Incident report · read from Anthropic's status page

Anthropic incident: Elevated errors for Claude Fable 5.1, Sonnet 5.5, and Haiku 5.5

Resolved after 33 m (23 Oct 2026 23:37 – 24 Oct 2026 00:11 UTC), impact critical, affecting Claude Cowork, Claude API (api.anthropic.com), claude.ai and Claude Code.

Timeline

1. 23 Oct 2026 at 23:37 UTC investigating

   We are investigating elevated errors on requests to Claude Fable 5.1. We will provide an update as soon as possible.

2. 23 Oct 2026 at 23:39 UTC identified

   We have identified the cause of elevated errors on requests to Claude Fable 5.1, Sonnet 5.5, and Haiku 5.5, as well as fast mode requests to Opus 5.5 and are working on a fix. We will provide an update as soon as possible.

3. 23 Oct 2026 at 23:54 UTC monitoring

   We are seeing success rates return to normal for all affected models, and are continuing to monitor to ensure no further issues.

4. 24 Oct 2026 at 00:11 UTC resolved

   The issue affecting Claude models has been resolved. Impact occurred from 16:28 PT / 23:28 UTC on October 23 to 16:59 PT / 23:59 UTC on October 23.

Affected components

• Claude Cowork: major outage for 16 m
• Claude API (api.anthropic.com): major outage for 16 m
• claude.ai: major outage for 16 m
• Claude Code: major outage for 16 m
• Claude Cowork: degraded for 17 m
• Claude API (api.anthropic.com): degraded for 17 m
• claude.ai: degraded for 17 m
• Claude Code: degraded for 17 m

What the crowd did

• 0 clicks, 2 zombies at their worst, 1 breaches, over 35 m — the siege in full

That is this site's own record of the crowd at Anthropic's gate, not anything Anthropic published.

Source

Anthropic's own report of this incident, on Anthropic's status page. This page is a record of Anthropic's own report; where the two disagree, theirs is right.

Last checked 30 Oct 2026 at 15:32 UTC.

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