Worked on the grpc/grpc repository to enhance stability and interoperability at the Objective-C and Swift boundary. Addressed a crash in CFStreamEndpointImpl::Shutdown by ensuring the client was unset only once, improving resource management and preventing double-unsetting errors. Introduced a concurrency safety feature for GRPCAuthorizationProtocol by marking the getTokenWithHandler block parameter as NS_SWIFT_SENDABLE, which strengthened thread-safety for Swift callers. The work focused on core C++ and Objective-C, with attention to crash fixes and Swift interoperability. These targeted improvements increased reliability for production clients and reduced risks associated with concurrent access and language interoperation in critical networking components.