diff --git a/AGENTS.md b/AGENTS.md
index 5f72c558db8..d32e8688587 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -29,6 +29,7 @@ Telegraph style. Root rules only. Read scoped `AGENTS.md` before subtree work.
 - Extension prod code: no core `src/**`, `src/plugin-sdk-internal/**`, other extension `src/**`, or relative outside package.
 - Core/tests: no deep plugin internals (`extensions/*/src/**`, `onboard.js`). Use `api.ts`, SDK facade, generic contracts.
 - Extension-owned behavior stays extension-owned: repair, detection, onboarding, auth/provider defaults, provider tools/settings.
+- Owner boundary: fix owner-specific behavior in the owner module. Shared/core gets generic seams only; no owner ids, dependency strings, defaults, migrations, or recovery policy. If a bug names an extension or its dependency, start in that extension and add a generic core seam only when multiple owners need it.
 - Legacy config repair: doctor/fix paths, not startup/load-time core migrations.
 - Core test asserting extension-specific behavior: move to owner extension or generic contract test.
 - New seams: backwards-compatible, documented, versioned. Third-party plugins exist.