What causes "no `.baml` files found in {}" in BoundaryML/baml?

Add at least one `.baml` file to the project root (or its baml_src directory).

no `.baml` files found in {}

Error message

no `.baml` files found in {}

What it means

The BAML CLI playground launcher (workspace_roots in playground_command.rs) loads the detected project and requires at least one `.baml` source file at the project root. If the resolved project directory contains no `.baml` files, it bails with this message naming the root path. This guards the playground from serving an empty project with nothing to render or compile.

Source

Thrown at baml_language/crates/baml_cli/src/playground_command.rs:124

        return match resolve_source_location(from, file, None)? {
            SourceLocation::StandaloneFile { file, .. } => Ok(vec![file]),
            SourceLocation::Project { .. } => unreachable!("file mode resolved as a project"),
        };
    }

    let search_start = resolve_project_search_start(from)
        .with_context(|| "could not resolve playground project search path")?;
    let Some(marked_root) = find_baml_project_root(&search_start) else {
        anyhow::bail!(
            "`{}` doesn't look like it belongs to a BAML project — no `baml.toml` \
             and no `baml_src/` directory found in it or its ancestors.",
            search_start.display()
        );
    };
    let project = load_project_from(Some(&marked_root))?;
    let root = project.root().to_path_buf();
    if project.files.is_empty() {
        anyhow::bail!("no `.baml` files found in {}", root.display());
    }
    Ok(vec![root])
}

fn resolve_playground_assets() -> Result<Option<PathBuf>> {
    if std::env::var_os("BAML_PLAYGROUND_DEV_PORT").is_some()
        || std::env::var_os("BAML_PLAYGROUND_DIR").is_some()
    {
        return Ok(None);
    }

    if let Some(dir) = discover_playground_dir()? {
        return Ok(Some(dir));
    }

    anyhow::bail!(
        "could not find packaged playground assets. For local debugging, run \
         `pnpm --filter app-vscode-webview dev -- --host 127.0.0.1 --port 4000` \

View on GitHub (pinned to bd85ce9dee)

Solutions

Add at least one `.baml` file to the project root (or its baml_src directory).
Check the path printed in the error — that directory is where files must live; move your `.baml` files there.
If the project marker points at the wrong root, remove/relocate the stray baml_src directory or manifest.
Restore deleted or ignored `.baml` files (check .gitignore).

Example fix

// before: baml_src/ exists but is empty
mkdir baml_src && baml playground  // fails

// after: put sources in baml_src
mv *.baml baml_src/
baml playground

Defensive patterns

Strategy: validation

Validate before calling

# before running `baml playground`
shopt -s nullglob
files=(baml_src/*.baml)
if [ ${#files[@]} -eq 0 ]; then echo "No .baml files in baml_src/"; exit 1; fi

Prevention

Keep all BAML sources inside baml_src/ and never rename them to other extensions.
Run `baml validate` or list files in baml_src before launching the playground.
Ensure .gitignore does not exclude .baml files.

When it happens

Trigger: Running `baml playground` (or its callers like project-mode validation tests) in a directory that has a project marker (baml_src/ or manifest) but zero `.baml` files: `project.files.is_empty()` after `load_project_from(Some(&marked_root))`.

Common situations: A baml_src folder was created (e.g. `baml init` partially failed or files were moved/deleted); the `.baml` files live in a subdirectory outside the marked root; a rename from `.baml` to another extension; a fresh repo cloned without generated sources.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/42d9e4e935edefba. Report an issue: GitHub.