Document Suno browser handoff decision

docs/ARCHITECTURE.md

@@ -84,9 +84,12 @@ and explicitly apply the processed text before any Suno handoff.
 
 ## Suno Boundary
 
-The initial requirement is browser/site handoff that fills fields but
-does not press Generate. Treat this integration as replaceable because
-website UI/behavior can change.
+The initial requirement is browser/site handoff to the Suno Create page
+in Custom mode. The integration attempts to fill the supported title,
+lyrics and style fields but does not press Generate. If a field cannot
+be filled, it returns a field-specific result so Presentation can report
+it and offer the approved text for copying. Treat this integration as
+replaceable because website UI/behavior can change.
 
 ## Instrument Selector Boundary
 

docs/OPEN_QUESTIONS.md

@@ -15,7 +15,10 @@ finalized.
 -   Exact list of supported languages/dialects for MVP.
 -   Arabic diacritization policy: full tashkeel vs
     pronunciation-targeted tashkeel.
--   Exact Suno fields to populate and supported handoff mechanism.
+-   Resolved: Suno handoff opens the browser-based Create page in Custom
+    mode and attempts to fill title, lyrics and style fields. It never
+    starts generation. Field-fill failures are reported with the
+    approved text available for copying.
 -   Whether Suno integration is permitted/reliable under the intended
     account/workflow and current terms.
 -   Project storage technology and whether cloud sync is required later.

docs/PRODUCT.md

@@ -19,8 +19,10 @@ instructions for Suno.
 4.  User reviews and manually edits every generated component.
 5.  Project versions are saved.
 6.  User presses **Send to Suno**.
-7.  The app opens Suno and fills the appropriate fields. It does not
-    trigger Generate.
+7.  The app opens the Suno Create page in Custom mode and fills the
+    supported title, lyrics and style fields. It does not trigger
+    Generate. If a field cannot be filled, the app reports that result
+    and keeps its approved text ready for the user to copy.
 
 ## Song Controls
 
@@ -92,5 +94,9 @@ Normal users cannot view or modify these rules in the initial version.
 ## Initial Boundary
 
 Suno remains responsible for music generation and playback. The macOS
-app prepares the project and fills Suno fields only. Generated songs do
-not need to return to the app in the initial version.
+app opens the browser-based Suno Create page in Custom mode and fills
+the supported title, lyrics and style fields only. It never triggers
+Generate. If Suno changes its interface and a field cannot be filled,
+the app reports that field and keeps the approved text available to
+copy. Generated songs do not need to return to the app in the initial
+version.