[R] Solving the Jane Street Dormant LLM Challenge: A Systematic Approach to Backdoor Discovery

Submitted by: Adam Kruger Date: March 23, 2026 Models Solved: 3/3 (M1, M2, M3) + Warmup Background When we first encountered the Jane Street Dormant LLM Challenge, our immediate assumption was informed by years of security operations experience: there would be a flag. A structured token, a passphrase, a UUID — something concrete and verifiable, like a CTF challenge. We spent considerable early effort probing for exactly this: asking models to reveal credentials, testing if triggered states would emit bearer tokens, searching for hidden authentication payloads tied to the puzzle's API infrastructure at dormant-puzzle.janestreet.com . That assumption was wrong, and recognizing that it was wrong was itself a breakthrough. The "flags" in this challenge are not strings to extract — they are beh