Changes / Anthropic / Elevated errors for multiple models

Anthropic: Major incident: Elevated errors for multiple models

Summary

Anthropic reported a major incident causing elevated request errors across claude.ai, Claude API (api.anthropic.com), Claude Code, and Claude Cowork, initially affecting Claude Mythos 5.1, Claude Fable 5.1, and Claude Opus 5. Starting 2026-09-03 13:26 UTC, it was resolved at 2026-09-03 16:23 UTC (2 h 57 min); a fix was deployed.

Machine-written from the diff below (Sol; type: incident outage). Check the diff before relying on it.

Major incidentLabel: outage (model (Jev), 81%)Changed Detected Source: stspg.io

What changed

AddedTitle#1
Before: not present
After: Elevated errors for multiple models
AddedImpact#2
Before: not present
After: major
AddedStatus#3
Before: not present
After: resolved
AddedStart time#4
Before: not present
After: 2026-09-03 13:26 UTC
AddedResolved time#5
Before: not present
After: 2026-09-03 16:23 UTC
AddedAffected components#6
Before: not present
After: claude.ai, Claude API (api.anthropic.com), Claude Code, Claude Cowork
AddedUpdateinvestigating#7
Before: not present
After: We are investigating elevated errors on requests to Claude Mythos 5.1, Claude Fable 5.1, and Claude Opus 5. We will provide an update as soon as possible.
AddedUpdateidentified#8
Before: not present
After: We have identified the cause of elevated errors on requests to Claude Mythos 5.1, Claude Fable 5.1, and Claude Opus 5 and are working on a fix. We will provide an update as soon as possible.
AddedUpdateidentified#9
Before: not present
After: An exhaustive list of affected models: Mythos/Fable 5.1, Mythos/Fable 5, Opus 5, Opus 4.8, Opus 4.6.
AddedUpdateidentified#10
Before: not present
After: We are continuing to work on a fix for this issue.
AddedUpdateidentified#11
Before: not present
After: The only affected models right now are Opus 4.8 and Opus 5. The rest of the models have recovered to baseline error rate.
AddedUpdatemonitoring#12
Before: not present
After: A fix has been deployed for Claude Mythos 5.1, Claude Fable 5.1, and Claude Opus 5 and we are monitoring for recovery.
AddedUpdateresolved#13
Before: not present
After: The issue affecting Claude Mythos 5.1, Claude Fable 5.1, and Claude Opus 5 has been resolved. Impact has ended as of 9:16 PT / 16:16 UTC.

First version of this incident archived by Rewindex. View the live incident.

History of this incident

When (UTC)ChangeKind
Major incident: Elevated errors for multiple models (this change)
Anthropic reported a major incident causing elevated request errors across claude.ai, Claude API (api.anthropic.com), Claude Code, and Claude Cowork, initially affecting Claude Mythos 5.1, Claude Fable 5.1, and Claude Opus 5. Starting 2026-09-03 13:26 UTC, it was resolved at 2026-09-03 16:23 UTC (2 h 57 min); a fix was deployed.
Major incident

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