openai/codex · error · io::Error

MCP stdin closed

Error message

MCP stdin closed

What it means

Error "MCP stdin closed" thrown in openai/codex.

Source

Thrown at codex-rs/rmcp-client/src/local_stdio_transport.rs:150

impl Transport<RoleClient> for LocalStdioTransport {
    type Error = io::Error;

    #[expect(
        clippy::await_holding_invalid_type,
        reason = "complete JSON-RPC frames must hold the stdin lock across writes"
    )]
    fn send(
        &mut self,
        item: TxJsonRpcMessage<RoleClient>,
    ) -> impl Future<Output = Result<(), Self::Error>> + Send + 'static {
        let stdin = Arc::clone(&self.stdin);
        async move {
            let mut message = serde_json::to_vec(&item).map_err(io::Error::other)?;
            message.push(b'\n');
            let mut guard = stdin.lock().await;
            let stdin = guard
                .as_mut()
                .ok_or_else(|| io::Error::new(io::ErrorKind::BrokenPipe, "MCP stdin closed"))?;
            stdin.write_all(&message).await?;
            stdin.flush().await
        }
    }

    fn receive(&mut self) -> impl Future<Output = Option<RxJsonRpcMessage<RoleClient>>> + Send {
        self.receive_message()
    }

    async fn close(&mut self) -> Result<(), Self::Error> {
        self.stdin.lock().await.take();
        match tokio::time::timeout(Duration::from_secs(3), self.child.wait()).await {
            Ok(status) => {
                status?;
                Ok(())
            }
            Err(_) => self.child.kill().await,
        }

View on GitHub (pinned to 339751715c)

When it happens

Trigger: Thrown at codex-rs/rmcp-client/src/local_stdio_transport.rs:150 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of openai/codex@339751715c (2026-08-25). Data as JSON: /api/errors/1d7ac4e1020ee7db. Report an issue: GitHub.