# rpc error: code = Unknown desc = unknown field in response: "extra_data"

- **ID:** `go/grpc-unknown-field`
- **Domain:** go
- **Category:** data_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

Client's proto definition is outdated and doesn't include a field that the server sends.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 1.8 | active | — | — |

## Workarounds

1. **** (100% success)
   ```
   Run protoc with the latest .proto file to update the generated Go code.
   ```
2. **** (60% success)
   ```
   decoder := protojson.UnmarshalOptions{DiscardUnknown: true}; err := decoder.Unmarshal(data, msg)
   ```

## Dead Ends

- **** — gRPC by default ignores unknown fields, but this error suggests strict parsing is enabled. (80% fail)
- **** — Incorrect field number can cause data corruption. (90% fail)