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Code RoomCallback to async regression
MediumPrep Room Coding #4233

Callback to async regression

Vibe & agenticConcurrencyCode quality & reviewMid–Senior~20 min

A legacy Node.js module uses error-first callbacks throughout. You ask an AI agent to migrate it to async/await. It converts each function and the code reads beautifully. Below is one converted function — what behavior regressed, and how would your verification have caught it?

Implement
batch_wall_clock_ms(durations: list[int], max_concurrency: int) → int
Examples
in[[100,100,100],1]out300
in[[100,100,100],3]out100
in[[100,200,50],2]out200
What a strong answer looks like

Treat the AI’s output as a draft to verify, not an answer to trust. Name the specific flaw and the input that triggers it, say how you’d catch it (tests, edge cases, reading critically), and how you’d re-prompt or decompose to get it right.

0:00 of about 20 min

Vibe & agentic: describe the solution in plain language (or narrate it) and the coach grades your approach.

Which questions mattered is sealed until you submit. Telling you now would just be handing over the edge cases.