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OpenAI's flagship frontier model for the most complex coding and professional reasoning work, with a ~1M-token context window and configurable reasoning effort.
Every value carries a primary source and a verification date.
Sourced evaluation scores, each verified against its primary source.
SWE-bench Pro
On SWE-Bench Pro, GPT-5.5 reaches 58.6%, solving more tasks end-to-end in a single pass than previous models
GPQA Diamond
GPT-5.5: 0.936
Humanity's Last Exam (no tools)
and GPT-5.5 (xhigh) with a score of 44.3%
Humanity's Last Exam (with tools)
GPT-5.5: 0.522 (52.2%)
Terminal-Bench 2.1
GPT-5.5 (Terminus-2) 78.2
GPT-5.5 lands in the API at $5 / $30 per million tokens
GPT-5.5 became available to API developers on April 24, 2026 at $5 per million input tokens and $30 per million output tokens with a 1M-token context window. GPT-5.5 Pro is priced at $30 per million input tokens and $180 per million output tokens.
OpenAI releases GPT-5.5 and GPT-5.5 Pro
OpenAI released GPT-5.5 and GPT-5.5 Pro on April 23, 2026, calling GPT-5.5 its "smartest and most intuitive to use model yet," with gains in agentic coding, knowledge work, math, and scientific research. The models reached the API on April 24. GPT-5.5 rolled out to Plus, Pro, Business, and Enterprise tiers in ChatGPT; GPT-5.5 Pro went to Pro, Business, and Enterprise. OpenAI framed the launch as a step toward a unified "super app."
OpenAI treats GPT-5.5 biology and cyber capabilities as "High" risk
In the GPT-5.5 system card (April 23, 2026; updated April 24 for API safeguards), OpenAI classifies the model's biological/chemical and cybersecurity capabilities as "High" under its Preparedness Framework and ships what it calls its strongest set of safeguards to date. OpenAI says it ran full predeployment evaluations and targeted red-teaming with roughly 200 early-access partners; GPT-5.5 did not reach the "Critical" cybersecurity level but is a step up from GPT-5.4.