# org.apache.kafka.common.errors.UnsupportedVersionException: The broker does not support the group protocol version required by the consumer

- **ID:** `kafka/unsupported-version-join-group`
- **Domain:** kafka
- **Category:** protocol_error
- **Verification:** ai_generated
- **Fix Rate:** 88%

## Root Cause

Consumer requests a group protocol version (e.g., 2) that broker does not support due to version mismatch between consumer and broker.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 3.0.0 | active | — | — |
| 3.3.0 | active | — | — |
| 3.6.0 | active | — | — |

## Workarounds

1. **Set consumer's 'group.protocol' to 'classic' and ensure broker supports classic protocol (Kafka 3.0+).** (85% success)
   ```
   Set consumer's 'group.protocol' to 'classic' and ensure broker supports classic protocol (Kafka 3.0+).
   ```
2. **Upgrade broker to version that supports the consumer's group protocol (e.g., upgrade to 3.6 for consumer protocol v2).** (95% success)
   ```
   Upgrade broker to version that supports the consumer's group protocol (e.g., upgrade to 3.6 for consumer protocol v2).
   ```
3. **Downgrade consumer client library to match broker version (e.g., use kafka-clients 3.3.0 with broker 3.3.0).** (90% success)
   ```
   Downgrade consumer client library to match broker version (e.g., use kafka-clients 3.3.0 with broker 3.3.0).
   ```

## Dead Ends

- **** — Classic protocol may not be supported by older brokers; error persists if broker version is too low. (75% fail)
- **** — Consumer version mismatch with broker causes unsupported version errors; both must be compatible. (90% fail)
- **** — Inter-broker protocol version affects broker communication, not consumer group protocol; does not fix consumer-side error. (80% fail)