Hmbown/CodeWhale · warning

first Stop

Error message

first Stop

What it means

Test assertion `manager.cancel_agent(&agent_id).expect("first Stop")` in the model-wait-cancel fan-in test at `crates/tui/src/tools/subagent/tests.rs:6587`. The test puts an agent into ModelWait state and issues the first Stop/cancel; the expect asserts cancellation of a live agent succeeds and returns its termination record. A panic here means the manager refused or failed the first cancel.

Solutions

1. Print the cancel_agent error (replace expect with a descriptive panic including the Err) to see why the first Stop was rejected.
2. Verify the agent was registered with the same manager and id used in cancel_agent.
3. Check cancel_agent's state gating: ModelWait agents must remain cancellable; fix the state machine if it now returns an error for ModelWait.
4. Re-run with the unmodified test to confirm it is a regression from a recent commit (git blame the cancel path).

Example fix

// before
let first = manager.cancel_agent(&agent_id).expect("first Stop");
// after
let first = manager.cancel_agent(&agent_id)
    .unwrap_or_else(|e| panic!("first Stop of {agent_id} failed: {e:?}"));

// Before cancelling, confirm the agent is known and cancellable:
assert!(manager.get_worker_record(&agent_id).is_some(), "agent must be registered before first Stop");

let first = manager.cancel_agent(&agent_id).unwrap_or_else(|e| panic!("first Stop failed: {e:?}"));

When it happens

Trigger: `cancel_agent` returns Err for an agent it should know about — e.g. the agent was never registered with this manager (wrong SubAgentManager instance or tmp path), the id string 'agent_model_wait_cancel' mismatches, or a change to cancel_agent makes ModelWait a non-cancellable state.

Common situations: Refactors of the subagent state machine (adding states, gating cancellation by status) that forget ModelWait; test setup reordering so the manager is constructed with a different store dir than the agent was registered under.

Understand the failure class

Background: "Invalid state transition" errors: "status must be X, actually Y", "already rejected/charging/uninstalled", "cannot ... while running" — what they mean when a library rejects your call — this error's family across 31 libraries.

Related errors

• first coordination interrupt
• parent cancellation fan-in
• repeated Stop
• worker record
• worker record remains inspectable

AI-assisted analysis of Hmbown/CodeWhale@73e0f67d83 (2026-09-22). Data as JSON: /api/errors/7a38629112bb27a5. Report an issue: GitHub.

Appendix: source

Thrown at crates/tui/src/tools/subagent/tests.rs:6587

    let (completion_tx, mut completion_rx) = mpsc::channel::<SubAgentCompletion>(16);
    let (mailbox, mut mailbox_rx) = Mailbox::new(CancellationToken::new());
    let (event_tx, mut event_rx) = mpsc::channel(8);
    let mut runtime = runtime_with_depth(1, Some(completion_tx));
    runtime.mailbox = Some(mailbox);
    runtime.event_tx = Some(event_tx);
    agent.terminal_delivery = Some(SubAgentTerminalDeliveryContext::from_runtime(&runtime));
    manager.agents.insert(agent_id.clone(), agent);
    manager.register_worker(make_worker_spec(&agent_id, tmp.path().to_path_buf()));
    manager.record_worker_event(
        &agent_id,
        AgentWorkerStatus::ModelWait,
        Some(SUBAGENT_MODEL_WAIT_REASON.to_string()),
        Some(1),
        None,
    );

    let first = manager.cancel_agent(&agent_id).expect("first Stop");
    let second = manager.cancel_agent(&agent_id).expect("repeated Stop");
    assert_eq!(first.status, SubAgentStatus::Cancelled);
    assert_eq!(second.status, SubAgentStatus::Cancelled);
    assert_eq!(
        first
            .checkpoint
            .as_ref()
            .map(|checkpoint| checkpoint.reason.as_str()),
        Some("test_checkpoint")
    );

    let completion = completion_rx
        .try_recv()
        .expect("parent cancellation fan-in");
    assert!(completion.payload.contains(r#""status":"cancelled""#));
    assert!(completion_rx.try_recv().is_err());

    let terminal_mail = mailbox_rx

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