The Crossed Wires Debugging Lab

The Crossed WiresEvents & ConcurrencyHardPreparing workspaceAutosaved

00:00

Incident Dossier

The Crossed Wires

A wallet moves funds between accounts. Two concurrent moves between the same pair of accounts can each grab one account lock and wait on the other. The system stops making progress until something times out.

Initial failing signaltwo moves between same accounts never completeExpected completed == true · received completed == false

Progress

1Reproduce the bugRun checks

2Edit the fixOpen

3Pass checksOpen

4Submit fixOpen

Reproduction Steps

Run npm test.
Look at the lock acquisition order in `move`.
Two concurrent moves with swapped arguments acquire the same locks in opposite orders.
Acquire the two locks in a fixed order (e.g. sort the account ids).

Focus Mode

Start

src/wallet.js

Likely area

src/wallet.js

Progressive hints

Hints reveal broad direction first, then narrow toward the suspect path without showing hidden tests or exact solution code.

TopicEvents & Concurrency

DifficultyHard

Est. time28 min

Workspacecreating

Explorer

Preparing workspace files…

Evidence Map

Failing signal loaded from challenge API
Workspace files loaded from workspace API
Results rendered only after API run/submit

Autosaved

workspace

Outputread-onlyready$ workspace boot

Workspace booting...