Benchmark Almanac

Gray Swan Agent Red Teaming (ART) benchmark

Claude Mythos Preview 0.10% leads since April 2026
Claude 3.7 Sonnet 1.47% leads since July 2025
Claude Mythos Preview 0.10% leads since April 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.

Released
July 2025
Kind
Jailbreaks and prompt injection
Level
Expert
Scored
Graded by a model
Answers
Agent task
Tasks
Kept private
Strongest model tested
Claude Fable 5 #11 on the capability index
Last in a system card
October 2026
Last model added
October 2026
Scores refreshed
November 12th, 2026

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)
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 September 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.

Claude 3.7 Sonnet leads with 1.47% across all independent runs

Best score per model across the official leaderboard, Epoch AI’s own runs and any board Epoch AI copied. Each bar and row names its source.

Claude Mythos Preview leads with 0.10%, claims included

Best score per model from every source, including labs’ own numbers and claims Epoch AI collected from reports and papers. Labs pick their own settings, so a claim can beat an independent run of the same model.

The newest model with a score here came out in September 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%

Source: Labs’ model cards

Source: Official Gray Swan Agent Red Teaming (ART) benchmark leaderboard

Sources: Labs’ model cards and official Gray Swan Agent Red Teaming (ART) benchmark leaderboard

#ModelScoreSettingDateSource
1 Claude Mythos Preview 0.10% Apr 2026 Lab model card
2 Claude Opus 4.7 0.10% Apr 2026 Lab model card
3 Claude Opus 4.8 0.10% May 2026 Lab model card
4 Claude Fable 5 0.10% Jun 2026 Lab model card
5 Claude Sonnet 5 0.10% Jun 2026 Lab model card
6 Claude Opus 4.6 0.20% Feb 2026 Lab model card
7 Muse Spark 1.1 0.30% Jul 2026 Lab model card
8 Claude Sonnet 4.6 2.20% Feb 2026 Lab model card
9 Claude Opus 4.5 4.70% Nov 2025 Lab model card
10 Muse Spark 1.3 4.80% Oct 2026 Lab model card
11 Muse Spark 6.70% Jun 2026 Lab model card
12 Claude Sonnet 4.5 40% Sep 2025 Lab model card
13 Claude Haiku 4.5 51.1% Oct 2025 Lab model card
14 GPT-5 56.8% Aug 2025 Lab model card
#ModelScoreSettingDateSource
1 Claude 3.7 Sonnet 1.47% thinking; Polaris Feb 2025 Official leaderboard
2 Claude 3.5 Haiku 2.44% Algol Oct 2024 Official leaderboard
3 o3 2.50% Draco Apr 2025 Official leaderboard
4 o1 2.56% Canopus Dec 2024 Official leaderboard
5 GPT-4.5 2.58% Vega Feb 2025 Official leaderboard
6 c4ai-command-r-08-2024 3.72% Procyon Aug 2024 Official leaderboard
7 o3-mini 4.23% Regulus Jan 2025 Official leaderboard
8 Llama 3.3 70B Instruct 6.49% Capella Dec 2024 Official leaderboard
#ModelScoreSettingDateSource
1 Claude Mythos Preview 0.10% Apr 2026 Lab model card
2 Claude Opus 4.7 0.10% Apr 2026 Lab model card
3 Claude Opus 4.8 0.10% May 2026 Lab model card
4 Claude Fable 5 0.10% Jun 2026 Lab model card
5 Claude Sonnet 5 0.10% Jun 2026 Lab model card
6 Claude Opus 4.6 0.20% Feb 2026 Lab model card
7 Muse Spark 1.1 0.30% Jul 2026 Lab model card
8 Claude 3.7 Sonnet 1.47% thinking; Polaris Feb 2025 Official leaderboard
9 Claude Sonnet 4.6 2.20% Feb 2026 Lab model card
10 Claude 3.5 Haiku 2.44% Algol Oct 2024 Official leaderboard
11 o3 2.50% Draco Apr 2025 Official leaderboard
12 o1 2.56% Canopus Dec 2024 Official leaderboard
13 GPT-4.5 2.58% Vega Feb 2025 Official leaderboard
14 c4ai-command-r-08-2024 3.72% Procyon Aug 2024 Official leaderboard
15 o3-mini 4.23% Regulus Jan 2025 Official leaderboard
16 Claude Opus 4.5 4.70% Nov 2025 Lab model card
17 Muse Spark 1.3 4.80% Oct 2026 Lab model card
18 Llama 3.3 70B Instruct 6.49% Capella Dec 2024 Official leaderboard
19 Muse Spark 6.70% Jun 2026 Lab model card
20 Claude Sonnet 4.5 40% Sep 2025 Lab model card
21 Claude Haiku 4.5 51.1% Oct 2025 Lab model card
22 GPT-5 56.8% Aug 2025 Lab model card

The benchmark's own leaderboard has 20 entries, 8 of them models we track. Switch the scores above to rank them together.

5 models have held number one in labs’ own numbers since its release in July 2025 Number one over time 3 models have held number one with claims included since its release in July 2025

Lab claims count from the day the card came out, independent runs from the model’s release. We draw one row each for the benchmark’s own leaderboard and what labs claim in their cards.

Anthropic OpenAI
Own leaderboard Not tested since Jul 2025
Lab claims 5 leaders

Sources: Official Gray Swan Agent Red Teaming (ART) benchmark leaderboard and labs’ model cards

Scores over time

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

On the benchmark’s own leaderboard Reported by the lab in its model card Best so far
0% 20% 40% 60% 80% 100% 2025 2026 2027 Claude Mythos Preview Claude 3.7 Sonnet c4ai-command-r-08-2024 0% 20% 40% 60% 80% 100% 2025 2026 2027 Claude Mythos Preview Claude 3.5 Haiku

Sources: Official Gray Swan Agent Red Teaming (ART) benchmark leaderboard and 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.

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
Oct 23, 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
Jul 9, 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
Jun 30, 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
Jun 12, 2026 Muse Spark system card 6.7 GraySwan ART pass@1 ASR (Table 2, Figure 37) Robustness
Jun 9, 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
May 28, 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
Apr 16, 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
Apr 7, 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
Feb 17, 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
Feb 5, 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
Nov 24, 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
Oct 15, 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
Sep 29, 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
Aug 7, 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

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  • 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%