I think this depends on what reasoning level your Claude Code is set to.

Go to /models, select opus, and the dim text at the bottom will tell you the reasoning level.

High reasoning is a big difference versus 4.5. 4.6 high uses a lot of tokens for even small tasks, and if you have a large codebase it will fill almost all context then compact often.

I set reasoning to Medium after hitting these issues and it did not make much of a difference. Most of the context window is still filled during the Explore tool phase (that supposedly uses Haiku swarms) which wouldn't be impacted by Opus reasoning.

I'm using the 1M context 4.6 and it's great.