From 8bf9ec87000fffd3805ebaac3586a0502cf92900 Mon Sep 17 00:00:00 2001
From: Barry <91018388+barry166@users.noreply.github.com>
Date: Fri, 21 Aug 2026 21:45:41 +0800
Subject: [PATCH] docs: clarify $bindable fallback binding requirement (#18477)

---
 documentation/docs/02-runes/06-$bindable.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/documentation/docs/02-runes/06-$bindable.md b/documentation/docs/02-runes/06-$bindable.md
index 3675a56b16..a3be662785 100644
--- a/documentation/docs/02-runes/06-$bindable.md
+++ b/documentation/docs/02-runes/06-$bindable.md
@@ -52,3 +52,5 @@ In this case, you can specify a fallback value for when no prop is passed at all
 /// file: FancyInput.svelte
 let { value = $bindable('fallback'), ...props } = $props();
 ```
+
+When a bindable prop has a fallback value, the parent must pass a value other than `undefined` if it uses `bind:`. This avoids ambiguity about which value should apply, since the parent and child should share the same value for a binding.