Codex never tells MCP servers to stop after tool call interrupt/timeout

What version of Codex CLI is running?

codex-cli 0.137.0

What subscription do you have?

Pro 20x

Which model were you using?

gpt-5.5

What platform is your computer?

Darwin 25.6.0 arm64 arm

What terminal emulator and version are you using (if applicable)?

Terminal.app

Codex doctor report

What issue are you seeing?

When using Codex with tools from MCP servers, interrupting or timing out a tool call doesn't notify the server. Codex will drop the request future locally but sends nothing back, so MCP servers will try to execute the tool to completion anyways.

What steps can reproduce the bug?

1. Register a stdio MCP server that runs a tool call and logs whether it receives notifications/cancelled.
2. Ask Codex to call that tool then interrupt it or let it time out.
3. The server never gets notifications/cancelled and tries to keep running the tool even though its output will never be seen.

What is the expected behavior?

Codex should send notifications/cancelled when tool calls are cancelled so the server can stop executing it.

Additional information

I had Claude fix the bug at a9lim/codex@fix/mcp-client-cancellation