Let Compact continue on another model or vendor

api/openapi.yaml

@@ -817,7 +817,13 @@ paths:
       operationId: compactSession
       description: >
         Asks the idle session's agent for a handoff (goal, decisions, state, dead ends, open questions, files). When that turn ends,
-        the session is completed and a new session on the same task and model starts with the handoff as its first message.
+        the session is completed and a new session on the same task starts with the handoff as its first message, on the requested model
+        or else the old session's.
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema: { $ref: "#/components/schemas/CompactCreate" }
       responses:
         "202":
           description: The handoff turn was started.
@@ -1501,6 +1507,13 @@ components:
           type: string
           description: Model for this turn and later ones. When it differs from the session's model, the session switches before the message is sent.
 
+    CompactCreate:
+      type: object
+      properties:
+        model:
+          type: string
+          description: Model for the new session, on either vendor. The old session still writes the handoff. Defaults to the old session's model.
+
     Blob:
       type: object
       required: [id, content_type, created_by, created_at]