What causes "Error compiling prompt '{prompt_id}': {e}" in BerriAI/litellm?

Read the inner text after the colon — it contains the underlying error ('Failed to fetch prompt ...', JSON parse error, etc.) which tells you which sub-step failed.

BerriAI/litellm · error · ValueError

Error compiling prompt '{prompt_id}': {e}

Error message

Error compiling prompt '{prompt_id}': {e}

What it means

Raised by GenericPromptManager.compile_prompt_helper (sync path) as a catch-all: any Exception raised during fetch, parsing, or variable substitution for a prompt is re-wrapped into ValueError with the prompt_id in the message. The original stack trace is preserved as the cause (__context__), but the original exception type is hidden.

Source

Thrown at litellm/integrations/generic_prompt_management/generic_prompt_manager.py:306

        cache_key: Final = self._get_cache_key(prompt_id, prompt_label, prompt_version)
        try:
            # Fetch from API
            api_response: Final = self._fetch_prompt_from_api(prompt_id, prompt_spec)

            # Parse the response
            prompt_client = self._parse_api_response(prompt_id, prompt_spec, api_response)

            # Cache the result
            self._prompt_cache[cache_key] = prompt_client

            # Apply variables if provided
            if prompt_variables:
                prompt_client = self._apply_variables(prompt_client, prompt_variables)

            return prompt_client

        except Exception as e:
            raise ValueError(f"Error compiling prompt '{prompt_id}': {e}")

    async def async_compile_prompt_helper(
        self,
        prompt_id: str | None,
        prompt_variables: dict | None,
        dynamic_callback_params: StandardCallbackDynamicParams,
        prompt_spec: PromptSpec | None = None,
        prompt_label: str | None = None,
        prompt_version: int | None = None,
    ) -> PromptManagementClient:
        # Check cache first
        cached_prompt: Final = self._common_caching_logic(
            prompt_id=prompt_id,
            prompt_label=prompt_label,
            prompt_version=prompt_version,
            prompt_variables=prompt_variables,
        )
        if cached_prompt:

View on GitHub (pinned to 6c2dcb801b)

Solutions

Read the inner text after the colon — it contains the underlying error ('Failed to fetch prompt ...', JSON parse error, etc.) which tells you which sub-step failed.
Fix that root cause: unreachable API -> network/api_base; parse errors -> response format; apply-variables errors -> supply all template variables.
Check the server response with curl for the same prompt_id to confirm the expected structure (required fields for _parse_api_response).
Ensure prompt_variables covers every {variable_name} placeholder defined in the stored template.

Example fix

# before: template on server is "Hello {name}, you are {age}"
resp = litellm.completion(model="prompt-model", messages=[...])  # missing vars

# after
resp = litellm.completion(
    model="prompt-model",
    messages=[...],
    variables={"name": "Ada", "age": "36"},
)

Defensive patterns

Strategy: try-catch

Validate before calling

def validate_prompt_variables(template: str, variables: dict) -> None:
    import string
    needed = set(string.Formatter().parse(template and template or "")) and \
             {fname for _, fname, _, _ in string.Formatter().parse(template) if fname}
    missing = needed - set(variables or {})
    if missing:
        raise ValueError(f"Missing prompt variables: {sorted(missing)}")

Try / catch

try:
    resp = litellm.completion(model="prompt-model", messages=msgs, variables=vars)
except ValueError as e:
    if str(e).startswith("Error compiling prompt"):
        # inspect the suffix: fetch failure, parse failure, or variable mismatch
        log_prompt_compile_failure(prompt_id, str(e))
        raise
    raise

Prevention

Pre-flight the prompt API with a curl/script that fetches and parses the prompt once before serving.
Keep template variable names and caller-supplied variables in one shared definition.
Warm the prompt cache after config changes so first user request is not the compile path.

When it happens

Trigger: Any failure inside the sync compile pipeline: network error from _fetch_prompt_from_api, JSON decode error, an unexpected API response shape in _parse_api_response (e.g. missing keys), or a KeyError/ValueError from _apply_variables when template variables mismatch. Because the result is cached, this only fires on cache misses.

Common situations: First request after startup when the cache is cold and the prompt API is misconfigured or unreachable; the prompt template on the server referencing a variable the caller did not supply; the server response format changing after a prompt-management API upgrade.

Related errors

AI-assisted analysis of BerriAI/litellm@6c2dcb801b (2026-08-15). Data as JSON: /api/errors/27763ce495f0e7e7. Report an issue: GitHub.