From ed6f011e69db0714cb14976cf2c853fa6c49c27b Mon Sep 17 00:00:00 2001
From: Julien Calixte <julien.calixte@theodo.com>
Date: Sat, 20 Jun 2026 14:39:06 +0200
Subject: [PATCH] feat(editor): reset the playhead when a different model loads

---
 src/store/simulation.ts | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/src/store/simulation.ts b/src/store/simulation.ts
index 620c446..6613dac 100644
--- a/src/store/simulation.ts
+++ b/src/store/simulation.ts
@@ -61,6 +61,17 @@ export const useSimulationStore = defineStore("simulation", () => {
     if (playhead.value > n - 1) playhead.value = Math.max(0, n - 1)
   })
 
+  // Loading a different document (sample / import / new) restarts playback from the
+  // top. Editing the current one keeps the same id, so the playhead stays put — and
+  // undo/redo restore snapshots in place (same id), so they don't jump it either.
+  watch(
+    () => modelStore.model.id,
+    () => {
+      playing.value = false
+      playhead.value = 0
+    },
+  )
+
   /** A node's value at the current playhead, or null when there's nothing to show. */
   function valueAt(id: string): number | null {
     if (!active.value) return null