If a model keeps getting safety-switched mid-session, use it as a subagent reviewer instead

Quick workflow that fixed an annoyance for me, posting in case it helps someone.

I build a health app with Claude Code, so there's a lot of medical and supplement stuff in the project. I wanted Fable 5 to look over it, because it thinks differently to Opus. But every time I set Fable as the session model, it got switched back to Opus partway through. My guess is the subject matter (drug interactions, doses, that sort of thing) sets off a safety check more easily when Fable is the one running the session. Fighting it got me nowhere.

What worked instead: leave the main session on my usual model (Opus), and spin Fable up as a subagent for the jobs where I actually want a different model. Reviews, audits, design and copy checks. The stuff where you want a fresh pair of eyes instead of your own thinking handed back to you.

Three reasons it ended up better than running the whole session on Fable, even ignoring the safety thing:

1. A different model is just better at reviewing. Same reason someone else spots the typo you've read past ten times. My main model wrote the code and the copy, so a different one reading it caught things mine couldn't see, including a real accessibility bug and a wrong claim I'd have shipped.

2. It keeps your main chat clean. The subagent goes off and reads twenty files, or takes a load of screenshots, in its own context, and just hands you back the answer. Your main session never has to carry all that, so you can run a few reviews without running out of room.

3. It matches what each job needs. For a review you want a different angle, so a different model. For actually writing the code you want something that already knows your project, so your main model. One model trying to do both does both worse.

So if you're stuck because a model keeps getting safety-switched, or you just want a second opinion without giving up a whole session to it: don't make it the driver, make it the reviewer. Spin it up as a subagent for the one job and bring the answer back to your main session.

Happy to share how I set the subagent up if that's useful.