[FEATURE] Expose MCP "notifications/cancelled" to the LLM

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

I have a long-running tool call. I would like to conversationally ask claude-code to "run tool X, but let's give up if it doesn't finish within 5 minutes". It doesn't seem capable of engaging with such a request.

When asked about why, it provides some details:

No, I cannot cancel or timeout MCP tool calls once they've started. Here's why:

  MCP Tools (like X):
  - Execute synchronously and block until completion
  - No cancellation mechanism available
  - No timeout parameter in the tool definition
  - I must wait for them to complete or error out

  This is different from Bash commands:
  - Bash tool has run_in_background parameter
  - Can monitor with BashOutput tool
  - Can kill with KillShell tool
  - Has configurable timeout (up to 10 minutes)

And yet in the MCP spec we see there's a cancellation API:

When a party wants to cancel an in-progress request, it sends a notifications/cancelled notification containing:
* The ID of the request to cancel
* An optional reason string that can be logged or displayed

I also observe that when I interrupt using the escape key, the request does cancel (though I haven't confirmed the mechanism), so this seems generally possible.

Proposed Solution

I'd like to enable claude-code to reason about long running MCP tool calls similarly to how it can reason about long-running bash commands.

Alternative Solutions

_No response_

Priority

Medium - Would be very helpful

Feature Category

MCP server integration

Use Case Example

_No response_

Additional Context

_No response_