Breaking

Anthropic reports partial Claude outage affecting Opus 5, Fable 5.1 and Mythos 5.1

September 21, 2026 at 21:51 EDT

Foundation Models
AI Agents
Software Dev & Coding

Anthropic reported a major-impact Claude incident on September 22, 2026, saying elevated errors hit requests to Claude Mythos 5.1, Claude Fable 5.1 and Claude Opus 5 across claude.ai, the Claude API, Claude Code and Claude Cowork. The company first opened the incident at 00:57 UTC, identified the cause at 01:17 UTC, and at 01:35 UTC said Fable 5, Fable 5.1, Mythos 5 and Mythos 5.1 had returned to normal success rates while remaining Claude Opus 5 errors were still being fixed.

Sep. 22, 2026 · Anthropic

Claude outage hits frontier models

Elevated errors disrupted Claude Opus 5, Claude Fable 5.1 and Claude Mythos 5.1 across the app, API and coding products. Fable and Mythos traffic later returned to normal success rates, while Opus 5 errors remained under repair.

models initially affected

components in partial outage

01:35

UTC partial recovery note

components operational

Component impact, shown to scale

partial outage

operational

The disruption was concentrated in the consumer app, API, Claude Code and Claude Cowork, while Claude Console and Claude for Government stayed operational.

Incident sequence

00:57 UTC

Investigation opened

→

01:17 UTC

Cause identified

→

01:35 UTC

Fable and Mythos recover

→

Next

Opus 5 fix continues

Recovery signal

Fable 5, Fable 5.1, Mythos 5 and Mythos 5.1 were reported back at normal success rates by the later update.

Developer friction

Interrupted coding sessions and 500-style failures showed how agent workflows depend on steady model availability.

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