# GPT-5.5

> OpenAI's mid-2026 flagship: a fast, frontier model for agentic coding, tool use, and professional work.

- Maker: OpenAI
- Line: GPT (Flagship / Thinking)
- Canonical page: https://ai-tldr.dev/models/gpt-5-5/
- Updated: 2026-09-21

## In short

GPT-5.5 is OpenAI's April 2026 flagship model, announced on April 23, 2026 and made available in the API on April 24, 2026. It has a 1.05M-token context window and costs $5.00 per million input tokens and $30.00 per million output tokens. You can use it through OpenAI API.

## Facts

| Fact | Value | Source |
| --- | --- | --- |
| Context window | 1.05M (max output 128K) | [1] |
| Input price | $5.00 / 1M tokens (cached $0.50) | [2] |
| Output price | $30.00 / 1M tokens | [2] |
| Licence | Proprietary · API only | [1] |
| Released | April 2026 | [3] |
| Parameters | Undisclosed | [1] |
| Knowledge cutoff | 1 December 2025 | [1] |

## Sources

1. [OpenAI models overview](https://developers.openai.com/api/docs/models)
2. [GPT-5.5 model docs (OpenAI)](https://developers.openai.com/api/docs/models/gpt-5.5)
3. [Introducing GPT-5.5 (OpenAI announcement)](https://openai.com/index/introducing-gpt-5-5/)

## Overview

GPT-5.5 is OpenAI's April 2026 flagship model, announced on April 23, 2026 and made available in the API on April 24, 2026. OpenAI positioned it as 'a new class of intelligence for coding and professional work,' built to be a faster, sharper thinker that uses fewer tokens than the previous GPT-5.4 generation while delivering stronger results.

The model accepts text and image input and produces text output. It has a 1,050,000-token context window and can return up to 128,000 output tokens, with a knowledge cutoff of December 1, 2025. It supports streaming, function calling, structured outputs, and a broad set of hosted tools including web search, file search, image generation, code interpreter, hosted shell, computer use, and MCP.

GPT-5.5 is designed for complex agentic tasks: multi-step, tool-using workflows where the model must plan and execute over long horizons. OpenAI highlights improvements in recovering from errors mid-task, making efficient tool calls, maintaining coherence over long contexts, and calibration. It rolled out first to ChatGPT Plus, Pro, Business, and Enterprise tiers and inside the Codex coding assistant.

On September 14, 2026 OpenAI announced a retirement date for the model in its consumer and coding surfaces: 'GPT-5.5 will retire from ChatGPT, ChatGPT Work, and Codex on October 14, 2026, across all plans.' OpenAI directs Codex users signed in with ChatGPT to GPT-5.6 Sol (`gpt-5.6-sol`), and tells users to update saved model settings, workspace defaults, custom agents, scheduled tasks and scripts that still select GPT-5.5 before that date.

## Pricing

- Input: $5.00 / 1M tokens
- Cached input: $0.50 / 1M tokens
- Output: $30.00 / 1M tokens

Source: https://developers.openai.com/api/docs/models/gpt-5.5

## Strengths

- Frontier-level agentic coding, debugging, and long-horizon tool use
- Very large 1,050,000-token context window for long documents and codebases
- Improved token efficiency versus the prior GPT-5.4 generation
- Broad native tool support (web/file search, code interpreter, computer use, MCP)
- Strong scientific and technical research workflow performance

## Best for

- Agentic software engineering: writing, debugging, and shipping code across tools
- Long-context document and data analysis
- Autonomous multi-step research and knowledge work
- Operating software and orchestrating tool-using agents

## How to access

- [OpenAI API](https://developers.openai.com/api/docs/models/gpt-5.5) — model id `gpt-5.5`

## GPT (Flagship / Thinking) versions

- GPT-5.5 (23 April 2026) — this page
- [GPT-5.4](https://ai-tldr.dev/models/gpt-5-4/) (5 March 2026)
- [GPT-5.2](https://ai-tldr.dev/models/gpt-5-2/) (11 December 2025)
- [GPT-5.1](https://ai-tldr.dev/models/gpt-5-1/) (12 November 2025)
- [GPT-5](https://ai-tldr.dev/models/gpt-5/) (7 August 2025)
- [GPT-4o](https://ai-tldr.dev/models/gpt-4o/) (13 May 2024)

## FAQ

### What is GPT-5.5's role in OpenAI's GPT lineup?

GPT-5.5, announced on April 23, 2026, was OpenAI's April 2026 GPT flagship and was succeeded by the GPT-5.6 series (Sol, Terra, Luna) on July 9, 2026. OpenAI described GPT-5.5 as a new class of intelligence for coding and professional work, designed to be faster and more token-efficient than the prior GPT-5.4 generation while excelling at agentic, tool-using tasks.

### What is GPT-5.5's context window and knowledge cutoff?

GPT-5.5 has a 1,050,000-token context window and can produce up to 128,000 output tokens per response. Its training knowledge cutoff is December 1, 2025. It accepts both text and image inputs and returns text output, making it suitable for long-document and large-codebase work.

### How much does the GPT-5.5 API cost?

Per OpenAI's official model docs, GPT-5.5 costs $5.00 per 1M input tokens and $30.00 per 1M output tokens, with cached input priced at $0.50 per 1M tokens. Prompts exceeding 272K input tokens are billed at higher session rates.

### Is GPT-5.5 being retired, and what should I switch to?

Yes, in OpenAI's own surfaces. OpenAI announced on September 14, 2026 that GPT-5.5 retires from ChatGPT, ChatGPT Work and Codex on October 14, 2026 across all plans, and points Codex users signed in with ChatGPT to GPT-5.6 Sol (`gpt-5.6-sol`). Saved model settings, workspace defaults, custom agents, scheduled tasks and scripts that name GPT-5.5 need updating before that date.

### What is GPT-5.5 best at?

GPT-5.5 is built for complex agentic work: multi-step coding, debugging, research, and operating software across tools over long time horizons. OpenAI emphasizes better mid-task error recovery, more efficient tool calls, and improved coherence across its very large context window.

## Links

- [GPT-5.5 model docs (OpenAI)](https://developers.openai.com/api/docs/models/gpt-5.5)
- [OpenAI models overview](https://developers.openai.com/api/docs/models)
- [Introducing GPT-5.5 (OpenAI announcement)](https://openai.com/index/introducing-gpt-5-5/)
- [OpenAI releases GPT-5.5 (TechCrunch)](https://techcrunch.com/2026/04/23/openai-chatgpt-gpt-5-5-ai-model-superapp/)
- [GPT-5.5 (Wikipedia)](https://en.wikipedia.org/wiki/GPT-5.5)
- [ChatGPT What's New — GPT-5.5 retirement notice](https://learn.chatgpt.com/docs/whats-new)

Source: AI/TLDR LLM registry, https://ai-tldr.dev/models/gpt-5-5/