What this model error usually means
OpenAI: gpt-oss-20b (free) returning 403 / model permission denied means you should first confirm whether model ID openai/gpt-oss-20b:free is visible for this OpenAI key, then separate permission, context, capability, rate limit, or route issues.
- Model: openai/gpt-oss-20b:free
- Provider: OpenAI
- Status code: 403