Three 2026 agent benchmarks: code, generalist, multi-environment SWE-bench code 2,294 GitHub issues, 12 Python repos agent gets: repo + issue text produces: patch FAIL_TO_PASS: now passes PASS_TO_PASS: stays passing Verified (OpenAI): 500 clean tasks removes ambiguity, weak tests, unclear fixes SWE-bench+: contamination audit 32.67% solution leakage; 31.08% weak tests GAIA generalist 466 questions, 300 private leaderboard simple for humans (92%) hard for AI (GPT-4+plugins: 15%) Level 1 single tool, simple factual lookup Level 2 multi-step reasoning search + extract + compute Level 3 long tool chain + multimodal images, PDFs, chained web navigation AgentBench multi-env 8 environments, ~4k-13k turns/split code: Bash, DB, KG games: Alfworld, LTP web: WebShop, Mind2Web open-ended generation what benchmarks do not measure operational cost: tokens, wall-clock, steps-to-resolution safety behavior under adversarial conditions (Lesson 27) performance on your domain (custom evals, Lesson 30) tail failures (benchmarks average; operators care about the worst 1%) always report both raw score AND Verified / +-audited score single-number leaderboard fixation is the #1 anti-pattern. report distributions.