About GPT 5.5 Pro
GPT 5.5 Pro is OpenAI's premium-tier reasoning model, the most capable variant of the 5.5 family. Targets the hardest professional workflows — multi-step reasoning, complex coding, deep research, and agentic tasks where accuracy is worth a premium over throughput.
Note: Prompts exceeding 272K input tokens incur 2x input and 1.5x output pricing for the full session.
| Metric | Value |
|---|---|
| Context Length | 1,050,000 tokens |
| Max Output Tokens | 128,000 tokens |
| Multilingual | Yes |
Ready to build with GPT 5.5 Pro?
Try GPT 5.5 Pro in the Workbench to prompt it, compare outputs, and iterate on prompts without writing any code. When you're ready to ship, call the same model from our API and build your own apps on top of it.
curl -sSf -X POST https://hub.oxen.ai/api/ai/chat/completions \
-H "Content-Type: application/json" \
-H "Authorization: Bearer $OXEN_API_KEY" \
-d '{
"model": "gpt-5-5-pro-2026-04-23",
"messages": [
{
"role": "user",
"content": "Try sending a message."
}
]
}'API endpoint
See the API reference for request and response formats.
POST
https://hub.oxen.ai/api/ai/chat/completions