Benchmark Almanac

Destructive production evaluation (Anthropic)

Claude Mythos Preview 0.30% Only in system cards

Agents finish a task in a simulated production system under time pressure. Scored on destructive actions and on giving up too early.

In-house Anthropic evaluation. Claude Opus 4.6 simulates the tool results.

Made by Anthropic Deception and alignment Tasks kept private Last in a system card Apr 2026 Last model added Apr 2026
Level
Expert Specialists with years of training, often over hours of work
Scored
Graded by a model A language model scores each response, usually against a rubric.
Answers
Agent task Many steps in a terminal, browser, desktop, app, game or robot.
2
Models scored in lab cards
2
System cards report it, from 1 lab

Claude Mythos Preview leads with 0.30%

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.

  1. 1 Claude Mythos Preview 0.30%
  2. 2 Claude Opus 4.7 2.50%
#ModelScoreSettingDateSource
1 Claude Mythos Preview 0.30% Apr 2026 Model card
2 Claude Opus 4.7 2.50% Apr 2026 Model card

Scores over time

All the scores we have, one dot each, so a model tested at several settings appears more than once.

Reported by the lab in its model card
0% 20% 40% 60% 80% 100% 2026 Claude Mythos Preview 0% 20% 40% 60% 80% 100% 2026 Claude Mythos Preview

Labs report it only in system cards

We read the headline results of 479 launch posts from 51 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.

DateDocumentScoreAs the document writes itSection
16 Apr 2026 Claude Opus 4.7 system card 2.5 Destructive Production Eval (synthetic backend), destructive action rate, printed on chart, lower is better. Ineffective (over-refusal) 1.1%. Verbalized evaluation awareness in about 9% of transcripts (6.3.1.1, Figure 6.3.1.1.A) Alignment
7 Apr 2026 Claude Mythos Preview system card 0.3 Destructive Actions in (simulated) Production, dedicated synthetic-backend evaluation, destructive action rate, lower is better, stated in text; ineffective an additional 0.5 (4.3.1.1, Figure 4.3.1.1.A) Alignment

More in Safety and alignment

All 444 in Safety and alignment
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  • StrongREJECT In use Forbidden-prompt jailbreak benchmark with a rubric grader that scores how useful a non-refusal actually is. Inkling 98.6%
  • AgentDojo In use Agents do tool-use tasks while tools and data carry prompt injections. Attack success rate counts hijacked runs. Grok 4 Fast 0%
  • MASK In use Measures whether a model contradicts its own elicited beliefs under pressure to lie. Honesty separated from accuracy. Muse Spark Open 98.1%
  • 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. GPT-6 Astra 8.50%
  • Agentic misalignment suite (Anthropic) In use Agents in simulated company settings face threats or goal conflicts that invite blackmail, leaking or sabotage. Score is the misaligned action rate. Claude Sonnet 4.5 0%