A subagent is an agent created by another agent through a tool call, operating in its own session with a specific context window to return a single tool result, without the ability to create further subagents. This structure is designed to manage context isolation rather than build hierarchical relationships.
For someone tracking Claude Code, Cursor, Codex, and similar AI tools, the key takeaway is the strategic use of subagents for isolating context in complex AI workflows. By spawning a subagent to handle tasks like searching, you can effectively manage and conserve the parent agent's context window, allowing you to maintain performance and efficiency in AI-driven coding environments. This approach can optimize your AI productivity by minimizing context noise and ensuring relevant results are returned.