revised

packages/svelte/src/internal/client/runtime.js

@@ -414,7 +414,13 @@ export function update_reaction(reaction) {
 	skipped_deps = 0;
 	untracked_writes = null;
 	active_reaction = (flags & (BRANCH_EFFECT | ROOT_EFFECT)) === 0 ? reaction : null;
-	skip_reaction = !is_flushing_effect && (flags & UNOWNED) !== 0;
+	// prettier-ignore
+	skip_reaction =
+		(flags & UNOWNED) !== 0 &&
+		(!is_flushing_effect ||
+				(/** @type {Derived} */ (reaction).parent !== null &&
+				(/** @type {Derived} */ (reaction).parent.f & DERIVED) !== 0));
+
 	derived_sources = null;
 	set_component_context(reaction.ctx);
 	untracking = false;
@@ -946,14 +952,14 @@ export function get(signal) {
 		var parent = derived.parent;
 
 		if (parent !== null) {
-			// Attach the derived to the nearest parent effect or derived
-			if ((parent.f & DERIVED) !== 0) {
-				var parent_derived = /** @type {Derived} */ (parent);
-
-				if (!parent_derived.children?.includes(derived)) {
-					(parent_derived.children ??= []).push(derived);
-				}
+			// If the derived is owned by another derived then mark it as unowned
+			// as the derived value might have been shared and thus we cannot determine
+			// a true
+			if ((parent.f & DERIVED) !== 0 && (parent.f & UNOWNED) === 0) {
+				debugger;
+				derived.f ^= UNOWNED;
 			} else {
+				// Otherwise we can attach the derieved to the parent effect
 				var parent_effect = /** @type {Effect} */ (parent);
 
 				if (!parent_effect.deriveds?.includes(derived)) {

packages/svelte/tests/signals/test.ts

@@ -538,6 +538,64 @@ describe('signals', () => {
 		};
 	});
 
+	test('mixed nested deriveds correctly cleanup when no longer connected to graph #1', () => {
+		let a: Derived<unknown>;
+		let b: Derived<unknown>;
+		let s = state(0);
+
+		const destroy = effect_root(() => {
+			render_effect(() => {
+				a = derived(() => {
+					b = derived(() => {
+						$.get(s);
+					});
+					$.untrack(() => {
+						$.get(b);
+					});
+					$.get(s);
+				});
+				$.get(a);
+			});
+		});
+
+		return () => {
+			flushSync();
+			assert.equal(a?.deps?.length, 1);
+			assert.equal(s?.reactions?.length, 1);
+			destroy();
+			assert.equal(s?.reactions, null);
+		};
+	});
+
+	test('mixed nested deriveds correctly cleanup when no longer connected to graph #2', () => {
+		let a: Derived<unknown>;
+		let b: Derived<unknown>;
+		let s = state(0);
+
+		const destroy = effect_root(() => {
+			render_effect(() => {
+				a = derived(() => {
+					b = derived(() => {
+						$.get(s);
+					});
+					effect_root(() => {
+						$.get(b);
+					});
+					$.get(s);
+				});
+				$.get(a);
+			});
+		});
+
+		return () => {
+			flushSync();
+			assert.equal(a?.deps?.length, 1);
+			assert.equal(s?.reactions?.length, 1);
+			destroy();
+			assert.equal(s?.reactions, null);
+		};
+	});
+
 	test('deriveds update upon reconnection #1', () => {
 		let a = state(false);
 		let b = state(false);