Keep concurrent subagents to 3–5 — beyond that, merge cost eats your parallelism gains

SmartScope·medium signal

The 2026 sweet spot for Claude Code subagents is three to five running concurrently; past that you spend more time reconciling summaries than you save by fanning out. Anthropic's Dynamic Workflows release lets the lead push the ceiling to tens or hundreds, but that only pays off for tasks that genuinely fan out (e.g., a benchmark sweep across 80 model-prompt combos) — for everyday coding the 3–5 rule holds. Treat high parallelism as a special case you justify, not a default you reach for.