fix(openai): bridge gpt-5.6+ tools to /v1/responses without reasoning…

[lkapadiya-DO]

…_effort

Implement BerriAI#34043 on the 1.94.0 DO release line so gpt-5.6 family tool calls on chat/completions auto-route to Responses even when reasoning_effort is unset. Keep gpt-5.4/5.5 tools-only on chat completions.

OpenAI rejects gpt-5.6 family tool calls on chat/completions when a default reasoning_effort is applied server-side. Port BerriAI#34043 onto the DO release bridge so tools-only requests auto-route to Responses.

JIRA: https://do-internal.atlassian.net/browse/INF-991

Relevant issues

BerriAI#33221

Test

Case 1: 5.6 + tools, no reasoning_effort
Request:

curl -sS -X POST "$BASE_URL/v1/chat/completions" \
  -H "Authorization: Bearer $MODEL_ACCESS_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "openai-gpt-5.6-sol",
    "messages": [
      {
        "role": "user",
        "content": "What'\''s the weather like in Boston today? in celsius"
      }
    ],
    "tools": [
      {
        "type": "function",
        "function": {
          "name": "get_current_weather",
          "description": "Get the current weather in a given location",
          "parameters": {
            "type": "object",
            "properties": {
              "location": {
                "type": "string",
                "description": "The city and state, e.g. San Francisco, CA"
              },
              "unit": {
                "type": "string",
                "enum": ["celsius", "fahrenheit"]
              }
            },
            "required": ["location"]
          }
        }
      }
    ]
  }' | jq .

Response(Before this change):

{
  "error": {
    "message": "Function tools with reasoning_effort are not supported for gpt-5.6-sol in /v1/chat/completions. To use function tools, use /v1/responses or set reasoning_effort to 'none'.",
    "type": "invalid_request_error"
  },
  "message": "Function tools with reasoning_effort are not supported for gpt-5.6-sol in /v1/chat/completions. To use function tools, use /v1/responses or set reasoning_effort to 'none'.",
  "status_code": 400
}

Response(After this change):

{
  "choices": [
    {
      "finish_reason": "tool_calls",
      "index": 0,
      "logprobs": null,
      "message": {
        "content": null,
        "reasoning_content": null,
        "refusal": null,
        "role": "assistant",
        "tool_calls": [
          {
            "function": {
              "arguments": "{\"location\":\"Boston, MA\",\"unit\":\"celsius\"}",
              "name": "get_current_weather"
            },
            "id": "call_sVZWp6N06UeVte1rBQ4gHmvm",
            "type": "function"
          }
        ]
      }
    }
  ],
  "created": 1785253709,
  "id": "chatcmpl-1820079d-330f-46a0-8a86-58f1ee1f28b6",
  "model": "openai-gpt-5.6-sol",
  "object": "chat.completion",
  "usage": {
    "cache_created_input_tokens": 0,
    "cache_creation": {
      "ephemeral_1h_input_tokens": 0,
      "ephemeral_5m_input_tokens": 0
    },
    "cache_read_input_tokens": 0,
    "completion_tokens": 26,
    "completion_tokens_details": {
      "reasoning_tokens": 0
    },
    "prompt_tokens": 82,
    "prompt_tokens_details": {
      "cached_tokens": 0
    },
    "speed": null,
    "total_tokens": 108
  }
}

Case 2: Streaming + tools, no reasoning_effort

Request:

curl -sS -N -X POST "$BASE_URL/v1/chat/completions" \
  -H "Authorization: Bearer $MODEL_ACCESS_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "openai-gpt-5.6-sol",
    "stream": true,
    "messages": [{"role": "user", "content": "Weather in Boston. Use the tool."}],
    "tools": [{
      "type": "function",
      "function": {
        "name": "get_current_weather",
        "description": "Get weather",
        "parameters": {
          "type": "object",
          "properties": {"location": {"type": "string"}},
          "required": ["location"]
        }
      }
    }]
  }'

Response(Before this change):

{"error":{"message":"Function tools with reasoning_effort are not supported for gpt-5.6-sol in /v1/chat/completions. To use function tools, use /v1/responses or set reasoning_effort to 'none'.","type":"invalid_request_error"},"message":"Function tools with reasoning_effort are not supported for gpt-5.6-sol in /v1/chat/completions. To use function tools, use /v1/responses or set reasoning_effort to 'none'.","status_code":400}

Response(After this change):

data: {"choices":[{"delta":{"content":"","role":"assistant"},"finish_reason":null,"index":0,"logprobs":null}],"created":1785256488,"id":"chatcmpl-d5bc9dd0-decf-4339-bc69-fdd043c3a97e","model":"openai-gpt-5.6-sol","object":"chat.completion.chunk"}

data: {"choices":[{"delta":{"tool_calls":[{"function":{"arguments":"","name":"get_current_weather"},"id":"call_Ek9RoMV8xcH9STAV4YYU58X3","index":0,"type":"function"}]},"finish_reason":null,"index":0,"logprobs":null}],"created":1785256488,"id":"chatcmpl-d5bc9dd0-decf-4339-bc69-fdd043c3a97e","model":"openai-gpt-5.6-sol","object":"chat.completion.chunk"}

data: {"choices":[{"delta":{"tool_calls":[{"function":{"arguments":"{\""},"index":0,"type":"function"}]},"finish_reason":null,"index":0,"logprobs":null}],"created":1785256488,"id":"chatcmpl-64f417da-6343-4b46-88cd-fd08d5dc0c97","model":"openai-gpt-5.6-sol","object":"chat.completion.chunk"}

data: {"choices":[{"delta":{"tool_calls":[{"function":{"arguments":"location"},"index":0,"type":"function"}]},"finish_reason":null,"index":0,"logprobs":null}],"created":1785256488,"id":"chatcmpl-f7f1f16c-2394-4599-899b-340e5a8b50a4","model":"openai-gpt-5.6-sol","object":"chat.completion.chunk"}

data: {"choices":[{"delta":{"tool_calls":[{"function":{"arguments":"\":\""},"index":0,"type":"function"}]},"finish_reason":null,"index":0,"logprobs":null}],"created":1785256488,"id":"chatcmpl-b9b48f4a-ec3e-407c-8a2c-5804e5be06db","model":"openai-gpt-5.6-sol","object":"chat.completion.chunk"}

data: {"choices":[{"delta":{"tool_calls":[{"function":{"arguments":"Boston"},"index":0,"type":"function"}]},"finish_reason":null,"index":0,"logprobs":null}],"created":1785256488,"id":"chatcmpl-fe730778-bc4f-4f5b-89af-90caff9d4e65","model":"openai-gpt-5.6-sol","object":"chat.completion.chunk"}

data: {"choices":[{"delta":{"tool_calls":[{"function":{"arguments":","},"index":0,"type":"function"}]},"finish_reason":null,"index":0,"logprobs":null}],"created":1785256488,"id":"chatcmpl-4e05f9da-ffc3-4a21-92a3-594490d675eb","model":"openai-gpt-5.6-sol","object":"chat.completion.chunk"}

data: {"choices":[{"delta":{"tool_calls":[{"function":{"arguments":" MA"},"index":0,"type":"function"}]},"finish_reason":null,"index":0,"logprobs":null}],"created":1785256488,"id":"chatcmpl-7f319d6a-53c1-48d0-873e-b6b02ffdeafd","model":"openai-gpt-5.6-sol","object":"chat.completion.chunk"}

data: {"choices":[{"delta":{"tool_calls":[{"function":{"arguments":"\"}"},"index":0,"type":"function"}]},"finish_reason":null,"index":0,"logprobs":null}],"created":1785256488,"id":"chatcmpl-5a95f24e-82b9-4f62-a911-20d22b07180f","model":"openai-gpt-5.6-sol","object":"chat.completion.chunk"}

data: {"choices":[{"delta":{},"finish_reason":"tool_calls","index":0,"logprobs":null}],"created":1785256488,"id":"chatcmpl-79e8ca2a-b0b1-475d-bfdb-f927bc22088d","model":"openai-gpt-5.6-sol","object":"chat.completion.chunk"}

data: {"choices":[],"created":1785256488,"id":"chatcmpl-79e8ca2a-b0b1-475d-bfdb-f927bc22088d","model":"openai-gpt-5.6-sol","object":"chat.completion.chunk","usage":{"cache_created_input_tokens":0,"cache_creation":{"ephemeral_1h_input_tokens":0,"ephemeral_5m_input_tokens":0},"cache_read_input_tokens":0,"completion_tokens":21,"completion_tokens_details":{"reasoning_tokens":0},"prompt_tokens":48,"prompt_tokens_details":{"cached_tokens":0},"speed":null,"total_tokens":69}}

data: [DONE]

Case 3: Multi-tool call

Request:

curl -sS -X POST "$BASE_URL/v1/chat/completions" \
  -H "Authorization: Bearer $MODEL_ACCESS_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "openai-gpt-5.6-sol",
    "messages": [{"role": "user", "content": "What is the weather in Boston and the time in UTC? Use tools."}],
    "tools": [
      {
        "type": "function",
        "function": {
          "name": "get_current_weather",
          "description": "Get weather",
          "parameters": {
            "type": "object",
            "properties": {"location": {"type": "string"}},
            "required": ["location"]
          }
        }
      },
      {
        "type": "function",
        "function": {
          "name": "get_time",
          "description": "Get current time for a timezone",
          "parameters": {
            "type": "object",
            "properties": {"timezone": {"type": "string"}},
            "required": ["timezone"]
          }
        }
      }
    ]
  }' | jq '{finish: .choices[0].finish_reason, tools: [.choices[0].message.tool_calls[]?.function.name], error}'

Response(Before this change):

{
  "finish": null,
  "tools": [],
  "error": {
    "message": "Function tools with reasoning_effort are not supported for gpt-5.6-sol in /v1/chat/completions. To use function tools, use /v1/responses or set reasoning_effort to 'none'.",
    "type": "invalid_request_error"
  }
}

Response(After this change):

{
  "finish": "tool_calls",
  "tools": [
    "get_current_weather",
    "get_time"
  ],
  "error": null
}

Test plan
[x] Unit: responses_api_bridge + is_model_gpt_5_6_plus tests
[x] Preview via inference-proxy