Supersedes #28288 (closed).
## Why
A short WebSocket interruption currently ends every client-side process
handle, even though exec-server keeps the server session and its
processes alive for a short time.
This is especially visible for executor-backed stdio MCP servers: a
temporary connection loss becomes a permanent `Transport closed` error.
The server already has the information needed to resume the session, but
the client opens a fresh session instead of using it.
This change reconnects below the process and MCP layers. Existing
process handles stay valid, missed output is recovered, and the same
server-side processes continue running.
## State machine
One logical `ExecServerClient` stays alive while its underlying RPC
connection changes generations.
```text
transport closes
+------------------------------------------------+
| v
+-------------+ +-------------+
| Connected | | Recovering |
+-------------+ +-------------+
^ |
| session resumed, processes caught up | retryable error
+------------------------------------------------+ loops until deadline
|
| deadline or permanent error
v
+-------------+
| Failed |
+-------------+
```
### `Connected`
- New RPC calls use the current connection.
- Process notifications are published in sequence order.
- A disconnect only starts recovery if it came from the current
connection generation. Late events from older generations cannot replace
the active connection.
### `Recovering`
- New calls wait instead of choosing a half-connected RPC client.
- Existing process handles, wake subscriptions, and event subscriptions
stay open.
- Streaming HTTP response bodies fail immediately because their byte
streams cannot be resumed safely.
- Recovery first waits for process starts that were already in flight. A
start whose result became ambiguous is cleaned up after reconnection
instead of being silently adopted.
- The client reconnects with the learned `session_id`. The server may
briefly report that the old connection is still attached, so that error
is retried until the detach finishes.
- The notification consumer starts before the resume handshake
completes. This prevents a busy process from filling the notification
queue and blocking the initialize response.
- Before installing the new connection, the client catches up every
recoverable process with `process/read`.
### `Failed`
- Recovery stops after 25 seconds or after a permanent error.
- Waiting calls are released with one stable disconnect error.
- Existing process sessions receive a terminal failure instead of
waiting forever.
## Recovering process events
Output, exit, and close events share one sequence. During normal
operation, the client buffers early events until every lower sequence
has been published.
After reconnection, the client reads each process starting after its
last published sequence:
1. Retained output chunks are inserted by sequence number.
2. Exit and close state are reconstructed in their sequence positions.
3. Events already received as live notifications are ignored as
duplicates.
4. Newly contiguous events are published in order.
5. If the server no longer retains enough output to fill a sequence gap,
only that process is terminated and failed. The recovered connection
remains usable for other processes.
The server reports its full next event sequence for unbounded reads,
including exit and close events. Closed processes remain readable for
the same 30-second window used to retain detached sessions.
## Other details
- Detached server sessions are retained for 30 seconds, leaving margin
around the client's 25-second recovery deadline.
- Session attach and detach update the active notification sender under
the same attachment lock, so an old connection cannot clear a newly
attached sender.
- A dedicated error code distinguishes the temporary "session is still
attached" race from permanent initialization errors.
- Process starts are identity-checked on both client and server. Cleanup
from an older start cannot remove a newer process that reused the same
ID.
- Mutating requests that were already in flight when the transport
closed are not replayed, because the client cannot know whether the
server applied them. Requests started after recovery is known wait for
the replacement connection.
- We assume the server/client version stays in sync (on the before/after
this PR)
## User impact
Long-running commands and stdio MCP servers can survive a temporary
exec-server WebSocket interruption without changing process IDs or
losing output produced during the outage.
## Why
This is the second-to-last place in the exec-server protocol that needs
to migrate to URIs to support cross-OS operation.
## What
- Change `ExecParams.cwd` to `PathUri`.
- Keep the cwd URI-shaped through core and rmcp producers, converting it
to `AbsolutePathBuf` only in `LocalProcess::start_process`.
- Reject non-native cwd URIs before launch and update the affected
protocol documentation and call sites.
## 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
A Mac Bazel run hit a flake in
`server::handler::tests::output_and_exit_are_retained_after_notification_receiver_closes`
where the read path observed process exit but lost the expected buffered
stdout (`first\nsecond\n`). See the [GitHub Actions
job](https://github.com/openai/codex/actions/runs/24758468552/job/72436716505)
and [BuildBuddy
invocation](https://app.buildbuddy.io/invocation/37475a12-4ef2-45fb-ab8a-e49a2aba1d59).
The underlying race is that process exit is not the same thing as
stdout/stderr closure. If a child or grandchild inherits the pipe write
end, or a process duplicates it with `dup2`, the watched process can
exit while the stream is still open and more output can still arrive.
The exec-server was starting exited-process retention cleanup from the
exit event, so the process entry could be removed before the output
streams had actually closed.
While stress-testing the exec-server unit suite,
`server::handler::tests::long_poll_read_fails_after_session_resume`
exposed a separate test race: it started a short-lived command that
could exit and wake the pending long-poll read before the session-resume
assertion observed the resumed-session error. That test is intended to
cover resume eviction, not process-exit delivery, so this change keeps
the process alive and quiet while the second connection resumes the
session.
## What changed
- Keep exec-server process entries retained until stdout/stderr streams
close, then start the post-exit retention timer from the closed event.
- Wake long-poll readers when the closed event is emitted.
- Add focused `local_process` unit coverage that proves late output is
still retained after the short test retention interval has elapsed, and
that closed process entries are eventually evicted.
- Add a local and remote regression test where a parent exits while a
child keeps inherited stdout open. The child waits on an explicit
release file, so the test deterministically observes exit first,
releases the child, then requires a nonzero-wait read from the exit
sequence to receive the late output.
- In `codex-rs/exec-server/src/server/handler/tests.rs`, make
`long_poll_read_fails_after_session_resume` run a long-lived silent
command instead of a short command that prints and exits. This isolates
the test to session-resume behavior and prevents a normal process exit
from satisfying the pending long-poll read first.
## Testing
- `cargo test -p codex-exec-server
exec_process_retains_output_after_exit_until_streams_close`
- `cargo test -p codex-exec-server local_process::tests`
- `cargo test -p codex-exec-server`
- `just fix -p codex-exec-server`
- `bazel test //codex-rs/exec-server:exec-server-unit-tests
//codex-rs/exec-server:exec-server-exec_process-test
//codex-rs/exec-server:exec-server-file_system-test
//codex-rs/exec-server:exec-server-http_client-test
//codex-rs/exec-server:exec-server-initialize-test
//codex-rs/exec-server:exec-server-process-test
//codex-rs/exec-server:exec-server-websocket-test`
- `bazel test --runs_per_test=25
//codex-rs/exec-server:exec-server-unit-tests`
## Documentation
No docs update needed; this is an internal exec-server correctness fix.
## Summary
- Reject new exec-server client operations once the transport has
disconnected.
- Convert pending RPC calls into closed errors instead of synthetic
server errors.
- Cover pending read and later write behavior after remote executor
disconnect.
## Verification
- `just fmt`
- `cargo check -p codex-exec-server`
## Stack
```text
@ #18027 [6/6] Fail exec client operations after disconnect
│
o #18212 [5/6] Wire executor-backed MCP stdio
│
o #18087 [4/6] Abstract MCP stdio server launching
│
o #18020 [3/6] Add pushed exec process events
│
o #18086 [2/6] Support piped stdin in exec process API
│
o #18085 [1/6] Add MCP server environment config
│
o main
```
---------
Co-authored-by: Codex <noreply@openai.com>
## Summary
- Add a pushed `ExecProcessEvent` stream alongside retained
`process/read` output.
- Publish local and remote output, exit, close, and failure events.
- Cover the event stream with shared local/remote exec process tests.
## Testing
- `cargo check -p codex-exec-server`
- `cargo check -p codex-rmcp-client`
- Not run: `cargo test` per repo instruction; CI will cover.
## Stack
```text
o #18027 [6/6] Fail exec client operations after disconnect
│
o #18212 [5/6] Wire executor-backed MCP stdio
│
o #18087 [4/6] Abstract MCP stdio server launching
│
@ #18020 [3/6] Add pushed exec process events
│
o #18086 [2/6] Support piped stdin in exec process API
│
o #18085 [1/6] Add MCP server environment config
│
o main
```
---------
Co-authored-by: Codex <noreply@openai.com>
## Summary
- Add an explicit stdin mode to process/start.
- Keep normal non-interactive exec stdin closed while allowing
pipe-backed processes.
## Stack
```text
o #18027 [8/8] Fail exec client operations after disconnect
│
o #18025 [7/8] Cover MCP stdio tests with executor placement
│
o #18089 [6/8] Wire remote MCP stdio through executor
│
o #18088 [5/8] Add executor process transport for MCP stdio
│
o #18087 [4/8] Abstract MCP stdio server launching
│
o #18020 [3/8] Add pushed exec process events
│
@ #18086 [2/8] Support piped stdin in exec process API
│
o #18085 [1/8] Add MCP server environment config
│
o main
```
Co-authored-by: Codex <noreply@openai.com>
## Summary
- add an exec-server `envPolicy` field; when present, the server starts
from its own process env and applies the shell environment policy there
- keep `env` as the exact environment for local/embedded starts, but
make it an overlay for remote unified-exec starts
- move the shell-environment-policy builder into `codex-config` so Core
and exec-server share the inherit/filter/set/include behavior
- overlay only runtime/sandbox/network deltas from Core onto the
exec-server-derived env
## Why
Remote unified exec was materializing the shell env inside Core and
forwarding the whole map to exec-server, so remote processes could
inherit the orchestrator machine's `HOME`, `PATH`, etc. This keeps the
base env on the executor while preserving Core-owned runtime additions
like `CODEX_THREAD_ID`, unified-exec defaults, network proxy env, and
sandbox marker env.
## Validation
- `just fmt`
- `git diff --check`
- `cargo test -p codex-exec-server --lib`
- `cargo test -p codex-core --lib unified_exec::process_manager::tests`
- `cargo test -p codex-core --lib exec_env::tests`
- `cargo test -p codex-core --lib exec_env_tests` (compile-only; filter
matched 0 tests)
- `cargo test -p codex-config --lib shell_environment` (compile-only;
filter matched 0 tests)
- `just bazel-lock-update`
## Known local validation issue
- `just bazel-lock-check` is not runnable in this checkout: it invokes
`./scripts/check-module-bazel-lock.sh`, which is missing.
---------
Co-authored-by: Codex <noreply@openai.com>
Co-authored-by: pakrym-oai <pakrym@openai.com>
Problem: After #17294 switched exec-server tests to launch the top-level
`codex exec-server` command, parallel remote exec-process cases can
flake while waiting for the child server's listen URL or transport
shutdown.
Solution: Serialize remote exec-server-backed process tests and harden
the harness so spawned servers are killed on drop and shutdown waits for
the child process to exit.
## Why
`argument-comment-lint` was green in CI even though the repo still had
many uncommented literal arguments. The main gap was target coverage:
the repo wrapper did not force Cargo to inspect test-only call sites, so
examples like the `latest_session_lookup_params(true, ...)` tests in
`codex-rs/tui_app_server/src/lib.rs` never entered the blocking CI path.
This change cleans up the existing backlog, makes the default repo lint
path cover all Cargo targets, and starts rolling that stricter CI
enforcement out on the platform where it is currently validated.
## What changed
- mechanically fixed existing `argument-comment-lint` violations across
the `codex-rs` workspace, including tests, examples, and benches
- updated `tools/argument-comment-lint/run-prebuilt-linter.sh` and
`tools/argument-comment-lint/run.sh` so non-`--fix` runs default to
`--all-targets` unless the caller explicitly narrows the target set
- fixed both wrappers so forwarded cargo arguments after `--` are
preserved with a single separator
- documented the new default behavior in
`tools/argument-comment-lint/README.md`
- updated `rust-ci` so the macOS lint lane keeps the plain wrapper
invocation and therefore enforces `--all-targets`, while Linux and
Windows temporarily pass `-- --lib --bins`
That temporary CI split keeps the stricter all-targets check where it is
already cleaned up, while leaving room to finish the remaining Linux-
and Windows-specific target-gated cleanup before enabling
`--all-targets` on those runners. The Linux and Windows failures on the
intermediate revision were caused by the wrapper forwarding bug, not by
additional lint findings in those lanes.
## Validation
- `bash -n tools/argument-comment-lint/run.sh`
- `bash -n tools/argument-comment-lint/run-prebuilt-linter.sh`
- shell-level wrapper forwarding check for `-- --lib --bins`
- shell-level wrapper forwarding check for `-- --tests`
- `just argument-comment-lint`
- `cargo test` in `tools/argument-comment-lint`
- `cargo test -p codex-terminal-detection`
## Follow-up
- Clean up remaining Linux-only target-gated callsites, then switch the
Linux lint lane back to the plain wrapper invocation.
- Clean up remaining Windows-only target-gated callsites, then switch
the Windows lint lane back to the plain wrapper invocation.
This PR partially rebase `unified_exec` on the `exec-server` and adapt
the `exec-server` accordingly.
## What changed in `exec-server`
1. Replaced the old "broadcast-driven; process-global" event model with
process-scoped session events. The goal is to be able to have dedicated
handler for each process.
2. Add to protocol contract to support explicit lifecycle status and
stream ordering:
- `WriteResponse` now returns `WriteStatus` (Accepted, UnknownProcess,
StdinClosed, Starting) instead of a bool.
- Added seq fields to output/exited notifications.
- Added terminal process/closed notification.
3. Demultiplexed remote notifications into per-process channels. Same as
for the event sys
4. Local and remote backends now both implement ExecBackend.
5. Local backend wraps internal process ID/operations into per-process
ExecProcess objects.
6. Remote backend registers a session channel before launch and
unregisters on failed launch.
## What changed in `unified_exec`
1. Added unified process-state model and backend-neutral process
wrapper. This will probably disappear in the future, but it makes it
easier to keep the work flowing on both side.
- `UnifiedExecProcess` now handles both local PTY sessions and remote
exec-server processes through a shared `ProcessHandle`.
- Added `ProcessState` to track has_exited, exit_code, and terminal
failure message consistently across backends.
2. Routed write and lifecycle handling through process-level methods.
## Some rationals
1. The change centralizes execution transport in exec-server while
preserving policy and orchestration ownership in core, avoiding
duplicated launch approval logic. This comes from internal discussion.
2. Session-scoped events remove coupling/cross-talk between processes
and make stream ordering and terminal state explicit (seq, closed,
failed).
3. The failure-path surfacing (remote launch failures, write failures,
transport disconnects) makes command tool output and cleanup behavior
deterministic
## Follow-ups:
* Unify the concept of thread ID behind an obfuscated struct
* FD handling
* Full zsh-fork compatibility
* Full network sandboxing compatibility
* Handle ws disconnection
Add environment manager that is a singleton and is created early in
app-server (before skill manager, before config loading).
Use an environment variable to point to a running exec server.
## Summary
- match the exec-process structure to filesystem PR #15232
- expose `ExecProcess` on `Environment`
- make `LocalProcess` the real implementation and `RemoteProcess` a thin
network proxy over `ExecServerClient`
- make `ProcessHandler` a thin RPC adapter delegating to `LocalProcess`
- add a shared local/remote process test
## Validation
- `just fmt`
- `CARGO_TARGET_DIR=~/.cache/cargo-target/codex cargo test -p
codex-exec-server`
- `just fix -p codex-exec-server`
---------
Co-authored-by: Codex <noreply@openai.com>
jif ·
Adam Perry @ OpenAI ·
pakrym-oai ·
Michael Bolin ·
starr-openai ·
Ahmed Ibrahim ·
David de Regt ·
Eric Traut ·