sgl-project/sglang · error · ValueError

Config file must be YAML format, got: {path.suffix}

Error message

Config file must be YAML format, got: {path.suffix}

What it means

The config parser only accepts files with a .yaml or .yml suffix (case-insensitive) and rejects anything else before touching the file. This is a cheap guard so mispointed files fail loudly.

Source

Thrown at python/sglang/srt/utils/server_args_config_parser.py:136

                config_data = yaml.safe_load(file)
        except Exception as e:
            logger.error(f"Failed to read config file {file_path}: {e}")
            raise

        # Handle empty files or None content
        if config_data is None:
            config_data = {}

        if not isinstance(config_data, dict):
            raise ValueError("Config file must contain a dictionary at root level")

        return config_data

    def _validate_yaml_file(self, file_path: str) -> None:
        """Validate that the file is a YAML file."""
        path = Path(file_path)
        if path.suffix.lower() not in [".yaml", ".yml"]:
            raise ValueError(f"Config file must be YAML format, got: {path.suffix}")

        if not path.exists():
            raise ValueError(f"Config file not found: {file_path}")

    def _convert_config_to_args(self, config: Dict[str, Any]) -> List[str]:
        """Convert configuration dictionary to argument list."""
        args = []

        for key, value in config.items():
            key_norm = key.replace("-", "_")
            if key_norm in self.unsupported_actions:
                action = self.unsupported_actions[key_norm]
                msg = f"Unsupported config option '{key_norm}' with action '{action.__class__.__name__}'"
                raise ValueError(msg)
            if isinstance(value, bool):
                self._add_boolean_arg(args, key, value)
            elif isinstance(value, list):
                self._add_list_arg(args, key, value)

View on GitHub (pinned to 0132848349)

Solutions

1. Rename or convert the file to .yaml/.yml
2. If the file is JSON, convert it to YAML key:value mapping first
3. Double-check the argument order — --config expects the config path, not the model path

Example fix

# before
python -m sglang.launch_server --config settings.json
# after
python -m sglang.launch_server --config settings.yaml

from pathlib import Path
assert Path(cfg).suffix.lower() in {".yaml", ".yml"}, "config must be .yaml/.yml"

When it happens

Trigger: Passing --config server.json, --config config.txt, or any path whose Path.suffix is not .yaml/.yml.

Common situations: Renaming a JSON or template file to use with --config, or passing the model path instead of the config path by mistake.

Related errors

• Multiple config files specified! Only one allowed.
• Config file must contain a dictionary at root level
• Config file not found: {file_path}
• Unsupported config option '{key_norm}' with action '{action.
• {selection_error}{component_suffix}

AI-assisted analysis of sgl-project/sglang@0132848349 (2026-08-28). Data as JSON: /api/errors/fd57b628cb1a9881. Report an issue: GitHub.