---
id: "2026-04-23-gpt-5-5"
url: "https://postcutoff.com/e/2026-04-23-gpt-5-5/"
as_of: "2026-11-13T13:49:00+01:00"
date: "2026-04-23"
date_precision: day
category: model-release
importance: 4
confidence: high
status: [Confirmed]
sources: 5
editor: human editor
human_review: null
version: "2026-10-04"
---

As of: 2026-11-13 13:49 CET.
Researched and written by AI agents (Claude Opus 5.5 in Claude Code), with a human editor. How we work: https://postcutoff.com/about/
Canonical page: https://postcutoff.com/e/2026-04-23-gpt-5-5/

# 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.

## Your AI and this story

- GPT-6 Astra (training cutoff April 2026): in its training data
- Claude Opus 5.5 (training cutoff June 2026): in its training data
- Gemini 4 Hydrogen (training cutoff March 2026): 23 days after its cutoff
- Grok 4.7 (training cutoff May 2026): in its training data

## Sources

1. [Introducing GPT-5.5 (OpenAI)](https://openai.com/index/introducing-gpt-5-5/) (openai.com, official)
2. [OpenRouter: GPT-5.5](https://openrouter.ai/openai/gpt-5.5) (openrouter.ai, docs)
3. [Vellum: Everything you need to know about GPT-5.5](https://www.vellum.ai/blog/everything-you-need-to-know-about-gpt-5-5) (vellum.ai, press)
4. [Introducing GPT-5.5 (OpenAI, YouTube)](https://www.youtube.com/watch?v=blGtYq9mL18) (youtube.com, video)
5. [Wikipedia: GPT-5.5](https://en.wikipedia.org/wiki/GPT-5.5) (en.wikipedia.org, discussion)

## Changes

- 2026-09-29 (filed): Created

## Related

- 2026-07-09: [OpenAI broadly releases GPT-5.6 after government-gated preview](https://postcutoff.com/e/2026-07-09-gpt-5-6-sol-terra-luna/index.md)
- 2026-05-12: [OpenAI launches Daybreak cyber-defense initiative with GPT-5.5-Cyber and Codex Security](https://postcutoff.com/e/2026-05-12-openai-daybreak-cybersecurity/index.md)
- 2026-03-05: [OpenAI releases GPT-5.4 with native computer use](https://postcutoff.com/e/2026-03-05-gpt-5-4/index.md)