OpenAI announced the release of GPT-5.5 and GPT-5.5 Pro to its API, marking a significant update for developers. GPT-5.5, billed as a 'frontier model for complex professional work,' introduces a 1M token context window, image input, structured outputs, function calling, prompt caching, and built-in computer use. Its Pro variant is designed for tougher problems requiring more compute, available via Responses API and Batch.

The release builds on OpenAI's ongoing API enhancements. In March 2026, the company launched GPT-5.4 mini and nano for high-volume workloads, with GPT-5.4 Pro introduced for professional tasks. Earlier updates included expanding input file support to document, presentation, spreadsheet, code, and text formats, and launching WebSocket mode for the Responses API. In December 2025, OpenAI added Custom voices for eligible customers in its new audio snapshots.

Key technical updates focus on improving efficiency and functionality. GPT-5.5's 1M token context window allows it to handle longer-running conversations, while built-in computer use supports screenshot-based UI interaction. The Pro variant, with enhanced reasoning effort, is positioned to tackle more complex professional problems. OpenAI also expanded the Sora API with reusable character references and longer video generations, with 1080p output billed at $0.70 per second.

A concrete takeaway: OpenAI's GPT-5.5 API release provides developers with advanced tools for complex professional work, featuring a 1M token context window, image input, and built-in computer use, with its Pro variant designed for tougher problems requiring more compute. These updates aim to enhance efficiency and functionality for developers working on complex AI applications.