docs

docs/architecture/website/FORM_SUBMISSION.md

@@ -5,6 +5,8 @@ It applies to all write operations (create, update, delete).
 
 There are no exceptions.
 
+Authoritative contract: [`WEBSITE_CONTRACT.md`](docs/architecture/website/WEBSITE_CONTRACT.md:1).
+
 ⸻
 
 Core Principle
@@ -13,6 +15,21 @@ Read and Write paths are different.
 
 What is displayed is never sent back.
 
+## Non-negotiable write boundary
+
+All writes MUST enter the system through **Next.js Server Actions**.
+
+Forbidden:
+
+- client components performing write HTTP requests
+- client components calling API clients for mutations
+
+Allowed:
+
+- client submits intent (FormData, button action)
+- server action performs UX validation
+- server action calls the API
+
 ⸻
 
 High-Level Flow
@@ -153,4 +170,4 @@ Summary
 	•	Read Flow: DTO → ViewModel → UI
 	•	Write Flow: UI → Command DTO → Core
 
-What is shown is never sent back.
+What is shown is never sent back.