Gemma 4 <unused24> Token Bug: What to Do
A practical guide to diagnosing and mitigating abnormal repeated token output such as <unused24> in Gemma 4 local inference.
April 6, 20261 min read
Gemma 4
Debugging
Tokens
llama.cpp
Some users report Gemma 4 responses degrading into repeated control-like tokens such as <unused24>.
This is usually an integration/runtime pathology, not a normal inference pattern.
Typical Triggers
- unstable runtime/model pairing
- aggressive generation settings
- edge-case template or tokenizer handling
Fast Mitigation Steps
- Reduce temperature and simplify generation settings.
- Retest with a known stable prompt format.
- Confirm runtime version against known issue threads.
- Test a different model file variant/quantization.
- Upgrade/downgrade runtime based on issue status.
Prevention Practices
- keep a known-good baseline config
- avoid changing multiple variables at once
- validate after each runtime update
Final Takeaway
When token repetition artifacts appear, treat it as a stack compatibility incident and isolate variables quickly.
Structured troubleshooting resolves these faster than prompt tinkering.