BoundaryML/baml · error

pack produced no output at {}

Error message

pack produced no output at {}

What it means

After `baml pack` exits successfully, run_baml_pack verifies the output file actually exists at the deterministic path under target/size-gate/. If the CLI exited 0 but wrote nothing (or wrote elsewhere), this bail catches it, protecting the measurement step from operating on a missing artifact.

Source

Thrown at baml_language/crates/tools_size_gate/src/measure.rs:152

    }

    eprintln!("  packing {} -> {}", pack.function, output.display());
    let status = Command::new(&cli_path)
        .arg("pack")
        .arg("--file")
        .arg(&fixture)
        .arg(&pack.function)
        .arg("-o")
        .arg(&output)
        .current_dir(workspace_root)
        .status()
        .with_context(|| format!("failed to run {} pack", cli_path.display()))?;
    if !status.success() {
        bail!("`baml pack` failed for fixture {}", fixture.display());
    }

    if !output.exists() {
        bail!("pack produced no output at {}", output.display());
    }
    Ok(output)
}

/// Deterministic output path for a packed artifact.
fn pack_output_path(workspace_root: &Path, name: &str) -> PathBuf {
    workspace_root
        .join("target/size-gate")
        .join(exe_filename(name))
}

/// Find the built artifact in the target directory (public for --no-build mode).
pub(crate) fn locate_artifact_public(
    workspace_root: &Path,
    name: &str,
    config: &ArtifactConfig,
) -> Result<PathBuf> {
    locate_artifact(workspace_root, name, config)

View on GitHub (pinned to bd85ce9dee)

Solutions

1. Inspect target/size-gate/ to see where output actually landed
2. Confirm the CLI version supports -o and writes to it exactly
3. Re-run after freeing disk space / ruling out concurrent cargo clean
4. Run the pack command manually and check the exit code and output path

Example fix

// before: old CLI ignores -o
baml pack -i fixture -o out   # exits 0, no file
// after
baml --version   # ensure >= version that honors -o, then rerun size-gate

let out = pack_output_path(workspace, name);
if !out.exists() {
    eprintln!("pack output missing at {} — check CLI version supports -o", out.display());
    std::process::exit(1);
}

When it happens

Trigger: Pack CLI exits 0 without producing the output: -o path ignored by an older CLI version, pack writes to a different directory, or the CLI silently skips on empty/invalid input.

Common situations: Using a baml CLI version whose pack flag semantics differ; disk full silently truncating output; output path cleaned concurrently by another CI job running cargo clean.

Understand the failure class

Background: "File not found" and ENOENT errors: why libraries can't find a file that should exist — this error's family across 50 libraries.

Related errors

• no `.baml` files found in {}
• Schema inconsistency: {message}
• `baml pack` failed for fixture {}
• Internal error occurred while resolving repr of field {:?}
• InternalError

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/c0be2b1914c25d09. Report an issue: GitHub.