The course
Every brief looks easy. That’s how you ship bugs.
Write the spec; the agent builds it; the hidden tests grade what you shipped. Each hole is a normal-looking public brief whose hidden tests grade the messy reality a serious spec encodes: cents math, race conditions, the empty state nobody specs. Fewer prompts, lower score.
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HoleChallengeDifficultyAcceptanceYour best
front nine · warmups5
15The Guest List liveThree tables and a count. The constraints you forget are the bugs in production.intermediate31%·
15The Guest List live
Three tables and a count. The constraints you forget are the bugs in production.intermediate·31%
01Mini Checkout + Promo Code Engine liveA familiar checkout brief where vague specs collapse under ecommerce edge cases.intermediate38%·
01Mini Checkout + Promo Code Engine live
A familiar checkout brief where vague specs collapse under ecommerce edge cases.intermediate·38%
18Date-Range Picker + Timezones preview“Looks fine” until DST and a viewer in another timezone.intermediate··
18Date-Range Picker + Timezones preview
“Looks fine” until DST and a viewer in another timezone.intermediate··
23Multi-Step Form Wizard previewFour steps, a Back button, and a browser that fights you.warmup··
23Multi-Step Form Wizard preview
Four steps, a Back button, and a browser that fights you.warmup··
24Notification Center previewA bell with an unread count that never drifts.intermediate··
24Notification Center preview
A bell with an unread count that never drifts.intermediate··
back nine · graded holes20
04Charge Processor liveA processor, one method, a request key. What happens when the same request arrives twice is the whole game.expert13%·
04Charge Processor live
A processor, one method, a request key. What happens when the same request arrives twice is the whole game.expert·13%
05Buried Answers liveA search function, a pile of docs, a question. Whether it surfaces the real answer is the whole game.expert15%·
05Buried Answers live
A search function, a pile of docs, a question. Whether it surfaces the real answer is the whole game.expert·15%
14Harden the Gauntlet liveThe service runs fine on day one. The attack corpus decides if it survives day two.expert27%·
14Harden the Gauntlet live
The service runs fine on day one. The attack corpus decides if it survives day two.expert·27%
16Seal the Vault liveAnyone can encrypt a string. The attacks decide whether you actually protected it.expert12%·
16Seal the Vault live
Anyone can encrypt a string. The attacks decide whether you actually protected it.expert·12%
03Rate Limiter liveA limit per client and one method. Who counts as the same client is the whole game.expert16%·
03Rate Limiter live
A limit per client and one method. Who counts as the same client is the whole game.expert·16%
06Interest Accrual livePrincipal, a rate, two dates, one number. How you count the days between them is the whole game.expert14%·
06Interest Accrual live
Principal, a rate, two dates, one number. How you count the days between them is the whole game.expert·14%
07Money-Market Yield liveA principal, a rate, two dates, one number. The size of the year you divide by is the whole game.expert14%·
07Money-Market Yield live
A principal, a rate, two dates, one number. The size of the year you divide by is the whole game.expert·14%
08European Day Count liveTwo dates, one integer count of days. What you do with a date on the 31st is the whole game.expert14%·
08European Day Count live
Two dates, one integer count of days. What you do with a date on the 31st is the whole game.expert·14%
09Settlement Date liveA trade date and an offset, one settlement date out. The days you are allowed to skip are the whole game.expert14%·
09Settlement Date live
A trade date and an offset, one settlement date out. The days you are allowed to skip are the whole game.expert·14%
10Future Value liveA principal, a rate, a horizon, one number. How often the rate compounds is the whole game.expert14%·
10Future Value live
A principal, a rate, a horizon, one number. How often the rate compounds is the whole game.expert·14%
11Present Value liveA future cashflow, a rate, a horizon, one number. How often you compound the discount is the whole game.expert14%·
11Present Value live
A future cashflow, a rate, a horizon, one number. How often you compound the discount is the whole game.expert·14%
12Year Fraction liveTwo dates, one fraction of a year. The year you divide by, when a leap year is involved, is the whole game.expert14%·
12Year Fraction live
Two dates, one fraction of a year. The year you divide by, when a leap year is involved, is the whole game.expert·14%
22Auth Form + Rate Limits liveA sign-in that knows when two emails are one account — and locks the account, not the string.expert19%·
22Auth Form + Rate Limits live
A sign-in that knows when two emails are one account — and locks the account, not the string.expert·19%
13Fixed-Block Pool Allocator livefrontierThree functions in C. The memory you forget to give back is the whole game.expert33%·
13Fixed-Block Pool Allocator livefrontier
Three functions in C. The memory you forget to give back is the whole game.expert·33%
02Full-Stack Checkout livefrontierThe same checkout brief, except the agent builds a real multi-file app and the money logic lives on the server.expert··
02Full-Stack Checkout livefrontier
The same checkout brief, except the agent builds a real multi-file app and the money logic lives on the server.expert··
17Team Invites + Role Management previewSaaS settings workflow with hidden lifecycle and permission traps.expert··
17Team Invites + Role Management preview
SaaS settings workflow with hidden lifecycle and permission traps.expert··
21Infinite Feed + Optimistic Writes previewEndless scroll that doesn’t duplicate, jump, or lie.expert··
21Infinite Feed + Optimistic Writes preview
Endless scroll that doesn’t duplicate, jump, or lie.expert··
25Search with Filters + URL State previewShareable, back-button-correct, race-free search.expert··
25Search with Filters + URL State preview
Shareable, back-button-correct, race-free search.expert··
20CSV Import + Schema Drift previewReal spreadsheets are dirtier than your parser thinks.expert··
20CSV Import + Schema Drift preview
Real spreadsheets are dirtier than your parser thinks.expert··
19Realtime Cursor Presence previewMultiplayer cursors that don’t turn into ghosts.expert··
19Realtime Cursor Presence preview
Multiplayer cursors that don’t turn into ghosts.expert··
your best is graded out of 100 (functional + hidden + style) · x/y hidden = hidden tests passed · the to-par chip is golf flavor for dropped hidden tests · acceptance = share of specs that clear the hole
Flagship arenas
Bigger games than a single spec.
These put you in a loop instead of grading one prompt: route a team of agents to ship a task, tune a retrieval pipeline until it surfaces buried answers, or build the evaluator that catches a model’s mistakes.
intermediate live
Day One
A checkout that's quietly wrong. Find the store's hidden rules by running it.
expert live
The Shift
Don't write the checkout. Direct a team of agents to ship it right.
expert live
The Closer
Every other hole grades your spec. This one grades how you drive the build.
expert live
The Conductor
Don't fix one build. Author one orchestration that survives a world it never saw.
expert live
The Relay
Two domains, one number. Route the symptom to the station that owns it.
expert live
The Stacks
Build the retrieval, not the answer. Tune a search pipeline until it finds what's buried.
expert live
Build the Eval
You don't fix the AI. You build the eval that catches when it's wrong.