What causes "jj {} failed: {}" in nikivdev/code?

Read the jj message appended after 'jj {} failed:' — it is jj's own diagnostic

jj {} failed: {}

Error message

jj {} failed: {}

What it means

Generic failure wrapper for fire-and-forget jj commands (via `jj_run_in`). When the spawned `jj <args>` process exits non-zero, the function combines the command name with the captured stderr (falling back to stdout when stderr is empty) and bails with this formatted message. It surfaces jj's own diagnostics verbatim to the caller.

Source

Thrown at src/commit.rs:8463

    }
    false
}

fn jj_run_in(repo_root: &Path, args: &[&str]) -> Result<()> {
    let output = Command::new(jj_bin())
        .current_dir(repo_root)
        .args(args)
        .output()
        .with_context(|| format!("failed to run jj {}", args.join(" ")))?;
    if !output.status.success() {
        let stderr = String::from_utf8_lossy(&output.stderr);
        let stdout = String::from_utf8_lossy(&output.stdout);
        let msg = if stderr.trim().is_empty() {
            stdout.trim()
        } else {
            stderr.trim()
        };
        bail!("jj {} failed: {}", args.join(" "), msg);
    }
    Ok(())
}

fn jj_capture_in(repo_root: &Path, args: &[&str]) -> Result<String> {
    let output = Command::new(jj_bin())
        .current_dir(repo_root)
        .args(args)
        .output()
        .with_context(|| format!("failed to run jj {}", args.join(" ")))?;
    if !output.status.success() {
        let stderr = String::from_utf8_lossy(&output.stderr);
        let stdout = String::from_utf8_lossy(&output.stdout);
        let msg = if stderr.trim().is_empty() {
            stdout.trim()
        } else {
            stderr.trim()
        };

View on GitHub (pinned to a747e741ae)

Solutions

Read the jj message appended after 'jj {} failed:' — it is jj's own diagnostic
Re-run the exact jj command manually in the repo root to reproduce
Check that the jj binary version supports the flags used
Ensure the workspace is valid (`jj st` succeeds) before retrying

Example fix

// before
Error: jj describe failed: Error: working copy is stale
// after
$ jj workspace update-stale  # or `jj st` to auto-update
$ tool commit                 # retry the operation

Defensive patterns

Strategy: try-catch

Validate before calling

let out = Command::new("jj").args(["st"]).output()?;
if !out.status.success() {
    return Err(anyhow!("jj workspace not usable: {}",
        String::from_utf8_lossy(&out.stderr)));
}

Try / catch

if let Err(e) = result {
    let msg = e.to_string();
    if msg.contains("failed:") {
        eprintln!("jj command failed; rerun manually to debug: jj <subcommand>");
    }
    return Err(e);
}

Prevention

Sanity-check the workspace with `jj st` before automating jj commands
Verify jj version supports all flags used (e.g. `jj --version`)
Use `FLOW_JJ_BIN` to pin the intended jj binary in scripts
Log the exact args so failures can be reproduced manually

When it happens

Trigger: Any call to the fire-and-forget jj helper where `output.status.success()` is false — e.g. `jj new`, `jj describe`, or `jj bookmark set` failing due to invalid arguments, unresolvable revisions, or workspace issues.

Common situations: Typo'd or unsupported jj subcommand/flag on older jj versions; referencing a revision that does not exist; jj workspace not initialized in the repo; authentication or git-backend errors surfaced through jj.

Related errors

AI-assisted analysis of nikivdev/code@a747e741ae (2026-09-01). Data as JSON: /api/errors/979e833b6be3691f. Report an issue: GitHub.