fix

packages/svelte/src/internal/client/reactivity/deriveds.js

@@ -28,7 +28,7 @@ import { block, destroy_effect } from './effects.js';
 import { inspect_effects, internal_set, set_inspect_effects, source } from './sources.js';
 import { get_stack } from '../dev/tracing.js';
 import { tracing_mode_flag } from '../../flags/index.js';
-import { capture, suspend } from '../dom/blocks/boundary.js';
+import { capture, get_boundary, suspend } from '../dom/blocks/boundary.js';
 import { component_context } from '../context.js';
 import { UNINITIALIZED } from '../../../constants.js';
 
@@ -127,6 +127,16 @@ export function async_derived(fn, location) {
 					restore();
 					from_async_derived = null;
 
+					if (signal.v !== UNINITIALIZED) {
+						var boundary = get_boundary(parent);
+						// @ts-ignore
+						var forks = boundary.fn.forks;
+						var entry = forks.get(signal);
+						if (entry === undefined) {
+							entry = { v: signal.v };
+							forks.set(signal, entry);
+						}
+					}
 					internal_set(signal, v);
 
 					if (DEV && location !== undefined) {

packages/svelte/src/internal/client/reactivity/sources.js

@@ -171,7 +171,7 @@ export function set(source, value) {
  */
 export function internal_set(source, value) {
 	if (!source.equals(value)) {
-		possibly_fork(source);
+		possibly_fork_reactions(source);
 
 		var old_value = source.v;
 		source.v = value;
@@ -342,7 +342,7 @@ function fork_dependencies(signal, forks) {
  * @param {Value} signal
  * @returns {void}
  */
-function possibly_fork(signal) {
+function possibly_fork_reactions(signal) {
 	var reactions = signal.reactions;
 	if (reactions === null) return;
 
@@ -362,7 +362,7 @@ function possibly_fork(signal) {
 		// If the signal a) was previously clean or b) is an unowned derived, then mark it
 		if ((flags & (CLEAN | UNOWNED)) !== 0) {
 			if ((flags & DERIVED) !== 0) {
-				possibly_fork(/** @type {Derived} */ (reaction));
+				possibly_fork_reactions(/** @type {Derived} */ (reaction));
 			} else {
 				if ((reaction.f & ASYNC_DERIVED) !== 0) {
 					// if (active_effect === signal) {