# Anthropic: Critical incident: Elevated errors for Claude Fable 5.1, Sonnet 5.5, and Haiku 5.5

**Summary:** _summary pending_
- Kind: Major incident · Label: critical (vendor)
- Changed: 2026-10-23 23:39 UTC · Detected: 2026-10-23 23:43 UTC
- [Source: https://status.claude.com/incidents/h101vcmhnfky](https://status.claude.com/incidents/h101vcmhnfky)
- [Company: Anthropic](https://rewindex.com/company/anthropic.md)
- Versions: before (none: first archived) → after incident\_version:1/h101vcmhnfky@c158901ca049
- Change 1 of 3 for this incident

Incident page (full timeline): [Elevated errors for Claude Fable 5.1, Sonnet 5.5, and Haiku 5.5](https://rewindex.com/company/anthropic/incidents/h101vcmhnfky.md)
## What changed

**1. Added: Title**

```diff
+ Elevated errors for Claude Fable 5.1, Sonnet 5.5, and Haiku 5.5
```

**2. Added: Impact**

```diff
+ critical
```

**3. Added: Status**

```diff
+ identified
```

**4. Added: Start time**

```diff
+ 2026-10-23 23:39 UTC
```

**5. Added: Affected components**

```diff
+ claude.ai, Claude API - api.anthropic.com, Claude Code, Claude Cowork
```

**6. Added: Update** (investigating) · 2026-10-23 23:37 UTC

```diff
+ We are investigating elevated errors on requests to Claude Fable 5.1. We will provide an update as soon as possible.
```

**7. Added: Update** (identified) · 2026-10-23 23:39 UTC

```diff
+ We have identified the cause of elevated errors on requests to Claude Fable 5.1, Sonnet 5.5, and Haiku 5.5, as well as fast mode requests to Opus 5.5 and are working on a fix. We will provide an update as soon as possible.
```

## History of this incident

| When (UTC) | Change | Label |
| --- | --- | --- |
| 2026-10-23 23:39 UTC | Critical incident: Elevated errors for Claude Fable 5.1, Sonnet 5.5, and Haiku 5.5 (this change) | critical |
| 2026-10-24 00:04 UTC | [Incident updated: Elevated errors for Claude Fable 5.1, Sonnet 5.5, and Haiku 5.5](https://rewindex.com/change/r922de7a570d14f.md) |  |
| 2026-10-24 00:13 UTC | [Incident updated: Elevated errors for Claude Fable 5.1, Sonnet 5.5, and Haiku 5.5](https://rewindex.com/change/r478a76f29dd22e.md) |  |

Next: [change](https://rewindex.com/change/r922de7a570d14f.md) · All Anthropic changes: [timeline](https://rewindex.com/company/anthropic/changes.md)
_Diff excerpts are shown on normalized text: dates, counters and tokens appear as ‹date›, ‹count›, ‹tok›; noise-only edits are hidden. Rewindex shows the changed passages, not a copy of the page._


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Canonical: https://rewindex.com/change/i735fd0dfe8e3ef · Markdown: https://rewindex.com/change/i735fd0dfe8e3ef.md · JSON: https://rewindex.com/api/v1/changes/i735fd0dfe8e3ef · Generated 2026-10-24T09:15:22.187Z