## Why
A long-running unified exec process started with `tty: false` could not
be interrupted via `write_stdin`: ordinary non-TTY stdin writes are
rejected once stdin is closed, but an exact U+0003 payload should still
map to a process interrupt. The interrupt should flow through the same
process lifecycle path as a real signal so Codex preserves
process-reported output and exit metadata instead of fabricating a
Ctrl-C exit code or tearing down the session early.
## What Changed
- Add `process/signal` to exec-server with `ProcessSignal::Interrupt`
and an empty response.
- Add a non-consuming `ProcessHandle::signal` path for spawned
processes; on Unix it sends SIGINT to the process group and leaves
terminate/hard-kill unchanged.
- Route non-TTY U+0003 `write_stdin` through `process.signal(...)`
instead of `terminate`, then let the normal post-write collection path
drain output and observe exit.
- Add exec-server coverage where a shell `trap INT` handler prints the
signal and exits with its own code.
- Add unified exec coverage where a `tty: false` process traps SIGINT,
emits output, and exits with its own code.
## Validation
- `just test -p codex-exec-server
exec_process_signal_interrupts_process`
- `just test -p codex-exec-server`
- `just test -p codex-core
write_stdin_ctrl_c_interrupts_non_tty_session`
## Why
Interrupted `shell_command` calls can race with the outer tool-dispatch
cancellation path. When that happens, the runtime future may be dropped
before the spawned process gets a chance to run `SIGTERM` cleanup. For
bwrapd-backed Linux sandbox commands, that can leave synthetic
protected-path mount bookkeeping such as `.git/.codex` registrations
under `/tmp` behind after a TUI interruption.
The relevant cancellation points are the outer dispatch race in
[`core/src/tools/parallel.rs`](https://github.com/openai/codex/blob/bd184ba84703cc924921ed883f0cf17d3dba60ff/codex-rs/core/src/tools/parallel.rs#L91-L132)
and the process shutdown logic in
[`core/src/exec.rs`](https://github.com/openai/codex/blob/bd184ba84703cc924921ed883f0cf17d3dba60ff/codex-rs/core/src/exec.rs#L1367-L1393).
## What changed
- Keep `shell_command` dispatch alive long enough for the runtime to
finish cancellation cleanup instead of immediately returning the
synthetic aborted response.
- Fold shell-turn cancellation into the existing `ExecExpiration` path
in
[`core/src/tools/runtimes/shell.rs`](https://github.com/openai/codex/blob/bd184ba84703cc924921ed883f0cf17d3dba60ff/codex-rs/core/src/tools/runtimes/shell.rs#L267-L274),
so cancellation and timeout behavior stay centralized.
- On cancellation, send `SIGTERM` first, wait briefly for cleanup to
run, then hard-kill any remaining descendants in the original process
group.
- Treat `ESRCH` as an already-gone process-group cleanup case in
`codex-utils-pty`, which keeps best-effort teardown from surfacing a
stale-process race as an error.
## Verification
- `cargo test -p codex-core cancellation`
- Added regression coverage for:
- `shell_tool_cancellation_waits_for_runtime_cleanup`
- `process_exec_tool_call_cancellation_allows_sigterm_cleanup`
This PR changes stdio MCP child processes to run in their own process
group
* Add guarded teardown in codex-rmcp-client: send SIGTERM to the group
first, then SIGKILL after a short grace period.
* Add terminate_process_group helper in process_group.rs.
* Add Unix regression test in process_group_cleanup.rs to verify wrapper
+ grandchild are reaped on client drop.
Addresses reported MCP process/thread storm: #10581
pakrym-oaiandGitHub
viyatb-oaiandGitHub
Eric TrautandGitHub
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