alt Hacker NewsSo this only switches models if the cache is cold, because otherwise the economics of switching don't work. But most agentic work involves long strings of successive tool calls that benefit from a hot cache. Hot cache calls reduce input cost by 90%. This can basically only deliver cost savings in turns where the AI delivers a result to the user, the user waits at least 5 minutes (or the length of the cache), and then responds.
But user->AI calls are very much the rare case now, the more agentic the workload. Most of them will be tool->result->tool without the user involved. And token burn is highest with these long running agentic chains, but that's precisely where routing doesn't work because of the KV cache.
How do you deal with that?
> So this only switches models if the cache is cold
Not exactly. It can also make sense if the cache is hot to switch models. For example, we might currently be on Deepseek and the next task is SO HARD that it doesn't make sense to not use frontier (1 turn to crack versus 100 turns for Deepseek to crack). Likewise, the router may judge that it's likely that the next few set of tool-calls will be ridiculously easy, and so switching to Deepseek will save over time.
Remember that Deepseek can be something like 30x cheaper even cold.
There is a more fine-grained view of caching here, because each model can have a different amount of the prefix already cached as well (since we were switching a bunch) so even if the cache is somewhat warm it may make sense to switch.