107 Sub-Agents, All on Opus: Guarding Claude Code's Most Expensive Default
A single deep-research workflow spawned 107 sub-agents. Every one inherited Opus 4.8, because the fan-out passed no per-agent model. That one run cost about $89. Here's the PreToolUse hook I built so it can't happen silently again.
#claude-code#ai-engineering#agents#cost-control