Could you say more about how caching works? One major advantage of sticking with a single model is saving money on cached input tokens. I'd imagine if you swap between a bunch of models, you may improve performance but cost would would balloon out of control

The trick is to rarely switch, or switch at task boundaries. Often the conclusion of routing is actually "this one model is actually at the pareto front for this task, just use it always".

But then it's better to just not have a gateway switch models at all.

Just have the harness able to choose which model its sub-agents use, then tell it how to split up tasks and which models to use when doing so.

That is another way to do. Or we can automatically figure out which models the subagents should be using for you. And update them as new models come out and the work your subagents do changes. More than one way to skin a cat.

This does make sense. I generally only switch between models in pi when creating a new session. And it is apparent from the promt if this just a "how to see open ports on linux" or "make a concrete plan for feature X"

Generally you should only have two models in the pool per domain. I wrote some of my learnings building a router here: https://try.works/first-principles-of-model-routing

and caching is related to performance too ofc

Author here. Took out some of the technical details about the harness, but it was mostly just OpenCode's default compaction.

The harness was extremely simple: A handful of MCPs + Skill.MDs and OpenCode with a stayalive daemon inserting "continue" every time it went idle