GPT-5.5 (Reasoning)
by OpenAI
GPT-5.5 (Reasoning) is a reasoning model from OpenAI, released on April 23, 2026. It has a 1.1M-token context window and can generate up to 128K output tokens. API pricing is $5 per 1M input tokens and $30 per 1M output tokens.
GPT-5.5 is OpenAI's smartest model yet, designed for real work across agentic coding, computer use, knowledge work, and early scientific research. It matches GPT-5.4 per-token latency in real-world serving while reaching a much higher level of intelligence and using significantly fewer tokens to complete the same tasks. GPT-5.5 supports a 1M-token context window in the API and a 400K-token context window in Codex, with state-of-the-art results on Terminal-Bench 2.0, OSWorld-Verified, GDPval, FrontierMath, and CyberGym.
Key specs
| Provider | OpenAI |
|---|---|
| Release date | 2026-04-23 |
| License | proprietary |
| Context window | 1.1M tokens |
| Max output | 128K tokens |
| Input price | $5 / 1M tokens |
| Output price | $30 / 1M tokens |
| Intelligence Score | 47.2 |
| Coding index | 36 |
| Output speed | 169 tokens/s |
| Time to first token | 2.16 s |
Quick answers
What is the context window of GPT-5.5 (Reasoning)?
GPT-5.5 (Reasoning) has a context window of 1.1M tokens, with a maximum output of 128K tokens per response.
How much does GPT-5.5 (Reasoning) cost?
GPT-5.5 (Reasoning) costs $5 per 1M input tokens and $30 per 1M output tokens through the API.
Is GPT-5.5 (Reasoning) open source?
No. GPT-5.5 (Reasoning) is a proprietary model from OpenAI (proprietary license).
When was GPT-5.5 (Reasoning) released?
OpenAI released GPT-5.5 (Reasoning) on April 23, 2026.
Compare on the AI leaderboard · All AI models
More models from OpenAI
- GPT-6 Astra (Reasoning) — OpenAI
- GPT-6.1 Sol (Reasoning) — OpenAI
- GPT-5.6 Terra (Reasoning) — OpenAI
- GPT-6 Sol (Reasoning) — OpenAI
- GPT-5.5 Pro (Reasoning) — OpenAI
- GPT-6 Luna (Reasoning) — OpenAI