What causes "shell command failed (status={}): {}" in Hmbown/CodeWhale?

Read the stderr in the message; it is the underlying tool's own output and names the root cause.

shell command failed (status={}): {}

Error message

shell command failed (status={}): {}

What it means

Thrown by ShellDispatcher when a dispatched shell command runs to completion but exits non-zero (crates/tui/src/shell_dispatcher.rs). The captured stderr, trimmed, is appended after the status code. Spawn failures are a different error ('failed to execute shell command'), so this one strictly means the process started, ran, and failed by its own exit code.

Source

Thrown at crates/tui/src/shell_dispatcher.rs:410

                if self.restore {
                    let _ = crossterm::terminal::enable_raw_mode();
                }
            }
        }
        let _guard = FgRawModeGuard {
            restore: raw_mode_was_enabled,
        };

        let mut cmd = self.build_command(shell_command);
        cmd.current_dir(cwd);

        let output = cmd
            .output()
            .with_context(|| format!("failed to execute shell command: {shell_command}"))?;

        if !output.status.success() {
            let stderr = String::from_utf8_lossy(&output.stderr);
            anyhow::bail!(
                "shell command failed (status={}): {}",
                output.status,
                stderr.trim()
            );
        }

        let stdout = String::from_utf8_lossy(&output.stdout).trim().to_string();
        Ok(stdout)
    }

    // -- Detection --------------------------------------------------------

    fn detect_shell() -> ShellKind {
        #[cfg(test)]
        {
            // Non-blocking on purpose. This runs inside the `LazyLock`
            // initializer in `global_dispatcher()`, and a test that holds the
            // env barrier can reach `global_dispatcher()` while another thread

View on GitHub (pinned to 0c42157ee5)

Solutions

Read the stderr in the message; it is the underlying tool's own output and names the root cause.
Re-run the command directly in a terminal from the same cwd to see full, untrimmed output.
If the non-zero exit is expected (grep no-match, diff), make the command exit 0 itself: append '|| true' or restructure.
If the shell selection is wrong (command exists in another shell), fix shell detection; spawn failure is the sibling error to compare against.

Example fix

# before
!grep -q TODO src/main.rs
# exits 1 when no match -> error surfaced

# after
!grep -q TODO src/main.rs || true

Defensive patterns

Strategy: try-catch

Validate before calling

// Preflight: confirm the binary resolves in the dispatcher's shell and cwd
let check = Command::new("sh")
    .arg("-c")
    .arg(format!("command -v -- {binary:?} >/dev/null 2>&1"))
    .current_dir(cwd)
    .status()?;
if !check.success() {
    eprintln!("{binary} not found on PATH for this shell/cwd");
}

Try / catch

match dispatcher.run(&cmd, cwd).await {
    Err(err) if err.to_string().starts_with("shell command failed (status=") => {
        // the command ran and exited non-zero; stderr is embedded in the message
        let root = err.to_string(); // surface it, do not retry blindly
    }
    Err(err) => { /* spawn/execution failure: check PATH and shell selection */ }
    Ok(stdout) => { /* use stdout */ }
}

Prevention

Expect non-zero exits from signal-style commands (grep -q, diff --exit-code) and neutralize with '|| true' where the exit code is not an error.
Run builds and tests from the same cwd the session uses so relative paths resolve identically.
Read the embedded stderr before assuming the dispatcher itself misbehaved.

When it happens

Trigger: Running a bang command or shell tool whose process exits non-zero: failing builds ('!cargo build'), failing tests, grep with no matches (exit 1), 'git diff --exit-code' with changes. The dispatcher runs the command in the session cwd, so path-dependent commands that fail there land here.

Common situations: Build or test pipelines invoked from the TUI where the underlying tool already printed the real cause to stderr; commands that use exit codes as signals (grep -q, diff --exit-code); commands assuming a different working directory than the session cwd.

Related errors

AI-assisted analysis of Hmbown/CodeWhale@0c42157ee5 (2026-08-20). Data as JSON: /api/errors/6c51c9d1e58b0fb2. Report an issue: GitHub.