### Overview This PR adds the first piece of tracing for app-server JSON-RPC requests. There are two main changes: - JSON-RPC requests can now take an optional W3C trace context at the top level via a `trace` field (`traceparent` / `tracestate`). - app-server now creates a dedicated request span for every inbound JSON-RPC request in `MessageProcessor`, and uses the request-level trace context as the parent when present. For compatibility with existing flows, app-server still falls back to the TRACEPARENT env var when there is no request-level traceparent. This PR is intentionally scoped to the app-server boundary. In a followup, we'll actually propagate trace context through the async handoff into core execution spans like run_turn, which will make app-server traces much more useful. ### Spans A few details on the app-server span shape: - each inbound request gets its own server span - span/resource names are based on the JSON-RPC method (`initialize`, `thread/start`, `turn/start`, etc.) - spans record transport (stdio vs websocket), request id, connection id, and client name/version when available - `initialize` stores client metadata in session state so later requests on the same connection can reuse it |
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codex-protocol
This crate defines the "types" for the protocol used by Codex CLI, which includes both "internal types" for communication between codex-core and codex-tui, as well as "external types" used with codex app-server.
This crate should have minimal dependencies.
Ideally, we should avoid "material business logic" in this crate, as we can always introduce Ext-style traits to add functionality to types in other crates.