Overstory turns a single coding session into a multi-agent team by spawning worker agents in isolated git worktrees and coordinating them through a custom SQLite mail system. Work from multiple agents is merged back with tiered conflict resolution. A pluggable AgentRuntime interface supports 11 different runtimes including Claude Code, Pi, Gemini CLI, Aider, and Goose. New projects spawn Claude agents headlessly and surface them through a web UI, with tmux as an opt-in escape hatch for live steering.