Add todo mode and replace the plan with TODO.md

api/openapi.yaml

@@ -145,6 +145,43 @@ paths:
         "400": { $ref: "#/components/responses/Error" }
         "404": { $ref: "#/components/responses/Error" }
 
+  /api/projects/{projectId}/todo:
+    parameters:
+      - { name: projectId, in: path, required: true, schema: { type: string } }
+    get:
+      operationId: getTodo
+      description: The items of TODO.md at the root of the project's default branch, in file order.
+      responses:
+        "200":
+          description: The items; exists is false when the default branch has no TODO.md.
+          content:
+            application/json:
+              schema: { $ref: "#/components/schemas/Todo" }
+        "404": { $ref: "#/components/responses/Error" }
+
+  /api/projects/{projectId}/todo/tasks:
+    parameters:
+      - { name: projectId, in: path, required: true, schema: { type: string } }
+    post:
+      operationId: startTodoItem
+      description: >
+        Creates a task for a TODO.md item, recording the item as its todo_item, and starts its agent with the item as
+        the first message. Refused while another active task has the same item.
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema: { $ref: "#/components/schemas/TodoStart" }
+      responses:
+        "201":
+          description: The new task.
+          content:
+            application/json:
+              schema: { $ref: "#/components/schemas/Task" }
+        "400": { $ref: "#/components/responses/Error" }
+        "404": { $ref: "#/components/responses/Error" }
+        "409": { $ref: "#/components/responses/Error" }
+
   /api/tasks/{taskId}:
     parameters:
       - { name: taskId, in: path, required: true, schema: { type: string } }
@@ -643,6 +680,31 @@ components:
         created_at: { type: string, format: date-time }
         closed_at: { type: string, format: date-time, description: When the task was merged or discarded. }
         merge_commit: { type: string, description: "merged: the squash commit on the default branch; empty when there was nothing to merge." }
+        todo_item: { type: string, description: "The title of the TODO.md item the task was started from; absent for other tasks." }
+
+    Todo:
+      type: object
+      required: [exists, items]
+      properties:
+        exists: { type: boolean, description: Whether the default branch has a TODO.md at its root. }
+        items:
+          type: array
+          items: { $ref: "#/components/schemas/TodoItem" }
+
+    TodoItem:
+      type: object
+      required: [title, body, section]
+      properties:
+        title: { type: string, description: "The item's first line, without its list marker: the item's identity." }
+        body: { type: string, description: The item's further lines, as Markdown with the item's indentation removed. }
+        section: { type: string, description: The text of the nearest heading above the item; empty when there is none. }
+
+    TodoStart:
+      type: object
+      required: [title]
+      properties:
+        title: { type: string, description: The title of the item to start. }
+        model: { type: string }
 
     Unmerged:
       type: object