Claude Opus 4.1 changelog

Claude Opus 4.1 retired

Requests to claude-opus-4-1-20250805 on the Claude API now return an error. It remains on Bedrock and Google Cloud.

Who is affected:

Apps still calling Claude Opus 4.1 on the Claude API.

Action needed:

Switch to Claude Opus 5 or newer.

Claude Opus 4.1 deprecated

Anthropic announced that claude-opus-4-1-20250805 would retire on the Claude API on August 5, 2026.

Who is affected:

Apps calling claude-opus-4-1-20250805.

Action needed:

Migrate to Claude Opus 4.8 or newer.

Anthropic confirms three infrastructure bugs degraded Claude responses in August and September 2025

Anthropic published a postmortem saying three separate infrastructure bugs, the first introduced on August 5, intermittently degraded Claude's response quality until early September. A load balancing change on August 29 increased affected traffic. The Hacker News thread drew 381 points and 116 comments.

Who is affected:

Users of Claude Sonnet 4, Opus 4 and 4.1, and Haiku 3.5 on the Claude API and in Claude Code between August 5 and mid-September 2025.

What to do:

No action needed. Anthropic says all three bugs are fixed.