Five Claude Models Face Elevated Errors as Anthropic Investigates

Anthropic opened an investigation into elevated errors affecting five Claude models on October 25, 2026, putting a broad set of Claude services under the spotlight. The incident appeared on the Claude Status page at 06:14 UTC, and seven minutes later, the investigation remained unresolved.

The incident, titled “Elevated errors for multiple models,” was published in Investigating status. Anthropic said it was examining elevated errors on requests to Claude Mythos 5.1, Claude Fable 5.1, Claude Opus 5.5, Claude Sonnet 5.5, and Claude Haiku 5.5, with an update promised as soon as possible.

Four Claude Components Show Partial Outage

The incident record identifies four affected services: claude.ai, Claude API, Claude Code, and Claude Cowork. The Claude Status page marked all four components as Partial Outage when Anthropic posted the investigation.

That status applied across the main Claude experience, the API, coding tools, and Cowork. Claude Console (platform.claude.com) and Claude for Government remained marked Operational.

• claude.ai — Partial Outage, with 99.58 percent uptime over the past 90 days
• Claude API (api.anthropic.com) — Partial Outage, with 99.64 percent uptime
• Claude Code — Partial Outage, with 99.58 percent uptime
• Claude Cowork — Partial Outage, with 99.57 percent uptime
• Claude Console (platform.claude.com) — Operational, with 99.84 percent uptime
• Claude for Government — Operational, with 100 percent uptime

The status page listed the investigation as the unresolved incident for October 25, 2026. Seven minutes after the 06:14 UTC posting, no further update had appeared, leaving the investigation in the same status.

A Cluster of Model Incidents Stretches Across October

The new investigation follows three resolved incidents listed in the Claude Status page history for October 24, 2026. Their titles point to elevated errors across several Claude models, including Claude Fable 5, Claude Fable 5.1, Claude Opus 5.5, Claude Sonnet 5.5, and Claude Haiku 5.5.

• “Elevated errors for Claude Fable 5 and Claude Fable 5.1” was resolved at 05:53 UTC.
• “Elevated errors for Claude Opus 5.5” was resolved at 00:37 UTC.
• “Elevated errors for Claude Fable 5.1, Sonnet 5.5, and Haiku 5.5” was resolved at 00:11 UTC.

An Identified update on the third incident also cited fast mode requests to Opus 5.5. A Monitoring update at 23:54 UTC on October 23 said success rates were returning to normal for all affected models, adding another step to the sequence recorded in the incident history.

The October 24 incidents included impact times that began on October 23, including periods starting at 22:00 PT on October 23. The history therefore places the latest investigation inside a series of incidents involving multiple Claude models across consecutive days.

Earlier Service Issues Included Connectors and Fable 5

The status history also records service incidents from October 22 and October 21. On October 22, the incident titled “Elevated errors affecting Connectors” affected claude.ai and Claude Cowork.

Investigation began for that incident at 03:50 UTC. Anthropic deployed a fix with monitoring at 07:28 UTC, and the incident was resolved at 08:07 UTC.

On October 21, an incident titled “Degraded performance for Claude Fable 5” was investigated from 19:49 UTC and resolved at 20:29 UTC. The history also lists an incident under October 13, 2026.

For October 25, the key question remains whether the elevated errors across Claude Mythos 5.1, Claude Fable 5.1, Claude Opus 5.5, Claude Sonnet 5.5, and Claude Haiku 5.5 will follow the resolved pattern recorded earlier in the month. Anthropic has opened the investigation, marked four components as Partial Outage, and said it will provide an update as soon as possible.

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