- Introduce `authUnavailableError` with detailed recovery hints, status codes, and retry-after headers.
- Refactor scheduler logic to incorporate local retry deadlines and classify cooldown states without altering quota assessments.
- Refine error propagation to properly handle upstream errors and enrich context for retryable scenarios.
- Add comprehensive tests for retry deadlines, scheduler behavior, and error handling during credential unavailability.
- Ensure embedded recovery hints in HTTP headers for improved client-side handling and diagnostics.
Closes: #5842
- Introduce `isTransientTransportError` to identify transient transport errors such as TLS handshake, DNS, and connection resets.
- Extend retry logic to handle these errors without enforcing credential cooldown.
- Add new constants, such as `ErrorCodeTransientTransport`, to categorize and manage these errors.
- Refactor `conductor_selection` to distinguish request-retry round errors.
- Add comprehensive tests covering transport retries, cooldown behavior, and transient error handling.
Closes: #5829
- Introduce `IsTerminalAuthError` and `NewTerminalAuthError` to identify permanent upstream authentication failures.
- Return terminal auth errors from candidate selection and scheduling when all available credentials fail with unauthorized errors.
- Support `BuildErrorResponseBodyWithError` to format terminal upstream auth errors as non-retryable `upstream_authentication_required` responses.
- Propagate terminal error classifications and the `retryable` field across HTTP and WebSocket response handlers.
Closes: #5645
- Attach candidate upstream errors as causes to scheduler availability and cooldown errors.
- Introduce `errorWithCause` wrapper to extract and display upstream error summaries.
- Enrich auth selection error messages with upstream details and preserve model cooldown errors.
- Forward `Retry-After` response headers for model cooldown errors in Claude Code handler.
Closes: #5365
- Add request-scoped error rule extraction from auth metadata or runtime provider config (including OpenAI compatibility fallback)
- Match rules by HTTP/status-code plus error body substring or regex patterns
- Support `stop`, `stop-and-cooldown`, `continue`, `continue-and-cooldown` actions with normalized validation
- Apply matched actions to execution results via request-scoped vs force-cooldown error codes and stop/continue flow control
- Introduce request-stop error wrappers/helpers for matching and unwrapping scoped stop state
Closes: #5006
- Treat request-invalid/invalid-parameter 401 faults as request-scoped so auth/model cooldown is skipped.
- Export request-scoped/connection-lifecycle error codes and add helpers to explicitly create or mark request-scoped `Error`s.
- Improve request-fault detection by checking the raw message body when `Error.Code` formatting hides JSON payloads.
Closes: #4976
- Added a dedicated `connection_lifecycle` error code and lifecycle detection for context cancellation, EOF variants, and websocket close conditions.
- Introduced shared gating (`shouldSkipCredentialCooldown`) so transport/session lifecycle failures do not mark auth/model as unavailable or set retry cooldown.
- Kept request-scoped/invalid failures as high-priority and preserved status-bearing HTTP errors behavior so auth cooldown still applies when appropriate.
Closes: #4819#4787
- Enhanced response handling to support `response.incomplete` events across translator components and executors.
- Refactored `resultErrorFromError` to centralize error conversion and consolidate repeated logic for constructing custom errors.
- Updated handling of `max_output_tokens` and similar terminal reasons in OpenAI and Gemini translator workflows.
- Introduced `IsRequestScoped` and `IsRequestScopedError` to differentiate between request-scoped and non-request-scoped errors.
- Added comprehensive test cases for incomplete responses, terminal failures, and error propagation in both streaming and non-streaming conditions.
Closes: #3055
