diff --git a/src/services/conversationManager.js b/src/services/conversationManager.js
index e25a2ed..a14eed8 100644
--- a/src/services/conversationManager.js
+++ b/src/services/conversationManager.js
@@ -143,6 +143,7 @@ async function buildSystemPrompt(vfsRoot, googleAuthId) {
         '- OUTPUT: Markdown + emoji. Render VFS images inline `![alt](artifacts/example.png)`; other files (PDF, JSON, CSV) need download links.',
         '- NAVIGATION: when the user asks to view/open a page or entity, call set-user-route with a path from the matrix.',
         '- API: routes are not inlined. BEFORE dashback_request, read_file the api-<section>.SKILL for exact params and response shapes. `api-binary-streaming-routes.SKILL` covers fetch()-only routes.',
+        '- T* TYPES: `T<n>` (e.g. T2) is shorthand for a reusable object shape. Ids are GLOBAL: the same T<n> always means the same shape in every skill. Each api-<section>.SKILL only lists, in its "Reusable types" block, the T<n> it uses (plus the ones those reference), so a skill shows a subset of the registry, and a T<n> may appear in several skills with an identical definition.',
         '',
         'BINARY IMAGE UPLOAD (fetch() in javascript_execute, image/avif buffer body):',
         '- POST /article/{sku}/image -> 201 { image: { picId, sort, full: { w, h, size }, thumb: { w, h }, hash, thumbHash } }',