diff --git a/agent/prompt_builder.py b/agent/prompt_builder.py
index fc7a7d2f6eb..1c1977b034d 100644
--- a/agent/prompt_builder.py
+++ b/agent/prompt_builder.py
@@ -257,6 +257,10 @@ KANBAN_GUIDANCE = (
     "- **Deliverables.** Files a human wants go in "
     "`kanban_complete(artifacts=[<absolute paths>])` (top-level param; paths in "
     "`metadata` are NOT uploaded). Files must exist at completion.\n"
+    "- **Attachments.** Attach real downloadable artifacts instead of pasting "
+    "links in comments: `kanban_attach` (base64) or `kanban_attach_url` "
+    "(server-side public http(s) fetch); 25 MB cap, `kanban_attachments` "
+    "lists them. Workers may only attach to their own task.\n"
     "- **Created cards.** List ids in `kanban_complete(created_cards=[...])` "
     "ONLY when captured from a successful `kanban_create` return — never invent "
     "or paste ids; the kernel rejects the completion on any phantom id.\n"