OpenAI releases GPT-5.5 (codename Spud)
GPT-5.5 (codename "Spud") launched April 23, 2026 in ChatGPT (Thinking and Pro) and the API the next day, posting 82.7% on Terminal-Bench 2.0, 84.9% on GDPval and 78.7% on OSWorld-Verified; follow-ups included GPT-5.5 Instant for free users (May 5) and GPT-5.5-Cyber for vetted defenders (May 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.
Changelog
- 2026-09-29: created
Related events
- OpenAI releases GPT-5.4 with native computer use ★★★★
- OpenAI launches Daybreak cyber-defense initiative with GPT-5.5-Cyber and Codex Security ★★★
- OpenAI broadly releases GPT-5.6 (Sol, Terra, Luna) after government-gated preview ★★★★
Sources (5)
- officialIntroducing GPT-5.5 (OpenAI)
- videoIntroducing GPT-5.5 (OpenAI, YouTube)
- discussionWikipedia: GPT-5.5
- docsOpenRouter: GPT-5.5
- pressVellum: Everything you need to know about GPT-5.5
id: 2026-04-23-gpt-5-5 · updated 2026-09-29 · open in the interactive timeline