[Bug] Custom OpenAI-compatible provider errors with "Unknown parameter: 'reasoningSummary'" for GPT-5 series models

[Yang-Kevin-DH]

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

[github-actions]

This issue might be related to existing issues about custom providers receiving unsupported parameters. Please check:

• @ai-sdk/openai-compatible max_tokens error for GPT 5.x #5421: @ai-sdk/openai-compatible max_tokens error for GPT 5.x (similar parameter compatibility issue with custom providers)
• Azure models fail due to reasoning_effort being sent even with --variant none #12113: Azure models fail due to reasoning_effort being sent even with --variant none (same pattern of reasoning parameters being sent to backends that don't support them)

These issues may help understand the broader parameter-handling pattern and could be relevant to the solution.

[Yang-Kevin-DH]

Could help to fix as of add a parameter to trun off/on the 'reasoningSummary'?

[acanova]

Having the same problem recently, using LiteLLM base URL with GPT-5.2...

Some logs:
litellm.BadRequestError: OpenAIException - Error code: 400 - {'path': '/ai-orchestration-api/v1/openai/chat/completions',
'history': [{'response': {'response': '{\n "error": {\n "message": "Unknown parameter: 'reasoning_summary'.",\n "type": "invalid_request_error",\n "param": "reasoning_summary",\n "code": "unknown_parameter"\n }\n}

Found this, maybe useful for a fix?
code-yeongyu/oh-my-openagent#1788
code-yeongyu/oh-my-openagent#1794

[zsaylor]

Same here, same logs (on Mac though):
litellm.BadRequestError: OpenAIException - Unknown parameter: 'reasoningSummary'.. Received Model Group=openai/gpt-5.2
Available Model Group Fallbacks=None

[X4ndras]

Had a similar issue with Claude:

litellm.BadRequestError: Vertex_aiException BadRequestError - b'{"type":"error","error":{"type":"invalid_request_error","message":"invalid beta flag"},"request_id":"..."}'. Received Model Group=claude-sonnet-4.5
Available Model Group Fallbacks=None

and now I have the same issue with GPT models

litellm.BadRequestError: litellm.ContentPolicyViolationError: litellm.ContentPolicyViolationError: AzureException - Unknown parameter: 'reasoningSummary'.
model=gpt-5.1. content_policy_fallback=None. fallbacks=None.
Set 'content_policy_fallback' - https://docs.litellm.ai/docs/routing#fallbacks. Received Model Group=gpt-5.1
Available Model Group Fallbacks=None

[ggbetz]

This worked for me (config in opencode.json) with v1.20.10:

"provider": {
    "my-litellm-provider": {
    "npm": "@ai-sdk/openai-compatible",
      "options": {
        "baseURL": "https://my-provider.url/api/v1"
      },
      "models": {
        "azure.gpt-5.1": {
          "name": "my-gpt-5.1",
          "options": {
            "reasoningSummary": null,
          }
        },
      }

[shahrin014]

      "models": {
        "azure.gpt-5.1": {
          "name": "my-gpt-5.1",
          "options": {
            "reasoningSummary": null,
          }
        },
      }

This does not work for me ~ on
opencode version 1.2.10
oh-my-opencode version 3.8.5