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Gemini OpenAI-Compatible Format

You can call Gemini through the OpenAI Chat Completions compatible route. 
POST /v1/chat/completions
This page only documents compatibility-layer behavior that was revalidated against Crazyrouter production on 2026-03-22. Current primary example model:
  • gemini-3-pro-preview

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Current conclusion

This production recheck confirmed that:
  • gemini-3-pro-preview works through /v1/chat/completions for normal text chat
  • streaming returns standard chat.completion.chunk SSE objects
  • for Gemini-specific capabilities such as structured outputs, Google Search, and thinking, you should still prefer Gemini Native Format

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Basic conversation

cURL
curl https://crazyrouter.com/v1/chat/completions \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -d '{
    "model": "gemini-3-pro-preview",
    "messages": [
      {
        "role": "system",
        "content": "You are a concise assistant."
      },
      {
        "role": "user",
        "content": "Explain quantum entanglement in one sentence."
      }
    ],
    "max_tokens": 128
  }'
Verified response shape: 
{
  "object": "chat.completion",
  "model": "gemini-3-pro-preview",
  "choices": [
    {
      "message": {
        "role": "assistant",
        "content": "..."
      }
    }
  ]
}

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Python example

Python
from openai import OpenAI

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

response = client.chat.completions.create(
    model="gemini-3-pro-preview",
    messages=[
        {"role": "system", "content": "You are a concise assistant."},
        {"role": "user", "content": "Explain quantum entanglement in one sentence."}
    ],
    max_tokens=128
)

print(response.choices[0].message.content)

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Streaming output

This production recheck also confirmed streaming compatibility:
Python
stream = client.chat.completions.create(
    model="gemini-3-pro-preview",
    messages=[
        {"role": "user", "content": "Write one short sentence about AI."}
    ],
    max_tokens=64,
    stream=True
)

for chunk in stream:
    delta = chunk.choices[0].delta
    if delta.content is not None:
        print(delta.content, end="")
Observed SSE shape: 
data: {"object":"chat.completion.chunk","model":"gemini-3-pro-preview",...}
data: {"choices":[{"delta":{"content":"..."}}],...}
data: [DONE]

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When to use compatible vs native

  • If you already have OpenAI SDK code and only need standard chat, use the compatible route
  • If you need Gemini-native structured outputs, Google Search, thinking, or native metadata, use Gemini Native Format
This page still only covers the /v1/chat/completions compatibility layer and does not fold Gemini-backed image behavior into it. If you need Crazyrouter’s current public image contract, use the Nano Banana family pages for POST /v1/images/generations: Nano Banana, Nano Banana Pro, and Nano Banana 2.