[codex] Correlate protocol request failures

[juliusmarminge]

Summary

• attach method, request ID, and operation diagnostics to ACP and Codex App Server request/response failures
• retain complete encoded ACP failure causes while deriving stable protocol-facing messages
• preserve pending-request method context and clean it up without widening catch semantics
• centralize protocol error transformations on the error classes

Validation

• vp test packages/effect-acp/src/errors.test.ts packages/effect-acp/src/protocol.test.ts packages/effect-codex-app-server/src/protocol.test.ts (26 tests)
• vp check (0 errors; existing warnings only)
• vp run typecheck
• independent read-only review found no remaining actionable issues

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Note

Medium Risk
Touches core JSON-RPC error mapping and pending-request lifecycle in two protocol packages; behavior is mostly additive diagnostics but changes error shapes and ACP extension error handling semantics.

Overview
ACP and Codex App Server now attach method, request ID, and operation (receive-response, encoding failures, etc.) when outbound encoding fails or when a client request gets an error response, so failures can be tied to the call that caused them.

Pending outbound requests keep method alongside the deferred (not just ID), and protocol layers use that when mapping JSON-RPC errors into AcpRequestError / CodexAppServerRequestError. ACP also adds focused factories for extension response failures, response encoding errors, and unsupported streaming chunks, keeps full exit cause on protocol errors where relevant, and tightens extension-handler error handling to AcpProtocolParseError instead of a blanket catch. Encode/decode failure logging can include requestId where available.

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Note

Correlate protocol request failures with originating RPC method and request ID

• Adds method and requestId metadata to AcpRequestError and CodexAppServerRequestError so that protocol-level failures can be traced back to the originating request.
• Introduces AcpPendingRequest and CodexAppServerPendingRequest interfaces that store method alongside the deferred, enabling correlation when responses arrive.
• New factory methods (fromProtocolError, fromExtensionResponseFailure, fromExtensionResponseEncodingError, unsupportedStreamingResponse) produce structured errors tagged with specific operation values (receive-response, encode-extension-response, receive-streaming-response).
• Encoding failures in offerOutgoing and encodeWireMessage now propagate method and requestId into AcpProtocolParseError / CodexAppServerProtocolParseError.
• Pending entries are now cleaned up via tapError on send failure rather than swallowing the error path.

^{Macroscope summarized 878b3a6.}

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch codex/protocol-request-error-correlation

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[macroscopeapp]

Approvability

Verdict: Approved

Adds optional diagnostic context (method, requestId, operation) to protocol error objects for better error correlation. Backwards-compatible schema additions with comprehensive test coverage and no behavioral changes.

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