8.1Context Windows (July 2026)

As of July 2026 the frontier models — Claude Opus 4.8, OpenAI GPT-5.5, Google Gemini 3.1 Pro — ship context windows ranging from the 200K-token class up to 1M+. For the worked examples below we assume a 200K window with ~150K effectively usable after system prompts, tool definitions, and conversation overhead. The exact window matters less than the ratio: what fraction of it does browser state eat?