> ## Documentation Index
> Fetch the complete documentation index at: https://docs.crazyrouter.com/llms.txt
> Use this file to discover all available pages before exploring further.

# GPT-5 Thinking Mode

> Production-revalidated GPT-5.4 reasoning via the Responses API

> Дата обновления: 2026-06-06

# GPT-5 Thinking Mode

This page only documents GPT reasoning behavior that was revalidated against Crazyrouter production on `2026-03-22`.

The current primary example uses:

* `gpt-5.5`
* `POST /v1/responses`

<Note>
  Claude does not currently support `POST /v1/responses`. If you are integrating Claude, use `POST /v1/messages` or `POST /v1/chat/completions` instead of the request shape on this page.
</Note>

```
POST /v1/responses
```

***

## Basic usage

<CodeGroup>
  ```bash cURL theme={null}
  curl https://api.crazyrouter.com/v1/responses \
    -H "Content-Type: application/json" \
    -H "Authorization: Bearer YOUR_API_KEY" \
    -d '{
      "model": "gpt-5.5",
      "input": "Which is larger, 9.11 or 9.9? Explain briefly.",
      "reasoning": {
        "effort": "high",
        "summary": "detailed"
      }
    }'
  ```

  ```python Python theme={null}
  from openai import OpenAI

  client = OpenAI(
      api_key="YOUR_API_KEY",
      base_url="https://api.crazyrouter.com/v1"
  )

  response = client.responses.create(
      model="gpt-5.5",
      input="Which is larger, 9.11 or 9.9? Explain briefly.",
      reasoning={
          "effort": "high",
          "summary": "detailed"
      }
  )

  print(response.output_text)
  ```

  ```javascript Node.js theme={null}
  import OpenAI from "openai";

  const client = new OpenAI({
    apiKey: "YOUR_API_KEY",
    baseURL: "https://api.crazyrouter.com/v1",
  });

  const response = await client.responses.create({
    model: "gpt-5.5",
    input: "Which is larger, 9.11 or 9.9? Explain briefly.",
    reasoning: {
      effort: "high",
      summary: "detailed",
    },
  });

  console.log(response.output_text);
  ```
</CodeGroup>

***

## Verified response shape

Verified `output.type` values:

```json theme={null}
["reasoning", "message"]
```

Typical `reasoning` item shape:

```json theme={null}
{
  "id": "rs_xxx",
  "type": "reasoning",
  "encrypted_content": "...",
  "summary": [
    {
      "type": "summary_text",
      "text": "..."
    }
  ]
}
```

The final answer is returned through the `message` item:

```json theme={null}
{
  "type": "message",
  "content": [
    {
      "type": "output_text",
      "text": "..."
    }
  ]
}
```

***

## `reasoning` parameter

| Field     | Type   | Description                                                              |
| --------- | ------ | ------------------------------------------------------------------------ |
| `effort`  | string | Reasoning intensity. Verified values include `low`, `medium`, and `high` |
| `summary` | string | Summary granularity. `concise` and `detailed` were revalidated           |

### Practical rule

* If you only want stronger reasoning, send `effort`
* If you need an inspectable reasoning summary, send both `effort` and `summary`

In the current recheck:

* with only `effort`, the `reasoning` item existed but `summary` could be an empty array
* with `summary: "detailed"`, `summary_text` was returned reliably

***

## Extract the thinking summary

```python Python theme={null}
response = client.responses.create(
    model="gpt-5.5",
    input="Design a high-concurrency message queue architecture.",
    reasoning={
        "effort": "high",
        "summary": "detailed"
    }
)

for item in response.output:
    if item.type == "reasoning":
        for part in item.summary:
            if part.type == "summary_text":
                print("Thinking summary:", part.text)
    elif item.type == "message":
        for content in item.content:
            if content.type == "output_text":
                print("Final answer:", content.text)
```

***

## Streaming thinking

The following Responses SSE event names were revalidated in production:

* `response.reasoning_summary_part.added`
* `response.reasoning_summary_text.delta`
* `response.reasoning_summary_text.done`
* `response.output_text.delta`
* `response.output_text.done`
* `response.completed`

Example:

```python Python theme={null}
stream = client.responses.create(
    model="gpt-5.5",
    input="Explain briefly why 9.9 is larger than 9.11.",
    reasoning={
        "effort": "high",
        "summary": "detailed"
    },
    stream=True
)

for event in stream:
    if event.type == "response.reasoning_summary_text.delta":
        print(f"[Thinking summary] {event.delta}", end="")
    elif event.type == "response.output_text.delta":
        print(event.delta, end="")
```

***

## Current recommendation

* If you need a visible reasoning field, prefer `gpt-5.5` with the Responses API
* Do not treat `gpt-5.5` Chat Completions `reasoning_content` as the current primary contract
* If you only care about the final answer, Chat Completions with `reasoning_effort` is still fine

<Warning>
  Reasoning mode increases both latency and token usage. Higher `effort` generally costs more.
</Warning>