Under the hood
MCP tool calls now reuse an existing tool-use id instead of deriving one, and add a per-request header
What
When Claude Code makes an MCP (Model Context Protocol) tool call, it now prefers to use the tool-use id already attached to the call record, rather than deriving one from request headers as it did before. It also now adds a new per-request metadata header carrying the request id, in addition to the existing claudecode/toolUseId metadata.
Why
This is an internal correctness and traceability improvement for how MCP tool calls are identified, which can help with matching requests to responses correctly and debugging.