Client

VLM completion utilities using litellm for provider-agnostic inference.

vlm_completion

vlm_completion(
    config: VLMAPIConfig, prompt: str, image: Image
) -> str

Send image + prompt to any VLM via litellm. Returns raw text.

PARAMETER	DESCRIPTION
config	VLM API configuration. TYPE: VLMAPIConfig
prompt	Text prompt to send with the image. TYPE: str
image	PIL Image to send. TYPE: Image

RETURNS	DESCRIPTION
str	Raw text response from the model.

Source code in omnidocs/vlm/client.py

def vlm_completion(config: VLMAPIConfig, prompt: str, image: Image.Image) -> str:
    """
    Send image + prompt to any VLM via litellm. Returns raw text.

    Args:
        config: VLM API configuration.
        prompt: Text prompt to send with the image.
        image: PIL Image to send.

    Returns:
        Raw text response from the model.
    """
    import litellm

    b64 = _encode_image(image)
    messages = [
        {
            "role": "user",
            "content": [
                {"type": "text", "text": prompt},
                {"type": "image_url", "image_url": {"url": f"data:image/png;base64,{b64}"}},
            ],
        }
    ]

    kwargs = _build_kwargs(config, messages)
    response = litellm.completion(**kwargs)
    return response.choices[0].message.content

vlm_structured_completion

vlm_structured_completion(
    config: VLMAPIConfig,
    prompt: str,
    image: Image,
    response_schema: type[BaseModel],
) -> BaseModel

Send image + prompt, get structured Pydantic output.

Tries two strategies: 1. litellm's native response_format (works with OpenAI, Gemini, etc.) 2. Fallback: prompt-based JSON extraction for providers that don't support response_format (OpenRouter, some open-source models)

PARAMETER	DESCRIPTION
config	VLM API configuration. TYPE: VLMAPIConfig
prompt	Text prompt to send with the image. TYPE: str
image	PIL Image to send. TYPE: Image
response_schema	Pydantic model class for structured output. TYPE: type[BaseModel]

RETURNS	DESCRIPTION
BaseModel	Validated instance of response_schema.

Source code in omnidocs/vlm/client.py

def vlm_structured_completion(
    config: VLMAPIConfig,
    prompt: str,
    image: Image.Image,
    response_schema: type[BaseModel],
) -> BaseModel:
    """
    Send image + prompt, get structured Pydantic output.

    Tries two strategies:
    1. litellm's native response_format (works with OpenAI, Gemini, etc.)
    2. Fallback: prompt-based JSON extraction for providers that don't
       support response_format (OpenRouter, some open-source models)

    Args:
        config: VLM API configuration.
        prompt: Text prompt to send with the image.
        image: PIL Image to send.
        response_schema: Pydantic model class for structured output.

    Returns:
        Validated instance of response_schema.
    """
    import json

    import litellm

    b64 = _encode_image(image)
    messages = [
        {
            "role": "user",
            "content": [
                {"type": "text", "text": prompt},
                {"type": "image_url", "image_url": {"url": f"data:image/png;base64,{b64}"}},
            ],
        }
    ]

    # Strategy 1: Try response_format (native structured output)
    kwargs = _build_kwargs(config, messages)
    kwargs["response_format"] = response_schema
    try:
        response = litellm.completion(**kwargs)
        raw = response.choices[0].message.content
        return response_schema.model_validate_json(raw)
    except Exception:
        pass

    # Strategy 2: Fallback — prompt for JSON, parse manually
    schema_json = json.dumps(response_schema.model_json_schema(), indent=2)
    json_prompt = (
        f"{prompt}\n\n"
        f"Respond with ONLY valid JSON matching this schema (no markdown fencing, no extra text):\n"
        f"{schema_json}"
    )
    fallback_messages = [
        {
            "role": "user",
            "content": [
                {"type": "text", "text": json_prompt},
                {"type": "image_url", "image_url": {"url": f"data:image/png;base64,{b64}"}},
            ],
        }
    ]
    kwargs = _build_kwargs(config, fallback_messages)
    response = litellm.completion(**kwargs)
    raw = response.choices[0].message.content

    # Strip markdown fencing if present
    text = raw.strip()
    if text.startswith("```"):
        lines = text.splitlines()
        # Remove first line (```json) and last line (```)
        lines = [line for line in lines if not line.strip().startswith("```")]
        text = "\n".join(lines)

    return response_schema.model_validate_json(text)