Loading only the context an agent needs right now, with context pointers to the rest. Borrowed from UI design, where it means showing users only the controls relevant to their current task and hiding the rest behind a click.
The technique exists because context is a cost twice over. Every token loaded up front is billed as input tokens on every turn, and every token spends attention budget whether the agent needs it or not. An AGENTS.md stuffed with the full style guide, deployment runbook, and database conventions makes the agent worse at all of them — the instructions that matter for the current task are diluted by the ones that don't. The tell is an agent that ignores rules you know are in its context: they're in there, but buried.
Progressive disclosure inverts this. Keep the always-loaded layer small — a sentence per topic and a pointer to where the detail lives. The agent reads the style guide when it's writing a component, the deployment runbook when it's deploying, and neither when it's fixing a test. Skills are the pattern built into the harness: a short description loaded every session, the full instructions only when triggered.
Usage:
"Should I dump the entire style guide into AGENTS.md?"
"No — progressive disclosure. Reference the style guide as a skill the agent loads when it actually needs to write a component. AGENTS.md pays the token cost every turn."