GPT-5.5
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OpenAI's flagship frontier model, positioned as a new class of intelligence for coding and professional work.
GPT-5.5 (API ID gpt-5.5) is OpenAI's current flagship API model, described in the API docs as "a new class of intelligence for coding and professional work." It offers a 1M-token context window and up to 128K output tokens, with a December 1, 2025 knowledge cutoff. OpenAI recommends starting with GPT-5.5 for complex reasoning and coding, and using the GPT-5.4 mini/nano tier for lower-latency, lower-cost workloads.
Strengths
- OpenAI's recommended model for complex reasoning and coding
- 1M-token context window with up to 128K output tokens
- Generally available via the OpenAI API with listed pricing of $5 input / $30 output per million tokens
Tradeoffs
- Most expensive tier in OpenAI's lineup; GPT-5.4 is positioned as the more affordable option for similar work
- API-only commercial model; no open weights