BerriAI/litellm · error · HTTPException

No messages found in rendered prompt

Error message

No messages found in rendered prompt

What it means

Dotprompt rendering guard: the template rendered successfully but produced no messages (empty render output or a template with no content), so the prompt cannot be converted into a chat request; rejected with 400.

Source

Thrown at litellm/proxy/prompts/prompt_endpoints.py:1246

        frontmatter, template_content = prompt_manager._parse_frontmatter(content=request.dotprompt_content)

        # Create PromptTemplate to leverage existing parameter extraction logic
        template: Final = PromptTemplate(content=template_content, metadata=frontmatter, template_id="test_prompt")

        # Extract model from template
        if not template.model:
            raise HTTPException(status_code=400, detail="Model is required in dotprompt metadata")

        # Always render the template to extract system messages and other metadata
        variables: Final = request.prompt_variables or {}
        rendered_content: Final = prompt_manager.jinja_env.from_string(template_content).render(**variables)

        # Convert rendered content to messages using DotpromptManager's method
        dotprompt_manager: Final = DotpromptManager()
        rendered_messages: Final = dotprompt_manager._convert_to_messages(rendered_content=rendered_content)

        if not rendered_messages:
            raise HTTPException(status_code=400, detail="No messages found in rendered prompt")

        # If conversation history is provided, use it but preserve system messages
        if request.conversation_history:
            # Extract system messages from rendered prompt
            system_messages: Final = [msg for msg in rendered_messages if msg.get("role") == "system"]
            # Use conversation history for user/assistant messages
            messages = system_messages + request.conversation_history
        else:
            messages = rendered_messages

        # Use PromptTemplate's optional_params which already extracts all parameters
        optional_params: Final = template.optional_params.copy()

        # Always stream the response
        optional_params["stream"] = True

        # Build request data for chat completion
        data: Final = {

View on GitHub (pinned to 77b7c6c40c)

Solutions

1. Ensure the prompt template renders at least one message; check template variables and frontmatter.

When it happens

Trigger: Thrown at litellm/proxy/prompts/prompt_endpoints.py:1246 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of BerriAI/litellm@77b7c6c40c (2026-08-18). Data as JSON: /api/errors/1eca748a80670f15. Report an issue: GitHub.