Clear it in 3 steps
Start the environment
Investigate the target
Submit the flag

worker-results.jsonl is generated from the FLAG injected at startup. Base64-decode results, XOR with worker SHA-1, and join by slot to recover the flag.
Inspect worker-results.jsonl and identify the target record
Base64-decode results, XOR with worker SHA-1, and join by slot
Verify that the reconstructed value has FLAG{...} format