Code RoomRegex mentions false positives
MediumPrep Room Coding #4054

Regex mentions false positives

Vibe & agenticAlgorithms & data structuresMid–Senior~17 min

You ask an AI for a Python regex to extract @mentions from chat messages so you can notify users. It returns `re.findall(r'@(\w+)', text)`. It pulls names fine until QA reports notifications firing from email addresses (`@gmail` in `a@gmail.com`), code blocks (`@property`), and it misses `@jean-luc` and `@O'Brien`. You re-prompt 'be more accurate' and it adds `\b`, which fixes nothing. How do you re-steer this to actually match your product's mention rules?

Implement
extract_mentions(text: str) → list[str]
Examples
in["hey @alice and @bob_smith"]out["alice","bob_smith"]
in["mail a@gmail.com now"]out[]
in["see ```@property``` but @data_team wins"]out["data_team"]
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 17 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.