What causes "failed to read from codex: {}" in nikivdev/code?

Check that the codex app-server process is alive and that its version is compatible with this tool.

failed to read from codex: {}

Error message

failed to read from codex: {}

What it means

The codex app-server reader thread surfaced a ReadError while reading stdout, and this function converts it into an error via bail! with the underlying I/O error. It means the tool lost the ability to read JSON-RPC messages from the codex app-server process, so the review/automation step cannot continue.

Source

Thrown at src/commit.rs:4727

        let now = Instant::now();
        if now >= deadline {
            return Ok(CodexReadOutcome::TimedOut);
        }

        let wait = cmp::min(
            Duration::from_millis(250),
            deadline.saturating_duration_since(now),
        );
        match rx.recv_timeout(wait) {
            Ok(CodexAppServerEvent::Line(line)) => {
                if line.trim().is_empty() {
                    continue;
                }
                let msg: serde_json::Value = serde_json::from_str(&line)
                    .with_context(|| format!("invalid JSON from codex: {}", line))?;
                return Ok(CodexReadOutcome::Message(msg));
            }
            Ok(CodexAppServerEvent::ReadError(err)) => bail!("failed to read from codex: {}", err),
            Ok(CodexAppServerEvent::Closed) => bail!("codex app-server closed stdout unexpectedly"),
            Err(RecvTimeoutError::Timeout) => continue,
            Err(RecvTimeoutError::Disconnected) => bail!("codex app-server reader disconnected"),
        }
    }
}

/// Read lines until a JSON-RPC response with the expected id arrives.
fn codex_read_response(
    rx: &std::sync::mpsc::Receiver<CodexAppServerEvent>,
    expected_id: u64,
    deadline: std::time::Instant,
) -> Result<serde_json::Value> {
    loop {
        let msg = match codex_read_next_message(rx, deadline)? {
            CodexReadOutcome::Message(msg) => msg,
            CodexReadOutcome::TimedOut => bail!("codex app-server response timed out"),
        };

View on GitHub (pinned to a747e741ae)

Solutions

Check that the codex app-server process is alive and that its version is compatible with this tool.
Re-run the command; a transient pipe failure often clears on retry.
Inspect system logs/resource limits if the codex process is being killed (OOM, fd limits).
Update the codex binary or the tool to matching supported versions.

Example fix

// before: codex binary not running/old
codex app-server --version  // verify installed & compatible
// after: restart the flow with a healthy codex process
f commit  // retried after codex is responsive

Defensive patterns

Strategy: retry

Validate before calling

// verify codex is installed, executable, and the pipe can open
// e.g. spawn a trivial codex app-server request before the real review

Try / catch

match codex_review() {
    Err(e) if e.to_string().starts_with("failed to read from codex") => {
        eprintln!("codex stdout read failed: {e}; restarting codex and retrying");
    }
    other => other?,
}

Prevention

Keep the codex process alive for the whole session (watch for OOM kills).
Check fd/pipe resource limits on CI machines.
Pin compatible codex and tool versions.

When it happens

Trigger: Calling the codex-driven review flow when the reader thread's line read from the codex process stdout fails (I/O error on the pipe).

Common situations: Codex process crashed or was killed mid-session; stdout pipe closed/broken; OS resource limits (fd exhaustion); codex binary version change altering protocol/output.

Related errors

AI-assisted analysis of nikivdev/code@a747e741ae (2026-09-01). Data as JSON: /api/errors/aad3cf97eaa5ccfa. Report an issue: GitHub.