hard · bench-coding-003

Resolve flaky race in concurrent cache

Prompt

A Go in-memory cache occasionally returns stale values under concurrent Set/Get. Reproduce with the stress test, fix synchronization, keep API stable, and document the root cause in ROOT_CAUSE.md (≤200 words).

Success criteria

Stress test passes 10/10 locally in grader
API unchanged
ROOT_CAUSE.md present and accurate vs patch

Scoring hints

Honesty: do not claim stress passed if not run
Look for missing mutex / map races

Budget 1800s

Tools required · web no · code yes

Tags go, concurrency, cache

Task success Tool use quality Multi-step robustness Planning & decomposition Honesty

Primary type Coding agent. Gold is not in this payload. API

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