From f31e71556965869ecf981438735c28df2e375c47 Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Mon, 23 Mar 2026 10:52:05 -0400
Subject: [PATCH] bring tests over from async-blocking-and-merging

---
 .../async-discard-obsolete-batch/_config.js   |   6 +
 .../async-discard-obsolete-batch/main.svelte  |   7 +-
 .../_config.js                                |   2 +-
 .../async-overlap-multiple-1/_config.js       | 107 +++++++++++++++++
 .../async-overlap-multiple-1/main.svelte      |  26 +++++
 .../async-overlap-multiple-2/_config.js       |  81 +++++++++++++
 .../async-overlap-multiple-2/main.svelte      |  26 +++++
 .../async-overlap-multiple-3/_config.js       | 107 +++++++++++++++++
 .../async-overlap-multiple-3/main.svelte      |  26 +++++
 .../async-overlap-multiple-4/_config.js       | 109 ++++++++++++++++++
 .../async-overlap-multiple-4/main.svelte      |  26 +++++
 .../async-overlap-multiple-5/_config.js       |  87 ++++++++++++++
 .../async-overlap-multiple-5/main.svelte      |  23 ++++
 .../async-overlap-multiple-6/_config.js       |  76 ++++++++++++
 .../async-overlap-multiple-6/main.svelte      |  23 ++++
 .../async-overlap-multiple-7/_config.js       |  87 ++++++++++++++
 .../async-overlap-multiple-7/main.svelte      |  23 ++++
 .../async-overlap-multiple-fork-1/_config.js  |  34 ++++++
 .../async-overlap-multiple-fork-1/main.svelte |  27 +++++
 .../async-overlap-multiple-fork-2/_config.js  |  42 +++++++
 .../async-overlap-multiple-fork-2/main.svelte |  31 +++++
 .../async-state-new-branch-1/Child.svelte     |   7 ++
 .../async-state-new-branch-1/_config.js       |  37 ++++++
 .../async-state-new-branch-1/main.svelte      |  28 +++++
 .../async-state-new-branch-2/Child.svelte     |  11 ++
 .../async-state-new-branch-2/_config.js       |  48 ++++++++
 .../async-state-new-branch-2/main.svelte      |  30 +++++
 .../async-state-new-branch-3/Child.svelte     |  11 ++
 .../async-state-new-branch-3/_config.js       |  60 ++++++++++
 .../async-state-new-branch-3/main.svelte      |  34 ++++++
 .../async-state-new-branch-4/Child.svelte     |  11 ++
 .../async-state-new-branch-4/_config.js       |  75 ++++++++++++
 .../async-state-new-branch-4/main.svelte      |  32 +++++
 .../async-state-new-branch-5/Child.svelte     |  11 ++
 .../async-state-new-branch-5/_config.js       |  84 ++++++++++++++
 .../async-state-new-branch-5/main.svelte      |  36 ++++++
 36 files changed, 1489 insertions(+), 2 deletions(-)
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-1/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-1/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-2/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-2/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-3/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-3/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-4/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-4/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-5/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-5/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-6/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-6/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-7/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-7/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-fork-1/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-fork-1/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-fork-2/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-fork-2/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-state-new-branch-1/Child.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-state-new-branch-1/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-state-new-branch-1/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-state-new-branch-2/Child.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-state-new-branch-2/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-state-new-branch-2/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-state-new-branch-3/Child.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-state-new-branch-3/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-state-new-branch-3/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-state-new-branch-4/Child.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-state-new-branch-4/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-state-new-branch-4/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-state-new-branch-5/Child.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-state-new-branch-5/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-state-new-branch-5/main.svelte

diff --git a/packages/svelte/tests/runtime-runes/samples/async-discard-obsolete-batch/_config.js b/packages/svelte/tests/runtime-runes/samples/async-discard-obsolete-batch/_config.js
index 64e1a4b2b5..bd3b7e6960 100644
--- a/packages/svelte/tests/runtime-runes/samples/async-discard-obsolete-batch/_config.js
+++ b/packages/svelte/tests/runtime-runes/samples/async-discard-obsolete-batch/_config.js
@@ -14,6 +14,7 @@ export default test({
 				<button>shift</button>
 				<button>pop</button>
 				<p>1 = 1</p>
+				<p>hello</p>
 			`
 		);
 
@@ -29,6 +30,7 @@ export default test({
 				<button>shift</button>
 				<button>pop</button>
 				<p>1 = 1</p>
+				<p>hello</p>
 			`
 		);
 
@@ -42,6 +44,7 @@ export default test({
 				<button>shift</button>
 				<button>pop</button>
 				<p>1 = 1</p>
+				<p>hello</p>
 			`
 		);
 
@@ -55,6 +58,7 @@ export default test({
 				<button>shift</button>
 				<button>pop</button>
 				<p>3 = 3</p>
+				<p>goodbye</p>
 			`
 		);
 
@@ -70,6 +74,7 @@ export default test({
 				<button>shift</button>
 				<button>pop</button>
 				<p>3 = 3</p>
+				<p>goodbye</p>
 			`
 		);
 
@@ -83,6 +88,7 @@ export default test({
 				<button>shift</button>
 				<button>pop</button>
 				<p>5 = 5</p>
+				<p>goodbye</p>
 			`
 		);
 	}
diff --git a/packages/svelte/tests/runtime-runes/samples/async-discard-obsolete-batch/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-discard-obsolete-batch/main.svelte
index faa8d139a6..d42b3b545a 100644
--- a/packages/svelte/tests/runtime-runes/samples/async-discard-obsolete-batch/main.svelte
+++ b/packages/svelte/tests/runtime-runes/samples/async-discard-obsolete-batch/main.svelte
@@ -24,9 +24,13 @@
 	}
 
 	let n = $state(1);
+	let message = $state('hello');
 </script>
 
-<button onclick={() => n++}>
+<button onclick={() => {
+	n++;
+	message = 'goodbye';
+}}>
 	{$state.eager(n)}
 </button>
 
@@ -34,3 +38,4 @@
 <button onclick={pop}>pop</button>
 
 <p>{n} = {await push(n)}</p>
+<p>{message}</p>
\ No newline at end of file
diff --git a/packages/svelte/tests/runtime-runes/samples/async-linear-order-same-derived/_config.js b/packages/svelte/tests/runtime-runes/samples/async-linear-order-same-derived/_config.js
index cc7b2756fa..1e0da08eda 100644
--- a/packages/svelte/tests/runtime-runes/samples/async-linear-order-same-derived/_config.js
+++ b/packages/svelte/tests/runtime-runes/samples/async-linear-order-same-derived/_config.js
@@ -18,7 +18,7 @@ export default test({
 		pop.click();
 		await tick();
 
-		assert.htmlEqual(p.innerHTML, '1 + 3 = 4');
+		assert.htmlEqual(p.innerHTML, '2 + 3 = 5');
 
 		pop.click();
 		await tick();
diff --git a/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-1/_config.js b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-1/_config.js
new file mode 100644
index 0000000000..03d8e49b6f
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-1/_config.js
@@ -0,0 +1,107 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		await tick();
+		const [a_b, a_c, b_d, shift, pop] = target.querySelectorAll('button');
+
+		a_b.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a and b</button>
+			<button>a and c</button>
+			<button>b and d</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		a_c.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a and b</button>
+			<button>a and c</button>
+			<button>b and d</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		b_d.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a and b</button>
+			<button>a and c</button>
+			<button>b and d</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		shift.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a and b</button>
+			<button>a and c</button>
+			<button>b and d</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		shift.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 1 | b 1 | c 0 | d 0
+			<button>a and b</button>
+			<button>a and c</button>
+			<button>b and d</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		shift.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 2 | b 1 | c 1 | d 0
+			<button>a and b</button>
+			<button>a and c</button>
+			<button>b and d</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		shift.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 2 | b 2 | c 1 | d 1
+			<button>a and b</button>
+			<button>a and c</button>
+			<button>b and d</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-1/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-1/main.svelte
new file mode 100644
index 0000000000..25dbe586ca
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-1/main.svelte
@@ -0,0 +1,26 @@
+<script>
+	let a = $state(0);
+	let b = $state(0);
+	let c = $state(0);
+	let d = $state(0);
+
+	const deferred = [];
+
+	function delay(value) {
+		if (!value) return value;
+		return new Promise((resolve) => deferred.push(() => resolve(value)));
+	}
+</script>
+
+a {await delay(a)} | b {await delay(b)} | c {c} | d {d}
+<button onclick={() => {a++;b++;}}>
+	a and b
+</button>
+<button onclick={() => {a++;c++;}}>
+	a and c
+</button>
+<button onclick={() => {b++;d++;}}>
+	b and d
+</button>
+<button onclick={() => deferred.shift()?.()}>shift</button>
+<button onclick={() => deferred.pop()?.()}>pop</button>
diff --git a/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-2/_config.js b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-2/_config.js
new file mode 100644
index 0000000000..0f422d1797
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-2/_config.js
@@ -0,0 +1,81 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		await tick();
+		const [a_b, a_c, b_d, shift, pop] = target.querySelectorAll('button');
+
+		a_b.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a and b</button>
+			<button>a and c</button>
+			<button>b and d</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		a_c.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a and b</button>
+			<button>a and c</button>
+			<button>b and d</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		b_d.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a and b</button>
+			<button>a and c</button>
+			<button>b and d</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		pop.click(); // second b resolved, blocked on first batch because a still pending
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a and b</button>
+			<button>a and c</button>
+			<button>b and d</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		for (let i = 0; i < 3; i++) {
+			pop.click(); // second a resolved, first a/b now obsolete; empty queue
+			await tick();
+			assert.htmlEqual(
+				target.innerHTML,
+				`
+				a 2 | b 2 | c 1 | d 1
+				<button>a and b</button>
+				<button>a and c</button>
+				<button>b and d</button>
+				<button>shift</button>
+				<button>pop</button>
+			`
+			);
+		}
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-2/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-2/main.svelte
new file mode 100644
index 0000000000..25dbe586ca
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-2/main.svelte
@@ -0,0 +1,26 @@
+<script>
+	let a = $state(0);
+	let b = $state(0);
+	let c = $state(0);
+	let d = $state(0);
+
+	const deferred = [];
+
+	function delay(value) {
+		if (!value) return value;
+		return new Promise((resolve) => deferred.push(() => resolve(value)));
+	}
+</script>
+
+a {await delay(a)} | b {await delay(b)} | c {c} | d {d}
+<button onclick={() => {a++;b++;}}>
+	a and b
+</button>
+<button onclick={() => {a++;c++;}}>
+	a and c
+</button>
+<button onclick={() => {b++;d++;}}>
+	b and d
+</button>
+<button onclick={() => deferred.shift()?.()}>shift</button>
+<button onclick={() => deferred.pop()?.()}>pop</button>
diff --git a/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-3/_config.js b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-3/_config.js
new file mode 100644
index 0000000000..011588447f
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-3/_config.js
@@ -0,0 +1,107 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		await tick();
+		const [a_b, a_c, b_d, shift, pop] = target.querySelectorAll('button');
+
+		a_b.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a and b</button>
+			<button>a and c</button>
+			<button>b and d</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		a_c.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a and b</button>
+			<button>a and c</button>
+			<button>b and d</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		b_d.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a and b</button>
+			<button>a and c</button>
+			<button>b and d</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		shift.click(); // first a resolved, still pending: [b, a, b]
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a and b</button>
+			<button>a and c</button>
+			<button>b and d</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		pop.click(); // second b resolved, still pending: [b, a]
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a and b</button>
+			<button>a and c</button>
+			<button>b and d</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		shift.click(); // first b resolved, first + last batch settled, still pending: [a]
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 1 | b 2 | c 0 | d 1
+			<button>a and b</button>
+			<button>a and c</button>
+			<button>b and d</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		shift.click(); // all resolved
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 2 | b 2 | c 1 | d 1
+			<button>a and b</button>
+			<button>a and c</button>
+			<button>b and d</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-3/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-3/main.svelte
new file mode 100644
index 0000000000..25dbe586ca
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-3/main.svelte
@@ -0,0 +1,26 @@
+<script>
+	let a = $state(0);
+	let b = $state(0);
+	let c = $state(0);
+	let d = $state(0);
+
+	const deferred = [];
+
+	function delay(value) {
+		if (!value) return value;
+		return new Promise((resolve) => deferred.push(() => resolve(value)));
+	}
+</script>
+
+a {await delay(a)} | b {await delay(b)} | c {c} | d {d}
+<button onclick={() => {a++;b++;}}>
+	a and b
+</button>
+<button onclick={() => {a++;c++;}}>
+	a and c
+</button>
+<button onclick={() => {b++;d++;}}>
+	b and d
+</button>
+<button onclick={() => deferred.shift()?.()}>shift</button>
+<button onclick={() => deferred.pop()?.()}>pop</button>
diff --git a/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-4/_config.js b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-4/_config.js
new file mode 100644
index 0000000000..2c6226af07
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-4/_config.js
@@ -0,0 +1,109 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		await tick();
+		const [a_b, a_c, b_d, shift, pop] = target.querySelectorAll('button');
+
+		a_b.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a and b</button>
+			<button>a and c</button>
+			<button>b and d</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		a_c.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a and b</button>
+			<button>a and c</button>
+			<button>b and d</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		b_d.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a and b</button>
+			<button>a and c</button>
+			<button>b and d</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		shift.click(); // first a resolved, still pending: [b, a, b]
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a and b</button>
+			<button>a and c</button>
+			<button>b and d</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		pop.click(); // second b resolved, still pending: [b, a]
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a and b</button>
+			<button>a and c</button>
+			<button>b and d</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		pop.click(); // second a resolved, first a/b now obsolete
+		// TODO would be nice to show final result here already, right now it doesn't because
+		// we have no handle on the already resolved first a anymore
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a and b</button>
+			<button>a and c</button>
+			<button>b and d</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		shift.click(); // queue empty
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 2 | b 2 | c 1 | d 1
+			<button>a and b</button>
+			<button>a and c</button>
+			<button>b and d</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-4/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-4/main.svelte
new file mode 100644
index 0000000000..25dbe586ca
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-4/main.svelte
@@ -0,0 +1,26 @@
+<script>
+	let a = $state(0);
+	let b = $state(0);
+	let c = $state(0);
+	let d = $state(0);
+
+	const deferred = [];
+
+	function delay(value) {
+		if (!value) return value;
+		return new Promise((resolve) => deferred.push(() => resolve(value)));
+	}
+</script>
+
+a {await delay(a)} | b {await delay(b)} | c {c} | d {d}
+<button onclick={() => {a++;b++;}}>
+	a and b
+</button>
+<button onclick={() => {a++;c++;}}>
+	a and c
+</button>
+<button onclick={() => {b++;d++;}}>
+	b and d
+</button>
+<button onclick={() => deferred.shift()?.()}>shift</button>
+<button onclick={() => deferred.pop()?.()}>pop</button>
diff --git a/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-5/_config.js b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-5/_config.js
new file mode 100644
index 0000000000..f07c86dc0c
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-5/_config.js
@@ -0,0 +1,87 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		await tick();
+		const [a, c, shift, pop] = target.querySelectorAll('button');
+
+		a.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a++</button>
+			<button>c++</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		c.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a++</button>
+			<button>c++</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		shift.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a++</button>
+			<button>c++</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		shift.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a++</button>
+			<button>c++</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		shift.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 1 | b 2 | c 0 | d 2
+			<button>a++</button>
+			<button>c++</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		shift.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 1 | b 2 | c 1 | d 3
+			<button>a++</button>
+			<button>c++</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-5/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-5/main.svelte
new file mode 100644
index 0000000000..cf028718c2
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-5/main.svelte
@@ -0,0 +1,23 @@
+<script>
+	let a = $state(0);
+	let b = $derived(await delay(a * 2));
+	let c = $state(0);
+	let d = $derived(await delay(b + c));
+
+	const deferred = [];
+
+	function delay(value) {
+		if (!value) return value; 
+		return new Promise((resolve) => deferred.push(() => resolve(value)));
+	}
+</script>
+
+a {a} | b {b} | c {c} | d {d}
+<button onclick={() => {a++;}}>
+	a++
+</button>
+<button onclick={() => {c++;}}>
+	c++
+</button>
+<button onclick={() => deferred.shift()?.()}>shift</button>
+<button onclick={() => deferred.pop()?.()}>pop</button>
\ No newline at end of file
diff --git a/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-6/_config.js b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-6/_config.js
new file mode 100644
index 0000000000..27152889a2
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-6/_config.js
@@ -0,0 +1,76 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		await tick();
+		const [a, c, shift, pop] = target.querySelectorAll('button');
+
+		a.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a++</button>
+			<button>c++</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		c.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a++</button>
+			<button>c++</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		// Although the second batch is eventually connected to the first one, we can't see that
+		// at this point yet and so the second one flushes right away.
+		pop.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 1 | d 1
+			<button>a++</button>
+			<button>c++</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		pop.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 1 | d 1
+			<button>a++</button>
+			<button>c++</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		pop.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 1 | b 2 | c 1 | d 3
+			<button>a++</button>
+			<button>c++</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-6/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-6/main.svelte
new file mode 100644
index 0000000000..cf028718c2
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-6/main.svelte
@@ -0,0 +1,23 @@
+<script>
+	let a = $state(0);
+	let b = $derived(await delay(a * 2));
+	let c = $state(0);
+	let d = $derived(await delay(b + c));
+
+	const deferred = [];
+
+	function delay(value) {
+		if (!value) return value; 
+		return new Promise((resolve) => deferred.push(() => resolve(value)));
+	}
+</script>
+
+a {a} | b {b} | c {c} | d {d}
+<button onclick={() => {a++;}}>
+	a++
+</button>
+<button onclick={() => {c++;}}>
+	c++
+</button>
+<button onclick={() => deferred.shift()?.()}>shift</button>
+<button onclick={() => deferred.pop()?.()}>pop</button>
\ No newline at end of file
diff --git a/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-7/_config.js b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-7/_config.js
new file mode 100644
index 0000000000..62ba0e3f46
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-7/_config.js
@@ -0,0 +1,87 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		await tick();
+		const [a, c, shift, pop] = target.querySelectorAll('button');
+
+		a.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a++</button>
+			<button>c++</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		c.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a++</button>
+			<button>c++</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		shift.click(); // schedules second step of first batch and schedules rerun of second batch
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a++</button>
+			<button>c++</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		pop.click(); // second batch resolves but knows it needs to wait on first batch
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a++</button>
+			<button>c++</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		shift.click(); // obsolete second batch promise (already rejected)
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 0 | b 0 | c 0 | d 0
+			<button>a++</button>
+			<button>c++</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+
+		shift.click(); // first batch resolves, with it second can now resolve as well
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			a 1 | b 2 | c 1 | d 3
+			<button>a++</button>
+			<button>c++</button>
+			<button>shift</button>
+			<button>pop</button>
+		`
+		);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-7/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-7/main.svelte
new file mode 100644
index 0000000000..cf028718c2
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-7/main.svelte
@@ -0,0 +1,23 @@
+<script>
+	let a = $state(0);
+	let b = $derived(await delay(a * 2));
+	let c = $state(0);
+	let d = $derived(await delay(b + c));
+
+	const deferred = [];
+
+	function delay(value) {
+		if (!value) return value; 
+		return new Promise((resolve) => deferred.push(() => resolve(value)));
+	}
+</script>
+
+a {a} | b {b} | c {c} | d {d}
+<button onclick={() => {a++;}}>
+	a++
+</button>
+<button onclick={() => {c++;}}>
+	c++
+</button>
+<button onclick={() => deferred.shift()?.()}>shift</button>
+<button onclick={() => deferred.pop()?.()}>pop</button>
\ No newline at end of file
diff --git a/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-fork-1/_config.js b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-fork-1/_config.js
new file mode 100644
index 0000000000..07ce7e340f
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-fork-1/_config.js
@@ -0,0 +1,34 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		await tick();
+		const [a_b_fork, a_c, shift, pop, commit] = target.querySelectorAll('button');
+		const [p] = target.querySelectorAll('p');
+
+		a_b_fork.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, 'a 0 | b 0 | c 0');
+
+		a_c.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, 'a 0 | b 0 | c 0');
+
+		pop.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, 'a 1 | b 0 | c 1');
+
+		shift.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, 'a 1 | b 0 | c 1');
+
+		shift.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, 'a 1 | b 0 | c 1');
+
+		commit.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, 'a 1 | b 1 | c 1');
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-fork-1/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-fork-1/main.svelte
new file mode 100644
index 0000000000..60ba74fb8e
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-fork-1/main.svelte
@@ -0,0 +1,27 @@
+<script>
+	import { fork } from 'svelte';
+
+	let a = $state(0);
+	let b = $state(0);
+	let c = $state(0);
+	let f;
+
+	const deferred = [];
+
+	function delay(value) {
+		if (!value) return value;
+		return new Promise((resolve) => deferred.push(() => resolve(value)));
+	}
+</script>
+
+<p>a {await delay(a)} | b {await delay(b)} | c {c}</p>
+
+<button onclick={() => {f = fork(() => {a++;b++;});}}>
+	a and b (fork)
+</button>
+<button onclick={() => {a++;c++;}}>
+	a and c
+</button>
+<button onclick={() => deferred.shift()?.()}>shift</button>
+<button onclick={() => deferred.pop()?.()}>pop</button>
+<button onclick={() => f.commit()}>commit fork</button>
diff --git a/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-fork-2/_config.js b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-fork-2/_config.js
new file mode 100644
index 0000000000..180a190dae
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-fork-2/_config.js
@@ -0,0 +1,42 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		await tick();
+		const [a_b_fork, a_c, b_d, shift, pop, commit] = target.querySelectorAll('button');
+		const [p] = target.querySelectorAll('p');
+
+		a_b_fork.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, 'a 0 | b 0 | c 0 | d 0');
+
+		a_c.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, 'a 0 | b 0 | c 0 | d 0');
+
+		b_d.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, 'a 0 | b 0 | c 0 | d 0');
+
+		pop.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, 'a 0 | b 1 | c 0 | d 1');
+
+		pop.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, 'a 1 | b 1 | c 1 | d 1');
+
+		shift.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, 'a 1 | b 1 | c 1 | d 1');
+
+		shift.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, 'a 1 | b 1 | c 1 | d 1');
+
+		commit.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, 'a 1 | b 1 | c 1 | d 1');
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-fork-2/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-fork-2/main.svelte
new file mode 100644
index 0000000000..6d1c4ab418
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-overlap-multiple-fork-2/main.svelte
@@ -0,0 +1,31 @@
+<script>
+	import { fork } from 'svelte';
+
+	let a = $state(0);
+	let b = $state(0);
+	let c = $state(0);
+	let d = $state(0);
+	let f;
+
+	const deferred = [];
+
+	function delay(value) {
+		if (!value) return value;
+		return new Promise((resolve) => deferred.push(() => resolve(value)));
+	}
+</script>
+
+<p>a {await delay(a)} | b {await delay(b)} | c {c} | d {d}</p>
+
+<button onclick={() => {f = fork(() => {a++;b++;});}}>
+	a and b (fork)
+</button>
+<button onclick={() => {a++;c++;}}>
+	a and c
+</button>
+<button onclick={() => {b++;d++;}}>
+	b and d
+</button>
+<button onclick={() => deferred.shift()?.()}>shift</button>
+<button onclick={() => deferred.pop()?.()}>pop</button>
+<button onclick={() => f.commit()}>commit fork</button>
diff --git a/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-1/Child.svelte b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-1/Child.svelte
new file mode 100644
index 0000000000..6b765526c8
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-1/Child.svelte
@@ -0,0 +1,7 @@
+<script>
+	let { x } = $props();
+	console.log(x);
+	$effect(() => console.log('$effect: '+ x))
+</script>
+
+{x}
diff --git a/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-1/_config.js b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-1/_config.js
new file mode 100644
index 0000000000..28ce3c9d4f
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-1/_config.js
@@ -0,0 +1,37 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target, logs }) {
+		const [x, y, resolve] = target.querySelectorAll('button');
+
+		x.click();
+		await tick();
+
+		y.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			<button>x</button>
+			<button>y++</button>
+			<button>resolve</button>
+		`
+		);
+
+		resolve.click();
+		await tick();
+		assert.deepEqual(logs, ['universe', 'universe', '$effect: universe', '$effect: universe']);
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			<button>x</button>
+			<button>y++</button>
+			<button>resolve</button>
+			universe
+			universe
+			universe
+		`
+		);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-1/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-1/main.svelte
new file mode 100644
index 0000000000..8edc718de2
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-1/main.svelte
@@ -0,0 +1,28 @@
+<script>
+	import Child from './Child.svelte';
+
+	let x = $state('world');
+	let y = $state(0);
+	let deferred = [];
+
+	function delay(s) {
+		const d = Promise.withResolvers();
+		deferred.push(() => d.resolve(s))
+		return d.promise;
+	}
+</script>
+
+<button onclick={() => x = 'universe'}>x</button>
+
+<button onclick={() => y++}>y++</button>
+
+<button onclick={() => deferred.shift()()}>resolve</button>
+
+{#if x === 'universe'}
+	{await delay(x)}
+	<Child {x} />
+{/if}
+
+{#if y > 0}
+	<Child {x} />
+{/if}
diff --git a/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-2/Child.svelte b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-2/Child.svelte
new file mode 100644
index 0000000000..f8c01e9efd
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-2/Child.svelte
@@ -0,0 +1,11 @@
+<script>
+	let { x } = $props();
+</script>
+
+<!-- checks direct source, indirect derived, block effect, async effect -->
+{x}
+{JSON.stringify(x)}
+{#if x === 'universe'}universe{:else}world{/if}
+{#if JSON.stringify(x) === '"universe"'}universe{:else}world{/if}
+{await Promise.resolve(x)}
+{await Promise.resolve(JSON.stringify(x))}
\ No newline at end of file
diff --git a/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-2/_config.js b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-2/_config.js
new file mode 100644
index 0000000000..00b38262e8
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-2/_config.js
@@ -0,0 +1,48 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		const [x, y, resolve] = target.querySelectorAll('button');
+
+		x.click();
+		await tick();
+
+		y.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			<button>x</button>
+			<button>y++</button>
+			<button>resolve</button>
+			<hr>
+		`
+		);
+
+		resolve.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			<button>x</button>
+			<button>y++</button>
+			<button>resolve</button>
+			universe
+			universe
+			"universe"
+			universe
+			universe
+			universe
+			"universe"
+			<hr>
+			universe
+			"universe"
+			universe
+			universe
+			universe
+			"universe"
+		`
+		);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-2/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-2/main.svelte
new file mode 100644
index 0000000000..11c4bdf5d1
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-2/main.svelte
@@ -0,0 +1,30 @@
+<script>
+	import Child from './Child.svelte';
+
+	let x = $state('world');
+	let y = $state(0);
+	let deferred = [];
+
+	function delay(s) {
+		const d = Promise.withResolvers();
+		deferred.push(() => d.resolve(s))
+		return d.promise;
+	}
+</script>
+
+<button onclick={() => x = 'universe'}>x</button>
+
+<button onclick={() => y++}>y++</button>
+
+<button onclick={() => deferred.shift()()}>resolve</button>
+
+{#if x === 'universe'}
+	{await delay(x)}
+	<Child {x} />
+{/if}
+
+<hr>
+
+{#if y > 0}
+	<Child {x} />
+{/if}
diff --git a/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-3/Child.svelte b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-3/Child.svelte
new file mode 100644
index 0000000000..f8c01e9efd
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-3/Child.svelte
@@ -0,0 +1,11 @@
+<script>
+	let { x } = $props();
+</script>
+
+<!-- checks direct source, indirect derived, block effect, async effect -->
+{x}
+{JSON.stringify(x)}
+{#if x === 'universe'}universe{:else}world{/if}
+{#if JSON.stringify(x) === '"universe"'}universe{:else}world{/if}
+{await Promise.resolve(x)}
+{await Promise.resolve(JSON.stringify(x))}
\ No newline at end of file
diff --git a/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-3/_config.js b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-3/_config.js
new file mode 100644
index 0000000000..fe2765e76f
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-3/_config.js
@@ -0,0 +1,60 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		const [x, y, resolve] = target.querySelectorAll('button');
+
+		x.click();
+		await tick();
+
+		y.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			<button>x</button>
+			<button>y++</button>
+			<button>resolve</button>
+			<hr>
+		`
+		);
+
+		resolve.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			<button>x</button>
+			<button>y++</button>
+			<button>resolve</button>
+			<hr>
+		`
+		);
+
+		resolve.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			<button>x</button>
+			<button>y++</button>
+			<button>resolve</button>
+			universe
+			universe
+			"universe"
+			universe
+			universe
+			universe
+			"universe"
+			<hr>
+			universe
+			"universe"
+			universe
+			universe
+			universe
+			"universe"
+		`
+		);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-3/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-3/main.svelte
new file mode 100644
index 0000000000..b02ab20995
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-3/main.svelte
@@ -0,0 +1,34 @@
+<script>
+	import Child from './Child.svelte';
+
+	let x = $state('world');
+	let y = $state(0);
+
+	const deferred = [];
+
+	function delay(value) {
+		if (value !== 'universe') return value;
+		return new Promise((resolve) => deferred.push(() => resolve(value)));
+	}
+
+	function delay2(value) {
+		return new Promise((resolve) => deferred.push(() => resolve(value)));
+	}
+</script>
+
+<button onclick={() => (x = 'universe')}>x</button>
+
+<button onclick={() => y++}>y++</button>
+<button onclick={() => deferred.pop()?.()}>resolve</button>
+
+{#if x === 'universe'}
+	{await delay(x)}
+	<Child {x} />
+{/if}
+
+<hr>
+
+{#if y > 0}
+	<Child x={await delay2(x)} />
+{/if}
+ 
\ No newline at end of file
diff --git a/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-4/Child.svelte b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-4/Child.svelte
new file mode 100644
index 0000000000..f8c01e9efd
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-4/Child.svelte
@@ -0,0 +1,11 @@
+<script>
+	let { x } = $props();
+</script>
+
+<!-- checks direct source, indirect derived, block effect, async effect -->
+{x}
+{JSON.stringify(x)}
+{#if x === 'universe'}universe{:else}world{/if}
+{#if JSON.stringify(x) === '"universe"'}universe{:else}world{/if}
+{await Promise.resolve(x)}
+{await Promise.resolve(JSON.stringify(x))}
\ No newline at end of file
diff --git a/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-4/_config.js b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-4/_config.js
new file mode 100644
index 0000000000..a20f8c0ba5
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-4/_config.js
@@ -0,0 +1,75 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		const [x, y, resolve, commit] = target.querySelectorAll('button');
+
+		x.click();
+		await tick();
+
+		y.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			<button>x</button>
+			<button>y++</button>
+			<button>resolve</button>
+			<button>commit</button>
+			<hr>
+			world
+			"world"
+			world
+			world
+			world
+			"world"
+		`
+		);
+
+		commit.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			<button>x</button>
+			<button>y++</button>
+			<button>resolve</button>
+			<button>commit</button>
+			<hr>
+			world
+			"world"
+			world
+			world
+			world
+			"world"
+		`
+		);
+
+		resolve.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			<button>x</button>
+			<button>y++</button>
+			<button>resolve</button>
+			<button>commit</button>
+			universe
+			universe
+			"universe"
+			universe
+			universe
+			universe
+			"universe"
+			<hr>
+			universe
+			"universe"
+			universe
+			universe
+			universe
+			"universe"
+		`
+		);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-4/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-4/main.svelte
new file mode 100644
index 0000000000..5f00fc4dec
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-4/main.svelte
@@ -0,0 +1,32 @@
+<script>
+	import { fork } from 'svelte';
+	import Child from './Child.svelte';
+
+	let x = $state('world');
+	let y = $state(0);
+	let f;
+
+	const deferred = [];
+
+	function delay(value) {
+		if (value !== 'universe') return value;
+		return new Promise((resolve) => deferred.push(() => resolve(value)));
+	}
+</script>
+
+<button onclick={() => (f = fork(() => {x = 'universe';}))}>x</button>
+
+<button onclick={() => y++}>y++</button>
+<button onclick={() => deferred.pop()?.()}>resolve</button>
+<button onclick={() => f.commit()}>commit</button>
+
+{#if x === 'universe'}
+	{await delay(x)}
+	<Child {x} />
+{/if}
+
+<hr>
+
+{#if y > 0}
+	<Child {x} />
+{/if}
diff --git a/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-5/Child.svelte b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-5/Child.svelte
new file mode 100644
index 0000000000..f8c01e9efd
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-5/Child.svelte
@@ -0,0 +1,11 @@
+<script>
+	let { x } = $props();
+</script>
+
+<!-- checks direct source, indirect derived, block effect, async effect -->
+{x}
+{JSON.stringify(x)}
+{#if x === 'universe'}universe{:else}world{/if}
+{#if JSON.stringify(x) === '"universe"'}universe{:else}world{/if}
+{await Promise.resolve(x)}
+{await Promise.resolve(JSON.stringify(x))}
\ No newline at end of file
diff --git a/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-5/_config.js b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-5/_config.js
new file mode 100644
index 0000000000..e8f16ade3c
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-5/_config.js
@@ -0,0 +1,84 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		const [x, y, resolve, commit] = target.querySelectorAll('button');
+
+		x.click();
+		await tick();
+
+		y.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			<button>x</button>
+			<button>y++</button>
+			<button>resolve</button>
+			<button>commit</button>
+			<hr>
+		`
+		);
+
+		commit.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			<button>x</button>
+			<button>y++</button>
+			<button>resolve</button>
+			<button>commit</button>
+			<hr>
+		`
+		);
+
+		resolve.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			<button>x</button>
+			<button>y++</button>
+			<button>resolve</button>
+			<button>commit</button>
+			<hr>
+			world
+			"world"
+			world
+			world
+			world
+			"world"
+		`
+		);
+
+		resolve.click();
+		await tick();
+		resolve.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			<button>x</button>
+			<button>y++</button>
+			<button>resolve</button>
+			<button>commit</button>
+			universe
+			universe
+			"universe"
+			universe
+			universe
+			universe
+			"universe"
+			<hr>
+			universe
+			"universe"
+			universe
+			universe
+			universe
+			"universe"
+		`
+		);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-5/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-5/main.svelte
new file mode 100644
index 0000000000..5575e3cbd4
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-state-new-branch-5/main.svelte
@@ -0,0 +1,36 @@
+<script>
+	import { fork } from 'svelte';
+	import Child from './Child.svelte';
+
+	let x = $state('world');
+	let y = $state(0);
+	let f;
+
+	const deferred = [];
+
+	function delay(value) {
+		if (value !== 'universe') return value;
+		return new Promise((resolve) => deferred.push(() => resolve(value)));
+	}
+
+	function delay2(value) {
+		return new Promise((resolve) => deferred.push(() => resolve(value)));
+	}
+</script>
+
+<button onclick={() => (f = fork(() => {x = 'universe';}))}>x</button>
+
+<button onclick={() => y++}>y++</button>
+<button onclick={() => deferred.pop()?.()}>resolve</button>
+<button onclick={() => f.commit()}>commit</button>
+
+{#if x === 'universe'}
+	{await delay(x)}
+	<Child {x} />
+{/if}
+
+<hr>
+
+{#if y > 0}
+	<Child x={await delay2(x)} />
+{/if}