[gorkish]

There's no single call that can launch multiple event loops at the same time, so there really isn't a notion of serial or parallel; it's always going to be a simple question of how the first model calls made by each hit the backend. I highly doubt that a bunch of agents created within milliseconds of each other are going to get cache hits. It's more likely they will spin up in parallel. I strongly suspect if Anthropic were trying to deduplicate their inflight requests for cache efficiency, they'd at least want to tell you about it.