Lying about identity (Anthropic)
Models play an operator-assigned human persona while users ask if they are human. Score is the rate of admitting to being an AI.
In-house Anthropic evaluation. The Fable 5 card adds a harder set with indirect user probes.
- Made by
- Anthropic
- Kind
- Deception and alignment
- Level
- Everyday
- Scored
- Graded by a model
- Answers
- Open-ended
- Tasks
- Kept private
- Strongest model tested
- Claude Fable 5 #11 on the capability index
- Last in a system card
- June 2026
- Last model added
- June 2026
Claude Fable 5 leads with 99%
Best score per model as labs report them in their own cards. Labs pick their own settings, so these compare less cleanly than independent runs.
Source: Labs’ model cards
| # | Model | Score | Setting | Date | Source |
|---|---|---|---|---|---|
| 1 | Claude Fable 5 | 99% | Jun 2026 | Lab model card | |
| 2 | Claude Opus 4.8 | 97% | May 2026 | Lab model card |
Anthropic’s own number for Claude Opus 4.8 passed 85% in May 2026
All the scores we have, one dot each, so a model tested at several settings appears more than once.
Source: Labs’ model cards
Labs report it only in system cards
We read the headline results of 522 launch posts from 52 labs, and none of them list this benchmark. Some system cards do, below.
2 system cards report it, from 1 lab
Besides launch posts, we read the system cards, model cards and technical reports labs publish with a release. They report far more, including safety and frontier-risk tests.
| Date | Document | Score | As the document writes it | Section |
|---|---|---|---|---|
| Jun 9, 2026 | Claude Fable 5 system card | 99 | Lying about identity, rate of acknowledging being an AI under an operator-assigned human persona, standard scenario set, Fable 5 truthful in 99% of cases; new harder set with indirect probes 59% (6.3.3.5, Figures 6.3.3.5.A and 6.3.3.5.B) | Alignment |
| May 28, 2026 | Claude Opus 4.8 system card | 97 | Lying about being human, rate of acknowledging being an AI under an operator-assigned human persona (6.3.3.5, Figure 6.3.3.5.A) | Alignment |
More in Safety and alignment
- FORTRESS In use Paired adversarial and benign national-security misuse prompts. Rubric-graded risk score on adversarial and over-refusal score on benign prompts. Claude Opus 5.5 5.78%
- StrongREJECT In use Forbidden-prompt jailbreak benchmark with a rubric grader that scores how useful a non-refusal actually is.
Inkling 98.6% - Gray Swan IPI Arena benchmark In use Indirect prompt-injection attacks from public red-teaming competitions replayed on tool, coding and browser agents. Attack success rate at k attempts.
Gemini 4 Carbon 0% - DistressBench In use Models reply as a chatbot to 718 simulated users in psychological crisis, in single-turn and multi-turn chats. Three judge models score replies against clinician-written rubrics.
Muse Spark 1.2 88.4% - Lakera B3 (Backbone Breaker Benchmark) In use Crowdsourced prompt-injection attacks hit backbone LLMs inside agent threat snapshots at three defense levels. The score is attack resistance, 100 minus the board's vulnerability percentage. Claude Opus 4.5 89%
- IHEval In use Models face conflicts between system, user and tool instructions. Reports a composite score for following the higher-priority instruction. GPT-4o 70%