Claude Code caps subagents at 20, blocks nesting

Claude Code capped concurrent subagents at 20 and turned off nested spawning by default, per a changelog tracker covering the project, releasebot.io.

Twenty concurrent subagents is now the hard ceiling on a process that used to run wild. Teams running these CLIs are the ones who eat the bill when a spawn chain runs away unchecked.

Recursive delegation doesn't have a natural stopping point. An agent spawning more agents has no built-in signal for enough already, because the prompt telling it to stop is exactly what's getting ignored. That's why the fix lives in the harness now, not the system prompt.

Claude Code also fixed a separate bug the same tracker flagged: --max-budget-usd wasn't stopping background subagents from spending past the limit. Cursor answered with its own fix around the same time, a subagentStart hook that lets developers intercept a spawn before it happens.

None of this is a safety story. It's cost containment for a runtime that turned recursive before anyone built a meter for it. I'd watch whether concurrency and spend caps show up as defaults in the next agent CLI release, not settings buried in a docs page.