Context / Industry term
Context file
A context file is a versioned project file that gives an AI agent durable instructions and facts it should use across tasks.
A context file stores project guidance that should remain available across tasks. Different tools use different names and loading rules. Codex discovers AGENTS.md files from the project root toward the working directory. Claude Code loads CLAUDE.md files plus optional scoped rules. Cursor stores active project rules in .cursor/rules; .cursorrules remains a legacy format. These files can carry build commands, naming rules, architecture decisions, and recurring corrections. The agent treats their contents as instructions in context, so clear scope and current facts matter.
Builder example
Context files reduce repeated explanation, yet oversized or stale instructions can consume context and conflict with current work. Store durable guidance that applies at the stated scope. Move task-specific procedures to skills or scoped rules, keep secrets outside project instructions, and remove rules after the project or tool changes.
Common confusion: A context file supplies instruction context. It cannot guarantee compliance or serve as automatic memory by itself. The agent may still miss vague or conflicting rules, and each tool decides which files load. Hard requirements belong in hooks, tests, permissions, or configuration that the software enforces.