Claude Fable 5.1
4 values about Claude Fable 5.1 from 1 document, in 3 metric families. In each family, values from its own document come first.
- Developer
- Anthropic
- Release date
- 1 Sep 2026The date of its first card in the dataset, the Claude Fable 5.1 & Claude Mythos 5.1 System Card.
- Availability
- Public
- Its own document
- Claude Fable 5.1 & Claude Mythos 5.1 System Card · 1 Sep 2026
- Also reported in
- No other document reports a value about it
Data as of 26 Sep 2026 · Dataset v0.1 · Methodology v0.1 · Changelog
Values by metric family
Each value as the document printed it. Select a value for its source, its checks and its history.
KeyVerifiedUnverifiedDisputedCorrected read off a figure or stated in wordsA value opens its source and history.
M7 · Harmful compliance and over-refusal 1 value
| Evaluation and metric | Value | Document |
|---|---|---|
| From its own documentClaude Fable 5.1 & Claude Mythos 5.1 System Card · 1 Sep 2026 | ||
| Multi-turn biological weaponsSafe response rateCondition: API | Claude Fable 5.1 & Claude Mythos 5.1 System Card1 Sep 2026 | |
M9 · Prompt injection 2 values
| Evaluation and metric | Value | Document |
|---|---|---|
| From its own documentClaude Fable 5.1 & Claude Mythos 5.1 System Card · 1 Sep 2026 | ||
| Browser use prompt injectionAttack success rate | Claude Fable 5.1 & Claude Mythos 5.1 System Card1 Sep 2026 | |
| Computer-use prompt injectionAttack success rate | Claude Fable 5.1 & Claude Mythos 5.1 System Card1 Sep 2026 | |
M10 · Dangerous capabilities and risk determinations 1 value
| Evaluation and metric | Value | Document |
|---|---|---|
| From its own documentClaude Fable 5.1 & Claude Mythos 5.1 System Card · 1 Sep 2026 | ||
| RSP determinationsCB / autonomy / cyber | Claude Fable 5.1 & Claude Mythos 5.1 System Card1 Sep 2026 | |
Risk determinations
The developer's formal decisions about Claude Fable 5.1 under its framework, as printed. Levels from different frameworks do not map onto one another.
| Domain | Level as printed | Framework and document |
|---|---|---|
| Bio/chem | CB-1 yes Responsible Scaling Policy Claude Fable 5.1 & Claude Mythos 5.1 System Card · 1 Sep 2026 | Responsible Scaling Policy Claude Fable 5.1 & Claude Mythos 5.1 System Card · 1 Sep 2026 |
| Bio/chem | CB-2 no Responsible Scaling Policy Claude Fable 5.1 & Claude Mythos 5.1 System Card · 1 Sep 2026 | Responsible Scaling Policy Claude Fable 5.1 & Claude Mythos 5.1 System Card · 1 Sep 2026 |
| Cyber | cyber Tier 1 Responsible Scaling Policy Claude Fable 5.1 & Claude Mythos 5.1 System Card · 1 Sep 2026 | Responsible Scaling Policy Claude Fable 5.1 & Claude Mythos 5.1 System Card · 1 Sep 2026 |
| AI R&D / autonomy | TM2 N/A Responsible Scaling Policy Claude Fable 5.1 & Claude Mythos 5.1 System Card · 1 Sep 2026 | Responsible Scaling Policy Claude Fable 5.1 & Claude Mythos 5.1 System Card · 1 Sep 2026 |