diff --git a/AGENTS.md b/AGENTS.md
index bffe2a3..bec095a 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -50,6 +50,7 @@ tests/
 - **Single crate**: Library (`src/lib.rs`) and binary (`src/bin/ranger/`) in one crate. No workspace.
 - **Single backlog per task**: Each task belongs to exactly one backlog. `backlog_id` and `position` live directly on the `tasks` table.
 - **Subtasks are tasks**: `parent_id` on tasks — subtasks get full task capabilities.
+- **Tags**: Free-form labels on tasks via a many-to-many join table (`task_tags`). Used for cross-cutting concerns like `web`, `cli`, `infra`. Filter tasks by tag with `--tag`.
 - **No compile-time checked queries**: Using `sqlx::query_as` with runtime binding, not `query_as!` macros. No need for `DATABASE_URL` at build time.
 
 ## Testing