Elevated errors for Claude Fable 5.1, Sonnet 5.5, and Haiku 5.5

What to do

• Check whether you use Anthropic claude.ai, Claude API (api.anthropic.com), Claude Code, Claude Cowork. Check your stack

  Paste a package.json, lockfile, Terraform or a list of domains at down.guide/stack to see every provider you depend on.

• Confirm your retries, queues and scheduled jobs caught up after the 34m it lasted.

  Anything that failed between 2026-10-23 23:37 UTC and 2026-10-24 00:11 UTC may need a replay.

• Subscribe to Anthropic's feed to hear about the next one first. RSS feed

  https://down.guide/feed?provider=anthropic works in Slack (/feed subscribe), Discord feed bots and any RSS reader.

Root cause

We have identified the cause of elevated errors on requests to Claude Fable 5.

Updates from Anthropic 4

1. investigatingOct 23, 2026, 11:37 PM UTC

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

   provider

2. identifiedOct 23, 2026, 11:39 PM UTC

   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.

   provider

3. monitoringOct 23, 2026, 11:54 PM UTC

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

   provider

4. resolvedOct 24, 2026, 12:11 AM UTC

   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.

   provider

Corrections

None so far.

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