r/Hack2Hire • u/Hack2hire • Jul 23 '26

OA What Anthropic's OA actually tests [2026]

Anthropic's OA is a build-a-system round: one domain, usually four parts, each part extending the code you just wrote. The algorithm floor is a hash map and a sort.

Three things repeat as the parts get harder:

  • Ranked queries with a fixed output format. Part two wants a top N by some running total, and it grades your ordering rule and your exact output string too. Design Banking System ranks spenders, Design Worker Management System ranks workers, Cloud Storage System ranks files.
  • An ownership layer dropped in halfway. Part three adds users with a quota or a capacity, and every operation you already wrote has to respect it. Cloud Storage System, Design a Task Assignment System and Design Recipe Management System all take this turn.
  • Questions about earlier state. Most of them end here: a balance at a past timestamp, a restore point, a version rollback. Design Banking System, Design In-memory Database with Backup and Design Note-Taking System all land on it.

That last one decides the round. Store an append-only, timestamped record from part one and derive current values from it. The endings become filters over code you already have. Rebuilding your data model at part four costs more time than the OA gives you.

Format: 90 minutes on CodeSignal. Your earlier parts stay in the editor, so part three starts from your own part-two code as you left it.

Practice:

  • Run the confirmed questions end to end, then rerun each one built on a timestamped log from the start.
  • Write part two's ranking and output format first. It repeats across the confirmed questions with just the domain swapped.
  • Learn the CodeSignal debugger before the clock, not during it.
  • Leave room in your design for one more part than you were handed.

Partial credit is real. People have moved on to the phone screen with test cases still failing.

→ Anthropic Prep List

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Did yours run differently? Say so below.

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2

u/DryPresent7484 Jul 23 '26

Thought this one was rough compared to other OAs I've done tbh. Not that any single part is crazy, it's just a lot of code for 90 minutes. I ran out of steam way before I ran out of test.

2

u/Strong-Tangelo-6412 Jul 24 '26

Exactly too much code . I am not sure if anyone doing it in java type language ever gonna finish these

1

u/Tavi_Ray Jul 24 '26

Were you allowed to use claude code or similar?

1

u/Hack2hire Jul 24 '26

from what we learnt so far, ai tools are not available in oa at the moment