How many agents can I run at once?

Your attention is the limit, not the tooling. Most people settle around three to five concurrent agents, because every agent produces work you have to review, and review does not parallelize. Machine resources rarely bind first; context and money do, since each agent burns its own tokens.

Claude Code caps concurrent subagents inside a single session at 20 by default, configurable with CLAUDE_CODE_MAX_CONCURRENT_SUBAGENTS. Separate top-level sessions have no such cap, so the ceiling there is genuinely yours. See how many agents can you actually run and running multiple Claude Code instances.