Cognition build day interview

Round 4 of 6 · 3 questions reported

Length: 480 min
Format: Build your own end-to-end coding agent from scratch
They grade: How far you get
Heads-up: The CEO described it in August 2025 as building "their own Devin in eight hours", or six. Windsurf reports from 2024 and 2025 had shorter practical rounds: a small pandas data pipeline in about 90 minutes, or working through open issues in an unfamiliar open-source library.

Questions Cognition asks in this round 3

Debug an open-source library and propose fixes for open issuesCodingLockedYou are dropped into the code of an existing open-source library you have probably not seen before. Find your way around it, work through some of its open issues and propose…
Possibly retired
Alien dictionary: letter order from a sorted word listCodingLockedYou are given a list of words from a language that uses lowercase English letters in an unknown order. The list is sorted by that language's alphabet.
Possibly retired
Build a small data pipeline with pandasCodingA Python project round: implement a small data pipeline with pandas in about 90 minutes, then walk an engineer through your solution and answer questions on how you would extend…
Possibly retired