From 16e9c70d1e97ef37800a67086b821e4bc77aa634 Mon Sep 17 00:00:00 2001
From: "github-actions[bot]"
 <41898282+github-actions[bot]@users.noreply.github.com>
Date: Mon, 19 Jan 2026 20:47:01 +0100
Subject: [PATCH 1/7] Version Packages (#17488)

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
---
 .changeset/social-foxes-pull.md | 5 -----
 packages/svelte/CHANGELOG.md    | 6 ++++++
 packages/svelte/package.json    | 2 +-
 packages/svelte/src/version.js  | 2 +-
 4 files changed, 8 insertions(+), 7 deletions(-)
 delete mode 100644 .changeset/social-foxes-pull.md

diff --git a/.changeset/social-foxes-pull.md b/.changeset/social-foxes-pull.md
deleted file mode 100644
index d164d43f7b..0000000000
--- a/.changeset/social-foxes-pull.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-fix: trigger `selectedcontent` reactivity
diff --git a/packages/svelte/CHANGELOG.md b/packages/svelte/CHANGELOG.md
index e222997351..d019b7883f 100644
--- a/packages/svelte/CHANGELOG.md
+++ b/packages/svelte/CHANGELOG.md
@@ -1,5 +1,11 @@
 # svelte
 
+## 5.47.1
+
+### Patch Changes
+
+- fix: trigger `selectedcontent` reactivity ([#17486](https://github.com/sveltejs/svelte/pull/17486))
+
 ## 5.47.0
 
 ### Minor Changes
diff --git a/packages/svelte/package.json b/packages/svelte/package.json
index 19e37aaa93..38cac7b1cd 100644
--- a/packages/svelte/package.json
+++ b/packages/svelte/package.json
@@ -2,7 +2,7 @@
   "name": "svelte",
   "description": "Cybernetically enhanced web apps",
   "license": "MIT",
-  "version": "5.47.0",
+  "version": "5.47.1",
   "type": "module",
   "types": "./types/index.d.ts",
   "engines": {
diff --git a/packages/svelte/src/version.js b/packages/svelte/src/version.js
index 38b2a77f4a..a5360f7195 100644
--- a/packages/svelte/src/version.js
+++ b/packages/svelte/src/version.js
@@ -4,5 +4,5 @@
  * The current version, as set in package.json.
  * @type {string}
  */
-export const VERSION = '5.47.0';
+export const VERSION = '5.47.1';
 export const PUBLIC_VERSION = '5';

From 2eb54f57ae9b2411a40f10266133356ab647d907 Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Mon, 19 Jan 2026 18:26:51 -0500
Subject: [PATCH 2/7] chore: tidy up benchmark code (#17490)

* add create_test utility

* add missing import

* DRY

* DRY out

* mol (this affects benchmark times, because create_test uses 1e3 iterations whereas the old code used 1e4)

* move utils.js

* WIP

* DRY

* reduce indirection

* more

* tidy up

* tidy up

* colocate

* DRY out
---
 benchmarking/benchmarks/reactivity/index.js   |  46 +-
 .../reactivity/kairo/kairo_avoidable.js       |  91 ----
 .../reactivity/kairo/kairo_broad.js           |  97 ----
 .../benchmarks/reactivity/kairo/kairo_deep.js |  97 ----
 .../reactivity/kairo/kairo_diamond.js         | 101 ----
 .../benchmarks/reactivity/kairo/kairo_mux.js  |  94 ----
 .../reactivity/kairo/kairo_repeated.js        |  98 ----
 .../reactivity/kairo/kairo_triangle.js        | 111 -----
 .../reactivity/kairo/kairo_unstable.js        |  97 ----
 .../benchmarks/reactivity/kairo/util.js       |   6 -
 benchmarking/benchmarks/reactivity/sbench.js  | 469 ++++++------------
 .../reactivity/tests/kairo_avoidable.bench.js |  35 ++
 .../reactivity/tests/kairo_broad.bench.js     |  41 ++
 .../reactivity/tests/kairo_deep.bench.js      |  41 ++
 .../reactivity/tests/kairo_diamond.bench.js   |  45 ++
 .../reactivity/tests/kairo_mux.bench.js       |  38 ++
 .../reactivity/tests/kairo_repeated.bench.js  |  42 ++
 .../reactivity/tests/kairo_triangle.bench.js  |  55 ++
 .../reactivity/tests/kairo_unstable.bench.js  |  41 ++
 .../{mol_bench.js => tests/mol.bench.js}      |  62 +--
 benchmarking/benchmarks/reactivity/util.js    |  73 +++
 21 files changed, 577 insertions(+), 1203 deletions(-)
 delete mode 100644 benchmarking/benchmarks/reactivity/kairo/kairo_avoidable.js
 delete mode 100644 benchmarking/benchmarks/reactivity/kairo/kairo_broad.js
 delete mode 100644 benchmarking/benchmarks/reactivity/kairo/kairo_deep.js
 delete mode 100644 benchmarking/benchmarks/reactivity/kairo/kairo_diamond.js
 delete mode 100644 benchmarking/benchmarks/reactivity/kairo/kairo_mux.js
 delete mode 100644 benchmarking/benchmarks/reactivity/kairo/kairo_repeated.js
 delete mode 100644 benchmarking/benchmarks/reactivity/kairo/kairo_triangle.js
 delete mode 100644 benchmarking/benchmarks/reactivity/kairo/kairo_unstable.js
 delete mode 100644 benchmarking/benchmarks/reactivity/kairo/util.js
 create mode 100644 benchmarking/benchmarks/reactivity/tests/kairo_avoidable.bench.js
 create mode 100644 benchmarking/benchmarks/reactivity/tests/kairo_broad.bench.js
 create mode 100644 benchmarking/benchmarks/reactivity/tests/kairo_deep.bench.js
 create mode 100644 benchmarking/benchmarks/reactivity/tests/kairo_diamond.bench.js
 create mode 100644 benchmarking/benchmarks/reactivity/tests/kairo_mux.bench.js
 create mode 100644 benchmarking/benchmarks/reactivity/tests/kairo_repeated.bench.js
 create mode 100644 benchmarking/benchmarks/reactivity/tests/kairo_triangle.bench.js
 create mode 100644 benchmarking/benchmarks/reactivity/tests/kairo_unstable.bench.js
 rename benchmarking/benchmarks/reactivity/{mol_bench.js => tests/mol.bench.js} (56%)
 create mode 100644 benchmarking/benchmarks/reactivity/util.js

diff --git a/benchmarking/benchmarks/reactivity/index.js b/benchmarking/benchmarks/reactivity/index.js
index 58b3f5cb29..2b75b3dfc6 100644
--- a/benchmarking/benchmarks/reactivity/index.js
+++ b/benchmarking/benchmarks/reactivity/index.js
@@ -1,12 +1,5 @@
-import { kairo_avoidable_owned, kairo_avoidable_unowned } from './kairo/kairo_avoidable.js';
-import { kairo_broad_owned, kairo_broad_unowned } from './kairo/kairo_broad.js';
-import { kairo_deep_owned, kairo_deep_unowned } from './kairo/kairo_deep.js';
-import { kairo_diamond_owned, kairo_diamond_unowned } from './kairo/kairo_diamond.js';
-import { kairo_mux_unowned, kairo_mux_owned } from './kairo/kairo_mux.js';
-import { kairo_repeated_unowned, kairo_repeated_owned } from './kairo/kairo_repeated.js';
-import { kairo_triangle_owned, kairo_triangle_unowned } from './kairo/kairo_triangle.js';
-import { kairo_unstable_owned, kairo_unstable_unowned } from './kairo/kairo_unstable.js';
-import { mol_bench_owned, mol_bench_unowned } from './mol_bench.js';
+import fs from 'node:fs';
+import path from 'node:path';
 import {
 	sbench_create_0to1,
 	sbench_create_1000to1,
@@ -19,10 +12,14 @@ import {
 	sbench_create_4to1,
 	sbench_create_signals
 } from './sbench.js';
+import { fileURLToPath } from 'node:url';
+import { create_test } from './util.js';
 
 // This benchmark has been adapted from the js-reactivity-benchmark (https://github.com/milomg/js-reactivity-benchmark)
 // Not all tests are the same, and many parts have been tweaked to capture different data.
 
+const dirname = path.dirname(fileURLToPath(import.meta.url));
+
 export const reactivity_benchmarks = [
 	sbench_create_signals,
 	sbench_create_0to1,
@@ -33,23 +30,16 @@ export const reactivity_benchmarks = [
 	sbench_create_1to2,
 	sbench_create_1to4,
 	sbench_create_1to8,
-	sbench_create_1to1000,
-	kairo_avoidable_owned,
-	kairo_avoidable_unowned,
-	kairo_broad_owned,
-	kairo_broad_unowned,
-	kairo_deep_owned,
-	kairo_deep_unowned,
-	kairo_diamond_owned,
-	kairo_diamond_unowned,
-	kairo_triangle_owned,
-	kairo_triangle_unowned,
-	kairo_mux_owned,
-	kairo_mux_unowned,
-	kairo_repeated_owned,
-	kairo_repeated_unowned,
-	kairo_unstable_owned,
-	kairo_unstable_unowned,
-	mol_bench_owned,
-	mol_bench_unowned
+	sbench_create_1to1000
 ];
+
+for (const file of fs.readdirSync(`${dirname}/tests`)) {
+	if (!file.includes('.bench.')) continue;
+
+	const name = file.replace('.bench.js', '');
+
+	const module = await import(`${dirname}/tests/${file}`);
+	const { owned, unowned } = create_test(name, module.default);
+
+	reactivity_benchmarks.push(owned, unowned);
+}
diff --git a/benchmarking/benchmarks/reactivity/kairo/kairo_avoidable.js b/benchmarking/benchmarks/reactivity/kairo/kairo_avoidable.js
deleted file mode 100644
index 9daea6de99..0000000000
--- a/benchmarking/benchmarks/reactivity/kairo/kairo_avoidable.js
+++ /dev/null
@@ -1,91 +0,0 @@
-import { assert, fastest_test } from '../../../utils.js';
-import * as $ from 'svelte/internal/client';
-import { busy } from './util.js';
-
-function setup() {
-	let head = $.state(0);
-	let computed1 = $.derived(() => $.get(head));
-	let computed2 = $.derived(() => ($.get(computed1), 0));
-	let computed3 = $.derived(() => (busy(), $.get(computed2) + 1)); // heavy computation
-	let computed4 = $.derived(() => $.get(computed3) + 2);
-	let computed5 = $.derived(() => $.get(computed4) + 3);
-
-	const destroy = $.effect_root(() => {
-		$.render_effect(() => {
-			$.get(computed5);
-			busy(); // heavy side effect
-		});
-	});
-
-	return {
-		destroy,
-		run() {
-			$.flush(() => {
-				$.set(head, 1);
-			});
-			assert($.get(computed5) === 6);
-			for (let i = 0; i < 1000; i++) {
-				$.flush(() => {
-					$.set(head, i);
-				});
-				assert($.get(computed5) === 6);
-			}
-		}
-	};
-}
-
-export async function kairo_avoidable_unowned() {
-	// Do 10 loops to warm up JIT
-	for (let i = 0; i < 10; i++) {
-		const { run, destroy } = setup();
-		run();
-		destroy();
-	}
-
-	const { run, destroy } = setup();
-
-	const { timing } = await fastest_test(10, () => {
-		for (let i = 0; i < 1000; i++) {
-			run();
-		}
-	});
-
-	destroy();
-
-	return {
-		benchmark: 'kairo_avoidable_unowned',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
-	};
-}
-
-export async function kairo_avoidable_owned() {
-	let run, destroy;
-
-	const destroy_owned = $.effect_root(() => {
-		// Do 10 loops to warm up JIT
-		for (let i = 0; i < 10; i++) {
-			const { run, destroy } = setup();
-			run();
-			destroy();
-		}
-
-		({ run, destroy } = setup());
-	});
-
-	const { timing } = await fastest_test(10, () => {
-		for (let i = 0; i < 1000; i++) {
-			run();
-		}
-	});
-
-	// @ts-ignore
-	destroy();
-	destroy_owned();
-
-	return {
-		benchmark: 'kairo_avoidable_owned',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
-	};
-}
diff --git a/benchmarking/benchmarks/reactivity/kairo/kairo_broad.js b/benchmarking/benchmarks/reactivity/kairo/kairo_broad.js
deleted file mode 100644
index 8dc5710c87..0000000000
--- a/benchmarking/benchmarks/reactivity/kairo/kairo_broad.js
+++ /dev/null
@@ -1,97 +0,0 @@
-import { assert, fastest_test } from '../../../utils.js';
-import * as $ from 'svelte/internal/client';
-
-function setup() {
-	let head = $.state(0);
-	let last = head;
-	let counter = 0;
-
-	const destroy = $.effect_root(() => {
-		for (let i = 0; i < 50; i++) {
-			let current = $.derived(() => {
-				return $.get(head) + i;
-			});
-			let current2 = $.derived(() => {
-				return $.get(current) + 1;
-			});
-			$.render_effect(() => {
-				$.get(current2);
-				counter++;
-			});
-			last = current2;
-		}
-	});
-
-	return {
-		destroy,
-		run() {
-			$.flush(() => {
-				$.set(head, 1);
-			});
-			counter = 0;
-			for (let i = 0; i < 50; i++) {
-				$.flush(() => {
-					$.set(head, i);
-				});
-				assert($.get(last) === i + 50);
-			}
-			assert(counter === 50 * 50);
-		}
-	};
-}
-
-export async function kairo_broad_unowned() {
-	// Do 10 loops to warm up JIT
-	for (let i = 0; i < 10; i++) {
-		const { run, destroy } = setup();
-		run();
-		destroy();
-	}
-
-	const { run, destroy } = setup();
-
-	const { timing } = await fastest_test(10, () => {
-		for (let i = 0; i < 1000; i++) {
-			run();
-		}
-	});
-
-	destroy();
-
-	return {
-		benchmark: 'kairo_broad_unowned',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
-	};
-}
-
-export async function kairo_broad_owned() {
-	let run, destroy;
-
-	const destroy_owned = $.effect_root(() => {
-		// Do 10 loops to warm up JIT
-		for (let i = 0; i < 10; i++) {
-			const { run, destroy } = setup();
-			run();
-			destroy();
-		}
-
-		({ run, destroy } = setup());
-	});
-
-	const { timing } = await fastest_test(10, () => {
-		for (let i = 0; i < 1000; i++) {
-			run();
-		}
-	});
-
-	// @ts-ignore
-	destroy();
-	destroy_owned();
-
-	return {
-		benchmark: 'kairo_broad_owned',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
-	};
-}
diff --git a/benchmarking/benchmarks/reactivity/kairo/kairo_deep.js b/benchmarking/benchmarks/reactivity/kairo/kairo_deep.js
deleted file mode 100644
index 8690c85f86..0000000000
--- a/benchmarking/benchmarks/reactivity/kairo/kairo_deep.js
+++ /dev/null
@@ -1,97 +0,0 @@
-import { assert, fastest_test } from '../../../utils.js';
-import * as $ from 'svelte/internal/client';
-
-let len = 50;
-const iter = 50;
-
-function setup() {
-	let head = $.state(0);
-	let current = head;
-	for (let i = 0; i < len; i++) {
-		let c = current;
-		current = $.derived(() => {
-			return $.get(c) + 1;
-		});
-	}
-	let counter = 0;
-
-	const destroy = $.effect_root(() => {
-		$.render_effect(() => {
-			$.get(current);
-			counter++;
-		});
-	});
-
-	return {
-		destroy,
-		run() {
-			$.flush(() => {
-				$.set(head, 1);
-			});
-			counter = 0;
-			for (let i = 0; i < iter; i++) {
-				$.flush(() => {
-					$.set(head, i);
-				});
-				assert($.get(current) === len + i);
-			}
-			assert(counter === iter);
-		}
-	};
-}
-
-export async function kairo_deep_unowned() {
-	// Do 10 loops to warm up JIT
-	for (let i = 0; i < 10; i++) {
-		const { run, destroy } = setup();
-		run();
-		destroy();
-	}
-
-	const { run, destroy } = setup();
-
-	const { timing } = await fastest_test(10, () => {
-		for (let i = 0; i < 1000; i++) {
-			run();
-		}
-	});
-
-	destroy();
-
-	return {
-		benchmark: 'kairo_deep_unowned',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
-	};
-}
-
-export async function kairo_deep_owned() {
-	let run, destroy;
-
-	const destroy_owned = $.effect_root(() => {
-		// Do 10 loops to warm up JIT
-		for (let i = 0; i < 10; i++) {
-			const { run, destroy } = setup();
-			run();
-			destroy();
-		}
-
-		({ run, destroy } = setup());
-	});
-
-	const { timing } = await fastest_test(10, () => {
-		for (let i = 0; i < 1000; i++) {
-			run();
-		}
-	});
-
-	// @ts-ignore
-	destroy();
-	destroy_owned();
-
-	return {
-		benchmark: 'kairo_deep_owned',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
-	};
-}
diff --git a/benchmarking/benchmarks/reactivity/kairo/kairo_diamond.js b/benchmarking/benchmarks/reactivity/kairo/kairo_diamond.js
deleted file mode 100644
index bf4e07ee89..0000000000
--- a/benchmarking/benchmarks/reactivity/kairo/kairo_diamond.js
+++ /dev/null
@@ -1,101 +0,0 @@
-import { assert, fastest_test } from '../../../utils.js';
-import * as $ from 'svelte/internal/client';
-
-let width = 5;
-
-function setup() {
-	let head = $.state(0);
-	let current = [];
-	for (let i = 0; i < width; i++) {
-		current.push(
-			$.derived(() => {
-				return $.get(head) + 1;
-			})
-		);
-	}
-	let sum = $.derived(() => {
-		return current.map((x) => $.get(x)).reduce((a, b) => a + b, 0);
-	});
-	let counter = 0;
-
-	const destroy = $.effect_root(() => {
-		$.render_effect(() => {
-			$.get(sum);
-			counter++;
-		});
-	});
-
-	return {
-		destroy,
-		run() {
-			$.flush(() => {
-				$.set(head, 1);
-			});
-			assert($.get(sum) === 2 * width);
-			counter = 0;
-			for (let i = 0; i < 500; i++) {
-				$.flush(() => {
-					$.set(head, i);
-				});
-				assert($.get(sum) === (i + 1) * width);
-			}
-			assert(counter === 500);
-		}
-	};
-}
-
-export async function kairo_diamond_unowned() {
-	// Do 10 loops to warm up JIT
-	for (let i = 0; i < 10; i++) {
-		const { run, destroy } = setup();
-		run();
-		destroy();
-	}
-
-	const { run, destroy } = setup();
-
-	const { timing } = await fastest_test(10, () => {
-		for (let i = 0; i < 1000; i++) {
-			run();
-		}
-	});
-
-	destroy();
-
-	return {
-		benchmark: 'kairo_diamond_unowned',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
-	};
-}
-
-export async function kairo_diamond_owned() {
-	let run, destroy;
-
-	const destroy_owned = $.effect_root(() => {
-		// Do 10 loops to warm up JIT
-		for (let i = 0; i < 10; i++) {
-			const { run, destroy } = setup();
-			run();
-			destroy();
-		}
-
-		({ run, destroy } = setup());
-	});
-
-	const { timing } = await fastest_test(10, () => {
-		for (let i = 0; i < 1000; i++) {
-			run();
-		}
-	});
-
-	// @ts-ignore
-	destroy();
-	destroy_owned();
-
-	return {
-		benchmark: 'kairo_diamond_owned',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
-	};
-}
diff --git a/benchmarking/benchmarks/reactivity/kairo/kairo_mux.js b/benchmarking/benchmarks/reactivity/kairo/kairo_mux.js
deleted file mode 100644
index fc252a27b5..0000000000
--- a/benchmarking/benchmarks/reactivity/kairo/kairo_mux.js
+++ /dev/null
@@ -1,94 +0,0 @@
-import { assert, fastest_test } from '../../../utils.js';
-import * as $ from 'svelte/internal/client';
-
-function setup() {
-	let heads = new Array(100).fill(null).map((_) => $.state(0));
-	const mux = $.derived(() => {
-		return Object.fromEntries(heads.map((h) => $.get(h)).entries());
-	});
-	const splited = heads
-		.map((_, index) => $.derived(() => $.get(mux)[index]))
-		.map((x) => $.derived(() => $.get(x) + 1));
-
-	const destroy = $.effect_root(() => {
-		splited.forEach((x) => {
-			$.render_effect(() => {
-				$.get(x);
-			});
-		});
-	});
-
-	return {
-		destroy,
-		run() {
-			for (let i = 0; i < 10; i++) {
-				$.flush(() => {
-					$.set(heads[i], i);
-				});
-				assert($.get(splited[i]) === i + 1);
-			}
-			for (let i = 0; i < 10; i++) {
-				$.flush(() => {
-					$.set(heads[i], i * 2);
-				});
-				assert($.get(splited[i]) === i * 2 + 1);
-			}
-		}
-	};
-}
-
-export async function kairo_mux_unowned() {
-	// Do 10 loops to warm up JIT
-	for (let i = 0; i < 10; i++) {
-		const { run, destroy } = setup();
-		run();
-		destroy();
-	}
-
-	const { run, destroy } = setup();
-
-	const { timing } = await fastest_test(10, () => {
-		for (let i = 0; i < 1000; i++) {
-			run();
-		}
-	});
-
-	destroy();
-
-	return {
-		benchmark: 'kairo_mux_unowned',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
-	};
-}
-
-export async function kairo_mux_owned() {
-	let run, destroy;
-
-	const destroy_owned = $.effect_root(() => {
-		// Do 10 loops to warm up JIT
-		for (let i = 0; i < 10; i++) {
-			const { run, destroy } = setup();
-			run();
-			destroy();
-		}
-
-		({ run, destroy } = setup());
-	});
-
-	const { timing } = await fastest_test(10, () => {
-		for (let i = 0; i < 1000; i++) {
-			run();
-		}
-	});
-
-	// @ts-ignore
-	destroy();
-	destroy_owned();
-
-	return {
-		benchmark: 'kairo_mux_owned',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
-	};
-}
diff --git a/benchmarking/benchmarks/reactivity/kairo/kairo_repeated.js b/benchmarking/benchmarks/reactivity/kairo/kairo_repeated.js
deleted file mode 100644
index 3bee06ca0e..0000000000
--- a/benchmarking/benchmarks/reactivity/kairo/kairo_repeated.js
+++ /dev/null
@@ -1,98 +0,0 @@
-import { assert, fastest_test } from '../../../utils.js';
-import * as $ from 'svelte/internal/client';
-
-let size = 30;
-
-function setup() {
-	let head = $.state(0);
-	let current = $.derived(() => {
-		let result = 0;
-		for (let i = 0; i < size; i++) {
-			result += $.get(head);
-		}
-		return result;
-	});
-
-	let counter = 0;
-
-	const destroy = $.effect_root(() => {
-		$.render_effect(() => {
-			$.get(current);
-			counter++;
-		});
-	});
-
-	return {
-		destroy,
-		run() {
-			$.flush(() => {
-				$.set(head, 1);
-			});
-			assert($.get(current) === size);
-			counter = 0;
-			for (let i = 0; i < 100; i++) {
-				$.flush(() => {
-					$.set(head, i);
-				});
-				assert($.get(current) === i * size);
-			}
-			assert(counter === 100);
-		}
-	};
-}
-
-export async function kairo_repeated_unowned() {
-	// Do 10 loops to warm up JIT
-	for (let i = 0; i < 10; i++) {
-		const { run, destroy } = setup();
-		run();
-		destroy();
-	}
-
-	const { run, destroy } = setup();
-
-	const { timing } = await fastest_test(10, () => {
-		for (let i = 0; i < 1000; i++) {
-			run();
-		}
-	});
-
-	destroy();
-
-	return {
-		benchmark: 'kairo_repeated_unowned',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
-	};
-}
-
-export async function kairo_repeated_owned() {
-	let run, destroy;
-
-	const destroy_owned = $.effect_root(() => {
-		// Do 10 loops to warm up JIT
-		for (let i = 0; i < 10; i++) {
-			const { run, destroy } = setup();
-			run();
-			destroy();
-		}
-
-		({ run, destroy } = setup());
-	});
-
-	const { timing } = await fastest_test(10, () => {
-		for (let i = 0; i < 1000; i++) {
-			run();
-		}
-	});
-
-	// @ts-ignore
-	destroy();
-	destroy_owned();
-
-	return {
-		benchmark: 'kairo_repeated_owned',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
-	};
-}
diff --git a/benchmarking/benchmarks/reactivity/kairo/kairo_triangle.js b/benchmarking/benchmarks/reactivity/kairo/kairo_triangle.js
deleted file mode 100644
index 11a419a52e..0000000000
--- a/benchmarking/benchmarks/reactivity/kairo/kairo_triangle.js
+++ /dev/null
@@ -1,111 +0,0 @@
-import { assert, fastest_test } from '../../../utils.js';
-import * as $ from 'svelte/internal/client';
-
-let width = 10;
-
-function count(number) {
-	return new Array(number)
-		.fill(0)
-		.map((_, i) => i + 1)
-		.reduce((x, y) => x + y, 0);
-}
-
-function setup() {
-	let head = $.state(0);
-	let current = head;
-	let list = [];
-	for (let i = 0; i < width; i++) {
-		let c = current;
-		list.push(current);
-		current = $.derived(() => {
-			return $.get(c) + 1;
-		});
-	}
-	let sum = $.derived(() => {
-		return list.map((x) => $.get(x)).reduce((a, b) => a + b, 0);
-	});
-
-	let counter = 0;
-
-	const destroy = $.effect_root(() => {
-		$.render_effect(() => {
-			$.get(sum);
-			counter++;
-		});
-	});
-
-	return {
-		destroy,
-		run() {
-			const constant = count(width);
-			$.flush(() => {
-				$.set(head, 1);
-			});
-			assert($.get(sum) === constant);
-			counter = 0;
-			for (let i = 0; i < 100; i++) {
-				$.flush(() => {
-					$.set(head, i);
-				});
-				assert($.get(sum) === constant - width + i * width);
-			}
-			assert(counter === 100);
-		}
-	};
-}
-
-export async function kairo_triangle_unowned() {
-	// Do 10 loops to warm up JIT
-	for (let i = 0; i < 10; i++) {
-		const { run, destroy } = setup();
-		run();
-		destroy();
-	}
-
-	const { run, destroy } = setup();
-
-	const { timing } = await fastest_test(10, () => {
-		for (let i = 0; i < 1000; i++) {
-			run();
-		}
-	});
-
-	destroy();
-
-	return {
-		benchmark: 'kairo_triangle_unowned',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
-	};
-}
-
-export async function kairo_triangle_owned() {
-	let run, destroy;
-
-	const destroy_owned = $.effect_root(() => {
-		// Do 10 loops to warm up JIT
-		for (let i = 0; i < 10; i++) {
-			const { run, destroy } = setup();
-			run();
-			destroy();
-		}
-
-		({ run, destroy } = setup());
-	});
-
-	const { timing } = await fastest_test(10, () => {
-		for (let i = 0; i < 1000; i++) {
-			run();
-		}
-	});
-
-	// @ts-ignore
-	destroy();
-	destroy_owned();
-
-	return {
-		benchmark: 'kairo_triangle_owned',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
-	};
-}
diff --git a/benchmarking/benchmarks/reactivity/kairo/kairo_unstable.js b/benchmarking/benchmarks/reactivity/kairo/kairo_unstable.js
deleted file mode 100644
index 54eb732cb2..0000000000
--- a/benchmarking/benchmarks/reactivity/kairo/kairo_unstable.js
+++ /dev/null
@@ -1,97 +0,0 @@
-import { assert, fastest_test } from '../../../utils.js';
-import * as $ from 'svelte/internal/client';
-
-function setup() {
-	let head = $.state(0);
-	const double = $.derived(() => $.get(head) * 2);
-	const inverse = $.derived(() => -$.get(head));
-	let current = $.derived(() => {
-		let result = 0;
-		for (let i = 0; i < 20; i++) {
-			result += $.get(head) % 2 ? $.get(double) : $.get(inverse);
-		}
-		return result;
-	});
-
-	let counter = 0;
-
-	const destroy = $.effect_root(() => {
-		$.render_effect(() => {
-			$.get(current);
-			counter++;
-		});
-	});
-
-	return {
-		destroy,
-		run() {
-			$.flush(() => {
-				$.set(head, 1);
-			});
-			assert($.get(current) === 40);
-			counter = 0;
-			for (let i = 0; i < 100; i++) {
-				$.flush(() => {
-					$.set(head, i);
-				});
-			}
-			assert(counter === 100);
-		}
-	};
-}
-
-export async function kairo_unstable_unowned() {
-	// Do 10 loops to warm up JIT
-	for (let i = 0; i < 10; i++) {
-		const { run, destroy } = setup();
-		run();
-		destroy();
-	}
-
-	const { run, destroy } = setup();
-
-	const { timing } = await fastest_test(10, () => {
-		for (let i = 0; i < 1000; i++) {
-			run();
-		}
-	});
-
-	destroy();
-
-	return {
-		benchmark: 'kairo_unstable_unowned',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
-	};
-}
-
-export async function kairo_unstable_owned() {
-	let run, destroy;
-
-	const destroy_owned = $.effect_root(() => {
-		// Do 10 loops to warm up JIT
-		for (let i = 0; i < 10; i++) {
-			const { run, destroy } = setup();
-			run();
-			destroy();
-		}
-
-		({ run, destroy } = setup());
-	});
-
-	const { timing } = await fastest_test(10, () => {
-		for (let i = 0; i < 1000; i++) {
-			run();
-		}
-	});
-
-	// @ts-ignore
-	destroy();
-	destroy_owned();
-
-	return {
-		benchmark: 'kairo_unstable_owned',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
-	};
-}
diff --git a/benchmarking/benchmarks/reactivity/kairo/util.js b/benchmarking/benchmarks/reactivity/kairo/util.js
deleted file mode 100644
index 75e3641ab9..0000000000
--- a/benchmarking/benchmarks/reactivity/kairo/util.js
+++ /dev/null
@@ -1,6 +0,0 @@
-export function busy() {
-	let a = 0;
-	for (let i = 0; i < 1_00; i++) {
-		a++;
-	}
-}
diff --git a/benchmarking/benchmarks/reactivity/sbench.js b/benchmarking/benchmarks/reactivity/sbench.js
index ddeaef2514..196c29dc8d 100644
--- a/benchmarking/benchmarks/reactivity/sbench.js
+++ b/benchmarking/benchmarks/reactivity/sbench.js
@@ -1,3 +1,4 @@
+/** @import { Source } from '../../../packages/svelte/src/internal/client/types.js' */
 import { fastest_test } from '../../utils.js';
 import * as $ from '../../../packages/svelte/src/internal/client/index.js';
 
@@ -7,360 +8,180 @@ const COUNT = 1e5;
  * @param {number} n
  * @param {any[]} sources
  */
-function create_data_signals(n, sources) {
+function create_sources(n, sources) {
 	for (let i = 0; i < n; i++) {
 		sources[i] = $.state(i);
 	}
+
 	return sources;
 }
 
 /**
- * @param {number} i
+ * @param {Source<number>} source
  */
-function create_computation_0(i) {
-	$.derived(() => i);
+function create_derived(source) {
+	$.derived(() => $.get(source));
 }
 
 /**
- * @param {any} s1
- */
-function create_computation_1(s1) {
-	$.derived(() => $.get(s1));
-}
-/**
- * @param {any} s1
- * @param {any} s2
+ *
+ * @param {string} label
+ * @param {(n: number, sources: Array<Source<number>>)} fn
+ * @param {number} count
+ * @param {number} num_sources
  */
-function create_computation_2(s1, s2) {
-	$.derived(() => $.get(s1) + $.get(s2));
-}
-
-function create_computation_1000(ss, offset) {
-	$.derived(() => {
-		let sum = 0;
-		for (let i = 0; i < 1000; i++) {
-			sum += $.get(ss[offset + i]);
+function create_sbench_test(label, count, num_sources, fn) {
+	return async () => {
+		// Do 3 loops to warm up JIT
+		for (let i = 0; i < 3; i++) {
+			fn(count, create_sources(num_sources, []));
 		}
-		return sum;
-	});
-}
 
-/**
- * @param {number} n
- */
-function create_computations_0to1(n) {
-	for (let i = 0; i < n; i++) {
-		create_computation_0(i);
-	}
-}
-
-/**
- * @param {number} n
- * @param {any[]} sources
- */
-function create_computations_1to1(n, sources) {
-	for (let i = 0; i < n; i++) {
-		const source = sources[i];
-		create_computation_1(source);
-	}
-}
+		const { timing } = await fastest_test(10, () => {
+			const destroy = $.effect_root(() => {
+				for (let i = 0; i < 10; i++) {
+					fn(count, create_sources(num_sources, []));
+				}
+			});
+			destroy();
+		});
 
-/**
- * @param {number} n
- * @param {any[]} sources
- */
-function create_computations_2to1(n, sources) {
-	for (let i = 0; i < n; i++) {
-		create_computation_2(sources[i * 2], sources[i * 2 + 1]);
-	}
+		return {
+			benchmark: label,
+			time: timing.time.toFixed(2),
+			gc_time: timing.gc_time.toFixed(2)
+		};
+	};
 }
 
-function create_computation_4(s1, s2, s3, s4) {
-	$.derived(() => $.get(s1) + $.get(s2) + $.get(s3) + $.get(s4));
-}
+export const sbench_create_signals = create_sbench_test(
+	'sbench_create_signals',
+	COUNT,
+	COUNT,
+	create_sources
+);
 
-function create_computations_1000to1(n, sources) {
+export const sbench_create_0to1 = create_sbench_test('sbench_create_0to1', COUNT, 0, (n) => {
 	for (let i = 0; i < n; i++) {
-		create_computation_1000(sources, i * 1000);
-	}
-}
-
-function create_computations_1to2(n, sources) {
-	for (let i = 0; i < n / 2; i++) {
-		const source = sources[i];
-		create_computation_1(source);
-		create_computation_1(source);
-	}
-}
-
-function create_computations_1to4(n, sources) {
-	for (let i = 0; i < n / 4; i++) {
-		const source = sources[i];
-		create_computation_1(source);
-		create_computation_1(source);
-		create_computation_1(source);
-		create_computation_1(source);
-	}
-}
-
-function create_computations_1to8(n, sources) {
-	for (let i = 0; i < n / 8; i++) {
-		const source = sources[i];
-		create_computation_1(source);
-		create_computation_1(source);
-		create_computation_1(source);
-		create_computation_1(source);
-		create_computation_1(source);
-		create_computation_1(source);
-		create_computation_1(source);
-		create_computation_1(source);
+		$.derived(() => i);
 	}
-}
+});
 
-function create_computations_1to1000(n, sources) {
-	for (let i = 0; i < n / 1000; i++) {
-		const source = sources[i];
-		for (let j = 0; j < 1000; j++) {
-			create_computation_1(source);
+export const sbench_create_1to1 = create_sbench_test(
+	'sbench_create_1to1',
+	COUNT,
+	COUNT,
+	(n, sources) => {
+		for (let i = 0; i < n; i++) {
+			create_derived(sources[i]);
 		}
 	}
-}
-
-function create_computations_4to1(n, sources) {
-	for (let i = 0; i < n; i++) {
-		create_computation_4(
-			sources[i * 4],
-			sources[i * 4 + 1],
-			sources[i * 4 + 2],
-			sources[i * 4 + 3]
-		);
-	}
-}
-
-/**
- * @param {any} fn
- * @param {number} count
- * @param {number} scount
- */
-function bench(fn, count, scount) {
-	let sources = create_data_signals(scount, []);
-
-	fn(count, sources);
-}
-
-export async function sbench_create_signals() {
-	// Do 3 loops to warm up JIT
-	for (let i = 0; i < 3; i++) {
-		bench(create_data_signals, COUNT, COUNT);
-	}
+);
 
-	const { timing } = await fastest_test(10, () => {
-		for (let i = 0; i < 100; i++) {
-			bench(create_data_signals, COUNT, COUNT);
+export const sbench_create_2to1 = create_sbench_test(
+	'sbench_create_2to1',
+	COUNT / 2,
+	COUNT,
+	(n, sources) => {
+		for (let i = 0; i < n; i++) {
+			$.derived(() => $.get(sources[i * 2]) + $.get(sources[i * 2 + 1]));
 		}
-	});
-
-	return {
-		benchmark: 'sbench_create_signals',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
-	};
-}
-
-export async function sbench_create_0to1() {
-	// Do 3 loops to warm up JIT
-	for (let i = 0; i < 3; i++) {
-		bench(create_computations_0to1, COUNT, 0);
 	}
-
-	const { timing } = await fastest_test(10, () => {
-		const destroy = $.effect_root(() => {
-			for (let i = 0; i < 10; i++) {
-				bench(create_computations_0to1, COUNT, 0);
-			}
-		});
-		destroy();
-	});
-
-	return {
-		benchmark: 'sbench_create_0to1',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
-	};
-}
-
-export async function sbench_create_1to1() {
-	// Do 3 loops to warm up JIT
-	for (let i = 0; i < 3; i++) {
-		bench(create_computations_1to1, COUNT, COUNT);
-	}
-
-	const { timing } = await fastest_test(10, () => {
-		const destroy = $.effect_root(() => {
-			for (let i = 0; i < 10; i++) {
-				bench(create_computations_1to1, COUNT, COUNT);
-			}
-		});
-		destroy();
-	});
-
-	return {
-		benchmark: 'sbench_create_1to1',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
-	};
-}
-
-export async function sbench_create_2to1() {
-	// Do 3 loops to warm up JIT
-	for (let i = 0; i < 3; i++) {
-		bench(create_computations_2to1, COUNT / 2, COUNT);
-	}
-
-	const { timing } = await fastest_test(10, () => {
-		const destroy = $.effect_root(() => {
-			for (let i = 0; i < 10; i++) {
-				bench(create_computations_2to1, COUNT / 2, COUNT);
-			}
-		});
-		destroy();
-	});
-
-	return {
-		benchmark: 'sbench_create_2to1',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
-	};
-}
-
-export async function sbench_create_4to1() {
-	// Do 3 loops to warm up JIT
-	for (let i = 0; i < 3; i++) {
-		bench(create_computations_4to1, COUNT / 4, COUNT);
+);
+
+export const sbench_create_4to1 = create_sbench_test(
+	'sbench_create_4to1',
+	COUNT / 4,
+	COUNT,
+	(n, sources) => {
+		for (let i = 0; i < n; i++) {
+			$.derived(
+				() =>
+					$.get(sources[i * 4]) +
+					$.get(sources[i * 4 + 1]) +
+					$.get(sources[i * 4 + 2]) +
+					$.get(sources[i * 4 + 3])
+			);
+		}
 	}
-
-	const { timing } = await fastest_test(10, () => {
-		const destroy = $.effect_root(() => {
-			for (let i = 0; i < 10; i++) {
-				bench(create_computations_4to1, COUNT / 4, COUNT);
-			}
-		});
-		destroy();
-	});
-
-	return {
-		benchmark: 'sbench_create_4to1',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
-	};
-}
-
-export async function sbench_create_1000to1() {
-	// Do 3 loops to warm up JIT
-	for (let i = 0; i < 3; i++) {
-		bench(create_computations_1000to1, COUNT / 1000, COUNT);
+);
+
+export const sbench_create_1000to1 = create_sbench_test(
+	'sbench_create_1000to1',
+	COUNT / 1000,
+	COUNT,
+	(n, sources) => {
+		for (let i = 0; i < n; i++) {
+			const offset = i * 1000;
+
+			$.derived(() => {
+				let sum = 0;
+				for (let i = 0; i < 1000; i++) {
+					sum += $.get(sources[offset + i]);
+				}
+				return sum;
+			});
+		}
 	}
-
-	const { timing } = await fastest_test(10, () => {
-		const destroy = $.effect_root(() => {
-			for (let i = 0; i < 10; i++) {
-				bench(create_computations_1000to1, COUNT / 1000, COUNT);
-			}
-		});
-		destroy();
-	});
-
-	return {
-		benchmark: 'sbench_create_1000to1',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
-	};
-}
-
-export async function sbench_create_1to2() {
-	// Do 3 loops to warm up JIT
-	for (let i = 0; i < 3; i++) {
-		bench(create_computations_1to2, COUNT, COUNT / 2);
+);
+
+export const sbench_create_1to2 = create_sbench_test(
+	'sbench_create_1to2',
+	COUNT,
+	COUNT / 2,
+	(n, sources) => {
+		for (let i = 0; i < n / 2; i++) {
+			const source = sources[i];
+			create_derived(source);
+			create_derived(source);
+		}
 	}
-
-	const { timing } = await fastest_test(10, () => {
-		const destroy = $.effect_root(() => {
-			for (let i = 0; i < 10; i++) {
-				bench(create_computations_1to2, COUNT, COUNT / 2);
-			}
-		});
-		destroy();
-	});
-
-	return {
-		benchmark: 'sbench_create_1to2',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
-	};
-}
-
-export async function sbench_create_1to4() {
-	// Do 3 loops to warm up JIT
-	for (let i = 0; i < 3; i++) {
-		bench(create_computations_1to4, COUNT, COUNT / 4);
+);
+
+export const sbench_create_1to4 = create_sbench_test(
+	'sbench_create_1to4',
+	COUNT,
+	COUNT / 4,
+	(n, sources) => {
+		for (let i = 0; i < n / 4; i++) {
+			const source = sources[i];
+			create_derived(source);
+			create_derived(source);
+			create_derived(source);
+			create_derived(source);
+		}
 	}
-
-	const { timing } = await fastest_test(10, () => {
-		const destroy = $.effect_root(() => {
-			for (let i = 0; i < 10; i++) {
-				bench(create_computations_1to4, COUNT, COUNT / 4);
-			}
-		});
-		destroy();
-	});
-
-	return {
-		benchmark: 'sbench_create_1to4',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
-	};
-}
-
-export async function sbench_create_1to8() {
-	// Do 3 loops to warm up JIT
-	for (let i = 0; i < 3; i++) {
-		bench(create_computations_1to8, COUNT, COUNT / 8);
+);
+
+export const sbench_create_1to8 = create_sbench_test(
+	'sbench_create_1to8',
+	COUNT,
+	COUNT / 8,
+	(n, sources) => {
+		for (let i = 0; i < n / 8; i++) {
+			const source = sources[i];
+			create_derived(source);
+			create_derived(source);
+			create_derived(source);
+			create_derived(source);
+			create_derived(source);
+			create_derived(source);
+			create_derived(source);
+			create_derived(source);
+		}
 	}
-
-	const { timing } = await fastest_test(10, () => {
-		const destroy = $.effect_root(() => {
-			for (let i = 0; i < 10; i++) {
-				bench(create_computations_1to8, COUNT, COUNT / 8);
+);
+
+export const sbench_create_1to1000 = create_sbench_test(
+	'sbench_create_1to1000',
+	COUNT,
+	COUNT / 1000,
+	(n, sources) => {
+		for (let i = 0; i < n / 1000; i++) {
+			const source = sources[i];
+			for (let j = 0; j < 1000; j++) {
+				create_derived(source);
 			}
-		});
-		destroy();
-	});
-
-	return {
-		benchmark: 'sbench_create_1to8',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
-	};
-}
-
-export async function sbench_create_1to1000() {
-	// Do 3 loops to warm up JIT
-	for (let i = 0; i < 3; i++) {
-		bench(create_computations_1to1000, COUNT, COUNT / 1000);
+		}
 	}
-
-	const { timing } = await fastest_test(10, () => {
-		const destroy = $.effect_root(() => {
-			for (let i = 0; i < 10; i++) {
-				bench(create_computations_1to1000, COUNT, COUNT / 1000);
-			}
-		});
-		destroy();
-	});
-
-	return {
-		benchmark: 'sbench_create_1to1000',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
-	};
-}
+);
diff --git a/benchmarking/benchmarks/reactivity/tests/kairo_avoidable.bench.js b/benchmarking/benchmarks/reactivity/tests/kairo_avoidable.bench.js
new file mode 100644
index 0000000000..bb8c234f05
--- /dev/null
+++ b/benchmarking/benchmarks/reactivity/tests/kairo_avoidable.bench.js
@@ -0,0 +1,35 @@
+import { assert } from '../../../utils.js';
+import * as $ from 'svelte/internal/client';
+import { busy } from '../util.js';
+
+export default () => {
+	let head = $.state(0);
+	let computed1 = $.derived(() => $.get(head));
+	let computed2 = $.derived(() => ($.get(computed1), 0));
+	let computed3 = $.derived(() => (busy(), $.get(computed2) + 1)); // heavy computation
+	let computed4 = $.derived(() => $.get(computed3) + 2);
+	let computed5 = $.derived(() => $.get(computed4) + 3);
+
+	const destroy = $.effect_root(() => {
+		$.render_effect(() => {
+			$.get(computed5);
+			busy(); // heavy side effect
+		});
+	});
+
+	return {
+		destroy,
+		run() {
+			$.flush(() => {
+				$.set(head, 1);
+			});
+			assert($.get(computed5) === 6);
+			for (let i = 0; i < 1000; i++) {
+				$.flush(() => {
+					$.set(head, i);
+				});
+				assert($.get(computed5) === 6);
+			}
+		}
+	};
+};
diff --git a/benchmarking/benchmarks/reactivity/tests/kairo_broad.bench.js b/benchmarking/benchmarks/reactivity/tests/kairo_broad.bench.js
new file mode 100644
index 0000000000..14e855566b
--- /dev/null
+++ b/benchmarking/benchmarks/reactivity/tests/kairo_broad.bench.js
@@ -0,0 +1,41 @@
+import { assert } from '../../../utils.js';
+import * as $ from 'svelte/internal/client';
+
+export default () => {
+	let head = $.state(0);
+	let last = head;
+	let counter = 0;
+
+	const destroy = $.effect_root(() => {
+		for (let i = 0; i < 50; i++) {
+			let current = $.derived(() => {
+				return $.get(head) + i;
+			});
+			let current2 = $.derived(() => {
+				return $.get(current) + 1;
+			});
+			$.render_effect(() => {
+				$.get(current2);
+				counter++;
+			});
+			last = current2;
+		}
+	});
+
+	return {
+		destroy,
+		run() {
+			$.flush(() => {
+				$.set(head, 1);
+			});
+			counter = 0;
+			for (let i = 0; i < 50; i++) {
+				$.flush(() => {
+					$.set(head, i);
+				});
+				assert($.get(last) === i + 50);
+			}
+			assert(counter === 50 * 50);
+		}
+	};
+};
diff --git a/benchmarking/benchmarks/reactivity/tests/kairo_deep.bench.js b/benchmarking/benchmarks/reactivity/tests/kairo_deep.bench.js
new file mode 100644
index 0000000000..1051b0c1cf
--- /dev/null
+++ b/benchmarking/benchmarks/reactivity/tests/kairo_deep.bench.js
@@ -0,0 +1,41 @@
+import { assert } from '../../../utils.js';
+import * as $ from 'svelte/internal/client';
+
+let len = 50;
+const iter = 50;
+
+export default () => {
+	let head = $.state(0);
+	let current = head;
+	for (let i = 0; i < len; i++) {
+		let c = current;
+		current = $.derived(() => {
+			return $.get(c) + 1;
+		});
+	}
+	let counter = 0;
+
+	const destroy = $.effect_root(() => {
+		$.render_effect(() => {
+			$.get(current);
+			counter++;
+		});
+	});
+
+	return {
+		destroy,
+		run() {
+			$.flush(() => {
+				$.set(head, 1);
+			});
+			counter = 0;
+			for (let i = 0; i < iter; i++) {
+				$.flush(() => {
+					$.set(head, i);
+				});
+				assert($.get(current) === len + i);
+			}
+			assert(counter === iter);
+		}
+	};
+};
diff --git a/benchmarking/benchmarks/reactivity/tests/kairo_diamond.bench.js b/benchmarking/benchmarks/reactivity/tests/kairo_diamond.bench.js
new file mode 100644
index 0000000000..cde53fa3eb
--- /dev/null
+++ b/benchmarking/benchmarks/reactivity/tests/kairo_diamond.bench.js
@@ -0,0 +1,45 @@
+import { assert } from '../../../utils.js';
+import * as $ from 'svelte/internal/client';
+
+let width = 5;
+
+export default () => {
+	let head = $.state(0);
+	let current = [];
+	for (let i = 0; i < width; i++) {
+		current.push(
+			$.derived(() => {
+				return $.get(head) + 1;
+			})
+		);
+	}
+	let sum = $.derived(() => {
+		return current.map((x) => $.get(x)).reduce((a, b) => a + b, 0);
+	});
+	let counter = 0;
+
+	const destroy = $.effect_root(() => {
+		$.render_effect(() => {
+			$.get(sum);
+			counter++;
+		});
+	});
+
+	return {
+		destroy,
+		run() {
+			$.flush(() => {
+				$.set(head, 1);
+			});
+			assert($.get(sum) === 2 * width);
+			counter = 0;
+			for (let i = 0; i < 500; i++) {
+				$.flush(() => {
+					$.set(head, i);
+				});
+				assert($.get(sum) === (i + 1) * width);
+			}
+			assert(counter === 500);
+		}
+	};
+};
diff --git a/benchmarking/benchmarks/reactivity/tests/kairo_mux.bench.js b/benchmarking/benchmarks/reactivity/tests/kairo_mux.bench.js
new file mode 100644
index 0000000000..cfc7592c15
--- /dev/null
+++ b/benchmarking/benchmarks/reactivity/tests/kairo_mux.bench.js
@@ -0,0 +1,38 @@
+import { assert } from '../../../utils.js';
+import * as $ from 'svelte/internal/client';
+
+export default () => {
+	let heads = new Array(100).fill(null).map((_) => $.state(0));
+	const mux = $.derived(() => {
+		return Object.fromEntries(heads.map((h) => $.get(h)).entries());
+	});
+	const splited = heads
+		.map((_, index) => $.derived(() => $.get(mux)[index]))
+		.map((x) => $.derived(() => $.get(x) + 1));
+
+	const destroy = $.effect_root(() => {
+		splited.forEach((x) => {
+			$.render_effect(() => {
+				$.get(x);
+			});
+		});
+	});
+
+	return {
+		destroy,
+		run() {
+			for (let i = 0; i < 10; i++) {
+				$.flush(() => {
+					$.set(heads[i], i);
+				});
+				assert($.get(splited[i]) === i + 1);
+			}
+			for (let i = 0; i < 10; i++) {
+				$.flush(() => {
+					$.set(heads[i], i * 2);
+				});
+				assert($.get(splited[i]) === i * 2 + 1);
+			}
+		}
+	};
+};
diff --git a/benchmarking/benchmarks/reactivity/tests/kairo_repeated.bench.js b/benchmarking/benchmarks/reactivity/tests/kairo_repeated.bench.js
new file mode 100644
index 0000000000..2887a39931
--- /dev/null
+++ b/benchmarking/benchmarks/reactivity/tests/kairo_repeated.bench.js
@@ -0,0 +1,42 @@
+import { assert } from '../../../utils.js';
+import * as $ from 'svelte/internal/client';
+
+let size = 30;
+
+export default () => {
+	let head = $.state(0);
+	let current = $.derived(() => {
+		let result = 0;
+		for (let i = 0; i < size; i++) {
+			result += $.get(head);
+		}
+		return result;
+	});
+
+	let counter = 0;
+
+	const destroy = $.effect_root(() => {
+		$.render_effect(() => {
+			$.get(current);
+			counter++;
+		});
+	});
+
+	return {
+		destroy,
+		run() {
+			$.flush(() => {
+				$.set(head, 1);
+			});
+			assert($.get(current) === size);
+			counter = 0;
+			for (let i = 0; i < 100; i++) {
+				$.flush(() => {
+					$.set(head, i);
+				});
+				assert($.get(current) === i * size);
+			}
+			assert(counter === 100);
+		}
+	};
+};
diff --git a/benchmarking/benchmarks/reactivity/tests/kairo_triangle.bench.js b/benchmarking/benchmarks/reactivity/tests/kairo_triangle.bench.js
new file mode 100644
index 0000000000..0abdd1e13d
--- /dev/null
+++ b/benchmarking/benchmarks/reactivity/tests/kairo_triangle.bench.js
@@ -0,0 +1,55 @@
+import { assert } from '../../../utils.js';
+import * as $ from 'svelte/internal/client';
+
+let width = 10;
+
+function count(number) {
+	return new Array(number)
+		.fill(0)
+		.map((_, i) => i + 1)
+		.reduce((x, y) => x + y, 0);
+}
+
+export default () => {
+	let head = $.state(0);
+	let current = head;
+	let list = [];
+	for (let i = 0; i < width; i++) {
+		let c = current;
+		list.push(current);
+		current = $.derived(() => {
+			return $.get(c) + 1;
+		});
+	}
+	let sum = $.derived(() => {
+		return list.map((x) => $.get(x)).reduce((a, b) => a + b, 0);
+	});
+
+	let counter = 0;
+
+	const destroy = $.effect_root(() => {
+		$.render_effect(() => {
+			$.get(sum);
+			counter++;
+		});
+	});
+
+	return {
+		destroy,
+		run() {
+			const constant = count(width);
+			$.flush(() => {
+				$.set(head, 1);
+			});
+			assert($.get(sum) === constant);
+			counter = 0;
+			for (let i = 0; i < 100; i++) {
+				$.flush(() => {
+					$.set(head, i);
+				});
+				assert($.get(sum) === constant - width + i * width);
+			}
+			assert(counter === 100);
+		}
+	};
+};
diff --git a/benchmarking/benchmarks/reactivity/tests/kairo_unstable.bench.js b/benchmarking/benchmarks/reactivity/tests/kairo_unstable.bench.js
new file mode 100644
index 0000000000..b09467326f
--- /dev/null
+++ b/benchmarking/benchmarks/reactivity/tests/kairo_unstable.bench.js
@@ -0,0 +1,41 @@
+import { assert } from '../../../utils.js';
+import * as $ from 'svelte/internal/client';
+
+export default () => {
+	let head = $.state(0);
+	const double = $.derived(() => $.get(head) * 2);
+	const inverse = $.derived(() => -$.get(head));
+	let current = $.derived(() => {
+		let result = 0;
+		for (let i = 0; i < 20; i++) {
+			result += $.get(head) % 2 ? $.get(double) : $.get(inverse);
+		}
+		return result;
+	});
+
+	let counter = 0;
+
+	const destroy = $.effect_root(() => {
+		$.render_effect(() => {
+			$.get(current);
+			counter++;
+		});
+	});
+
+	return {
+		destroy,
+		run() {
+			$.flush(() => {
+				$.set(head, 1);
+			});
+			assert($.get(current) === 40);
+			counter = 0;
+			for (let i = 0; i < 100; i++) {
+				$.flush(() => {
+					$.set(head, i);
+				});
+			}
+			assert(counter === 100);
+		}
+	};
+};
diff --git a/benchmarking/benchmarks/reactivity/mol_bench.js b/benchmarking/benchmarks/reactivity/tests/mol.bench.js
similarity index 56%
rename from benchmarking/benchmarks/reactivity/mol_bench.js
rename to benchmarking/benchmarks/reactivity/tests/mol.bench.js
index 536b078d74..56b6dc8b28 100644
--- a/benchmarking/benchmarks/reactivity/mol_bench.js
+++ b/benchmarking/benchmarks/reactivity/tests/mol.bench.js
@@ -1,4 +1,4 @@
-import { assert, fastest_test } from '../../utils.js';
+import { assert } from '../../../utils.js';
 import * as $ from 'svelte/internal/client';
 
 /**
@@ -18,7 +18,7 @@ function hard(n) {
 
 const numbers = Array.from({ length: 5 }, (_, i) => i);
 
-function setup() {
+export default () => {
 	let res = [];
 	const A = $.state(0);
 	const B = $.state(0);
@@ -62,60 +62,4 @@ function setup() {
 			assert(res[0] === 3198 && res[1] === 1601 && res[2] === 3195 && res[3] === 1598);
 		}
 	};
-}
-
-export async function mol_bench_owned() {
-	let run, destroy;
-
-	const destroy_owned = $.effect_root(() => {
-		// Do 10 loops to warm up JIT
-		for (let i = 0; i < 10; i++) {
-			const { run, destroy } = setup();
-			run(0);
-			destroy();
-		}
-
-		({ run, destroy } = setup());
-	});
-
-	const { timing } = await fastest_test(10, () => {
-		for (let i = 0; i < 1e4; i++) {
-			run(i);
-		}
-	});
-
-	// @ts-ignore
-	destroy();
-	destroy_owned();
-
-	return {
-		benchmark: 'mol_bench_owned',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
-	};
-}
-
-export async function mol_bench_unowned() {
-	// Do 10 loops to warm up JIT
-	for (let i = 0; i < 10; i++) {
-		const { run, destroy } = setup();
-		run(0);
-		destroy();
-	}
-
-	const { run, destroy } = setup();
-
-	const { timing } = await fastest_test(10, () => {
-		for (let i = 0; i < 1e4; i++) {
-			run(i);
-		}
-	});
-
-	destroy();
-
-	return {
-		benchmark: 'mol_bench_unowned',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
-	};
-}
+};
diff --git a/benchmarking/benchmarks/reactivity/util.js b/benchmarking/benchmarks/reactivity/util.js
new file mode 100644
index 0000000000..18c4f556af
--- /dev/null
+++ b/benchmarking/benchmarks/reactivity/util.js
@@ -0,0 +1,73 @@
+import * as $ from 'svelte/internal/client';
+import { fastest_test } from '../../utils.js';
+
+export function busy() {
+	let a = 0;
+	for (let i = 0; i < 1_00; i++) {
+		a++;
+	}
+}
+
+/**
+ *
+ * @param {string} label
+ * @param {() => { run: (i?: number) => void, destroy: () => void }} setup
+ */
+export function create_test(label, setup) {
+	return {
+		unowned: async () => {
+			// Do 10 loops to warm up JIT
+			for (let i = 0; i < 10; i++) {
+				const { run, destroy } = setup();
+				run(0);
+				destroy();
+			}
+
+			const { run, destroy } = setup();
+
+			const { timing } = await fastest_test(10, () => {
+				for (let i = 0; i < 1000; i++) {
+					run(i);
+				}
+			});
+
+			destroy();
+
+			return {
+				benchmark: `${label}_unowned`,
+				time: timing.time.toFixed(2),
+				gc_time: timing.gc_time.toFixed(2)
+			};
+		},
+		owned: async () => {
+			let run, destroy;
+
+			const destroy_owned = $.effect_root(() => {
+				// Do 10 loops to warm up JIT
+				for (let i = 0; i < 10; i++) {
+					const { run, destroy } = setup();
+					run(0);
+					destroy();
+				}
+
+				({ run, destroy } = setup());
+			});
+
+			const { timing } = await fastest_test(10, () => {
+				for (let i = 0; i < 1000; i++) {
+					run(i);
+				}
+			});
+
+			// @ts-ignore
+			destroy();
+			destroy_owned();
+
+			return {
+				benchmark: `${label}_owned`,
+				time: timing.time.toFixed(2),
+				gc_time: timing.gc_time.toFixed(2)
+			};
+		}
+	};
+}

From 46c810ce71d14e165cab23fb5556e0ebfe3abf7d Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Wed, 21 Jan 2026 13:57:18 -0500
Subject: [PATCH 3/7] chore: tidy up the benchmarking code (#17504)

* chore: tidy up the benchmarking code

* use built-in assert

* fix find-replace fail
---
 benchmarking/benchmarks/reactivity/sbench.js  |   6 +-
 .../reactivity/tests/kairo_avoidable.bench.js |   6 +-
 .../reactivity/tests/kairo_broad.bench.js     |   6 +-
 .../reactivity/tests/kairo_deep.bench.js      |   6 +-
 .../reactivity/tests/kairo_diamond.bench.js   |   8 +-
 .../reactivity/tests/kairo_mux.bench.js       |   6 +-
 .../reactivity/tests/kairo_repeated.bench.js  |   8 +-
 .../reactivity/tests/kairo_triangle.bench.js  |   8 +-
 .../reactivity/tests/kairo_unstable.bench.js  |   6 +-
 .../benchmarks/reactivity/tests/mol.bench.js  |   7 +-
 benchmarking/benchmarks/reactivity/util.js    |  12 +-
 .../benchmarks/ssr/wrapper/wrapper_bench.js   |  33 ++++-
 benchmarking/utils.js                         | 114 +++---------------
 13 files changed, 88 insertions(+), 138 deletions(-)

diff --git a/benchmarking/benchmarks/reactivity/sbench.js b/benchmarking/benchmarks/reactivity/sbench.js
index 196c29dc8d..47ff4a621a 100644
--- a/benchmarking/benchmarks/reactivity/sbench.js
+++ b/benchmarking/benchmarks/reactivity/sbench.js
@@ -37,7 +37,7 @@ function create_sbench_test(label, count, num_sources, fn) {
 			fn(count, create_sources(num_sources, []));
 		}
 
-		const { timing } = await fastest_test(10, () => {
+		const { time, gc_time } = await fastest_test(10, () => {
 			const destroy = $.effect_root(() => {
 				for (let i = 0; i < 10; i++) {
 					fn(count, create_sources(num_sources, []));
@@ -48,8 +48,8 @@ function create_sbench_test(label, count, num_sources, fn) {
 
 		return {
 			benchmark: label,
-			time: timing.time.toFixed(2),
-			gc_time: timing.gc_time.toFixed(2)
+			time: time.toFixed(2),
+			gc_time: gc_time.toFixed(2)
 		};
 	};
 }
diff --git a/benchmarking/benchmarks/reactivity/tests/kairo_avoidable.bench.js b/benchmarking/benchmarks/reactivity/tests/kairo_avoidable.bench.js
index bb8c234f05..d4ba858824 100644
--- a/benchmarking/benchmarks/reactivity/tests/kairo_avoidable.bench.js
+++ b/benchmarking/benchmarks/reactivity/tests/kairo_avoidable.bench.js
@@ -1,4 +1,4 @@
-import { assert } from '../../../utils.js';
+import assert from 'node:assert';
 import * as $ from 'svelte/internal/client';
 import { busy } from '../util.js';
 
@@ -23,12 +23,12 @@ export default () => {
 			$.flush(() => {
 				$.set(head, 1);
 			});
-			assert($.get(computed5) === 6);
+			assert.equal($.get(computed5), 6);
 			for (let i = 0; i < 1000; i++) {
 				$.flush(() => {
 					$.set(head, i);
 				});
-				assert($.get(computed5) === 6);
+				assert.equal($.get(computed5), 6);
 			}
 		}
 	};
diff --git a/benchmarking/benchmarks/reactivity/tests/kairo_broad.bench.js b/benchmarking/benchmarks/reactivity/tests/kairo_broad.bench.js
index 14e855566b..aebae7a898 100644
--- a/benchmarking/benchmarks/reactivity/tests/kairo_broad.bench.js
+++ b/benchmarking/benchmarks/reactivity/tests/kairo_broad.bench.js
@@ -1,4 +1,4 @@
-import { assert } from '../../../utils.js';
+import assert from 'node:assert';
 import * as $ from 'svelte/internal/client';
 
 export default () => {
@@ -33,9 +33,9 @@ export default () => {
 				$.flush(() => {
 					$.set(head, i);
 				});
-				assert($.get(last) === i + 50);
+				assert.equal($.get(last), i + 50);
 			}
-			assert(counter === 50 * 50);
+			assert.equal(counter, 50 * 50);
 		}
 	};
 };
diff --git a/benchmarking/benchmarks/reactivity/tests/kairo_deep.bench.js b/benchmarking/benchmarks/reactivity/tests/kairo_deep.bench.js
index 1051b0c1cf..4a361e9bfc 100644
--- a/benchmarking/benchmarks/reactivity/tests/kairo_deep.bench.js
+++ b/benchmarking/benchmarks/reactivity/tests/kairo_deep.bench.js
@@ -1,4 +1,4 @@
-import { assert } from '../../../utils.js';
+import assert from 'node:assert';
 import * as $ from 'svelte/internal/client';
 
 let len = 50;
@@ -33,9 +33,9 @@ export default () => {
 				$.flush(() => {
 					$.set(head, i);
 				});
-				assert($.get(current) === len + i);
+				assert.equal($.get(current), len + i);
 			}
-			assert(counter === iter);
+			assert.equal(counter, iter);
 		}
 	};
 };
diff --git a/benchmarking/benchmarks/reactivity/tests/kairo_diamond.bench.js b/benchmarking/benchmarks/reactivity/tests/kairo_diamond.bench.js
index cde53fa3eb..17d9bd85e5 100644
--- a/benchmarking/benchmarks/reactivity/tests/kairo_diamond.bench.js
+++ b/benchmarking/benchmarks/reactivity/tests/kairo_diamond.bench.js
@@ -1,4 +1,4 @@
-import { assert } from '../../../utils.js';
+import assert from 'node:assert';
 import * as $ from 'svelte/internal/client';
 
 let width = 5;
@@ -31,15 +31,15 @@ export default () => {
 			$.flush(() => {
 				$.set(head, 1);
 			});
-			assert($.get(sum) === 2 * width);
+			assert.equal($.get(sum), 2 * width);
 			counter = 0;
 			for (let i = 0; i < 500; i++) {
 				$.flush(() => {
 					$.set(head, i);
 				});
-				assert($.get(sum) === (i + 1) * width);
+				assert.equal($.get(sum), (i + 1) * width);
 			}
-			assert(counter === 500);
+			assert.equal(counter, 500);
 		}
 	};
 };
diff --git a/benchmarking/benchmarks/reactivity/tests/kairo_mux.bench.js b/benchmarking/benchmarks/reactivity/tests/kairo_mux.bench.js
index cfc7592c15..4af6bf7873 100644
--- a/benchmarking/benchmarks/reactivity/tests/kairo_mux.bench.js
+++ b/benchmarking/benchmarks/reactivity/tests/kairo_mux.bench.js
@@ -1,4 +1,4 @@
-import { assert } from '../../../utils.js';
+import assert from 'node:assert';
 import * as $ from 'svelte/internal/client';
 
 export default () => {
@@ -25,13 +25,13 @@ export default () => {
 				$.flush(() => {
 					$.set(heads[i], i);
 				});
-				assert($.get(splited[i]) === i + 1);
+				assert.equal($.get(splited[i]), i + 1);
 			}
 			for (let i = 0; i < 10; i++) {
 				$.flush(() => {
 					$.set(heads[i], i * 2);
 				});
-				assert($.get(splited[i]) === i * 2 + 1);
+				assert.equal($.get(splited[i]), i * 2 + 1);
 			}
 		}
 	};
diff --git a/benchmarking/benchmarks/reactivity/tests/kairo_repeated.bench.js b/benchmarking/benchmarks/reactivity/tests/kairo_repeated.bench.js
index 2887a39931..cab7689fea 100644
--- a/benchmarking/benchmarks/reactivity/tests/kairo_repeated.bench.js
+++ b/benchmarking/benchmarks/reactivity/tests/kairo_repeated.bench.js
@@ -1,4 +1,4 @@
-import { assert } from '../../../utils.js';
+import assert from 'node:assert';
 import * as $ from 'svelte/internal/client';
 
 let size = 30;
@@ -28,15 +28,15 @@ export default () => {
 			$.flush(() => {
 				$.set(head, 1);
 			});
-			assert($.get(current) === size);
+			assert.equal($.get(current), size);
 			counter = 0;
 			for (let i = 0; i < 100; i++) {
 				$.flush(() => {
 					$.set(head, i);
 				});
-				assert($.get(current) === i * size);
+				assert.equal($.get(current), i * size);
 			}
-			assert(counter === 100);
+			assert.equal(counter, 100);
 		}
 	};
 };
diff --git a/benchmarking/benchmarks/reactivity/tests/kairo_triangle.bench.js b/benchmarking/benchmarks/reactivity/tests/kairo_triangle.bench.js
index 0abdd1e13d..b4b46c0209 100644
--- a/benchmarking/benchmarks/reactivity/tests/kairo_triangle.bench.js
+++ b/benchmarking/benchmarks/reactivity/tests/kairo_triangle.bench.js
@@ -1,4 +1,4 @@
-import { assert } from '../../../utils.js';
+import assert from 'node:assert';
 import * as $ from 'svelte/internal/client';
 
 let width = 10;
@@ -41,15 +41,15 @@ export default () => {
 			$.flush(() => {
 				$.set(head, 1);
 			});
-			assert($.get(sum) === constant);
+			assert.equal($.get(sum), constant);
 			counter = 0;
 			for (let i = 0; i < 100; i++) {
 				$.flush(() => {
 					$.set(head, i);
 				});
-				assert($.get(sum) === constant - width + i * width);
+				assert.equal($.get(sum), constant - width + i * width);
 			}
-			assert(counter === 100);
+			assert.equal(counter, 100);
 		}
 	};
 };
diff --git a/benchmarking/benchmarks/reactivity/tests/kairo_unstable.bench.js b/benchmarking/benchmarks/reactivity/tests/kairo_unstable.bench.js
index b09467326f..e7723fae0d 100644
--- a/benchmarking/benchmarks/reactivity/tests/kairo_unstable.bench.js
+++ b/benchmarking/benchmarks/reactivity/tests/kairo_unstable.bench.js
@@ -1,4 +1,4 @@
-import { assert } from '../../../utils.js';
+import assert from 'node:assert';
 import * as $ from 'svelte/internal/client';
 
 export default () => {
@@ -28,14 +28,14 @@ export default () => {
 			$.flush(() => {
 				$.set(head, 1);
 			});
-			assert($.get(current) === 40);
+			assert.equal($.get(current), 40);
 			counter = 0;
 			for (let i = 0; i < 100; i++) {
 				$.flush(() => {
 					$.set(head, i);
 				});
 			}
-			assert(counter === 100);
+			assert.equal(counter, 100);
 		}
 	};
 };
diff --git a/benchmarking/benchmarks/reactivity/tests/mol.bench.js b/benchmarking/benchmarks/reactivity/tests/mol.bench.js
index 56b6dc8b28..e66f0191d1 100644
--- a/benchmarking/benchmarks/reactivity/tests/mol.bench.js
+++ b/benchmarking/benchmarks/reactivity/tests/mol.bench.js
@@ -1,4 +1,4 @@
-import { assert } from '../../../utils.js';
+import assert from 'node:assert';
 import * as $ from 'svelte/internal/client';
 
 /**
@@ -59,7 +59,10 @@ export default () => {
 				$.set(A, 2 + i * 2);
 				$.set(B, 2);
 			});
-			assert(res[0] === 3198 && res[1] === 1601 && res[2] === 3195 && res[3] === 1598);
+			assert.equal(res[0], 3198);
+			assert.equal(res[1], 1601);
+			assert.equal(res[2], 3195);
+			assert.equal(res[3], 1598);
 		}
 	};
 };
diff --git a/benchmarking/benchmarks/reactivity/util.js b/benchmarking/benchmarks/reactivity/util.js
index 18c4f556af..ff0722d85e 100644
--- a/benchmarking/benchmarks/reactivity/util.js
+++ b/benchmarking/benchmarks/reactivity/util.js
@@ -25,7 +25,7 @@ export function create_test(label, setup) {
 
 			const { run, destroy } = setup();
 
-			const { timing } = await fastest_test(10, () => {
+			const { time, gc_time } = await fastest_test(10, () => {
 				for (let i = 0; i < 1000; i++) {
 					run(i);
 				}
@@ -35,8 +35,8 @@ export function create_test(label, setup) {
 
 			return {
 				benchmark: `${label}_unowned`,
-				time: timing.time.toFixed(2),
-				gc_time: timing.gc_time.toFixed(2)
+				time: time.toFixed(2),
+				gc_time: gc_time.toFixed(2)
 			};
 		},
 		owned: async () => {
@@ -53,7 +53,7 @@ export function create_test(label, setup) {
 				({ run, destroy } = setup());
 			});
 
-			const { timing } = await fastest_test(10, () => {
+			const { time, gc_time } = await fastest_test(10, () => {
 				for (let i = 0; i < 1000; i++) {
 					run(i);
 				}
@@ -65,8 +65,8 @@ export function create_test(label, setup) {
 
 			return {
 				benchmark: `${label}_owned`,
-				time: timing.time.toFixed(2),
-				gc_time: timing.gc_time.toFixed(2)
+				time: time.toFixed(2),
+				gc_time: gc_time.toFixed(2)
 			};
 		}
 	};
diff --git a/benchmarking/benchmarks/ssr/wrapper/wrapper_bench.js b/benchmarking/benchmarks/ssr/wrapper/wrapper_bench.js
index ba0457b80e..6fc992d4a2 100644
--- a/benchmarking/benchmarks/ssr/wrapper/wrapper_bench.js
+++ b/benchmarking/benchmarks/ssr/wrapper/wrapper_bench.js
@@ -1,13 +1,16 @@
+import * as fs from 'node:fs';
+import * as path from 'node:path';
 import { render } from 'svelte/server';
-import { fastest_test, read_file, write } from '../../../utils.js';
+import { fastest_test } from '../../../utils.js';
 import { compile } from 'svelte/compiler';
 
 const dir = `${process.cwd()}/benchmarking/benchmarks/ssr/wrapper`;
 
 async function compile_svelte() {
-	const output = compile(read_file(`${dir}/App.svelte`), {
+	const output = compile(read(`${dir}/App.svelte`), {
 		generate: 'server'
 	});
+
 	write(`${dir}/output/App.js`, output.js.code);
 
 	const module = await import(`${dir}/output/App.js`);
@@ -17,12 +20,13 @@ async function compile_svelte() {
 
 export async function wrapper_bench() {
 	const App = await compile_svelte();
+
 	// Do 3 loops to warm up JIT
 	for (let i = 0; i < 3; i++) {
 		render(App);
 	}
 
-	const { timing } = await fastest_test(10, () => {
+	const { time, gc_time } = await fastest_test(10, () => {
 		for (let i = 0; i < 100; i++) {
 			render(App);
 		}
@@ -30,7 +34,26 @@ export async function wrapper_bench() {
 
 	return {
 		benchmark: 'wrapper_bench',
-		time: timing.time.toFixed(2),
-		gc_time: timing.gc_time.toFixed(2)
+		time: time.toFixed(2),
+		gc_time: gc_time.toFixed(2)
 	};
 }
+
+/**
+ * @param {string} file
+ */
+function read(file) {
+	return fs.readFileSync(file, 'utf-8').replace(/\r\n/g, '\n');
+}
+
+/**
+ * @param {string} file
+ * @param {string} contents
+ */
+function write(file, contents) {
+	try {
+		fs.mkdirSync(path.dirname(file), { recursive: true });
+	} catch {}
+
+	fs.writeFileSync(file, contents);
+}
diff --git a/benchmarking/utils.js b/benchmarking/utils.js
index 684d2ee02b..5581135e00 100644
--- a/benchmarking/utils.js
+++ b/benchmarking/utils.js
@@ -1,78 +1,30 @@
 import { performance, PerformanceObserver } from 'node:perf_hooks';
 import v8 from 'v8-natives';
-import * as fs from 'node:fs';
-import * as path from 'node:path';
 
 // Credit to https://github.com/milomg/js-reactivity-benchmark for the logic for timing + GC tracking.
 
-class GarbageTrack {
-	track_id = 0;
-	observer = new PerformanceObserver((list) => this.perf_entries.push(...list.getEntries()));
-	perf_entries = [];
-	periods = [];
+async function track(fn) {
+	v8.collectGarbage();
 
-	watch(fn) {
-		this.track_id++;
-		const start = performance.now();
-		const result = fn();
-		const end = performance.now();
-		this.periods.push({ track_id: this.track_id, start, end });
+	/** @type {PerformanceEntry[]} */
+	const entries = [];
 
-		return { result, track_id: this.track_id };
-	}
+	const observer = new PerformanceObserver((list) => entries.push(...list.getEntries()));
+	observer.observe({ entryTypes: ['gc'] });
 
-	/**
-	 * @param {number} track_id
-	 */
-	async gcDuration(track_id) {
-		await promise_delay(10);
+	const start = performance.now();
+	fn();
+	const end = performance.now();
 
-		const period = this.periods.find((period) => period.track_id === track_id);
-		if (!period) {
-			// eslint-disable-next-line @typescript-eslint/prefer-promise-reject-errors
-			return Promise.reject('no period found');
-		}
+	await new Promise((f) => setTimeout(f, 10));
 
-		const entries = this.perf_entries.filter(
-			(e) => e.startTime >= period.start && e.startTime < period.end
-		);
-		return entries.reduce((t, e) => e.duration + t, 0);
-	}
+	const gc_time = entries
+		.filter((e) => e.startTime >= start && e.startTime < end)
+		.reduce((t, e) => e.duration + t, 0);
 
-	destroy() {
-		this.observer.disconnect();
-	}
+	observer.disconnect();
 
-	constructor() {
-		this.observer.observe({ entryTypes: ['gc'] });
-	}
-}
-
-function promise_delay(timeout = 0) {
-	return new Promise((resolve) => setTimeout(resolve, timeout));
-}
-
-/**
- * @param {{ (): void; (): any; }} fn
- */
-function run_timed(fn) {
-	const start = performance.now();
-	const result = fn();
-	const time = performance.now() - start;
-	return { result, time };
-}
-
-/**
- * @param {() => void} fn
- */
-async function run_tracked(fn) {
-	v8.collectGarbage();
-	const gc_track = new GarbageTrack();
-	const { result: wrappedResult, track_id } = gc_track.watch(() => run_timed(fn));
-	const gc_time = await gc_track.gcDuration(track_id);
-	const { result, time } = wrappedResult;
-	gc_track.destroy();
-	return { result, timing: { time, gc_time } };
+	return { time: end - start, gc_time };
 }
 
 /**
@@ -80,40 +32,12 @@ async function run_tracked(fn) {
  * @param {() => void} fn
  */
 export async function fastest_test(times, fn) {
+	/** @type {Array<{ time: number, gc_time: number }>} */
 	const results = [];
-	for (let i = 0; i < times; i++) {
-		const run = await run_tracked(fn);
-		results.push(run);
-	}
-	const fastest = results.reduce((a, b) => (a.timing.time < b.timing.time ? a : b));
 
-	return fastest;
-}
-
-/**
- * @param {boolean} a
- */
-export function assert(a) {
-	if (!a) {
-		throw new Error('Assertion failed');
+	for (let i = 0; i < times; i++) {
+		results.push(await track(fn));
 	}
-}
-
-/**
- * @param {string} file
- */
-export function read_file(file) {
-	return fs.readFileSync(file, 'utf-8').replace(/\r\n/g, '\n');
-}
-
-/**
- * @param {string} file
- * @param {string} contents
- */
-export function write(file, contents) {
-	try {
-		fs.mkdirSync(path.dirname(file), { recursive: true });
-	} catch {}
 
-	fs.writeFileSync(file, contents);
+	return results.reduce((a, b) => (a.time < b.time ? a : b));
 }

From c41fef1ef104f4797cca45051774d4a662156f9a Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Wed, 21 Jan 2026 14:45:07 -0500
Subject: [PATCH 4/7] Nicer bench output (#17505)

* test

* dont coerce to string

* more readable output for pnpm bench

* oops

* fix
---
 benchmarking/benchmarks/reactivity/sbench.js  |  4 +-
 benchmarking/benchmarks/reactivity/util.js    |  8 +--
 .../benchmarks/ssr/wrapper/wrapper_bench.js   |  4 +-
 benchmarking/run.js                           | 64 +++++++++++--------
 package.json                                  |  2 +-
 5 files changed, 48 insertions(+), 34 deletions(-)

diff --git a/benchmarking/benchmarks/reactivity/sbench.js b/benchmarking/benchmarks/reactivity/sbench.js
index 47ff4a621a..9c41f60746 100644
--- a/benchmarking/benchmarks/reactivity/sbench.js
+++ b/benchmarking/benchmarks/reactivity/sbench.js
@@ -48,8 +48,8 @@ function create_sbench_test(label, count, num_sources, fn) {
 
 		return {
 			benchmark: label,
-			time: time.toFixed(2),
-			gc_time: gc_time.toFixed(2)
+			time,
+			gc_time
 		};
 	};
 }
diff --git a/benchmarking/benchmarks/reactivity/util.js b/benchmarking/benchmarks/reactivity/util.js
index ff0722d85e..6a2e44f5ae 100644
--- a/benchmarking/benchmarks/reactivity/util.js
+++ b/benchmarking/benchmarks/reactivity/util.js
@@ -35,8 +35,8 @@ export function create_test(label, setup) {
 
 			return {
 				benchmark: `${label}_unowned`,
-				time: time.toFixed(2),
-				gc_time: gc_time.toFixed(2)
+				time,
+				gc_time
 			};
 		},
 		owned: async () => {
@@ -65,8 +65,8 @@ export function create_test(label, setup) {
 
 			return {
 				benchmark: `${label}_owned`,
-				time: time.toFixed(2),
-				gc_time: gc_time.toFixed(2)
+				time,
+				gc_time
 			};
 		}
 	};
diff --git a/benchmarking/benchmarks/ssr/wrapper/wrapper_bench.js b/benchmarking/benchmarks/ssr/wrapper/wrapper_bench.js
index 6fc992d4a2..6e790ee2b8 100644
--- a/benchmarking/benchmarks/ssr/wrapper/wrapper_bench.js
+++ b/benchmarking/benchmarks/ssr/wrapper/wrapper_bench.js
@@ -34,8 +34,8 @@ export async function wrapper_bench() {
 
 	return {
 		benchmark: 'wrapper_bench',
-		time: time.toFixed(2),
-		gc_time: gc_time.toFixed(2)
+		time,
+		gc_time
 	};
 }
 
diff --git a/benchmarking/run.js b/benchmarking/run.js
index bd96b9c2dc..f7b8128886 100644
--- a/benchmarking/run.js
+++ b/benchmarking/run.js
@@ -10,46 +10,60 @@ const suites = [
 	{ benchmarks: ssr_benchmarks, name: 'server-side rendering benchmarks' }
 ];
 
-// eslint-disable-next-line no-console
-console.log('\x1b[1m', '-- Benchmarking Started --', '\x1b[0m');
+const COLUMN_WIDTHS = [25, 9, 9];
+const TOTAL_WIDTH = COLUMN_WIDTHS.reduce((a, b) => a + b);
+
+const pad_right = (str, n) => str + ' '.repeat(n - str.length);
+const pad_left = (str, n) => ' '.repeat(n - str.length) + str;
+
 $.push({}, true);
+
 try {
 	for (const { benchmarks, name } of suites) {
 		let suite_time = 0;
 		let suite_gc_time = 0;
-		// eslint-disable-next-line no-console
+
 		console.log(`\nRunning ${name}...\n`);
+		console.log(
+			pad_right('Benchmark', COLUMN_WIDTHS[0]) +
+				pad_left('Time', COLUMN_WIDTHS[1]) +
+				pad_left('GC time', COLUMN_WIDTHS[2])
+		);
+		console.log('='.repeat(TOTAL_WIDTH));
 
 		for (const benchmark of benchmarks) {
 			const results = await benchmark();
-			// eslint-disable-next-line no-console
-			console.log(results);
-			total_time += Number(results.time);
-			total_gc_time += Number(results.gc_time);
-			suite_time += Number(results.time);
-			suite_gc_time += Number(results.gc_time);
+			console.log(
+				pad_right(results.benchmark, COLUMN_WIDTHS[0]) +
+					pad_left(results.time.toFixed(2), COLUMN_WIDTHS[1]) +
+					pad_left(results.gc_time.toFixed(2), COLUMN_WIDTHS[2])
+			);
+			total_time += results.time;
+			total_gc_time += results.gc_time;
+			suite_time += results.time;
+			suite_gc_time += results.gc_time;
 		}
 
-		console.log(`\nFinished ${name}.\n`);
-
-		// eslint-disable-next-line no-console
-		console.log({
-			suite_time: suite_time.toFixed(2),
-			suite_gc_time: suite_gc_time.toFixed(2)
-		});
+		console.log('='.repeat(TOTAL_WIDTH));
+		console.log(
+			pad_right('suite', COLUMN_WIDTHS[0]) +
+				pad_left(suite_time.toFixed(2), COLUMN_WIDTHS[1]) +
+				pad_left(suite_gc_time.toFixed(2), COLUMN_WIDTHS[2])
+		);
+		console.log('='.repeat(TOTAL_WIDTH));
 	}
 } catch (e) {
-	// eslint-disable-next-line no-console
-	console.log('\x1b[1m', '\n-- Benchmarking Failed --\n', '\x1b[0m');
 	// eslint-disable-next-line no-console
 	console.error(e);
 	process.exit(1);
 }
+
 $.pop();
-// eslint-disable-next-line no-console
-console.log('\x1b[1m', '\n-- Benchmarking Complete --\n', '\x1b[0m');
-// eslint-disable-next-line no-console
-console.log({
-	total_time: total_time.toFixed(2),
-	total_gc_time: total_gc_time.toFixed(2)
-});
+
+console.log('');
+
+console.log(
+	pad_right('total', COLUMN_WIDTHS[0]) +
+		pad_left(total_time.toFixed(2), COLUMN_WIDTHS[1]) +
+		pad_left(total_gc_time.toFixed(2), COLUMN_WIDTHS[2])
+);
diff --git a/package.json b/package.json
index 12e59a2665..aa9c8cafa3 100644
--- a/package.json
+++ b/package.json
@@ -21,7 +21,7 @@
     "test": "vitest run",
     "changeset:version": "changeset version && pnpm -r generate:version && git add --all",
     "changeset:publish": "changeset publish",
-    "bench": "node --allow-natives-syntax ./benchmarking/run.js",
+    "bench": "NODE_ENV=production node --allow-natives-syntax ./benchmarking/run.js",
     "bench:compare": "node --allow-natives-syntax ./benchmarking/compare/index.js",
     "bench:debug": "node --allow-natives-syntax --inspect-brk ./benchmarking/run.js"
   },

From 0025d42366fa3652216cac8bf3adc1389ae49a3d Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Wed, 21 Jan 2026 15:53:37 -0500
Subject: [PATCH 5/7] chore: skippable benchmarks (#17506)

* chore: add benchmark filtering mechanism

* tweak

* fix

* try this

* better logging for bench:compare

* fix
---
 benchmarking/benchmarks/reactivity/sbench.js  | 35 ++++----
 benchmarking/benchmarks/reactivity/util.js    | 84 +++++++++----------
 .../benchmarks/ssr/wrapper/wrapper_bench.js   | 29 +++----
 benchmarking/compare/runner.js                | 11 ++-
 benchmarking/run.js                           | 32 +++++--
 package.json                                  |  4 +-
 6 files changed, 104 insertions(+), 91 deletions(-)

diff --git a/benchmarking/benchmarks/reactivity/sbench.js b/benchmarking/benchmarks/reactivity/sbench.js
index 9c41f60746..e197f970c8 100644
--- a/benchmarking/benchmarks/reactivity/sbench.js
+++ b/benchmarking/benchmarks/reactivity/sbench.js
@@ -26,31 +26,28 @@ function create_derived(source) {
 /**
  *
  * @param {string} label
- * @param {(n: number, sources: Array<Source<number>>)} fn
+ * @param {(n: number, sources: Array<Source<number>>) => void} fn
  * @param {number} count
  * @param {number} num_sources
  */
 function create_sbench_test(label, count, num_sources, fn) {
-	return async () => {
-		// Do 3 loops to warm up JIT
-		for (let i = 0; i < 3; i++) {
-			fn(count, create_sources(num_sources, []));
-		}
+	return {
+		label,
+		fn: async () => {
+			// Do 3 loops to warm up JIT
+			for (let i = 0; i < 3; i++) {
+				fn(count, create_sources(num_sources, []));
+			}
 
-		const { time, gc_time } = await fastest_test(10, () => {
-			const destroy = $.effect_root(() => {
-				for (let i = 0; i < 10; i++) {
-					fn(count, create_sources(num_sources, []));
-				}
+			return await fastest_test(10, () => {
+				const destroy = $.effect_root(() => {
+					for (let i = 0; i < 10; i++) {
+						fn(count, create_sources(num_sources, []));
+					}
+				});
+				destroy();
 			});
-			destroy();
-		});
-
-		return {
-			benchmark: label,
-			time,
-			gc_time
-		};
+		}
 	};
 }
 
diff --git a/benchmarking/benchmarks/reactivity/util.js b/benchmarking/benchmarks/reactivity/util.js
index 6a2e44f5ae..da5e5c51f5 100644
--- a/benchmarking/benchmarks/reactivity/util.js
+++ b/benchmarking/benchmarks/reactivity/util.js
@@ -15,34 +15,9 @@ export function busy() {
  */
 export function create_test(label, setup) {
 	return {
-		unowned: async () => {
-			// Do 10 loops to warm up JIT
-			for (let i = 0; i < 10; i++) {
-				const { run, destroy } = setup();
-				run(0);
-				destroy();
-			}
-
-			const { run, destroy } = setup();
-
-			const { time, gc_time } = await fastest_test(10, () => {
-				for (let i = 0; i < 1000; i++) {
-					run(i);
-				}
-			});
-
-			destroy();
-
-			return {
-				benchmark: `${label}_unowned`,
-				time,
-				gc_time
-			};
-		},
-		owned: async () => {
-			let run, destroy;
-
-			const destroy_owned = $.effect_root(() => {
+		unowned: {
+			label: `${label}_unowned`,
+			fn: async () => {
 				// Do 10 loops to warm up JIT
 				for (let i = 0; i < 10; i++) {
 					const { run, destroy } = setup();
@@ -50,24 +25,47 @@ export function create_test(label, setup) {
 					destroy();
 				}
 
-				({ run, destroy } = setup());
-			});
+				const { run, destroy } = setup();
+
+				const result = await fastest_test(10, () => {
+					for (let i = 0; i < 1000; i++) {
+						run(i);
+					}
+				});
 
-			const { time, gc_time } = await fastest_test(10, () => {
-				for (let i = 0; i < 1000; i++) {
-					run(i);
-				}
-			});
+				destroy();
+
+				return result;
+			}
+		},
+		owned: {
+			label: `${label}_owned`,
+			fn: async () => {
+				let run, destroy;
 
-			// @ts-ignore
-			destroy();
-			destroy_owned();
+				const destroy_owned = $.effect_root(() => {
+					// Do 10 loops to warm up JIT
+					for (let i = 0; i < 10; i++) {
+						const { run, destroy } = setup();
+						run(0);
+						destroy();
+					}
 
-			return {
-				benchmark: `${label}_owned`,
-				time,
-				gc_time
-			};
+					({ run, destroy } = setup());
+				});
+
+				const result = await fastest_test(10, () => {
+					for (let i = 0; i < 1000; i++) {
+						run(i);
+					}
+				});
+
+				// @ts-ignore
+				destroy();
+				destroy_owned();
+
+				return result;
+			}
 		}
 	};
 }
diff --git a/benchmarking/benchmarks/ssr/wrapper/wrapper_bench.js b/benchmarking/benchmarks/ssr/wrapper/wrapper_bench.js
index 6e790ee2b8..9a8dda617d 100644
--- a/benchmarking/benchmarks/ssr/wrapper/wrapper_bench.js
+++ b/benchmarking/benchmarks/ssr/wrapper/wrapper_bench.js
@@ -18,26 +18,23 @@ async function compile_svelte() {
 	return module.default;
 }
 
-export async function wrapper_bench() {
-	const App = await compile_svelte();
+export const wrapper_bench = {
+	label: 'wrapper_bench',
+	fn: async () => {
+		const App = await compile_svelte();
 
-	// Do 3 loops to warm up JIT
-	for (let i = 0; i < 3; i++) {
-		render(App);
-	}
-
-	const { time, gc_time } = await fastest_test(10, () => {
-		for (let i = 0; i < 100; i++) {
+		// Do 3 loops to warm up JIT
+		for (let i = 0; i < 3; i++) {
 			render(App);
 		}
-	});
 
-	return {
-		benchmark: 'wrapper_bench',
-		time,
-		gc_time
-	};
-}
+		return await fastest_test(10, () => {
+			for (let i = 0; i < 100; i++) {
+				render(App);
+			}
+		});
+	}
+};
 
 /**
  * @param {string} file
diff --git a/benchmarking/compare/runner.js b/benchmarking/compare/runner.js
index a2e8646379..11e40ed983 100644
--- a/benchmarking/compare/runner.js
+++ b/benchmarking/compare/runner.js
@@ -1,10 +1,13 @@
 import { reactivity_benchmarks } from '../benchmarks/reactivity/index.js';
 
 const results = [];
-for (const benchmark of reactivity_benchmarks) {
-	const result = await benchmark();
-	console.error(result.benchmark);
-	results.push(result);
+
+for (let i = 0; i < reactivity_benchmarks.length; i += 1) {
+	const benchmark = reactivity_benchmarks[i];
+
+	process.stderr.write(`Running ${i + 1}/${reactivity_benchmarks.length} ${benchmark.label} `);
+	results.push({ benchmark: benchmark.label, ...(await benchmark.fn()) });
+	process.stderr.write('\x1b[2K\r');
 }
 
 process.send(results);
diff --git a/benchmarking/run.js b/benchmarking/run.js
index f7b8128886..2b09f7c592 100644
--- a/benchmarking/run.js
+++ b/benchmarking/run.js
@@ -2,13 +2,28 @@ import * as $ from '../packages/svelte/src/internal/client/index.js';
 import { reactivity_benchmarks } from './benchmarks/reactivity/index.js';
 import { ssr_benchmarks } from './benchmarks/ssr/index.js';
 
-let total_time = 0;
-let total_gc_time = 0;
+// e.g. `pnpm bench kairo` to only run the kairo benchmarks
+const filters = process.argv.slice(2);
 
 const suites = [
-	{ benchmarks: reactivity_benchmarks, name: 'reactivity benchmarks' },
-	{ benchmarks: ssr_benchmarks, name: 'server-side rendering benchmarks' }
-];
+	{
+		benchmarks: reactivity_benchmarks.filter(
+			(b) => filters.length === 0 || filters.some((f) => b.label.includes(f))
+		),
+		name: 'reactivity benchmarks'
+	},
+	{
+		benchmarks: ssr_benchmarks.filter(
+			(b) => filters.length === 0 || filters.some((f) => b.label.includes(f))
+		),
+		name: 'server-side rendering benchmarks'
+	}
+].filter((suite) => suite.benchmarks.length > 0);
+
+if (suites.length === 0) {
+	console.log('No benchmarks matched provided filters');
+	process.exit(1);
+}
 
 const COLUMN_WIDTHS = [25, 9, 9];
 const TOTAL_WIDTH = COLUMN_WIDTHS.reduce((a, b) => a + b);
@@ -16,6 +31,9 @@ const TOTAL_WIDTH = COLUMN_WIDTHS.reduce((a, b) => a + b);
 const pad_right = (str, n) => str + ' '.repeat(n - str.length);
 const pad_left = (str, n) => ' '.repeat(n - str.length) + str;
 
+let total_time = 0;
+let total_gc_time = 0;
+
 $.push({}, true);
 
 try {
@@ -32,9 +50,9 @@ try {
 		console.log('='.repeat(TOTAL_WIDTH));
 
 		for (const benchmark of benchmarks) {
-			const results = await benchmark();
+			const results = await benchmark.fn();
 			console.log(
-				pad_right(results.benchmark, COLUMN_WIDTHS[0]) +
+				pad_right(benchmark.label, COLUMN_WIDTHS[0]) +
 					pad_left(results.time.toFixed(2), COLUMN_WIDTHS[1]) +
 					pad_left(results.gc_time.toFixed(2), COLUMN_WIDTHS[2])
 			);
diff --git a/package.json b/package.json
index aa9c8cafa3..24be8bd2bc 100644
--- a/package.json
+++ b/package.json
@@ -22,8 +22,8 @@
     "changeset:version": "changeset version && pnpm -r generate:version && git add --all",
     "changeset:publish": "changeset publish",
     "bench": "NODE_ENV=production node --allow-natives-syntax ./benchmarking/run.js",
-    "bench:compare": "node --allow-natives-syntax ./benchmarking/compare/index.js",
-    "bench:debug": "node --allow-natives-syntax --inspect-brk ./benchmarking/run.js"
+    "bench:compare": "NODE_ENV=production node --allow-natives-syntax ./benchmarking/compare/index.js",
+    "bench:debug": "NODE_ENV=production node --allow-natives-syntax --inspect-brk ./benchmarking/run.js"
   },
   "devDependencies": {
     "@changesets/cli": "^2.29.8",

From 5ce61868893b5d78cc139fbd76be3ef33f4ec124 Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Wed, 21 Jan 2026 16:05:37 -0500
Subject: [PATCH 6/7] fix (#17507)

---
 .../reactivity/tests/repeated_deps.bench.js   | 35 +++++++++++++++++++
 1 file changed, 35 insertions(+)
 create mode 100644 benchmarking/benchmarks/reactivity/tests/repeated_deps.bench.js

diff --git a/benchmarking/benchmarks/reactivity/tests/repeated_deps.bench.js b/benchmarking/benchmarks/reactivity/tests/repeated_deps.bench.js
new file mode 100644
index 0000000000..a8fbcfdbd6
--- /dev/null
+++ b/benchmarking/benchmarks/reactivity/tests/repeated_deps.bench.js
@@ -0,0 +1,35 @@
+import assert from 'node:assert';
+import * as $ from 'svelte/internal/client';
+
+const ARRAY_SIZE = 1000;
+
+export default () => {
+	const signals = Array.from({ length: ARRAY_SIZE }, (_, i) => $.state(i));
+	const order = $.state(0);
+
+	// break skipped_deps fast path by changing order of reads
+	const total = $.derived(() => {
+		const ord = $.get(order);
+		let sum = 0;
+		for (let i = 0; i < ARRAY_SIZE; i++) {
+			sum += /** @type {number} */ ($.get(signals[(i + ord) % ARRAY_SIZE]));
+		}
+		return sum;
+	});
+
+	const destroy = $.effect_root(() => {
+		$.render_effect(() => {
+			$.get(total);
+		});
+	});
+
+	return {
+		destroy,
+		run() {
+			for (let i = 0; i < 5; i++) {
+				$.flush(() => $.set(order, i));
+				assert.equal($.get(total), (ARRAY_SIZE * (ARRAY_SIZE - 1)) / 2); // sum of 0..999
+			}
+		}
+	};
+};

From c9ebd6a88553a3041d68c6063ec095fdd601f4b7 Mon Sep 17 00:00:00 2001
From: Elliott Johnson <sejohnson@torchcloudconsulting.com>
Date: Wed, 21 Jan 2026 14:09:30 -0700
Subject: [PATCH 7/7] feat: export `parseCss` from `svelte/compiler` (#17496)

* feat: export  from

* changeset

* fix: Errors

* set_source, so state is correct if an error occurs

* simplify

---------

Co-authored-by: Rich Harris <rich.harris@vercel.com>
---
 .changeset/loud-buses-guess.md                |   5 +
 packages/svelte/src/compiler/index.js         |  26 +++-
 .../src/compiler/phases/1-parse/index.js      |  14 ++
 .../src/compiler/phases/1-parse/read/style.js |  30 ++--
 packages/svelte/tests/css-parse.test.ts       | 138 ++++++++++++++++++
 packages/svelte/types/index.d.ts              |   6 +
 6 files changed, 205 insertions(+), 14 deletions(-)
 create mode 100644 .changeset/loud-buses-guess.md
 create mode 100644 packages/svelte/tests/css-parse.test.ts

diff --git a/.changeset/loud-buses-guess.md b/.changeset/loud-buses-guess.md
new file mode 100644
index 0000000000..d6c7c3d5a4
--- /dev/null
+++ b/.changeset/loud-buses-guess.md
@@ -0,0 +1,5 @@
+---
+'svelte': minor
+---
+
+feat: export `parseCss` from `svelte/compiler`
diff --git a/packages/svelte/src/compiler/index.js b/packages/svelte/src/compiler/index.js
index 9095a2a2f2..acfef6a320 100644
--- a/packages/svelte/src/compiler/index.js
+++ b/packages/svelte/src/compiler/index.js
@@ -3,8 +3,9 @@
 /** @import { AST } from './public.js' */
 import { walk as zimmerframe_walk } from 'zimmerframe';
 import { convert } from './legacy.js';
-import { parse as _parse } from './phases/1-parse/index.js';
+import { parse as _parse, Parser } from './phases/1-parse/index.js';
 import { remove_typescript_nodes } from './phases/1-parse/remove_typescript_nodes.js';
+import { parse_stylesheet } from './phases/1-parse/read/style.js';
 import { analyze_component, analyze_module } from './phases/2-analyze/index.js';
 import { transform_component, transform_module } from './phases/3-transform/index.js';
 import { validate_component_options, validate_module_options } from './validate-options.js';
@@ -118,6 +119,29 @@ export function parse(source, { modern, loose } = {}) {
 	return to_public_ast(source, ast, modern);
 }
 
+/**
+ * The parseCss function parses a CSS stylesheet, returning its abstract syntax tree.
+ *
+ * @param {string} source The CSS source code
+ * @returns {Omit<AST.CSS.StyleSheet, 'attributes' | 'content'>}
+ */
+export function parseCss(source) {
+	source = remove_bom(source);
+	state.reset({ warning: () => false, filename: undefined });
+
+	state.set_source(source);
+
+	const parser = Parser.forCss(source);
+	const children = parse_stylesheet(parser);
+
+	return {
+		type: 'StyleSheet',
+		start: 0,
+		end: source.length,
+		children
+	};
+}
+
 /**
  * @param {string} source
  * @param {AST.Root} ast
diff --git a/packages/svelte/src/compiler/phases/1-parse/index.js b/packages/svelte/src/compiler/phases/1-parse/index.js
index 3b5f83d58f..88b4352e8a 100644
--- a/packages/svelte/src/compiler/phases/1-parse/index.js
+++ b/packages/svelte/src/compiler/phases/1-parse/index.js
@@ -34,6 +34,20 @@ export class Parser {
 	/** */
 	index = 0;
 
+	/**
+	 * Creates a minimal parser instance for CSS-only parsing.
+	 * Skips Svelte component parsing setup.
+	 * @param {string} source
+	 * @returns {Parser}
+	 */
+	static forCss(source) {
+		const parser = Object.create(Parser.prototype);
+		parser.template = source;
+		parser.index = 0;
+		parser.loose = false;
+		return parser;
+	}
+
 	/** Whether we're parsing in TypeScript mode */
 	ts = false;
 
diff --git a/packages/svelte/src/compiler/phases/1-parse/read/style.js b/packages/svelte/src/compiler/phases/1-parse/read/style.js
index 80ab234d92..c88a3707c1 100644
--- a/packages/svelte/src/compiler/phases/1-parse/read/style.js
+++ b/packages/svelte/src/compiler/phases/1-parse/read/style.js
@@ -24,10 +24,11 @@ const REGEX_HTML_COMMENT_CLOSE = /-->/;
  */
 export default function read_style(parser, start, attributes) {
 	const content_start = parser.index;
-	const children = read_body(parser, '</style');
+	const children = read_body(parser, (p) => p.match('</style') || p.index >= p.template.length);
 	const content_end = parser.index;
 
-	parser.read(/^<\/style\s*>/);
+	parser.eat('</style', true);
+	parser.read(/^\s*>/);
 
 	return {
 		type: 'StyleSheet',
@@ -46,20 +47,14 @@ export default function read_style(parser, start, attributes) {
 
 /**
  * @param {Parser} parser
- * @param {string} close
- * @returns {any[]}
+ * @param {(parser: Parser) => boolean} finished
+ * @returns {Array<AST.CSS.Rule | AST.CSS.Atrule>}
  */
-function read_body(parser, close) {
+function read_body(parser, finished) {
 	/** @type {Array<AST.CSS.Rule | AST.CSS.Atrule>} */
 	const children = [];
 
-	while (parser.index < parser.template.length) {
-		allow_comment_or_whitespace(parser);
-
-		if (parser.match(close)) {
-			return children;
-		}
-
+	while ((allow_comment_or_whitespace(parser), !finished(parser))) {
 		if (parser.match('@')) {
 			children.push(read_at_rule(parser));
 		} else {
@@ -67,7 +62,7 @@ function read_body(parser, close) {
 		}
 	}
 
-	e.expected_token(parser.template.length, close);
+	return children;
 }
 
 /**
@@ -627,3 +622,12 @@ function allow_comment_or_whitespace(parser) {
 		parser.allow_whitespace();
 	}
 }
+
+/**
+ * Parse standalone CSS content (not wrapped in `<style>`).
+ * @param {Parser} parser
+ * @returns {Array<AST.CSS.Rule | AST.CSS.Atrule>}
+ */
+export function parse_stylesheet(parser) {
+	return read_body(parser, (p) => p.index >= p.template.length);
+}
diff --git a/packages/svelte/tests/css-parse.test.ts b/packages/svelte/tests/css-parse.test.ts
new file mode 100644
index 0000000000..fcb9bdc010
--- /dev/null
+++ b/packages/svelte/tests/css-parse.test.ts
@@ -0,0 +1,138 @@
+import { assert, describe, it } from 'vitest';
+import { parseCss } from 'svelte/compiler';
+
+describe('parseCss', () => {
+	it('parses a simple rule', () => {
+		const ast = parseCss('div { color: red; }');
+		assert.equal(ast.type, 'StyleSheet');
+		assert.equal(ast.children.length, 1);
+		assert.equal(ast.children[0].type, 'Rule');
+	});
+
+	it('parses at-rules', () => {
+		const ast = parseCss('@media (min-width: 800px) { div { color: red; } }');
+		assert.equal(ast.children.length, 1);
+		assert.equal(ast.children[0].type, 'Atrule');
+		if (ast.children[0].type === 'Atrule') {
+			assert.equal(ast.children[0].name, 'media');
+		}
+	});
+
+	it('parses @import', () => {
+		const ast = parseCss("@import 'foo.css';");
+		assert.equal(ast.children.length, 1);
+		assert.equal(ast.children[0].type, 'Atrule');
+		if (ast.children[0].type === 'Atrule') {
+			assert.equal(ast.children[0].name, 'import');
+			assert.equal(ast.children[0].block, null);
+		}
+	});
+
+	it('parses multiple rules', () => {
+		const ast = parseCss('div { color: red; } span { color: blue; }');
+		assert.equal(ast.children.length, 2);
+	});
+
+	it('has correct start/end positions', () => {
+		const ast = parseCss('div { color: red; }');
+		assert.equal(ast.start, 0);
+		assert.equal(ast.end, 19);
+	});
+
+	it('strips BOM', () => {
+		const ast = parseCss('\uFEFFdiv { color: red; }');
+		assert.equal(ast.start, 0);
+		assert.equal(ast.end, 19);
+	});
+
+	it('parses nested rules', () => {
+		const ast = parseCss('div { color: red; span { color: blue; } }');
+		assert.equal(ast.children.length, 1);
+		const rule = ast.children[0];
+		assert.equal(rule.type, 'Rule');
+		if (rule.type === 'Rule') {
+			assert.equal(rule.block.children.length, 2); // declaration + nested rule
+		}
+	});
+
+	it('parses empty stylesheet', () => {
+		const ast = parseCss('');
+		assert.equal(ast.type, 'StyleSheet');
+		assert.equal(ast.children.length, 0);
+		assert.equal(ast.start, 0);
+		assert.equal(ast.end, 0);
+	});
+
+	it('parses whitespace-only stylesheet', () => {
+		const ast = parseCss('   \n\t  ');
+		assert.equal(ast.children.length, 0);
+	});
+
+	it('parses comments', () => {
+		const ast = parseCss('/* comment */ div { color: red; }');
+		assert.equal(ast.children.length, 1);
+		assert.equal(ast.children[0].type, 'Rule');
+	});
+
+	it('parses complex selectors', () => {
+		const ast = parseCss('div > span + p ~ a { color: red; }');
+		assert.equal(ast.children.length, 1);
+		const rule = ast.children[0];
+		if (rule.type === 'Rule') {
+			assert.equal(rule.prelude.type, 'SelectorList');
+			assert.equal(rule.prelude.children.length, 1);
+			// div > span + p ~ a has 4 relative selectors
+			assert.equal(rule.prelude.children[0].children.length, 4);
+		}
+	});
+
+	it('parses pseudo-classes and pseudo-elements', () => {
+		const ast = parseCss('div:hover::before { color: red; }');
+		assert.equal(ast.children.length, 1);
+		const rule = ast.children[0];
+		if (rule.type === 'Rule') {
+			const selectors = rule.prelude.children[0].children[0].selectors;
+			assert.equal(selectors.length, 3); // div, :hover, ::before
+			assert.equal(selectors[0].type, 'TypeSelector');
+			assert.equal(selectors[1].type, 'PseudoClassSelector');
+			assert.equal(selectors[2].type, 'PseudoElementSelector');
+		}
+	});
+
+	it('parses @keyframes', () => {
+		const ast = parseCss('@keyframes fade { from { opacity: 0; } to { opacity: 1; } }');
+		assert.equal(ast.children.length, 1);
+		assert.equal(ast.children[0].type, 'Atrule');
+		if (ast.children[0].type === 'Atrule') {
+			assert.equal(ast.children[0].name, 'keyframes');
+			assert.notEqual(ast.children[0].block, null);
+		}
+	});
+
+	it('parses class and id selectors', () => {
+		const ast = parseCss('.foo#bar { color: red; }');
+		assert.equal(ast.children.length, 1);
+		const rule = ast.children[0];
+		if (rule.type === 'Rule') {
+			const selectors = rule.prelude.children[0].children[0].selectors;
+			assert.equal(selectors.length, 2);
+			assert.equal(selectors[0].type, 'ClassSelector');
+			assert.equal(selectors[1].type, 'IdSelector');
+		}
+	});
+
+	it('parses attribute selectors', () => {
+		const ast = parseCss('[data-foo="bar"] { color: red; }');
+		assert.equal(ast.children.length, 1);
+		const rule = ast.children[0];
+		if (rule.type === 'Rule') {
+			const selectors = rule.prelude.children[0].children[0].selectors;
+			assert.equal(selectors.length, 1);
+			assert.equal(selectors[0].type, 'AttributeSelector');
+			if (selectors[0].type === 'AttributeSelector') {
+				assert.equal(selectors[0].name, 'data-foo');
+				assert.equal(selectors[0].value, 'bar');
+			}
+		}
+	});
+});
diff --git a/packages/svelte/types/index.d.ts b/packages/svelte/types/index.d.ts
index c0b89d8736..9e569126bb 100644
--- a/packages/svelte/types/index.d.ts
+++ b/packages/svelte/types/index.d.ts
@@ -884,6 +884,12 @@ declare module 'svelte/compiler' {
 		modern?: false;
 		loose?: boolean;
 	} | undefined): Record<string, any>;
+	/**
+	 * The parseCss function parses a CSS stylesheet, returning its abstract syntax tree.
+	 *
+	 * @param source The CSS source code
+	 * */
+	export function parseCss(source: string): Omit<AST.CSS.StyleSheet, "attributes" | "content">;
 	/**
 	 * @deprecated Replace this with `import { walk } from 'estree-walker'`
 	 * */