# GPT-5.5

> **TL;DR.** GPT-5.

- **Category:** AI / Language Models / Frontier
- **Stage:** validating
- **Age:** 54 days
- **Origin date:** 2026-04-23
- **First detected:** 2026-04-24
- **Canonical URL:** https://earlyterms.com/term/gpt-5-5
- **Sources:** 7 primary URLs

## Definition

GPT-5.5 is OpenAI's frontier language model released on April 23, 2026 — the first fully retrained base model since GPT-4.5, with every GPT-5.x release between them being a post-training iteration. Designed for autonomous, multi-step agentic tasks, it matches GPT-5.4's per-token latency while delivering higher intelligence with fewer tokens.

OpenAI released GPT-5.5 (internal codename "Spud") simultaneously to ChatGPT Plus, Pro, Business, and Enterprise users and in the Codex coding agent on [April 23, 2026](https://openai.com/index/introducing-gpt-5-5/). API pricing is $5/$30 per million input/output tokens, with a GPT-5.5 Pro tier at $30/$180 and 1M context window. Terminal-Bench 2.0: 82.7%; SWE-Bench Pro: 58.6%; GDPval: 84.9%.

## Analogy

Think of it as a new chassis, not a new coat of paint — full retrain versus post-training tuning.

## Why it's emerging now

On April 23, 2026, OpenAI released GPT-5.5 — the first fully retrained base model since GPT-4.5 — into ChatGPT and Codex simultaneously. The new architecture sets benchmark leads on Terminal-Bench 2.0 (82.7%) and GDPval (84.9%), with biosecurity risk rated 'High' under OpenAI's Preparedness Framework.

## Related terms

- *competitor:* Claude Opus 4.7
- *competitor:* claude-opus-4-7
- *competitor:* Claude Mythos
- *competitor:* claude-mythos
- *competitor:* Gemini 3.1 Flash
- *competitor:* gemini-3-1-flash
- *related:* OpenAI Codex CLI
- *related:* openai-codex-cli
- *parent:* agentic coding
- *parent:* agentic-coding
- *related:* GPT-5.4
- *related:* context window

## Sources

1. [OpenAI — Introducing GPT-5.5](https://openai.com/index/introducing-gpt-5-5/)
2. [TechCrunch — OpenAI releases GPT-5.5, one step closer to AI super app](https://techcrunch.com/2026/04/23/openai-chatgpt-gpt-5-5-ai-model-superapp/)
3. [Axios — OpenAI releases 'Spud' GPT-5.5 model](https://www.axios.com/2026/04/23/openai-releases-spud-gpt-model)
4. [XBOW — GPT-5.5: Mythos-Like Hacking, Open to All](https://xbow.com/blog/mythos-like-hacking-open-to-all)
5. [MarkTechPost — GPT-5.5 fully retrained agentic model](https://www.marktechpost.com/2026/04/23/openai-releases-gpt-5-5-a-fully-retrained-agentic-model-that-scores-82-7-on-terminal-bench-2-0-and-84-9-on-gdpval/)
6. [One Useful Thing — Sign of the Future: GPT-5.5 (Ethan Mollick)](https://www.oneusefulthing.org/p/sign-of-the-future-gpt-55)
7. [Hacker News — GPT-5.5 (1,447 points)](https://news.ycombinator.com/item?id=47879092)

---
_Generated by EarlyTerms · https://earlyterms.com/term/gpt-5-5_