Benchmark Almanac

Gray Swan Agent Red Teaming (ART) benchmark

Claude Mythos Preview 0.10% leads since Apr 2026 Only in system cards

Agents face curated prompt injections from a large public red-teaming competition across 44 deployment scenarios. Score is attack success rate.

Gray Swan ran it for OpenAI with attacks from its Shade platform. Gray Swan keeps the attack set private. It has a user-side (direct) subset and an environment-side (indirect) subset. Reported as pass@k ASR, the share of targets broken by at least one of k sampled attacks.

In the authors’ words

Recent advances have enabled LLM-powered AI agents to autonomously execute complex tasks by combining language model reasoning with tools, memory, and web access. But can these systems be trusted to follow deployment policies in realistic environments, especially under attack? To investigate, we ran the largest public red-teaming competition to date, targeting 22 frontier AI agents across 44 realistic deployment scenarios. Participants submitted 1.8 million prompt-injection attacks, with over 60,000 successfully eliciting policy violations such as unauthorized data access, illicit financial actions, and regulatory noncompliance. We use these results to build the Agent Red Teaming (ART) benchmark - a curated set of high-impact attacks - and evaluate it across 19 state-of-the-art models. Nearly all agents exhibit policy violations for most behaviors within 10-100 queries, with high attack transferability across models and tasks. Importantly, we find limited correlation between agent robustness and model size, capability, or inference-time compute, suggesting that additional defenses are needed against adversarial misuse. Our findings highlight critical and persistent vulnerabilities in today's AI agents. By releasing the ART benchmark and accompanying evaluation framework, we aim to support more rigorous security assessment and drive progress toward safer agent deployment.

Abstract of Security Challenges in AI Agent Deployment: Insights from a Large Scale Public Competition (arXiv:2507.20526, CC0)
Made by Gray Swan + UK AI Security Institute Released Jul 2025 Jailbreaks and prompt injection Tasks kept private Last in a system card Oct 2026 Last model added Oct 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.
14
Models scored in lab cards
14
System cards report it, from 3 labs

5 models share the top score of 0.10% among models released by Sep 2026

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.

The newest model with a score here came out in Sep 2026, and nobody has reported a newer one. Among the 20 highest-ranked models on the capability index, these have no score yet:

  1. 1 Claude Mythos Preview 0.10%
  2. 2 Claude Opus 4.7 0.10%
  3. 3 Claude Opus 4.8 0.10%
  4. 4 Claude Fable 5 0.10%
  5. 5 Claude Sonnet 5 0.10%
  6. 6 Claude Opus 4.6 0.20%
  7. 7 Muse Spark 1.1 0.30%
  8. 8 Claude Sonnet 4.6 2.20%
  9. 9 Claude Opus 4.5 4.70%
  10. 10 Muse Spark 1.3 4.80%
  11. 11 Muse Spark 6.70%
  12. 12 Claude Sonnet 4.5 40%
  13. 13 Claude Haiku 4.5 51.1%
  14. 14 GPT-5 56.8%
#ModelScoreSettingDateSource
1 Claude Mythos Preview 0.10% Apr 2026 Model card
2 Claude Opus 4.7 0.10% Apr 2026 Model card
3 Claude Opus 4.8 0.10% May 2026 Model card
4 Claude Fable 5 0.10% Jun 2026 Model card
5 Claude Sonnet 5 0.10% Jun 2026 Model card
6 Claude Opus 4.6 0.20% Feb 2026 Model card
7 Muse Spark 1.1 0.30% Jul 2026 Model card
8 Claude Sonnet 4.6 2.20% Feb 2026 Model card
9 Claude Opus 4.5 4.70% Nov 2025 Model card
10 Muse Spark 1.3 4.80% Oct 2026 Model card
11 Muse Spark 6.70% Jun 2026 Model card
12 Claude Sonnet 4.5 40% Sep 2025 Model card
13 Claude Haiku 4.5 51.1% Oct 2025 Model card
14 GPT-5 56.8% Aug 2025 Model card

5 models have held number one since its release in Jul 2025

Lab claims count from the day the card came out, independent runs from the model’s release.

OpenAI Anthropic
Lab claims 5 leaders

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 Best so far
0% 20% 40% 60% 80% 100% 2026 2027 Claude Mythos Preview Claude Opus 4.5 Claude Sonnet 4.5 GPT-5 0% 20% 40% 60% 80% 100% 2026 2027 Claude Mythos Preview Claude Sonnet 4.5

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.

14 system cards report it, from 3 labs

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
23 Oct 2026 Muse Spark 1.3 system card 4.8 Gray Swan ART indirect ASR@100, Muse Spark 1.3 (API) (Table 2, Figure 30) Robustness
9 Jul 2026 Muse Spark 1.1 system card 0.3 GraySwan ART pass@1 ASR (Table 2, Figure 31). pass@10 3.2, pass@100 23.8 Robustness
30 Jun 2026 Claude Sonnet 5 system card 0.1 Gray Swan ART benchmark, attack success rate at k=1 with thinking, 19 scenarios, lower is better (k=10 1.3%, k=100 9.9%. Without thinking 0.2%, 1.6%, 12.0%) (5.2.1, Figure 5.2.1.A) Robustness
12 Jun 2026 Muse Spark system card 6.7 GraySwan ART pass@1 ASR (Table 2, Figure 37) Robustness
9 Jun 2026 Claude Fable 5 system card 0.1 Gray Swan Agent Red Teaming (ART), indirect prompt injection, attack success rate at k=1, extended thinking, row labeled Mythos 5 (Fable 5 shares the core model and inherits these gains per 5.2); k=10 0.5%, k=100 4.8%, printed on chart, lower is better (Figure 5.2.1.A) Robustness
28 May 2026 Claude Opus 4.8 system card 0.1 Gray Swan Agent Red Teaming (ART) benchmark, indirect prompt injection on 19 scenarios, attack success rate at k=1 with extended thinking (k=10 1.4%, k=100 9.6%. Without thinking 0.2%, 1.9%, 14.4%), printed on chart, lower is better (5.2.1, Figure 5.2.1.A) Robustness
16 Apr 2026 Claude Opus 4.7 system card 0.1 Gray Swan ART indirect prompt injection, attack success at k=1, 19 scenarios, 0.1 with and without thinking, printed on chart. k=10 0.5 and 0.6, k=100 4.8 and 6.0 (text assigns 6.0 to no thinking and 4.8 to adaptive thinking, chart labels the reverse) (5.2.1, Figure 5.2.1.A) Robustness
7 Apr 2026 Claude Mythos Preview system card 0.1 Gray Swan ART indirect prompt injection, attack success at k=1, thinking, lower is better, values printed on chart; k=10 0.6, k=100 6.1. Without thinking 0.1, 0.5, 4.8 (Figure 8.3.2.1.A) Robustness
17 Feb 2026 Claude Sonnet 4.6 system card 2.2 Gray Swan ART indirect prompt injection, attack success at k=10, thinking; k=100 15.94, k=1 not printed (Figure 5.2.1.A) Robustness
5 Feb 2026 Claude Opus 4.6 system card 0.2 Gray Swan Agent Red Teaming, indirect prompt injection only, attack success rate k=1, extended thinking, lower is better, value printed on chart; k=10 2.2, k=100 21.7; without thinking 0.2, 2.1 and 14.8 (Figure 5.2.1.A) Robustness
24 Nov 2025 Claude Opus 4.5 system card 4.7 Gray Swan Agent Red Teaming, direct and indirect prompt injection plus jailbreaks, attack success rate k=1, extended thinking, lower is better (Figure 5.2.1.B; k=10 33.6%, k=100 63.0%; indirect only k=1 0.3%, k=100 25.0% in Figure 5.2.1.A) Robustness
15 Oct 2025 Claude Haiku 4.5 system card 51.1 Gray Swan ART attack success rate at k=10, Haiku 4.5 Thinking; 58.4 without thinking, k=1 not printed (Figure 3.2.1.A) Robustness
29 Sep 2025 Claude Sonnet 4.5 system card 40 Gray Swan Agent Red Teaming (ART), attack success rate at k=10, Sonnet 4.5 Thinking, lower is better. 53.6 without thinking. k=1 not printed (Figure 4.2.1.A) Robustness
7 Aug 2025 GPT-5 system card 56.8 Agent Red Teaming (ART) benchmark, behavior attack success rate at k=10 queries, printed chart label (Figure 8, 4.2) Robustness

More in Safety and alignment

All 444 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%
  • 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%