# Claude: Intermittent error spikes for Claude Mythos 5.1 and Claude Fable 5.1

- Impact (vendor’s label): major
- Status: resolved
- Started: 2026-09-15 09:48 UTC · Resolved: 2026-09-15 11:14 UTC · Duration: 1.4 h
- Updates: 4 · Affected components: Claude Cowork, Claude API (api.anthropic.com), claude.ai, Claude Code
- [Vendor status page: https://stspg.io/x1qpycpg6ln7](https://stspg.io/x1qpycpg6ln7)
- [Company: Claude](https://rewindex.com/company/claude.md)

## Summary

Claude reported major intermittent errors for Claude Mythos 5.1 and Claude Fable 5.1 affecting claude.ai, Claude API (api.anthropic.com), Claude Code and Claude Cowork. The incident ran from 2026-09-15 09:48 UTC to 2026-09-15 11:14 UTC, lasting 1 h 26 min. A fix was deployed at 10:50 UTC, followed by monitoring and resolution. _(machine-written, sol)_
## Timeline of updates

- **investigating** 2026-09-15 09:48 UTC: We are investigating elevated errors on requests to Claude Mythos 5.1 and Claude Fable 5.1. We will provide an update as soon as possible.
- **investigating** 2026-09-15 09:52 UTC: We are investigating elevated errors on requests to Claude Mythos 5.1 and Claude Fable 5.1. We will provide an update as soon as possible.
- **monitoring** 2026-09-15 10:50 UTC: A fix has been deployed for Claude Mythos 5.1 and Claude Fable 5.1 and we are monitoring to ensure it has resolved the issue.
- **resolved** 2026-09-15 11:14 UTC: A fix has been deployed for Claude Mythos 5.1 and Claude Fable 5.1 and we are monitoring to ensure it has resolved the issue.

## Rewindex changes for this incident

- 2026-09-15 09:48 UTC: [Major incident: Intermittent error spikes for Claude Mythos 5.1 and Claude Fable 5.1](https://rewindex.com/change/ib3fc50d64d3886.md)


---
Canonical: https://rewindex.com/company/claude/incidents/6304r9jjhj34 · Markdown: https://rewindex.com/company/claude/incidents/6304r9jjhj34.md · JSON: https://rewindex.com/api/v1/companies/claude/incidents/6304r9jjhj34 · Generated 2026-10-18T12:41:51.218Z