I think Fable is predisposed to try and verify it's changes. Which is a very good thing. It takes a lot of prompts to get Opus to do what Fable does unprompted.

That is exactly what I would want from a junior developer - make sure the bug exists, find a way to fix it, verify the bug is fixed.

The problem, as was correctly identified in the blog post - is that instead of stopping and asking for elevated permission it relentlessly tries to find a hack on it's own. (An equivalent situation for a human developer would be needing some access to a third-party sandbox, and instead of asking a senior for credentials, tries to setup his own sandbox from scratch)