headroomlabs-ai/headroom · error · ValueError

Language '{language}' is not supported by tree-sitter. Suppo

Error message

Language '{language}' is not supported by tree-sitter. Supported: python, javascript, typescript, go, rust, java, c, cpp, csharp, php. Error: {e}

What it means

Raised from the except block around parser construction in _get_parser: building the tree_sitter.Parser and binding get_language(language) failed for the requested name. The supported set is python, javascript, typescript, go, rust, java, c, cpp, csharp, php; anything else (or a grammar whose wheel is missing/broken) surfaces here with the underlying exception chained via 'Error: {e}'.

Source

Thrown at headroom/transforms/code_compressor.py:168

        _tree_sitter_local.parsers = parsers

    if language not in parsers:
        try:
            from tree_sitter import Parser
            from tree_sitter_language_pack import get_language

            parser = Parser()
            # `language` is a validated runtime str; get_language types its arg
            # as a Literal of supported names, which a dynamic str can't satisfy.
            parser.language = get_language(language)  # type: ignore[arg-type]
            parsers[language] = parser
            logger.debug(
                "Loaded tree-sitter parser for %s (thread %s)",
                language,
                threading.current_thread().name,
            )
        except Exception as e:
            raise ValueError(
                f"Language '{language}' is not supported by tree-sitter. "
                f"Supported: python, javascript, typescript, go, rust, java, c, cpp, csharp, php. "
                f"Error: {e}"
            ) from e

    return parsers[language]


def is_tree_sitter_available() -> bool:
    """Check if tree-sitter is installed and available.

    Returns:
        True if tree-sitter-languages package is installed.
    """
    return _check_tree_sitter_available()


def is_tree_sitter_loaded() -> bool:

View on GitHub (pinned to 322425c43b)

Solutions

1. Use one of the supported names exactly: python, javascript, typescript, go, rust, java, c, cpp, csharp, php.
2. Check the chained 'Error:' suffix — if it names a missing grammar module, reinstall the grammar pack (pip install --force-reinstall tree-sitter-language-pack).
3. For unsupported languages, route the content through the plain-text compressor instead.

Example fix

# before
parser = _get_parser("ts")  # ValueError: not supported

# after
_LANGUAGE_ALIASES = {"ts": "typescript", "py": "python", "c++": "cpp"}
parser = _get_parser(_LANGUAGE_ALIASES.get(lang, lang))

SUPPORTED = {"python","javascript","typescript","go","rust","java","c","cpp","csharp","php"}
if language not in SUPPORTED:
    language = None  # plain-text path

def is_supported_ts_language(lang: str) -> bool:
    return lang in {"python","javascript","typescript","go","rust","java","c","cpp","csharp","php"}

try:
    parser = _get_parser(language)
except ValueError as e:
    if "not supported by tree-sitter" in str(e):
        parser = None
    else:
        raise

When it happens

Trigger: Calling _get_parser with a language outside the supported list (e.g. 'ruby', 'kotlin', 'perl' would be caught earlier by quarantine), or a supported name whose grammar package is not installed/broken so get_language raises.

Common situations: Sending Ruby/Scala/Lua files into code-aware compression; a partially installed tree-sitter-language-pack where one grammar wheel failed; a typo in a config language key ('ts' instead of 'typescript').

Related errors

• Language '{language}' is quarantined for code-aware compress
• invalid pipeline config TOML: {0}
• recommendations file not found: {0}
• bedrock_eventstream_parse_failed
• items_json must be JSON: {e}

AI-assisted analysis of headroomlabs-ai/headroom@322425c43b (2026-08-15). Data as JSON: /api/errors/b7ab5f24c2a22afe. Report an issue: GitHub.