Apply C++ move semantics and lambda modifiers only when necessary. The `mutable` keyword should only be used in lambdas when you need to modify captured variables, including when using move operations on them: ```cpp // Correct: mutable required for WTFMove(message) context->postImmediateCppTask([protectedThis = Ref { *this }, message = WTFMove(message)](ScriptExecutionContext& ctx) mutable { // Using WTFMove(message) inside the lambda }); // Incorrect: unnecessary mutable context->postImmediateCppTask([protectedThis = Ref { *this }, message](ScriptExecutionContext& ctx) mutable { // No modification of captured variables }); ``` Similarly, avoid redundant moves on function objects unless there's a specific rvalue ref-qualified overload of `operator()` you intend to call: ```cpp // Correct: Direct invocation completionCallback(); // Unnecessary: redundant move WTFMove(completionCallback)(); ``` Using move operations judiciously improves code clarity and helps avoid subtle bugs related to object ownership.