Description

Summary

OpenCode automatically injects the reasoningSummary parameter (likely defaulting to "auto" or similar) when calling GPT-5 series models (e.g., gpt-5, gpt-5-codex). This works for official OpenAI endpoints but breaks with custom OpenAI-compatible providers routed through LiteLLM (or Azure), where the backend models do not support this parameter.

This is a compatibility issue for users routing GPT-5-named models to third-party backends (e.g., DeepSeek, Gemini, or Azure deployments) via LiteLLM proxy.

Steps to Reproduce

1. Configure a custom OpenAI-compatible provider in opencode.jsonc:

   "provider": {
     "compatible": {
       "npm": "@ai-sdk/openai-compatible",
       "options": {
         "baseURL": "https://your-litellm-proxy/v1",
         "apiKey": "{env:YOUR_KEY}"
       },
       "models": {
         "gpt-5-codex": { "name": "GPT-5 Codex" },
         // other GPT-5 series models
       }
     }
   },
   "model": "compatible/gpt-5-codex"
   

Plugins

None

OpenCode version

V1.1.65

Steps to reproduce

litellm.BadRequestError: litellm.ContentPolicyViolationError: litellm.ContentPolicyViolationError: AzureException - Unknown parameter: 'reasoningSummary'.
model=gpt-5. content_policy_fallback=None. fallbacks=None.

Screenshot and/or share link

No response

Operating System

Windows11

Terminal

Powershell