I measured why I can't run more than 3 parallel agents in Claude Code

I've basically lived inside Claude Code for the last few weeks building some agent tooling, and I kept hitting a wall. No matter how much capacity I had, I couldn't sustain more than about three parallel agents before everything fell apart. Instead of just guessing, I went back through my history from the last 35 days, roughly 1,800+ turns, to see where the actual bottleneck was. It turns out it's a duty-cycle problem. The number of agents you can effectively manage is just the inverse of the time the agent spends waiting on you for a decision or a review. N ≈ 1 / (fraction of time an agent is waiting on you) Once I saw the math, it clicked. Adding more agents doesn't scale linearly because you become the primary latency source. The bigger cost, though, is the join. That's the process of reconciling all that finished parallel work back into one coherent state. The more agents I had running, the more time I spent manually merging their outputs and fixing the conflicts they created while working in parallel. The "join" is where most of my time actually goes. I'm currently building a way to automate this reconciliation process so the join doesn't eat the productivity gains of parallelism. For those of you running multiple agents on the same codebase, how are you handling the join right now? Are you doing it manually, or have you found a way to automate the state reconciliation?