Stop a Running Agent / Edit a previous prompt

[sertacakdogan]

Is your feature request related to a problem? Please describe.
I want user to be able to stop the running agent to give a new prompt & or edit a prompt as they wished.

Describe the solution you'd like

1. Configure stopping a running agent.
2. Provide editing feature to targeted prompts.

[ananthanarayanan431]

@adk-bot Any ETA for this?

[ananthanarayanan431]

@sertacakdogan do you have any workaround for this? until they implement

[klateefa]

@sertacakdogan Thanks for the update. The request is currently being reviewed, and I will let you know if anything further is needed. Thank you for your understanding.

[ecanlar]

@klateefa Hi! I'm really looking forward to this functionality. If there's a branch or a PR currently in progress, I'd be happy to help testing it in my environment and provide feedback to speed up the 'needs review' stage. Let me know! :)

[patrasap0908]

This one would be good to add. I can take this up if reviewed already, @klateefa @wuliang229.

[ecanlar]

How is this issue going? @klateefa @wuliang229.

[a2105z]

Taking this.

@klateefa @wuliang229 — claiming #3849. This has been open since December (8+ months). People keep asking for an ETA, a workaround, and a branch to test. Nobody has shipped it.

This is a ChatGPT-class UX hole, not a nice-to-have:

1. Stop a running agent. Once run_async / /run_sse is in a long tool call or a slow model stream, the user cannot abort it. Closing the tab does not reliably free the server. That wastes tokens, hangs tools, and makes every custom front-end feel broken. Same gap as Add an API Endpoint to Cancel In-Progress Agent Tasks #2425 / Add Force Stop Capability to Interrupt Agent Reasoning or Tool Calls #2853.
2. Edit a previous prompt. Users mistype, change their mind, or want to fork from an earlier turn. Today the only option is a new message on top of a polluted history. rewind_async already knows how to roll a session back to a given invocation — what is missing is wiring that to “replace this user turn and regenerate,” including cancelling if that turn is still running.

I am implementing both on Runner plus REST so adk web / Agent Engine clients can call them:

• Runner.cancel_async(...) — stop the live invocation (and persist interrupted=True)
• Runner.edit_message_async(...) — cancel if needed, rewind to that user turn, re-run with the edited prompt
• POST /apps/{app}/users/{user}/sessions/{session}/cancel
• POST /apps/{app}/users/{user}/sessions/{session}/edit

PR incoming.

[a2105z]

PR is up: #6841

Stop (cancel_async + POST .../cancel) and edit-prompt (edit_message_async + POST .../edit) are implemented and tested.