openai/codex · error · std::io::Error

short datagram write: wrote {written} bytes out of {}

Error message

short datagram write: wrote {written} bytes out of {}

What it means

Error "short datagram write: wrote {written} bytes out of {}" thrown in openai/codex.

Source

Thrown at codex-rs/shell-escalation/src/unix/socket.rs:189

        assert!(filled <= message_len);
        if filled == message_len {
            return Ok(assume_init_vec(payload));
        }
    }
    unreachable!("loop exits only after returning payload")
}

fn send_datagram_bytes(socket: &Socket, data: &[u8], fds: &[OwnedFd]) -> std::io::Result<()> {
    let control = make_control_message(fds)?;
    let payload = [IoSlice::new(data)];
    let msg = if control.is_empty() {
        MsgHdr::new().with_buffers(&payload)
    } else {
        MsgHdr::new().with_buffers(&payload).with_control(&control)
    };
    let written = socket.sendmsg(&msg, 0)?;
    if written != data.len() {
        return Err(std::io::Error::new(
            std::io::ErrorKind::WriteZero,
            format!(
                "short datagram write: wrote {written} bytes out of {}",
                data.len()
            ),
        ));
    }
    Ok(())
}

fn encode_length(len: usize) -> std::io::Result<[u8; LENGTH_PREFIX_SIZE]> {
    let len_u32 = u32::try_from(len).map_err(|_| {
        std::io::Error::new(
            std::io::ErrorKind::InvalidInput,
            format!("message too large: {len}"),
        )
    })?;
    Ok(len_u32.to_le_bytes())

View on GitHub (pinned to 339751715c)

When it happens

Trigger: Thrown at codex-rs/shell-escalation/src/unix/socket.rs:189 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/95eb2401d448df4f. Report an issue: GitHub.