BoundaryML/baml · error

failed to call object method function

Error message

failed to call object method function

What it means

This error means the C FFI function WrapCallObjectMethodFunction returned a zero-length buffer, so no InvocationResponse bytes exist. It indicates the native method invocation produced no response at all — the call never completed on the native side.

Solutions

1. Check FFI logs (BAML_FFI_CLIENT_LOG) for native-side panics preceding this error
2. Ensure the baml.Runtime outlives all objects created from it
3. Recreate the object/builder and retry the call
4. Verify Go bindings and native library versions match

Example fix

// before: using a type builder after runtime teardown
// after: hold runtime reference and build/finish within its lifetime
rt := b.NewRuntime(); defer keepAlive(rt)
tb := b.NewTypeBuilder(rt); _ = tb.AddProperty(...)

if rt == nil || !runtimeAlive(rt) { return fmt.Errorf("baml runtime not available for object method call") }

res, err := builder.Type()
if err != nil && strings.Contains(err.Error(), "failed to call object method function") {
    return fmt.Errorf("native call produced no response (runtime alive?): %w", err)
}

When it happens

Trigger: Calling any BAML object method (destructor, Type, ListProperties, AddProperty, Property, SetType) when the native runtime fails to produce a response buffer, e.g. runtime already destroyed or a native panic.

Common situations: Using a builder/object whose runtime was torn down; calling methods after a previous native-side panic; FFI bridge version mismatch.

Understand the failure class

Background: 'Something went wrong' / 'Request failed (500)' / 'HTTP error! status: 404' — what failed HTTP requests actually mean and how to find the real cause — this error's family across 28 libraries.

Related errors

• object method function returned nil pointer
• decodeLiteralValue: valueLiteral is nil
• destructor returned unexpected result
• encoding client registry
• encoding collector

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/e21ea38756502739. Report an issue: GitHub.

Appendix: source

Thrown at engine/language_client_go/baml_go/raw_objects/utils.go:179

	args := cffi.BamlObjectMethodInvocation{
		Kwargs:     cffi_kwargs,
		Object:     EncodeRawObject(object),
		MethodName: method_name,
	}

	encodedArgs, err := proto.Marshal(&args)
	if err != nil {
		return nil, fmt.Errorf("failed to marshal object method arguments: %w", err)
	}
	cEncodedArgs := (*C.char)(unsafe.Pointer(&encodedArgs[0]))

	cBuf := C.WrapCallObjectMethodFunction(object.Runtime(), cEncodedArgs, C.uintptr_t(len(encodedArgs)))

	content_bytes := C.GoBytes(unsafe.Pointer(cBuf.ptr), C.int32_t(cBuf.len))
	C.WrapFreeBuffer(cBuf) // Free the buffer after use
	if cBuf.len == 0 {
		return nil, fmt.Errorf("failed to call object method function")
	}
	if cBuf.ptr == nil {
		return nil, fmt.Errorf("object method function returned nil pointer")
	}

	var content_holder cffi.InvocationResponse
	err = proto.Unmarshal(content_bytes, &content_holder)
	if err != nil {
		return nil, fmt.Errorf("failed to unmarshal content bytes: %w", err)
	}

	parsed, err := decodeObjectResponse(object.Runtime(), &content_holder)
	if err != nil {
		return nil, fmt.Errorf("failed to decode object response: %w", err)
	}

	return parsed, nil
}

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