News · Claude
Claude describes external evaluations and alignment testing for Opus 5.5
Posted on X by Claude (@claudeai) on 22 September 2026. The headline is our summary; the post itself is quoted below.
Claude@claudeai ·
Opus 5.5 is our first model since we called for pacing the frontier. As with previous models, it was tested by external evaluators before release,…
The quote is the post as published on X; the original may include images, links or a thread.
Context
- Claude Code 2.1.280Released the same day (UTC). Added Claude Opus 5.5 (claude-opus-5-5), now the default Opus model — 1M context, $4/$20 per Mtok with $0.20/Mtok cache reads · Added mouse support…
- AI news in September 2026The month in one page: posts, releases, resets and blog posts.
- All Claude newsSelected posts, newest first.
Also tracked: Claude news · Claude resets · Claude Code release notes · Blog