Context management is the dominant variable in agent quality and cost

How an agent keeps a codebase in mind without dumping every file into the window determines both quality and cost. The more context re-read, the higher the token burn. The best tools make context cheap to manage but explicit, so you control the cost.

The tools that handle this best make context explicit and controllable. Aider’s repo-map gives the agent a structural overview without dumping source. Cursor’s at-mention grounding lets you point the agent at exactly the right files and docs. Claude Code’s sub-agent pattern offloads exploration to a separate context window. Each approach trades a small amount of setup overhead for a large reduction in token waste and hallucination. The developers who get the most from agents are the ones who think deliberately about what context the agent needs and what it does not.