From ac238fb6434fe1c7dba2e65e00ce15595f5c482a Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Tue, 31 Mar 2026 11:23:53 -0400
Subject: [PATCH] remove maybe_dirty_effects

---
 .../internal/client/dom/blocks/boundary.js    |  7 ++----
 .../src/internal/client/reactivity/batch.js   | 23 ++-----------------
 .../src/internal/client/reactivity/utils.js   |  3 +--
 3 files changed, 5 insertions(+), 28 deletions(-)

diff --git a/packages/svelte/src/internal/client/dom/blocks/boundary.js b/packages/svelte/src/internal/client/dom/blocks/boundary.js
index 63c0e83241..8a9ffccc18 100644
--- a/packages/svelte/src/internal/client/dom/blocks/boundary.js
+++ b/packages/svelte/src/internal/client/dom/blocks/boundary.js
@@ -104,9 +104,6 @@ export class Boundary {
 	/** @type {Set<Effect>} */
 	#dirty_effects = new Set();
 
-	/** @type {Set<Effect>} */
-	#maybe_dirty_effects = new Set();
-
 	/**
 	 * A source containing the number of pending async deriveds/expressions.
 	 * Only created if `$effect.pending()` is used inside the boundary,
@@ -266,7 +263,7 @@ export class Boundary {
 
 		// any effects that were previously deferred should be transferred
 		// to the batch, which will flush in the next microtask
-		batch.transfer_effects(this.#dirty_effects, this.#maybe_dirty_effects);
+		batch.transfer_effects(this.#dirty_effects);
 	}
 
 	/**
@@ -274,7 +271,7 @@ export class Boundary {
 	 * @param {Effect} effect
 	 */
 	defer_effect(effect) {
-		defer_effect(effect, this.#dirty_effects, this.#maybe_dirty_effects);
+		defer_effect(effect, this.#dirty_effects);
 	}
 
 	/**
diff --git a/packages/svelte/src/internal/client/reactivity/batch.js b/packages/svelte/src/internal/client/reactivity/batch.js
index 8a7619a892..78334539ca 100644
--- a/packages/svelte/src/internal/client/reactivity/batch.js
+++ b/packages/svelte/src/internal/client/reactivity/batch.js
@@ -186,12 +186,6 @@ export class Batch {
 	 */
 	#dirty_effects = new Set();
 
-	/**
-	 * Deferred effects that are MAYBE_DIRTY
-	 * @type {Set<Effect>}
-	 */
-	#maybe_dirty_effects = new Set();
-
 	/** @type {Map<Value, number>} */
 	wvs = new Map();
 
@@ -298,11 +292,6 @@ export class Batch {
 		// to be able to run them after processing the batch
 		if (!this.#is_deferred()) {
 			for (const e of this.#dirty_effects) {
-				this.#maybe_dirty_effects.delete(e);
-				this.schedule(e);
-			}
-
-			for (const e of this.#maybe_dirty_effects) {
 				this.schedule(e);
 			}
 		}
@@ -362,7 +351,6 @@ export class Batch {
 
 			// clear effects. Those that are still needed will be rescheduled through unskipping the skipped branches.
 			this.#dirty_effects.clear();
-			this.#maybe_dirty_effects.clear();
 
 			// append/remove branches
 			// console.group('branches');
@@ -437,7 +425,6 @@ export class Batch {
 				} else if (async_mode_flag && (flags & (RENDER_EFFECT | MANAGED_EFFECT)) !== 0) {
 					render_effects.push(effect);
 				} else if (is_dirty(effect)) {
-					if ((flags & BLOCK_EFFECT) !== 0) this.#maybe_dirty_effects.add(effect);
 					update_effect(effect);
 				}
 
@@ -467,7 +454,7 @@ export class Batch {
 	 */
 	#defer_effects(effects) {
 		for (var i = 0; i < effects.length; i += 1) {
-			defer_effect(effects[i], this.#dirty_effects, this.#maybe_dirty_effects);
+			defer_effect(effects[i], this.#dirty_effects);
 		}
 	}
 
@@ -743,19 +730,13 @@ export class Batch {
 
 	/**
 	 * @param {Set<Effect>} dirty_effects
-	 * @param {Set<Effect>} maybe_dirty_effects
 	 */
-	transfer_effects(dirty_effects, maybe_dirty_effects) {
+	transfer_effects(dirty_effects) {
 		for (const e of dirty_effects) {
 			this.#dirty_effects.add(e);
 		}
 
-		for (const e of maybe_dirty_effects) {
-			this.#maybe_dirty_effects.add(e);
-		}
-
 		dirty_effects.clear();
-		maybe_dirty_effects.clear();
 	}
 
 	/** @param {(batch: Batch) => void} fn */
diff --git a/packages/svelte/src/internal/client/reactivity/utils.js b/packages/svelte/src/internal/client/reactivity/utils.js
index 1d9c99a52c..daf29204ea 100644
--- a/packages/svelte/src/internal/client/reactivity/utils.js
+++ b/packages/svelte/src/internal/client/reactivity/utils.js
@@ -21,9 +21,8 @@ function clear_marked(deps) {
 /**
  * @param {Effect} effect
  * @param {Set<Effect>} dirty_effects
- * @param {Set<Effect>} maybe_dirty_effects
  */
-export function defer_effect(effect, dirty_effects, maybe_dirty_effects) {
+export function defer_effect(effect, dirty_effects) {
 	dirty_effects.add(effect);
 
 	// Since we're not executing these effects now, we need to clear any WAS_MARKED flags