BoundaryML/baml · error

failed to install {} into {}

Error message

failed to install {} into {}

What it means

`baml agent` skill installation failed at the final step of swapping the freshly prepared directory into place: fs::rename(next_dir, final_dir) returned an error, which is wrapped with context naming the skill and target directory. Commonly this is a cross-filesystem rename, an existing non-empty target, or a filesystem permission problem.

Source

Thrown at baml_language/crates/baml_cli/src/agent_command.rs:265

                format!("failed to clear old-skill slot {}", archive_dir.display())
            })?;
        }
        if let Some(parent) = archive_dir.parent() {
            fs::create_dir_all(parent)
                .with_context(|| format!("failed to create {}", parent.display()))?;
        }
        fs::rename(&final_dir, &archive_dir).with_context(|| {
            format!(
                "failed to archive existing {} into {}",
                final_dir.display(),
                archive_dir.display()
            )
        })?;
        archive = Some(archive_dir);
    }

    if let Err(err) = fs::rename(&next_dir, &final_dir) {
        let mut error = anyhow!(err).context(format!(
            "failed to install {} into {}",
            skill.name,
            final_dir.display()
        ));
        if let Some(archive_dir) = archive {
            if final_dir.exists() {
                error = error.context(format!(
                    "previous {} skill remains at {}",
                    skill.name,
                    archive_dir.display()
                ));
            } else if let Err(restore_err) = fs::rename(&archive_dir, &final_dir) {
                error = error.context(format!(
                    "failed to restore previous {} skill from {} to {}: {restore_err}",
                    skill.name,
                    archive_dir.display(),
                    final_dir.display()
                ));

View on GitHub (pinned to bd85ce9dee)

Solutions

1. Check write permissions on the target skills directory and its parent.
2. Ensure the staging dir and final dir are on the same filesystem (or copy+delete instead of rename).
3. Remove or back up the existing destination directory if it is blocking the rename.
4. Close processes locking the destination (editors, sync clients, antivirus).

Example fix

// before
fs::rename(&next_dir, &final_dir)?;
// after: fall back to copy when rename crosses devices
match fs::rename(&next_dir, &final_dir) {
    Ok(()) => {},
    Err(e) if e.kind() == std::io::ErrorKind::CrossesDevices => {
        copy_dir_all(&next_dir, &final_dir)?;
        fs::remove_dir_all(&next_dir)?;
    }
    Err(e) => return Err(e.into()),
}

// pre-flight checks before install
let dest = &final_dir;
assert!(dest.parent().map(|p| p.exists()).unwrap_or(false));
// check writability
std::fs::OpenOptions::new().write(true).open(dest.parent().join(".probe")).is_ok();

match fs::rename(&next_dir, &final_dir) {
    Ok(()) => {},
    Err(e) if e.kind() == std::io::ErrorKind::CrossesDevices => {
        copy_dir_all(&next_dir, &final_dir)?;
        fs::remove_dir_all(&next_dir)?;
    }
    Err(e) => return Err(anyhow!(e).context(format!("failed to install {}", skill.name))),
}

When it happens

Trigger: install_skills_to -> replace_skill_dir calling fs::rename on the staged skill dir when the destination path exists on a different filesystem/mount, is not writable, or cannot be replaced.

Common situations: Skills directory on a different mount/DFS than the temp staging dir; read-only or root-owned ~/.baml (or configured skills dir); antivirus/indexer holding the destination open on Windows.

Understand the failure class

Background: "failed to write file", "Could not save figure", "Error saving remote file" — file write failed: causes and fixes across languages and libraries — this error's family across 38 libraries.

Related errors

• access error: {message}
• ErrCacheDir
• failed create destination %s: %w
• IO error: {0}
• toolchain binary is not executable: {}{origin}

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/6ed9ce67ce4ac41e. Report an issue: GitHub.