[setoelkahfi]

The SDK records a $/cancel_request against the request it names, but a handler has to read responder.cancellation() for anything to happen, and none did. A client that cancels by JSON-RPC id instead of session/cancel was ignored.

• session/prompt: the handler watches the marker and stops the turn through cancel_turn, the path session/cancel already takes, so the running command is killed too. The prompt is still answered with a result and the cancelled stop reason, which keeps what was streamed.
• authenticate: the sign-in is dropped, which closes the loopback listener, and the request is answered -32800.
• The other handlers still ignore the notification, as the spec allows.

The select polls the turn before the marker. A turn registers for cancellation on its first poll, and a cancel that arrived while the prompt was queued on the session lock would otherwise run before there was anything to cancel.

Test: a_cancel_request_for_the_prompt_ends_the_turn_cancelled in tests/acp_client_terminal.rs drives the binary, sends $/cancel_request while a command runs in the client's terminal, and checks for terminal/kill and the cancelled stop reason.

[sigit-code-review]

This change enables the agent to honor $/cancel_request notifications for both prompt and sign-in requests, which previously required explicit handler support and were ignored if sent by JSON-RPC id. The main.rs changes ensure that prompt and authenticate handlers now check for cancellation and terminate appropriately: prompts are stopped via cancel_turn (which also kills any running command), and sign-ins are dropped with an error. The select! in the prompt handler ensures that cancellation is registered after the first poll, avoiding a race where cancellation could be missed if it arrived before the handler registered. The test suite adds a case to verify that $/cancel_request for a prompt id cancels the turn, kills the terminal, and returns the correct stop reason, using a new helper to generalize mid-command cancellation. Previous findings about cancellation not being honored for $/cancel_request are addressed by these changes.

---

Automated review by siGit Code Review · commit 3c5f670 · see the review dashboard