BoundaryML/baml · error

failed to get raw LLM response

Error message

failed to get raw LLM response: %w

What it means

This error wraps any failure from raw_objects.CallMethod when RawLLMResponse() fetches the 'raw_llm_response' attribute of a FunctionLog via the C FFI. It is a pass-through wrapper: the actionable cause (empty FFI response buffer, nil pointer, proto unmarshal failure, or object-response decode failure) lives in the wrapped error. It means the Go client could not retrieve the raw LLM response text from the runtime object.

Solutions

1. Unwrap the error (errors.Unwrap / %w chain) to see the concrete FFI failure ('failed to call object method function', 'nil pointer', decode failure).
2. Read RawLLMResponse() within the lifetime of the owning function call/stream.
3. Keep the generated Go client in sync with the BAML runtime (re-run `baml generate`).
4. If the wrapped error is an unmarshal/decode failure on a live object, report it upstream with your versions.

if fnLog == nil {
    return errors.New("function log is nil; cannot read RawLLMResponse")
}

func isCallMethodFailure(err error) bool {
    return strings.Contains(err.Error(), "failed to call object method")
}

raw, err := fnLog.RawLLMResponse()
if err != nil {
    log.Printf("RawLLMResponse unavailable: %v (wrapped: %v)", err, errors.Unwrap(err))
    return fmt.Errorf("baml raw LLM response inaccessible: %w", err)
}

When it happens

Trigger: Calling RawLLMResponse() on a functionLog whose runtime object was freed or is invalid; the FFI method call returned an empty buffer or nil pointer; the protobuf response failed to unmarshal/decode.

Common situations: Reading raw responses after a stream completed and objects were reclaimed; caching log references in long-running services; Go client vs BAML runtime version mismatch.

Related errors

• failed to get function name
• failed to get log type
• failed to get timing
• failed to get usage
• decodeLiteralValue: valueLiteral is nil

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/6006f4498465c70a. Report an issue: GitHub.

Appendix: source

Thrown at engine/language_client_go/pkg/rawobjects_function_log.go:100

func (f *functionLog) Usage() (Usage, error) {
	result, err := raw_objects.CallMethod(f, "usage", nil)
	if err != nil {
		return nil, fmt.Errorf("failed to get usage: %w", err)
	}

	usage, ok := result.(Usage)
	if !ok {
		return nil, fmt.Errorf("unexpected type for usage: %T", result)
	}

	return usage, nil
}

func (f *functionLog) RawLLMResponse() (string, error) {
	result, err := raw_objects.CallMethod(f, "raw_llm_response", nil)
	if err != nil {
		return "", fmt.Errorf("failed to get raw LLM response: %w", err)
	}

	response, ok := result.(string)
	if !ok {
		return "", fmt.Errorf("unexpected type for raw LLM response: %T", result)
	}

	return response, nil
}

func (f *functionLog) CallsCount() (int, error) {
	result, err := raw_objects.CallMethod(f, "calls_count", nil)
	if err != nil {
		return 0, fmt.Errorf("failed to get calls count: %w", err)
	}

	count, ok := result.(int)
	if !ok {

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