OpenAI releases GPT-5.5 (codename Spud)
Confirmed
Importance: major (4 of 5)Status
- Claim
Confirmed
- Our reporting
- High confidence
- Importance
- Major (4 of 5)
- Last verified
- 29 September 2026
Your AI and this story
- GPT-6 AstraIn its training data
- Claude Opus 5.5In its training data
- Gemini 4 Hydrogen23 days after its cutoff
- Grok 4.7In its training data
It is after the cutoff of Gemini 4 Hydrogen, and can be in the training data of GPT-6 Astra, Claude Opus 5.5 and Grok 4.7.
Key facts
- GPT-5.5 Thinking and Pro: April 23, 2026 (paid tiers); API: April 24, 2026
- GPT-5.5 Instant replaced GPT-5.3 Instant for free users on May 5, 2026
- GPT-5.5-Cyber: limited preview for vetted security teams May 7, 2026; fuller release June 22, 2026 with Daybreak expansion
- API price: $5 per 1M input / $30 per 1M output tokens; context 1.05M tokens, 128K max output (per pricing guides/OpenRouter)
- Terminal-Bench 2.0: 82.7%; FrontierMath Tier 1–3: 51.7%; Tier 4: 35.4%
- GDPval (44 occupations): 84.9%; OSWorld-Verified: 78.7%; Tau2-bench Telecom: 98.0%
- UK AI Security Institute cyber tasks: 71.4% (±8.0%) average pass rate
- Quirk: tendency to mention goblins and gremlins, traced to reward signals from training the ‘Nerdy’ personality; mitigated by retraining
What happened
OpenAI shipped GPT-5.5 as its new frontier model across ChatGPT, the API and Codex, with strong agentic, computer-use and knowledge-work results and leading scores (per OpenAI) versus Claude Opus 4.7 and Gemini 3.1 Pro on Terminal-Bench and FrontierMath. A cyber-specialized variant (GPT-5.5-Cyber) became the backbone of OpenAI’s Daybreak defender program.
Why it matters
GPT-5.5 was OpenAI’s flagship for most of Q2 2026 and the base for its cyber-defense strategy; its Instant variant brought the generation to free users.
Sources
5 sources from 5 sites. Numbers match the chips in the text.
5 sources: 2 primary, 1 press, 2 reactions
Primary
- Introducing GPT-5.5 (OpenAI)openai.com, official
- OpenRouter: GPT-5.5openrouter.ai, docs
Press
- Vellum: Everything you need to know about GPT-5.5vellum.ai, press
Reactions
- Introducing GPT-5.5 (OpenAI, YouTube)youtube.com, video
- Wikipedia: GPT-5.5en.wikipedia.org, discussion
Changes
- Filed