diff --git a/.planning/phases/01-foundation-broker-spike/01-RESEARCH.md b/.planning/phases/01-foundation-broker-spike/01-RESEARCH.md
index ff31526..4361071 100644
--- a/.planning/phases/01-foundation-broker-spike/01-RESEARCH.md
+++ b/.planning/phases/01-foundation-broker-spike/01-RESEARCH.md
@@ -915,7 +915,7 @@ serve({ fetch: app.fetch, port: 3000 })
 
 ---
 
-## Open Questions
+## Open Questions (DEFERRED TO SPIKE — resolved empirically in Plan 01-04)
 
 1. **Fastmail ctag/syncToken field presence on DAVCalendar**
    - What we know: `DAVCalendar` type has both `ctag` and `syncToken` fields