Frontier models sabotaging local AI implementations?

For a few days I've been working on creating a custom local-only harness for some work related research using Codex / GPT 5.6 Sol and the model feels not only dumber than usual, but straight up counter productive. It keeps adding unnecessary guardrails for the local agents, removes tools that I clearly specified I want them to have and always drifts from the original requirements. I need to ask it to change things multiple times, which ends up on some over-complicated final product.

This is not the first time either, for months I've been avoiding asking frontier llms for local AI advice as it always seems to be bad, obsolete, or clueless even with internet search. Sometimes it still recommends me Qwen3-Coder-Next for my set up when it's clearly an obsolete model. I'm pretty sure I'm not the only one either as I've heard from other people.

What have you been your experiences on this?