diff --git a/app/api/setup/finish/route.ts b/app/api/setup/finish/route.ts
index 4c0d11df..381cebbe 100644
--- a/app/api/setup/finish/route.ts
+++ b/app/api/setup/finish/route.ts
@@ -58,13 +58,16 @@ export async function POST(request: NextRequest) {
   }
 
   try {
-    // 1. Provision the admin account. Aborts cleanly if one already exists
-    //    (defence in depth - should be impossible in bootstrap state).
-    const created = await setInitialAdminPassword(adminPassword);
+    // 1. Provision the admin account. An admin.json file may already exist
+    //    from a previous ADMIN_PASSWORD env var or an aborted earlier wizard
+    //    run while setupComplete is still false — accept the wizard's
+    //    password as authoritative in that case. The finish route is gated
+    //    by the bootstrap state + one-time setup token, so this is safe.
+    const created = await setInitialAdminPassword(adminPassword, { allowOverwrite: true });
     if (!created) {
       return NextResponse.json(
-        { error: 'Admin account already exists; cannot finish setup again' },
-        { status: 409 },
+        { error: 'Failed to write admin credentials' },
+        { status: 500 },
       );
     }
 
diff --git a/lib/admin/password.ts b/lib/admin/password.ts
index 955d81fb..4f4fd7d7 100644
--- a/lib/admin/password.ts
+++ b/lib/admin/password.ts
@@ -189,11 +189,21 @@ export async function changeAdminPassword(currentPassword: string, newPassword:
 
 /**
  * Set the admin password without verifying a current one. Used by the setup
- * wizard during initial bootstrap. Refuses to overwrite an existing password.
+ * wizard during initial bootstrap.
+ *
+ * Refuses to overwrite an existing password unless `allowOverwrite` is true.
+ * The wizard's finish route passes `allowOverwrite: true` so a half-completed
+ * setup (admin.json left behind by an ADMIN_PASSWORD env var or an aborted
+ * earlier wizard run, while setupComplete is still false) can be recovered
+ * by simply running the wizard again. Safe because the finish route is
+ * already gated by the one-time setup token.
  */
-export async function setInitialAdminPassword(newPassword: string): Promise<boolean> {
+export async function setInitialAdminPassword(
+  newPassword: string,
+  options: { allowOverwrite?: boolean } = {},
+): Promise<boolean> {
   const existing = await readConfigData();
-  if (existing) return false;
+  if (existing && !options.allowOverwrite) return false;
   const hash = await hashPassword(newPassword);
   cachedConfig = { passwordHash: hash };
   cachedState = freshState();