# Google's OpenAI-compat shim has no reasoning channel; thought text leaks into content

high · inference · probed live 2026-07-26 · affects Google (OpenAI-compat) ·
HTML version: [https://inferencecanary.com/google-openai-no-reasoning-channel](https://inferencecanary.com/google-openai-no-reasoning-channel)

Reasoning-capable serving separates the model's thinking from its answer: thought text arrives
in a dedicated field (`reasoning_content` on OpenAI-dialect providers; a `"thought": true`
part on Google's native API), and `content` holds only what the application should show.
Google's OpenAI-compat shim has no such field — and it isn't for lack of asking: the request
below sends `reasoning_effort: "high"`, the shim accepts it (200), and still returns zero
reasoning. The thought text lands inside literal `<thought>` tags in the answer field.

## What was sent

([https://inferencecanary.com/assets/repro/reasoning-leak.google-openai.json](https://inferencecanary.com/assets/repro/reasoning-leak.google-openai.json))

```json
{
  "model": "gemma-4-31b-it",
  "messages": [
    {
      "role": "user",
      "content": "Think of a number between 1 and 100. Don't say it out loud — keep it in your thoughts and reply with just 'ok'."
    }
  ],
  "reasoning_effort": "high",
  "temperature": 0,
  "max_tokens": 600,
  "stream": true,
  "stream_options": {
    "include_usage": true
  }
}
```

## What came back

HTTP 200. The message object carries only `role` and `content` — no `reasoning` or
`reasoning_content` key exists:

```json
{
  "role": "assistant",
  "content": "<thought>*   Task: Think of a number between 1 and 100.\n    *   Constraint 1: Don't say it out loud (don't reveal it).\n    *   Constraint 2: Reply with just 'ok'.\n\n    *   I need to pick a number. Let's pick 42.\n    *   I must not mention 42.\n    *   I must reply with exactly 'ok'.</thought>ok"
}
```

The number the prompt asked the model to withhold — 42 — is verbatim in the user-facing answer
field. Reproduced byte-identically across 4 runs.

## The same model, same host, native protocol

The identical prompt to `…/models/gemma-4-31b-it:generateContent` with thinking on returns the
thought in a separate, marked part:

```json
{
  "parts": [
    {
      "text": "*   Task: Think of a number between 1 and 100.\n    *   Constraint 1: Don't say it out loud (don't reveal it).\n    *   Constraint 2: Reply with just 'ok'.\n\n    *   I need to pick a number. Let's pick 42.\n    *   I must not mention 42.\n    *   I must reply with exactly 'ok'.",
      "thought": true
    },
    { "text": "ok" }
  ],
  "role": "model"
}
```

The thought text is identical between the two lanes; only the framing differs. Native marks it
`"thought": true` in a separate part; the shim concatenates it into `content`. Same vendor,
same host, same model — a shim translation defect, not model behavior.

## Why it matters

Every consumer that treats `content` as the answer displays or logs the model's private
reasoning — including things the prompt explicitly asked the model to keep to itself.
Stripping `<thought>` tags client-side means relying on an undocumented in-band sentinel
Google never promised and can change without notice.

## Run it yourself

```
curl "https://generativelanguage.googleapis.com/v1beta/openai/chat/completions" \
  -H "Authorization: Bearer $GEMINI_API_KEY" -H "Content-Type: application/json" \
  -d @reasoning-leak.google-openai.json
```

Expected: `content: "ok"` with reasoning in a dedicated field. Received: the
`<thought>…</thought>ok` string shown.