diff --git a/AGENTS.md b/AGENTS.md
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@@ -16,6 +16,12 @@ Start with the root `README.md` for the dotfile-specific constraints and manual-
 
 - Treat Fish (`fish`) as the default interactive shell. Write user-facing shell commands using Fish-compatible syntax unless another shell is explicitly requested or required.
 
+## Knowledge base
+
+- The knowledge base is an Obsidian vault at `~/cloud/knowledge`.
+- Search the vault when a task depends on specific existing knowledge.
+- Add new knowledge to the vault when it is durable and noteworthy; skip routine or transient details.
+
 ## Ownership map
 
 | Path | Owns |