DEFER: the agent cannot withdraw a step it no longer needs

[President]

§6.6 (#496) lets the agent keep working while a step waits on DEFER. It gives the agent no way to say "I no longer need that step".

Example: a user asks the agent to refund $500 to card A. The refund gets DEFER and goes to an operator. Before the operator answers, the user writes: "Wrong card, use card B."

The refund to card A then:

• stays with the operator, next to the refund to card B, until it times out;
• if approved, leaves the Guardian holding a valid allow for an action the user withdrew, until the session ends;
• if not approved, sends the agent a deny it no longer needs.

Proposal: add one method, defer/cancel, with the deferred_request_id of the step.

• A pending step resolves to deny with resolution_method: cancelled, and the operator's approval request closes.
• A step that is already resolved keeps its resolution. The first resolution wins.

This follows MCP notifications/cancelled and A2A CancelTask. ASK has the same case, but it waits on #175.

What do you think?

[renezander030]

"First resolution wins" treats an allow the agent already used the same as one still sitting in the Guardian, and in your refund example those are different cases. If the cancel arrives after the operator approved but before the agent consumed the allow, I'd let it revoke the allow, and only a consumed allow keeps its resolution, with the cancel answered too_late so the operator knows the card A refund went out and needs reversing.
This is the check-before-consume ordering I use for approvals: https://gist.github.com/renezander030/ad81c7a805a09a844983f881e2c487e5