[5/6] Wire executor-backed MCP stdio by aibrahim-oai · Pull Request #18212 · openai/codex

aibrahim-oai · 2026-04-16T21:44:10Z

Summary

Add the executor-backed RMCP stdio transport.
Wire MCP stdio placement through the executor environment config.
Cover local and executor-backed stdio paths with the existing MCP test helpers.

Stack

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

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aibrahim-oai · 2026-04-17T06:07:49Z

@codex review this

Co-authored-by: Codex <noreply@openai.com>

aibrahim-oai · 2026-04-17T06:23:22Z

@codex review

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chatgpt-codex-connector · 2026-04-17T06:35:56Z

+
+    fn remote_env_policy() -> ExecEnvPolicy {
+        ExecEnvPolicy {
+            inherit: ShellEnvironmentPolicyInherit::Core,


Include HOME-like vars in remote MCP env inheritance

remote_env_policy() uses ShellEnvironmentPolicyInherit::Core, which only carries a minimal set of vars (e.g., PATH/SHELL/TMP*). Local stdio MCP launch includes DEFAULT_ENV_VARS like HOME/USER/LANG. Remote stdio servers that rely on HOME for config/auth paths can fail initialization when experimental_environment = "remote", creating behavior drift between local and remote placement.

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chatgpt-codex-connector · 2026-04-17T06:35:57Z

+
+    fn remote_env_policy() -> ExecEnvPolicy {
+        ExecEnvPolicy {
+            inherit: ShellEnvironmentPolicyInherit::Core,


Preserve HOME and user vars for remote MCP processes

remote_env_policy() inherits only Core, while local stdio includes DEFAULT_ENV_VARS (e.g., HOME, USER, LANG, TZ). Remote MCP servers that depend on home/profile paths for auth or config can fail only when experimental_environment = "remote", causing local/remote behavior drift.

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chatgpt-codex-connector · 2026-04-17T06:35:57Z

+        for chunk in response.chunks {
+            self.note_seq(chunk.seq);
+            self.push_process_output(chunk);


Deduplicate recovered chunks after broadcast lag

After RecvError::Lagged, recover_lagged_events() appends chunks from process.read(after_seq=last_seq), but the broadcast receiver will still yield retained events on later recv(). Since neither path filters by seq, the same output can be appended twice, yielding duplicated JSON-RPC frames and protocol-level failures.

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chatgpt-codex-connector · 2026-04-17T06:35:57Z

+        // accept arbitrary OsString values because it calls the OS directly; remote
+        // stdio must reject non-Unicode command, argument, or environment data
+        // before sending an executor request.
+        let argv = Self::process_api_argv(&program, &args).map_err(io::Error::other)?;


Resolve remote stdio command before building argv

Remote launch builds argv directly from raw program/args and skips the extension-aware resolver used by the local launcher. On Windows executors, script-based commands (npx, .cmd/.bat) may not resolve, so remote MCP stdio can fail even when the same config works locally.

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chatgpt-codex-connector · 2026-04-17T06:35:57Z

+
+    fn remote_env_policy() -> ExecEnvPolicy {
+        ExecEnvPolicy {
+            inherit: ShellEnvironmentPolicyInherit::Core,


Inherit HOME-like vars for remote MCP processes

remote_env_policy() uses ShellEnvironmentPolicyInherit::Core, which omits vars local stdio includes via DEFAULT_ENV_VARS (for example HOME, USER, LANG, TZ). Remote MCP servers that read config/auth data from home/profile paths can fail only when experimental_environment = "remote", creating local/remote behavior drift.

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chatgpt-codex-connector · 2026-04-17T06:35:57Z

+        for chunk in response.chunks {
+            self.note_seq(chunk.seq);
+            self.push_process_output(chunk);


Skip duplicate output after lag recovery

After RecvError::Lagged, recover_lagged_events() appends chunks from process.read(after_seq=last_seq), but the broadcast receiver can still deliver overlapping retained Output events. Because chunks are appended without seq dedupe, stdout lines can be duplicated and JSON-RPC frames may be replayed, breaking MCP message handling.

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chatgpt-codex-connector · 2026-04-17T06:35:57Z

+        // accept arbitrary OsString values because it calls the OS directly; remote
+        // stdio must reject non-Unicode command, argument, or environment data
+        // before sending an executor request.
+        let argv = Self::process_api_argv(&program, &args).map_err(io::Error::other)?;


Resolve remote stdio executable before process/start

Remote launch builds argv directly from raw program/args and skips resolver logic used by local launch. On Windows executors, script commands (.cmd/.bat, e.g. npx) may fail to execute remotely even when the same MCP config works locally.

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chatgpt-codex-connector · 2026-04-17T06:35:57Z

+        self.terminated = true;
+        self.process.terminate().await.map_err(io::Error::other)


Mark transport terminated only after terminate succeeds

close() sets self.terminated = true before awaiting process.terminate(). If terminate returns an error (e.g., transient remote RPC failure), Drop skips its termination fallback because terminated is already true, potentially leaking the remote MCP child process.

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chatgpt-codex-connector · 2026-04-17T06:35:57Z

+            Err(err) => {
+                let error = JSONRPCErrorError {
+                    code: INTERNAL_ERROR_CODE,
+                    message: format!("failed to create environment: {err}"),
+                    data: None,
+                };
+                self.outgoing.send_error(request, error).await;
+                return;


Degrade MCP status listing when env creation fails

list_mcp_server_status now returns a top-level internal error when environment_manager.current() fails. That aborts status listing for all servers, including local/HTTP servers that do not need executor-backed stdio, turning a recoverable environment issue into complete API failure.

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aibrahim-oai · 2026-04-17T08:46:24Z

@codex review this

## 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 - Move local MCP stdio process startup behind a launcher trait. - Preserve existing local stdio behavior while making transport creation explicit. ## Stack ```text o #18027 [6/6] Fail exec client operations after disconnect │ o #18212 [5/6] Wire executor-backed MCP stdio │ @ #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>

Co-authored-by: Codex <noreply@openai.com>

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chatgpt-codex-connector · 2026-04-17T19:51:55Z

+        }
+
+        let process = Arc::clone(&self.process);
+        tokio::spawn(async move {


Guard drop-time terminate against missing Tokio runtime

ExecutorProcessTransport::drop unconditionally calls tokio::spawn. If this transport is dropped after runtime teardown (or on a non-Tokio thread), tokio::spawn panics (no reactor running) during cleanup. That turns a shutdown path into a crash and can still leave the MCP child alive. Use Handle::try_current() or a non-panicking fallback.

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pakrym-oai · 2026-04-17T23:58:25Z

        let auth = self.auth_manager.auth().await;
+        let runtime_environment = match self.thread_manager.environment_manager().current().await {
+            Ok(Some(environment)) => {
+                McpRuntimeEnvironment::new(environment, config.cwd.to_path_buf())


Interesting, do we always start mcps in cwd?

pakrym-oai

A BOMB!

Add the executor-backed RMCP stdio transport, pass MCP runtime placement through manager construction, and cover stdio MCP tests with the remote-aware helpers. Co-authored-by: Codex <noreply@openai.com>

Allow stdio MCP env_vars entries to opt into local or remote sourcing while preserving the existing string form. Remote source names are inherited from the executor side through the existing process env policy, while local/default entries continue to be copied from Codex as explicit overlays. Add config, launcher, and remote-aware MCP tests that cover legacy env vars, local source vars, remote source filtering, and the effective executor env policy. Co-authored-by: Codex <noreply@openai.com>

Rename the runtime cwd carried into executor-backed MCP stdio to fallback_cwd so it is clear that per-server cwd still wins. Teach the stdio MCP test server to report its process cwd and add remote-aware coverage for configured cwd precedence plus remote fallback cwd behavior. Co-authored-by: Codex <noreply@openai.com>

Annotate empty env var slices in format_env_display tests so the generic env var display helper can infer the slice item type. Co-authored-by: Codex <noreply@openai.com>

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chatgpt-codex-connector · 2026-04-19T03:28:18Z

+                .chain(remote_env_vars.iter().cloned())
+                .collect()


Treat remote env var names as literals

remote_env_policy forwards remote_env_vars into include_only without escaping. include_only is matched as wildcard patterns, so a config like { name = "*", source = "remote" } will include all executor env vars (including secrets) instead of a single variable. Validate names or escape glob metacharacters before building include_only.

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Use the MCP env var config type when mutating the stdio test fixture so CI builds after env var source support. Co-authored-by: Codex <noreply@openai.com>

Move cwd assertions to a dedicated stdio test tool so existing echo metadata and truncation expectations stay unchanged. Co-authored-by: Codex <noreply@openai.com>

Drop the helper left unused after moving cwd assertions to the dedicated cwd tool. Co-authored-by: Codex <noreply@openai.com>

Compare the MCP cwd tool output after path normalization so Windows short-path spellings do not fail the cwd precedence test. Co-authored-by: Codex <noreply@openai.com>

Use canonical path equality for local MCP cwd assertions while preserving raw remote cwd comparison. Co-authored-by: Codex <noreply@openai.com>

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Comment thread codex-rs/rmcp-client/src/executor_process_transport.rs Outdated

Comment thread codex-rs/rmcp-client/src/executor_process_transport.rs Outdated

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aibrahim-oai added a commit that referenced this pull request Apr 17, 2026

codex: fix CI failure on PR #18212

5d8c233

Co-authored-by: Codex <noreply@openai.com>

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aibrahim-oai force-pushed the dev/remote-mcp-stdio-runtime branch from 0666bc7 to 39b8f9b Compare April 17, 2026 19:12

Base automatically changed from dev/remote-mcp-stdio-runtime to main April 17, 2026 19:34

aibrahim-oai added a commit that referenced this pull request Apr 17, 2026

codex: fix CI failure on PR #18212

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aibrahim-oai force-pushed the dev/remote-mcp-executor-stdio-full-ci branch from 05c5a98 to 2b8b185 Compare April 17, 2026 19:38

aibrahim-oai added a commit that referenced this pull request Apr 17, 2026

codex: fix CI failure on PR #18212

d8a06eb

Co-authored-by: Codex <noreply@openai.com>

aibrahim-oai force-pushed the dev/remote-mcp-executor-stdio-full-ci branch 3 times, most recently from 93f49bf to be849e0 Compare April 17, 2026 19:46

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Comment thread codex-rs/codex-mcp/src/mcp_connection_manager.rs Outdated

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aibrahim-oai force-pushed the dev/remote-mcp-executor-stdio-full-ci branch from 0ac58e2 to 5615470 Compare April 18, 2026 05:06

Wire executor-backed MCP stdio

c219aeb

Add the executor-backed RMCP stdio transport, pass MCP runtime placement through manager construction, and cover stdio MCP tests with the remote-aware helpers. Co-authored-by: Codex <noreply@openai.com>

aibrahim-oai force-pushed the dev/remote-mcp-executor-stdio-full-ci branch from 5615470 to c219aeb Compare April 18, 2026 05:24

aibrahim-oai and others added 2 commits April 18, 2026 02:47

codex: fix CI failure on PR #18212

48ee483

Annotate empty env var slices in format_env_display tests so the generic env var display helper can infer the slice item type. Co-authored-by: Codex <noreply@openai.com>

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aibrahim-oai and others added 5 commits April 18, 2026 23:29

codex: fix MCP list env var test

a3abe00

Use the MCP env var config type when mutating the stdio test fixture so CI builds after env var source support. Co-authored-by: Codex <noreply@openai.com>

codex: keep rmcp echo fixture stable

ff0c5c2

Move cwd assertions to a dedicated stdio test tool so existing echo metadata and truncation expectations stay unchanged. Co-authored-by: Codex <noreply@openai.com>

codex: remove unused rmcp echo helper

4d1aeab

Drop the helper left unused after moving cwd assertions to the dedicated cwd tool. Co-authored-by: Codex <noreply@openai.com>

codex: normalize cwd assertion paths

042feb9

Compare the MCP cwd tool output after path normalization so Windows short-path spellings do not fail the cwd precedence test. Co-authored-by: Codex <noreply@openai.com>

codex: compare cwd paths canonically

7eb0c40

Use canonical path equality for local MCP cwd assertions while preserving raw remote cwd comparison. Co-authored-by: Codex <noreply@openai.com>

aibrahim-oai merged commit 996aa23 into main Apr 19, 2026
67 of 74 checks passed

aibrahim-oai deleted the dev/remote-mcp-executor-stdio-full-ci branch April 19, 2026 04:47

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		self.terminated = true;
		self.process.terminate().await.map_err(io::Error::other)

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aibrahim-oai commented Apr 17, 2026

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aibrahim-oai commented Apr 16, 2026 •

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