From a04c6fad18755e70810295e70a4840f3a590e66c Mon Sep 17 00:00:00 2001
From: Victor Giers <mail@victorgiers.com>
Date: Wed, 15 Apr 2026 03:43:14 +0200
Subject: [PATCH] Add validation for startSceneTransition effect in
 migrate-scene-document.ts

---
 src/document/migrate-scene-document.ts | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/src/document/migrate-scene-document.ts b/src/document/migrate-scene-document.ts
index 2332f362..e5362ce7 100644
--- a/src/document/migrate-scene-document.ts
+++ b/src/document/migrate-scene-document.ts
@@ -3516,6 +3516,25 @@ function readProjectSequenceEffect(value: unknown, label: string): SequenceClip
           `${label}.targetEntityId`
         )
       };
+    case "startSceneTransition":
+      if (stepClass !== "impulse") {
+        throw new Error(
+          `${label}.startSceneTransition effects must use the impulse class.`
+        );
+      }
+
+      return {
+        stepClass: "impulse",
+        type: "startSceneTransition",
+        targetSceneId: expectString(
+          value.targetSceneId,
+          `${label}.targetSceneId`
+        ),
+        targetEntryEntityId: expectString(
+          value.targetEntryEntityId,
+          `${label}.targetEntryEntityId`
+        )
+      };
     case "toggleVisibility":
     case "setVisibility": {
       const isLegacyToggle = value.type === "toggleVisibility";