event ordering.
+    // On normal completion, loop() sets idle after the while loop exits (see below).
   }
   // altimate_change end
 
@@ -1110,6 +1112,11 @@ export namespace SessionPrompt {
       }
       continue
     }
+    // altimate_change start — set idle on normal loop exit; abort path is handled by processor catch block
+    if (!abort.aborted) {
+      await SessionStatus.set(sessionID, { type: "idle" })
+    }
+    // altimate_change end
     SessionCompaction.prune({ sessionID })
     // altimate_change start — session end telemetry
     const outcome = abort.aborted