LiteLLM / LiteLLM
LiteLLM OCI GPT-5 max_completion_tokens Parameter Mapping Error
Fix LiteLLM OCI adapter incorrectly mapping max_completion_tokens to maxTokens for GPT-5 models Includes evidence for LiteLLM troubleshooting demand.
- Category
- LiteLLM
- Error signature
Unsupported parameter: 'max_tokens' is not supported- Quick fix
- Compare the failing environment with a known working setup, then change one configuration value at a time.
- Updated
What this error means
Unsupported parameter: 'max_tokens' is not supported is a LiteLLM failure pattern reported for developers trying to fix litellm oci adapter incorrectly mapping max_completion_tokens to maxtokens for gpt-5 models. Based on the imported evidence, treat this as a tool-specific troubleshooting page rather than a generic API error.
Why this happens
Bug report (2026-05-07) shows LiteLLM OCI adapter translates max_completion_tokens=100 into legacy camelCase maxTokens, which OCI GPT-5 models reject with ‘Unsupported parameter: max_tokens is not supported’.
Common causes
- When calling OCI OpenAI GPT-5 models through LiteLLM, requests fail because LiteLLM maps the standard max_completion_tokens to OCI’s unsupported maxTokens field. This breaks production LLM integrations using OCI GPT-5.
- Bug report (2026-05-07) shows LiteLLM OCI adapter translates max_completion_tokens=100 into legacy camelCase maxTokens, which OCI GPT-5 models reject with ‘Unsupported parameter: max_tokens is not supported’.
Quick fixes
- Confirm the exact error signature matches
Unsupported parameter: 'max_tokens' is not supported. - Check the LiteLLM account, local tool state, and provider configuration involved in the failing workflow.
- 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
- Capture the exact error message and the command, editor action, or request that triggered it.
- Check whether the failure is account/auth, quota/rate, model/provider, local runtime, or deployment configuration.
- Review the source evidence below and compare it with your environment.
- Apply one change at a time and rerun the smallest failing action.
- 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
Evidence note: Bug report (2026-05-07) shows LiteLLM OCI adapter translates max_completion_tokens=100 into legacy camelCase maxTokens, which OCI GPT-5 models reject with ‘Unsupported parameter: max_tokens is not supported’.
Related errors
- OCI OpenAI API parameter compatibility errors
- LiteLLM adapter parameter mapping issues
FAQ
What should I check first?
Start with the exact Unsupported parameter: 'max_tokens' is not supported text and the smallest action that reproduces it.
Can I ignore this error?
No. Treat it as a failed LiteLLM 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 Unsupported parameter: 'max_tokens' is not supported.