[6/6] Fail exec client operations after disconnect by aibrahim-oai · Pull Request #18027 · openai/codex

aibrahim-oai · 2026-04-16T00:15:44Z

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

@  #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

## Summary - Add an MCP server environment setting with local as the default. - Thread the default through config serialization, schema generation, and existing config fixtures. ## 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 │ o #18086 [2/8] Support piped stdin in exec process API │ @ #18085 [1/8] 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>

Reject new exec-server operations once the transport disconnects and convert pending RPC calls into closed errors. This lets remote MCP stdio calls surface executor loss immediately instead of waiting for the MCP tool timeout. Co-authored-by: Codex <noreply@openai.com>

Preserve reader ordering for in-flight calls so responses queued before EOF are delivered before pending calls are failed as closed. Co-authored-by: Codex <noreply@openai.com>

aibrahim-oai · 2026-04-20T18:15:35Z

@codex review

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codex/codex-rs/exec-server/src/remote_file_system.rs

Lines 198 to 201 in c15c1d1

    
           ExecServerError::Closed => { 
        
               io::Error::new(io::ErrorKind::BrokenPipe, "exec-server transport closed") 
        
           } 
        
           _ => io::Error::other(error.to_string()),

Treat disconnected transport as BrokenPipe in FS mapping

ExecServerClient::call now returns ExecServerError::Disconnected(...) after transport loss, but this mapper only special-cases Closed. As a result, post-disconnect remote filesystem calls fall through to _ and become io::ErrorKind::Other instead of BrokenPipe, changing transport-failure semantics and potentially breaking callers that rely on BrokenPipe handling.

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pakrym-oai · 2026-04-20T19:51:13Z

+    // with the same message. This process/filesystem-level latch prevents
+    // callers from waiting on request-specific timeouts after the environment
+    // is gone.
+    disconnected: std::sync::RwLock<Option<String>>,


can this be a lighter sync primitive?

Use OnceLock for the one-way exec-server disconnect latch instead of a read/write lock. Co-authored-by: Codex <noreply@openai.com>

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chatgpt-codex-connector · 2026-04-20T20:46:25Z

+                    // registered process session before returning this call
+                    // error.
+                    let message = disconnected_message(/*reason*/ None);
+                    let message = mark_disconnected(&self.inner, message).await;


Defer session drain until disconnect event ordering is preserved

ExecServerClient::call now invokes mark_disconnected on any transport-closed call error. That immediately drains sessions via take_all_sessions(). Since this runs concurrently with the event-reader loop, notifications already queued before Disconnected can be handled after the drain and be dropped by get_session, losing tail output/exit/closed events for active processes.

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Record executor disconnects from call failures without draining sessions. Keep session failure publication in the reader task so queued process notifications are handled before disconnect. Co-authored-by: Codex <noreply@openai.com>

aibrahim-oai · 2026-04-20T22:00:06Z

@codex review this

Treat the latched exec-server disconnect error the same as a closed transport in the remote filesystem adapter. Co-authored-by: Codex <noreply@openai.com>

Clone the latched disconnect message before converting it into an ExecServerError. Co-authored-by: Codex <noreply@openai.com>

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chatgpt-codex-connector · 2026-04-20T22:20:18Z

+        if *self.disconnected_rx.borrow() {
+            return Err(RpcCallError::Closed);


Delay closed errors until notification queue is drained

RpcClient::call now returns Closed as soon as disconnected_rx flips, but incoming_rx can still hold earlier process notifications. Session::read treats this as terminal and caches a synthetic failure, so a read in this window can report closed=true before queued output/exited/closed events are published. Polling clients may stop and miss tail output.

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Serve disconnect-time process reads from the local event log so queued output is not hidden by a synthetic failure response. Co-authored-by: Codex <noreply@openai.com>

Explain why remote reads use the local retained event log after transport close. Co-authored-by: Codex <noreply@openai.com>

Annotate the new retained-read callsites for the argument comment lint. Co-authored-by: Codex <noreply@openai.com>

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chatgpt-codex-connector · 2026-04-20T22:46:10Z

+        if *self.disconnected_rx.borrow() {
+            return Err(RpcCallError::Closed);
+        }
+
        let request_id = RequestId::Integer(self.next_request_id.fetch_add(1, Ordering::SeqCst));
        let (response_tx, response_rx) = oneshot::channel();
        self.pending


Atomically gate new RPCs when transport disconnects

RpcClient::call reads disconnected_rx before registering the request in pending. If disconnect flips just after this check, the reader task can process Disconnected, run drain_pending, and exit before this call inserts its sender. write_tx.send may still succeed, leaving response_rx.await with no producer and the call hanging indefinitely.

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Remove the retained-output recovery path for executor disconnects and return the normal synthesized failure response instead. Co-authored-by: Codex <noreply@openai.com>

Check the disconnect latch while holding the pending request lock so calls cannot register after the reader drains pending requests. Co-authored-by: Codex <noreply@openai.com>

chatgpt-codex-connector · 2026-04-20T23:02:22Z

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chatgpt-codex-connector · 2026-04-20T23:02:31Z

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aibrahim-oai force-pushed the dev/remote-mcp-exec-disconnect branch from 26e6cb2 to cbf2f50 Compare April 16, 2026 05:10

aibrahim-oai force-pushed the dev/remote-mcp-stdio-tests branch 2 times, most recently from 04edeeb to db17256 Compare April 16, 2026 06:20

aibrahim-oai force-pushed the dev/remote-mcp-exec-disconnect branch from cbf2f50 to a5fb6ce Compare April 16, 2026 06:20

aibrahim-oai force-pushed the dev/remote-mcp-stdio-tests branch from db17256 to aa58931 Compare April 16, 2026 13:55

aibrahim-oai force-pushed the dev/remote-mcp-exec-disconnect branch from a5fb6ce to d73da80 Compare April 16, 2026 13:55

aibrahim-oai force-pushed the dev/remote-mcp-stdio-tests branch from aa58931 to c4a27cd Compare April 16, 2026 13:59

aibrahim-oai force-pushed the dev/remote-mcp-exec-disconnect branch from d73da80 to 82da696 Compare April 16, 2026 13:59

aibrahim-oai force-pushed the dev/remote-mcp-stdio-tests branch from c4a27cd to 1e3bb61 Compare April 16, 2026 15:56

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aibrahim-oai force-pushed the dev/remote-mcp-exec-disconnect branch from 7c6544f to b8070ad Compare April 18, 2026 05:25

aibrahim-oai and others added 3 commits April 20, 2026 10:42

Merge branch 'main' into dev/remote-mcp-exec-disconnect

12fec8b

codex: fix exec RPC disconnect race

c15c1d1

Preserve reader ordering for in-flight calls so responses queued before EOF are delivered before pending calls are failed as closed. Co-authored-by: Codex <noreply@openai.com>

chatgpt-codex-connector bot reviewed Apr 20, 2026

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pakrym-oai reviewed Apr 20, 2026

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pakrym-oai approved these changes Apr 20, 2026

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codex: address exec disconnect latch review

38dc8ea

Use OnceLock for the one-way exec-server disconnect latch instead of a read/write lock. Co-authored-by: Codex <noreply@openai.com>

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aibrahim-oai and others added 2 commits April 20, 2026 14:53

Merge branch 'main' into dev/remote-mcp-exec-disconnect

206ca37

codex: preserve exec disconnect event ordering

cad3075

Record executor disconnects from call failures without draining sessions. Keep session failure publication in the reader task so queued process notifications are handled before disconnect. Co-authored-by: Codex <noreply@openai.com>

aibrahim-oai and others added 2 commits April 20, 2026 15:01

codex: map disconnected remote fs calls to broken pipe

64fce0b

Treat the latched exec-server disconnect error the same as a closed transport in the remote filesystem adapter. Co-authored-by: Codex <noreply@openai.com>

codex: fix exec disconnect error cloning

7d95be5

Clone the latched disconnect message before converting it into an ExecServerError. Co-authored-by: Codex <noreply@openai.com>

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aibrahim-oai and others added 3 commits April 20, 2026 15:24

codex: preserve retained process output after disconnect

5e5c2b6

Serve disconnect-time process reads from the local event log so queued output is not hidden by a synthetic failure response. Co-authored-by: Codex <noreply@openai.com>

codex: document disconnect-time process reads

40be067

Explain why remote reads use the local retained event log after transport close. Co-authored-by: Codex <noreply@openai.com>

codex: fix disconnect read argument comments

53bee5f

Annotate the new retained-read callsites for the argument comment lint. Co-authored-by: Codex <noreply@openai.com>

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aibrahim-oai and others added 2 commits April 20, 2026 15:58

codex: simplify disconnect-time process reads

0825b23

Remove the retained-output recovery path for executor disconnects and return the normal synthesized failure response instead. Co-authored-by: Codex <noreply@openai.com>

codex: atomically gate RPC calls after disconnect

f67afbc

Check the disconnect latch while holding the pending request lock so calls cannot register after the reader drains pending requests. Co-authored-by: Codex <noreply@openai.com>

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[6/6] Fail exec client operations after disconnect#18027

[6/6] Fail exec client operations after disconnect#18027
aibrahim-oai merged 13 commits intomainfrom
dev/remote-mcp-exec-disconnect

aibrahim-oai commented Apr 16, 2026 •

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	ExecServerError::Closed => {
	io::Error::new(io::ErrorKind::BrokenPipe, "exec-server transport closed")
	}
	_ => io::Error::other(error.to_string()),

		if *self.disconnected_rx.borrow() {
		return Err(RpcCallError::Closed);

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aibrahim-oai commented Apr 16, 2026 •

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