Sample tasks · October 2026

Three tasks that frontier models fail.

One coding task, one ML-numerics task, one hardware task. Each has a Docker environment, a deterministic grader with a hidden answer key, and a reference solution that scores 1. We ran Opus 5.5, Opus 5.0, Fable 5.1 and Muse Wonder against them for two hours each. Every run scored 0, and the same items failed across models.

Results

Every run, one line each.

Each task is graded all-or-nothing over its hidden items. "Wrong" is the number of items the grader rejected. Full per-run logs ship with the tasks.

TaskModelRunsOutcome
never-learned-replies310 hidden plansOpus 5.53fail · 4, 20 and 12 / 310 wrong
Opus 5.01fail · 16 / 310 wrong
Fable 5.12fail · hit the 2 h limit, 57 and 125 / 310 wrong
attention-mask-fill-signoff40 deploymentsOpus 5.52fail · 10 / 40 wrong, both runs
Opus 5.01fail · 10 / 40 wrong
Muse Wonder1fail · 10 / 40 wrong
Muse Wonder Full1fail · 12 / 40 wrong
ram-boot-image256 hidden queriesOpus 5.52fail · 38 and 9 / 256 wrong
Fable 5.12fail · 9 and 38 / 256 wrong

Setup for every run: the task's own container with the agent added, the prompt as the only instruction, no network except the model's API, 2 hours of agent time. Tasks are in Terminal-Bench / Harbor format.

The tasks

Real codebases, exact answers, nothing to pattern-match.

never-learned-replies

Coding / ML infra. A nightly fine-tuning job trains on an endless chat log. From the sources of TRL, transformers and tokenizers alone (not installed, not runnable), decide which replies some schedule can never learn. Exact integers and fractions over 310 held-out plans.

  • Opus 5.5 gets the systems part right and breaks on the worst-case density questions
  • Fable 5.1 does not finish in 2 hours

attention-mask-fill-signoff

ML numerics. For 40 CPU transformer deployments, give the exact interval of additive-mask fill values that keeps every output finite and the leak within tolerance, from what the pinned PyTorch kernels actually compute in fp16 and bf16.

  • The same 10 deployments fail in all five runs across four models
  • Models reason from the maths of attention, not from the kernel

ram-boot-image

Hardware / EDA. From the Yosys 0.70 source alone (no synthesis tool, no compiler), predict for RAMs and ROMs coded in many Verilog styles which cells four FPGA flows create and the exact INIT contents of each. 256 hidden queries, hash-verified.

  • The same 9 queries fail in all four runs across two models
  • Every run kept a read port the real tool removes
Grader output

What a failed run looks like.

Excerpts from the grader logs, as shipped. Expected values are hidden here. The tasks come with the full logs and the model's deliverable for every run.

never-learned-replies · opus-5.5 · run1 · verifier.log
hidden data verified (310 plans) in 0.6 s
driver ready (9 package files)
plan p023 (density): FAIL wrong answer (expected [hidden], got q186085086086086076086/77777777777777777)
plan p037 (density): FAIL wrong answer (expected [hidden], got q158730/1111111)
plan p167 (density): FAIL wrong answer (expected [hidden], got q461760033189/11111111111111)
...
  first_risk: 70 plans, 0 failed
  risk_count: 80 plans, 0 failed
  count:      80 plans, 0 failed
  density:    80 plans, 4 failed
reward: 0
ram-boot-image · opus-5.5 · run2 · verifier_clean.log
FAIL xc7023:   wrong class: got FF, expected [hidden]
FAIL xc7030:   wrong class: got FF, expected [hidden]
FAIL xc7035:   wrong cells, class, init: got FF/0 cells, expected [hidden]
FAIL ice40013: wrong class: got FF, expected [hidden]
FAIL ice40047: wrong class: got FF, expected [hidden]
...
  xc7   items 64, failed 3
  ice40 items 64, failed 3
  ecp5  items 64, failed 2
  gw1n  items 64, failed 1
items 256, failed 9; 5.1 s
reward: 0
Why it holds up

Built so the only way to score is to be right.

Pinned inputs

Base image by digest, every source and wheel by SHA-256. The answer is a function of fixed bytes, and the reference solution derives it from those bytes alone.

Sealed grader

The grader never enters the image. It runs on a hash-checked runtime, and the agent's code runs as an unprivileged child. Package changes or tampering cannot change the grade.

No shortcut

The library or tool that decides the answer is not installed and cannot be built. No network. Guessing, bounding or conservative answers fail.

Calibrated for training

These three are tuned as frontier-breaking evals. For training we deliver tasks inside a target pass-rate band, measured on the model you choose, with per-item or dense reward if you prefer.

Get the three tasks.

We send the full package by private link: Docker environments, graders with answer keys, reference solutions, and every model run with its grader log and deliverable. One email with your name and lab is enough. We can also build one task to your spec as a trial.

Format
Terminal-Bench / Harbor, or NeMo Gym on request