Ollama gemma4 repetition loop during constrained JSON generation

What this error means

Word repetition loop fills num_predict budget, JSON unterminated — repeat_penalty has no effect is a Ollama failure pattern reported for developers trying to fix ollama gemma4 repetition loop when generating structured json with format parameter. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.

Why this happens

Ollama issue #15502: gemma4:31b enters word-repetition loops during constrained JSON generation with free-text string fields. repeat_penalty parameter has no effect at any value (1.0, 1.15, 1.5). Bug rate 60-100% across 39 trials. Three conditions required: gemma4 dense model, format= with JSON schema, free-text string fields. Category mapped to Ollama per approved list.

Common causes

• Ollama issue #15502: gemma4:31b enters word-repetition loops during constrained JSON generation with free-text string fields. repeat_penalty parameter has no effect at any value (1.0, 1.15, 1.5). Bug rate 60-100% across 39 trials. Three conditions required: gemma4 dense model, format= with JSON schema, free-text string fields. Category mapped to Ollama per approved list.

Quick fixes

1. Confirm the exact error signature matches Word repetition loop fills num_predict budget, JSON unterminated — repeat_penalty has no effect.
2. Check the Ollama account, local tool state, and provider configuration involved in the failing workflow.
3. Compare the failing environment with a known working setup, then change one configuration value at a time.

Platform/tool-specific checks

• Verify the command, editor, extension, or API client that produced the error.
• Compare local settings with CI, deployment, or editor-level settings when the error appears in only one environment.
• Avoid deleting credentials, local model data, or project settings until the failing scope is clear.

Step-by-step troubleshooting

1. Capture the exact error message and the command, editor action, or request that triggered it.
2. Check whether the failure is account/auth, quota/rate, model/provider, local runtime, or deployment configuration.
3. Review the source evidence below and compare it with your environment.
4. Apply one change at a time and rerun the smallest failing action.
5. Keep the working fix documented for the team or deployment environment.

How to prevent it

• Keep provider/tool configuration documented.
• Record non-secret diagnostics such as tool version, provider name, model name, and command path.
• Add a lightweight check before CI or production workflows depend on the tool.

Sources checked

• https://github.com/ollama/ollama/issues/15502

Evidence note: Ollama issue #15502: gemma4:31b enters word-repetition loops during constrained JSON generation with free-text string fields. repeat_penalty parameter has no effect at any value (1.0, 1.15, 1.5). Bug rate 60-100% across 39 trials. Three conditions required: gemma4 dense model, format= with JSON schema, free-text string fields. Category mapped to Ollama per approved list.

Related errors

• Ollama

FAQ

What should I check first?

Start with the exact Word repetition loop fills num_predict budget, JSON unterminated — repeat_penalty has no effect text and the smallest action that reproduces it.

Can I ignore this error?

No. Treat it as a failed Ollama workflow until the root cause is understood.

Is this guaranteed to have one fix?

No. The imported evidence supports the troubleshooting path above, but tool behavior can vary by account, plan, version, provider, and local configuration.

How do I know the fix worked?

Rerun the same command, editor action, or request. The fix is working when that action completes without Word repetition loop fills num_predict budget, JSON unterminated — repeat_penalty has no effect.