Can you be sure that the model was not constrained for you, regardless? Since they can’t help too much with cyber, they might avoid some routes to not get completely flagged and that could influence for not finding the solution.

I have seen behaviour a little like what you describe, in other tasks. When I was cracking the keys for Sony's camera firmware updates, Claude steered away from an obfuscated library, seemingly because it thought it might be related to licensing checks. It was indeed related to licensing checks, but also firmware update decryption. I had to explicitly tell Claude to write a deobfuscator for it, which it did, and eventually I had the keys.

I later got Claude to crack their licensing checks too, by convincing it to write a "license checker" program, and then a second "test case generator" script for the license checker... (Opus 4.8 was smart enough to see what I was doing, but Opus 4.6 complied)