Opus 5 ships with a 200K default context window, down 80%

Anthropic cut the default context window by 80% without announcing it, according to a blog post. Opus 4.8 and earlier models offer 1M tokens, at minimum on any paid plan; Opus 5 defaults to 200K. Getting the full million back costs nothing: flip on the Usage Credits toggle. No credit purchase, no auto-reload, no nonzero limit required.

Window size matters most in coding, where a single long task has to read the source and the logic end to end. Run short on room and the model compacts the context mid-job, losing details, producing more errors, and burning token quota re-reading the same files.

The author says his everyday work regularly runs well past 200K tokens, and every so often even 1M isn't enough.