Add concurrency caps, the two-pane web UI, AGENTS.md, and plan status

api/openapi.yaml

@@ -125,6 +125,25 @@ paths:
         "404": { $ref: "#/components/responses/Error" }
         "409": { $ref: "#/components/responses/Error" }
 
+  /api/tasks/{taskId}/events:
+    parameters:
+      - { name: taskId, in: path, required: true, schema: { type: string } }
+    get:
+      operationId: listTaskEvents
+      description: The task's events after a seq, oldest first. Page by passing the last seq back as after.
+      parameters:
+        - { name: after, in: query, required: false, schema: { type: integer, format: int64 } }
+        - { name: limit, in: query, required: false, schema: { type: integer, minimum: 1, maximum: 1000 } }
+      responses:
+        "200":
+          description: Up to limit events (default 500).
+          content:
+            application/json:
+              schema:
+                type: array
+                items: { $ref: "#/components/schemas/Event" }
+        "404": { $ref: "#/components/responses/Error" }
+
   /api/tasks/{taskId}/sessions:
     parameters:
       - { name: taskId, in: path, required: true, schema: { type: string } }
@@ -368,7 +387,10 @@ components:
         vendor: { type: string, enum: [claude] }
         model: { type: string, description: Requested model; empty means the vendor's default. }
         vendor_session_id: { type: string }
-        state: { type: string, enum: [idle, running, completed] }
+        state:
+          type: string
+          enum: [idle, queued, running, completed]
+          description: queued means a turn is waiting for a free slot under the concurrency caps.
         role: { type: string, enum: [implementer] }
         created_by: { type: string }
         created_at: { type: string, format: date-time }
@@ -415,7 +437,7 @@ components:
         task_id: { type: string }
         agent_session_id: { type: string }
         thread_id: { type: string }
-        kind: { type: string, enum: [question, report, session_error] }
+        kind: { type: string, enum: [question, report, session_error, rate_limited] }
         priority: { type: string, enum: [blocked, gate, review, fyi] }
         blocking: { type: boolean }
         payload:
@@ -424,6 +446,7 @@ components:
             question: question, why_blocked, options, recommended_option, attachments.
             report: done, open_questions, next_steps, risks, deviations.
             session_error: error.
+            rate_limited: vendor, rate_limit (the vendor's rate-limit status), error.
         state: { $ref: "#/components/schemas/InboxState" }
         snoozed_until: { type: string, format: date-time }
         created_at: { type: string, format: date-time }
@@ -491,9 +514,15 @@ components:
 
     Status:
       type: object
-      required: [started_at, db_bytes, last_event_seq, projects, active_tasks, sse_clients, live_agents]
+      required: [started_at, db_bytes, last_event_seq, projects, active_tasks, sse_clients, live_agents, running_turns, queued_turns, rate_limits]
       properties:
         live_agents: { type: integer, description: Agent processes currently running. }
+        running_turns: { type: integer }
+        queued_turns: { type: integer }
+        rate_limits:
+          type: object
+          description: The latest rate-limit status each vendor reported, keyed by vendor.
+          additionalProperties: { type: object }
         started_at: { type: string, format: date-time }
         db_bytes: { type: integer, format: int64 }
         last_event_seq: { type: integer, format: int64 }