test(agent): strengthen compact continuation coverage

Document why cloud compaction needs a hidden follow-up and assert the command returns the continuation turn's final stop reason.

Generated-By: PostHog Code
Task-Id: 233a983e-daa3-4d81-af56-bb43488687ab

Author: tatoalo

packages/agent/src/server/agent-server.test.ts

@@ -1463,6 +1463,10 @@ describe("AgentServer HTTP Mode", () => {
       });
 
       expect(response.status).toBe(200);
+      const body = (await response.json()) as {
+        result?: { stopReason?: string };
+      };
+      expect(body.result?.stopReason).toBe("end_turn");
       expect(prompt).toHaveBeenCalledTimes(2);
       expect(prompt.mock.calls[0]?.[0].prompt).toEqual([
         {

packages/agent/src/server/agent-server.ts

@@ -969,6 +969,8 @@ export class AgentServer {
             result.stopReason === "end_turn" &&
             isManualCompactPrompt(prompt)
           ) {
+            // `/compact` is an SDK-local command, so without a follow-up the
+            // cloud run reports completion before the model resumes the task.
             this.recordTurnUsage(result.usage);
             result = await this.promptWithUpstreamRetry({
               sessionId: this.session.acpSessionId,