OpenAI releases GPT-5.5 with 400K context window, higher pricing than GPT-5.4

OpenAI released GPT-5.5 on April 23, 2026, seven weeks after the March 5 launch of GPT-5.4. The company claims the model "understands what you're trying to do faster" and can "carry more of the work itself" compared to earlier versions.

Technical specifications

GPT-5.5 in Codex includes a 400K context window. The model is also available in Fast mode, which generates tokens 1.5x faster at 2.5x the cost. Specific pricing per million tokens was not disclosed, though OpenAI confirmed GPT-5.5 is priced higher than GPT-5.4.

Claimed improvements

According to OpenAI, GPT-5.5 shows gains in:

• Agentic coding
• Computer use
• Knowledge work
• Early scientific research
• Multi-part tasks requiring planning, tool use, and self-checking

The company states these improvements come without sacrificing speed or using more tokens. In Codex specifically, OpenAI claims GPT-5.5 "delivers better results with fewer tokens than GPT-5.4 for most users."

Model variants

GPT-5.5 ships with two variants:

GPT-5.5 Thinking: Designed for "faster help for harder problems, with smarter and more concise answers." Available to Plus, Pro, Business, and Enterprise users in ChatGPT.

GPT-5.5 Pro: According to OpenAI, early testers describe it as "a step up in both the difficulty and quality of work ChatGPT can take on, with latency improvements." Available to Pro, Business, and Enterprise users.

Availability

GPT-5.5 rolled out April 23 to Plus, Pro, Business, and Enterprise users in ChatGPT and Codex. The model is also available in Codex for Edu and Go plans. OpenAI stated API access is "coming very soon" but provided no specific date.

Codex expanded browser capabilities with this release, enabling interaction with web apps, flow testing, page navigation, and screenshot capture.

Safety testing

OpenAI reports conducting safety evaluations across its "full suite of safety and preparedness frameworks" with internal and external red teamers. The company specifically tested for advanced cybersecurity and biology capabilities and collected feedback from nearly 200 early-access partners before release.

What this means

The seven-week gap between GPT-5.4 and GPT-5.5 suggests OpenAI is maintaining a rapid iteration schedule in 2026. The 400K context window in Codex is a substantial increase for coding tasks, though the higher pricing may affect usage patterns. The lack of disclosed pricing details or benchmark scores makes it difficult to assess GPT-5.5's position relative to competing models from Anthropic, Google, and others. The emphasis on "token efficiency" while raising prices suggests OpenAI is balancing performance gains against compute costs.