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

Anthropic · anthropic.comImpact: majorResolved2026-09-15 11:14 UTC

Public — what happened

Summary

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.

Timeline

Started — 2026-09-15 09:48 UTC
Last update — 2026-09-15 11:14 UTC
Resolved — 2026-09-15 11:14 UTC

Source of record: provider status page. Mirrored as reported; times in UTC.

With SquidGrid — where it starts on the route

Independent path health

The status page is the symptom. SquidGrid measures the paths that reach Anthropic against their own baselines — whether the routes carrying your traffic degraded, at which handoff, and who owns that stretch.

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Related: Anthropic status & history. SquidGrid is not affiliated with Anthropic.