- Add reject flags and reason fields to `SchedulerPickResponse` with snake_case JSON unmarshaling support
- Terminate candidate selection with an auth error when scheduler rejection is flagged
- Normalize rejection response with default error code and reason in the plugin host
Closes: #6130
- Introduce `modelExecutionStatusError` to retain explicit HTTP status codes on model execution errors
- Propagate HTTP status codes from callback errors across Unix and Windows host callback dispatchers
- Update `marshalRPCError` to encode HTTP status codes into error envelopes using `pluginabi.NewErrorEnvelope`
Closes: #5970
- Add `Error.Error`, `Error.StatusCode`, `NewError`, and `NewErrorEnvelope` helpers in `sdk/pluginabi`.
- Support extracting and forwarding HTTP status codes in Go plugin executor examples and generator script.
- Document plugin executor error handling and client HTTP status mapping conventions.
Closes: #5809
- Added `rpcPluginError` to encapsulate plugin errors with HTTP status codes.
- Enhanced `decodeEnvelopeResult` to preserve and return detailed plugin errors with status codes.
- Introduced `isPluginErrorEnvelope` to identify plugin error envelopes.
- Updated plugin call logic in Unix and Windows loaders to differentiate plugin errors from system errors.
- Added unit tests to verify error handling and status code preservation.
