Codex starts stamping sessionId and originating windowId on every MCP request
GitHub·medium signal
PR #45409, merged 2026-09-14, adds sessionId and the originating windowId alongside the existing threadId and optional itemId in MCP request metadata. Code-mode cells retain their originating item and window across waits and compaction, including the window when no matching history item is found, with a regression test pinning that a cell resuming after compaction keeps its original IDs. For anyone building an MCP server that logs or authorizes per-caller, this is a richer provenance tuple than threadId alone.