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
09The Guest List liveThree tables and a count. The constraints you forget are the bugs in production.intermediate31%·
09The 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%
12Date-Range Picker + Timezones preview“Looks fine” until DST and a viewer in another timezone.intermediate··
12Date-Range Picker + Timezones preview
“Looks fine” until DST and a viewer in another timezone.intermediate··
17Multi-Step Form Wizard previewFour steps, a Back button, and a browser that fights you.warmup··
17Multi-Step Form Wizard preview
Four steps, a Back button, and a browser that fights you.warmup··
18Notification Center previewA bell with an unread count that never drifts.intermediate··
18Notification Center preview
A bell with an unread count that never drifts.intermediate··
back nine · graded holes14
08Harden the Gauntlet liveThe service runs fine on day one. The attack corpus decides if it survives day two.expert27%·
08Harden the Gauntlet live
The service runs fine on day one. The attack corpus decides if it survives day two.expert·27%
10Seal the Vault liveAnyone can encrypt a string. The attacks decide whether you actually protected it.expert12%·
10Seal the Vault live
Anyone can encrypt a string. The attacks decide whether you actually protected it.expert·12%
02Rate Limiter liveA limit per client and one method. Who counts as the same client is the whole game.expert16%·
02Rate Limiter live
A limit per client and one method. Who counts as the same client is the whole game.expert·16%
03Interest Accrual livePrincipal, a rate, two dates, one number. How you count the days between them is the whole game.expert14%·
03Interest Accrual live
Principal, a rate, two dates, one number. How you count the days between them is the whole game.expert·14%
04Money-Market Yield liveA principal, a rate, two dates, one number. The size of the year you divide by is the whole game.expert14%·
04Money-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%
05European Day Count liveTwo dates, one integer count of days. What you do with a date on the 31st is the whole game.expert14%·
05European 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%
06Settlement Date liveA trade date and an offset, one settlement date out. The days you are allowed to skip are the whole game.expert14%·
06Settlement 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%
16Auth Form + Rate Limits liveA sign-in that knows when two emails are one account — and locks the account, not the string.expert19%·
16Auth Form + Rate Limits live
A sign-in that knows when two emails are one account — and locks the account, not the string.expert·19%
07Fixed-Block Pool Allocator liveThree functions in C. The memory you forget to give back is the whole game.expert33%·
07Fixed-Block Pool Allocator live
Three functions in C. The memory you forget to give back is the whole game.expert·33%
11Team Invites + Role Management previewSaaS settings workflow with hidden lifecycle and permission traps.expert··
11Team Invites + Role Management preview
SaaS settings workflow with hidden lifecycle and permission traps.expert··
15Infinite Feed + Optimistic Writes previewEndless scroll that doesn’t duplicate, jump, or lie.expert··
15Infinite Feed + Optimistic Writes preview
Endless scroll that doesn’t duplicate, jump, or lie.expert··
19Search with Filters + URL State previewShareable, back-button-correct, race-free search.expert··
19Search with Filters + URL State preview
Shareable, back-button-correct, race-free search.expert··
14CSV Import + Schema Drift previewReal spreadsheets are dirtier than your parser thinks.expert··
14CSV Import + Schema Drift preview
Real spreadsheets are dirtier than your parser thinks.expert··
13Realtime Cursor Presence previewMultiplayer cursors that don’t turn into ghosts.expert··
13Realtime 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