From 99711d582263ce3dc0103baecf579e995363db86 Mon Sep 17 00:00:00 2001
From: Simon H <5968653+dummdidumm@users.noreply.github.com>
Date: Tue, 14 Oct 2025 18:25:52 +0200
Subject: [PATCH] fix: ensure map iteration order is correct (#16947)

quick follow-up to #16944
Resetting a map entry does not change its position in the map when iterating. We need to make sure that reset makes that batch jump "to the front" for the "reject all stale batches" logic below. Edge case for which I can't come up with a test case but it _is_ a possibility.
---
 packages/svelte/src/internal/client/reactivity/deriveds.js | 1 +
 1 file changed, 1 insertion(+)

diff --git a/packages/svelte/src/internal/client/reactivity/deriveds.js b/packages/svelte/src/internal/client/reactivity/deriveds.js
index fa780013e1..6aa9a1d9d9 100644
--- a/packages/svelte/src/internal/client/reactivity/deriveds.js
+++ b/packages/svelte/src/internal/client/reactivity/deriveds.js
@@ -144,6 +144,7 @@ export function async_derived(fn, location) {
 				batch.increment();
 
 				deferreds.get(batch)?.reject(STALE_REACTION);
+				deferreds.delete(batch); // delete to ensure correct order in Map iteration below
 				deferreds.set(batch, d);
 			}
 		}