It won't satisfy the people who just want to drop a model into their existing toolset and run, but I think there are a lot of ways to deal with this overthinking problem.

For instance, it's a step backward, but I put {"reasoning_effort":"none"} and led it by the nose:

   User: We're going to make <silly demo>.  Please create a plan, but do not write code yet.

   Agent: <short and reasonable plan>

   User: Now please follow that plan and write the code.  No other chat.

   Agent: <reasonable code in reasonable time>

Maybe this can be fixed with Jinja templates or something, or maybe it's a hack to your harness, but it shows you can get the model to reason reasonably.