From d8df737f56e4cca980409360959137be9208e4d2 Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Thu, 16 Oct 2025 19:50:10 -0400
Subject: [PATCH] WIP

---
 .../src/internal/client/reactivity/batch.js   | 71 +++++++++++--------
 1 file changed, 42 insertions(+), 29 deletions(-)

diff --git a/packages/svelte/src/internal/client/reactivity/batch.js b/packages/svelte/src/internal/client/reactivity/batch.js
index 1e5bbc3e4a..ce58d05087 100644
--- a/packages/svelte/src/internal/client/reactivity/batch.js
+++ b/packages/svelte/src/internal/client/reactivity/batch.js
@@ -143,8 +143,17 @@ export class Batch {
 
 		this.apply();
 
+		/** @type {EffectTarget} */
+		var target = {
+			parent: null,
+			effect: null,
+			effects: [],
+			render_effects: [],
+			block_effects: []
+		};
+
 		for (const root of root_effects) {
-			this.#traverse_effect_tree(root);
+			this.#traverse_effect_tree(root, target);
 		}
 
 		// if there is no outstanding async work, commit
@@ -155,22 +164,33 @@ export class Batch {
 
 			this.#commit();
 
-			// If sources are written to, then work needs to happen in a separate batch, else prior sources would be mixed with
-			// newly updated sources, which could lead to infinite loops when effects run over and over again.
-			previous_batch = this;
-			current_batch = null;
-
 			// batch_values = previous_batch_sources;
 			// flush_queued_effects(target.render_effects);
 			// flush_queued_effects(target.effects);
-
-			previous_batch = null;
 		} else {
 			// this.#defer_effects(target.render_effects);
 			// this.#defer_effects(target.effects);
 			// this.#defer_effects(target.block_effects);
 		}
 
+		if (this.#blocking_pending > 0) {
+			this.#defer_effects(target.effects);
+			this.#defer_effects(target.render_effects);
+			this.#defer_effects(target.block_effects);
+		} else {
+			// TODO append/detach blocks here as well, not in #commit
+
+			// If sources are written to, then work needs to happen in a separate batch, else prior sources would be mixed with
+			// newly updated sources, which could lead to infinite loops when effects run over and over again.
+			previous_batch = this;
+			current_batch = null;
+
+			flush_queued_effects(target.render_effects);
+			flush_queued_effects(target.effects);
+
+			previous_batch = null;
+		}
+
 		batch_values = null;
 	}
 
@@ -178,19 +198,11 @@ export class Batch {
 	 * Traverse the effect tree, executing effects or stashing
 	 * them for later execution as appropriate
 	 * @param {Effect} root
+	 * @param {EffectTarget} target
 	 */
-	#traverse_effect_tree(root) {
+	#traverse_effect_tree(root, target) {
 		root.f ^= CLEAN;
 
-		/** @type {EffectTarget} */
-		var target = {
-			parent: null,
-			effect: null,
-			effects: [],
-			render_effects: [],
-			block_effects: []
-		};
-
 		var effect = root.first;
 
 		while (effect !== null) {
@@ -249,16 +261,6 @@ export class Batch {
 				parent = parent.parent;
 			}
 		}
-
-		if (this.#blocking_pending > 0) {
-			this.#defer_effects(target.effects);
-			this.#defer_effects(target.render_effects);
-			this.#defer_effects(target.block_effects);
-		} else {
-			// TODO append/detach blocks here as well
-			flush_queued_effects(target.render_effects);
-			flush_queued_effects(target.effects);
-		}
 	}
 
 	/**
@@ -343,6 +345,15 @@ export class Batch {
 
 			let is_earlier = true;
 
+			/** @type {EffectTarget} */
+			var dummy_target = {
+				parent: null,
+				effect: null,
+				effects: [],
+				render_effects: [],
+				block_effects: []
+			};
+
 			for (const batch of batches) {
 				if (batch === this) {
 					is_earlier = false;
@@ -383,9 +394,11 @@ export class Batch {
 						batch.apply();
 
 						for (const root of queued_root_effects) {
-							batch.#traverse_effect_tree(root);
+							batch.#traverse_effect_tree(root, dummy_target);
 						}
 
+						// TODO do we need to do anything with `target`? defer block effects?
+
 						queued_root_effects = [];
 						batch.deactivate();
 					}