From 64fa513e8bf2ef9b7adb3d177e5083ebb80be5bb Mon Sep 17 00:00:00 2001
From: ComputerGuy <63362464+Ocean-OS@users.noreply.github.com>
Date: Wed, 16 Jul 2025 17:50:01 -0700
Subject: [PATCH 01/10] init

---
 .../phases/2-analyze/visitors/CallExpression.js    |  1 +
 .../3-transform/client/visitors/CallExpression.js  |  3 +++
 .../3-transform/server/visitors/CallExpression.js  |  2 +-
 packages/svelte/src/internal/client/index.js       |  1 +
 .../src/internal/client/reactivity/effects.js      | 14 ++++++++++++++
 packages/svelte/src/utils.js                       |  1 +
 6 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/packages/svelte/src/compiler/phases/2-analyze/visitors/CallExpression.js b/packages/svelte/src/compiler/phases/2-analyze/visitors/CallExpression.js
index 9b6337b9ed9a..25cff4bfe093 100644
--- a/packages/svelte/src/compiler/phases/2-analyze/visitors/CallExpression.js
+++ b/packages/svelte/src/compiler/phases/2-analyze/visitors/CallExpression.js
@@ -150,6 +150,7 @@ export function CallExpression(node, context) {
 
 			break;
 
+		case '$effect.active':
 		case '$effect.tracking':
 			if (node.arguments.length !== 0) {
 				e.rune_invalid_arguments(node, rune);
diff --git a/packages/svelte/src/compiler/phases/3-transform/client/visitors/CallExpression.js b/packages/svelte/src/compiler/phases/3-transform/client/visitors/CallExpression.js
index 3e2f1414e63b..746c051e3f30 100644
--- a/packages/svelte/src/compiler/phases/3-transform/client/visitors/CallExpression.js
+++ b/packages/svelte/src/compiler/phases/3-transform/client/visitors/CallExpression.js
@@ -17,6 +17,9 @@ export function CallExpression(node, context) {
 		case '$host':
 			return b.id('$$props.$$host');
 
+		case '$effect.active':
+			return b.call('$.effect_active');
+
 		case '$effect.tracking':
 			return b.call('$.effect_tracking');
 
diff --git a/packages/svelte/src/compiler/phases/3-transform/server/visitors/CallExpression.js b/packages/svelte/src/compiler/phases/3-transform/server/visitors/CallExpression.js
index 41d3202ce9ea..64d4f573c586 100644
--- a/packages/svelte/src/compiler/phases/3-transform/server/visitors/CallExpression.js
+++ b/packages/svelte/src/compiler/phases/3-transform/server/visitors/CallExpression.js
@@ -16,7 +16,7 @@ export function CallExpression(node, context) {
 		return b.void0;
 	}
 
-	if (rune === '$effect.tracking') {
+	if (rune === '$effect.tracking' || rune === '$effect.active') {
 		return b.false;
 	}
 
diff --git a/packages/svelte/src/internal/client/index.js b/packages/svelte/src/internal/client/index.js
index cddb432a982b..a186cdd86bbf 100644
--- a/packages/svelte/src/internal/client/index.js
+++ b/packages/svelte/src/internal/client/index.js
@@ -107,6 +107,7 @@ export {
 } from './reactivity/deriveds.js';
 export {
 	aborted,
+	effect_active,
 	effect_tracking,
 	effect_root,
 	legacy_pre_effect,
diff --git a/packages/svelte/src/internal/client/reactivity/effects.js b/packages/svelte/src/internal/client/reactivity/effects.js
index c4edd2bf8d95..ccc2d9c9ec44 100644
--- a/packages/svelte/src/internal/client/reactivity/effects.js
+++ b/packages/svelte/src/internal/client/reactivity/effects.js
@@ -165,6 +165,20 @@ export function effect_tracking() {
 	return active_reaction !== null && !untracking;
 }
 
+/**
+ * Internal representation of `$effect.active()`
+ * @returns {boolean}
+ */
+export function effect_active() {
+	if (active_reaction === null && active_effect === null) {
+		return false;
+	}
+	if (is_destroying_effect) {
+		return false;
+	}
+	return true;
+}
+
 /**
  * @param {() => void} fn
  */
diff --git a/packages/svelte/src/utils.js b/packages/svelte/src/utils.js
index cd79cfc27467..f49382921a5b 100644
--- a/packages/svelte/src/utils.js
+++ b/packages/svelte/src/utils.js
@@ -442,6 +442,7 @@ const RUNES = /** @type {const} */ ([
 	'$props.id',
 	'$bindable',
 	'$effect',
+	'$effect.active',
 	'$effect.pre',
 	'$effect.tracking',
 	'$effect.root',

From 45d3eeb4e6c905f44f1328200f7dc8e0c0e874b4 Mon Sep 17 00:00:00 2001
From: ComputerGuy <63362464+Ocean-OS@users.noreply.github.com>
Date: Fri, 18 Jul 2025 03:00:43 -0700
Subject: [PATCH 02/10] add types, DRY out some logic

---
 packages/svelte/src/ambient.d.ts              | 28 ++++++++++++
 .../svelte/src/internal/client/constants.js   |  5 +++
 .../src/internal/client/reactivity/effects.js | 43 +++++++++++++------
 packages/svelte/types/index.d.ts              | 28 ++++++++++++
 4 files changed, 91 insertions(+), 13 deletions(-)

diff --git a/packages/svelte/src/ambient.d.ts b/packages/svelte/src/ambient.d.ts
index 7c3b941ed1fb..aaaddbe544ff 100644
--- a/packages/svelte/src/ambient.d.ts
+++ b/packages/svelte/src/ambient.d.ts
@@ -237,6 +237,34 @@ declare namespace $derived {
 declare function $effect(fn: () => void | (() => void)): void;
 
 declare namespace $effect {
+	/**
+	 * The `$effect.active` rune is an advanced feature that indicates whether an effect or async `$derived` can be created in the current context.
+	 * Effects and async deriveds can only be created in root effects, which are created during component setup, or can be programmatically created via `$effect.root`.
+	 * 
+	 * Example:
+	 * ```svelte
+	 * <script>
+	 *   console.log('in component setup', $effect.active()); // true
+	 * 
+	 *   function onclick() {
+	 *     console.log('after component setup', $effect.active()); // false
+	 *   }
+	 *   function ondblclick() {
+	 *     $effect.root(() => {
+	 *       console.log('in root effect', $effect.active()); // true
+	 *       return () => {
+	 *         console.log('in effect teardown', $effect.active()); // false
+	 *       }
+	 *     })();
+	 *   }
+	 * </script>
+	 * <button {onclick}>Click me!</button>
+	 * <button {ondblclick}>Click me twice!</button>
+	 * ```
+	 * 
+	 * https://svelte.dev/docs/svelte/$effect#$effect.active
+	 */
+	export function active(): boolean;
 	/**
 	 * Runs code right before a component is mounted to the DOM, and then whenever its dependencies change, i.e. `$state` or `$derived` values.
 	 * The timing of the execution is right before the DOM is updated.
diff --git a/packages/svelte/src/internal/client/constants.js b/packages/svelte/src/internal/client/constants.js
index 50a7a21ae80f..de0ca92f1289 100644
--- a/packages/svelte/src/internal/client/constants.js
+++ b/packages/svelte/src/internal/client/constants.js
@@ -41,3 +41,8 @@ export const ELEMENT_NODE = 1;
 export const TEXT_NODE = 3;
 export const COMMENT_NODE = 8;
 export const DOCUMENT_FRAGMENT_NODE = 11;
+
+export const VALID_EFFECT_PARENT = 0;
+export const EFFECT_ORPHAN = 1;
+export const UNOWNED_DERIVED_PARENT = 2;
+export const EFFECT_TEARDOWN = 3;
\ No newline at end of file
diff --git a/packages/svelte/src/internal/client/reactivity/effects.js b/packages/svelte/src/internal/client/reactivity/effects.js
index ccc2d9c9ec44..7921b1e5e91f 100644
--- a/packages/svelte/src/internal/client/reactivity/effects.js
+++ b/packages/svelte/src/internal/client/reactivity/effects.js
@@ -33,7 +33,11 @@ import {
 	EFFECT_PRESERVED,
 	STALE_REACTION,
 	USER_EFFECT,
-	ASYNC
+	ASYNC,
+	EFFECT_ORPHAN,
+	EFFECT_TEARDOWN,
+	UNOWNED_DERIVED_PARENT,
+	VALID_EFFECT_PARENT
 } from '#client/constants';
 import * as e from '../errors.js';
 import { DEV } from 'esm-env';
@@ -44,19 +48,38 @@ import { Batch, schedule_effect } from './batch.js';
 import { flatten } from './async.js';
 
 /**
- * @param {'$effect' | '$effect.pre' | '$inspect'} rune
+ * @returns {number}
  */
-export function validate_effect(rune) {
+function active_root_effect() {
 	if (active_effect === null && active_reaction === null) {
-		e.effect_orphan(rune);
+		return EFFECT_ORPHAN;
 	}
 
 	if (active_reaction !== null && (active_reaction.f & UNOWNED) !== 0 && active_effect === null) {
-		e.effect_in_unowned_derived();
+		return UNOWNED_DERIVED_PARENT;
 	}
 
 	if (is_destroying_effect) {
-		e.effect_in_teardown(rune);
+		return EFFECT_TEARDOWN;
+	}
+
+	return VALID_EFFECT_PARENT;
+}
+
+/**
+ * @param {'$effect' | '$effect.pre' | '$inspect'} rune
+ */
+export function validate_effect(rune) {
+	const valid_effect_parent = active_root_effect();
+	switch(valid_effect_parent) {
+		case VALID_EFFECT_PARENT:
+			return;
+		case EFFECT_ORPHAN:
+			e.effect_orphan(rune);
+		case UNOWNED_DERIVED_PARENT:
+			e.effect_in_unowned_derived();
+		case EFFECT_TEARDOWN:
+			e.effect_in_teardown(rune);
 	}
 }
 
@@ -170,13 +193,7 @@ export function effect_tracking() {
  * @returns {boolean}
  */
 export function effect_active() {
-	if (active_reaction === null && active_effect === null) {
-		return false;
-	}
-	if (is_destroying_effect) {
-		return false;
-	}
-	return true;
+	return active_root_effect() === VALID_EFFECT_PARENT;
 }
 
 /**
diff --git a/packages/svelte/types/index.d.ts b/packages/svelte/types/index.d.ts
index a8b769d6d4c3..abe0213ed354 100644
--- a/packages/svelte/types/index.d.ts
+++ b/packages/svelte/types/index.d.ts
@@ -3311,6 +3311,34 @@ declare namespace $derived {
 declare function $effect(fn: () => void | (() => void)): void;
 
 declare namespace $effect {
+	/**
+	 * The `$effect.active` rune is an advanced feature that indicates whether an effect or async `$derived` can be created in the current context.
+	 * Effects and async deriveds can only be created in root effects, which are created during component setup, or can be programmatically created via `$effect.root`.
+	 * 
+	 * Example:
+	 * ```svelte
+	 * <script>
+	 *   console.log('in component setup', $effect.active()); // true
+	 * 
+	 *   function onclick() {
+	 *     console.log('after component setup', $effect.active()); // false
+	 *   }
+	 *   function ondblclick() {
+	 *     $effect.root(() => {
+	 *       console.log('in root effect', $effect.active()); // true
+	 *       return () => {
+	 *         console.log('in effect teardown', $effect.active()); // false
+	 *       }
+	 *     })();
+	 *   }
+	 * </script>
+	 * <button {onclick}>Click me!</button>
+	 * <button {ondblclick}>Click me twice!</button>
+	 * ```
+	 * 
+	 * https://svelte.dev/docs/svelte/$effect#$effect.active
+	 */
+	export function active(): boolean;
 	/**
 	 * Runs code right before a component is mounted to the DOM, and then whenever its dependencies change, i.e. `$state` or `$derived` values.
 	 * The timing of the execution is right before the DOM is updated.

From 9ae4a65c4ac1d8a0ba8069ac3a1da3889dca61a9 Mon Sep 17 00:00:00 2001
From: ComputerGuy <63362464+Ocean-OS@users.noreply.github.com>
Date: Fri, 18 Jul 2025 18:26:56 -0700
Subject: [PATCH 03/10] add docs

---
 documentation/docs/02-runes/04-$effect.md     | 24 +++++++++++++++++++
 .../src/internal/client/reactivity/effects.js |  2 ++
 2 files changed, 26 insertions(+)

diff --git a/documentation/docs/02-runes/04-$effect.md b/documentation/docs/02-runes/04-$effect.md
index 5820e178a078..4a27a7277851 100644
--- a/documentation/docs/02-runes/04-$effect.md
+++ b/documentation/docs/02-runes/04-$effect.md
@@ -255,6 +255,30 @@ const destroy = $effect.root(() => {
 destroy();
 ```
 
+## `$effect.active`
+
+The `$effect.active` rune is an advanced feature that indicates whether or not an effect or [async `$derived`](await-expressions) can be created in the current context. To improve performance and memory efficiency, effects and async deriveds can only be created when a root effect is active. Root effects are created during component setup, but they can also be programmatically created via `$effect.root`. 
+
+```svelte
+<script>
+	console.log('in component setup', $effect.active()); // true
+
+	function onclick() {
+		console.log('after component setup', $effect.active()); // false
+	}
+	function ondblclick() {
+		$effect.root(() => {
+			console.log('in root effect', $effect.active()); // true
+			return () => {
+				console.log('in effect teardown', $effect.active()); // false
+			}
+		})();
+	}
+</script>
+<button {onclick}>Click me!</button>
+<button {ondblclick}>Click me twice!</button>
+```
+
 ## When not to use `$effect`
 
 In general, `$effect` is best considered something of an escape hatch — useful for things like analytics and direct DOM manipulation — rather than a tool you should use frequently. In particular, avoid using it to synchronise state. Instead of this...
diff --git a/packages/svelte/src/internal/client/reactivity/effects.js b/packages/svelte/src/internal/client/reactivity/effects.js
index 7921b1e5e91f..75f8aa22f3d3 100644
--- a/packages/svelte/src/internal/client/reactivity/effects.js
+++ b/packages/svelte/src/internal/client/reactivity/effects.js
@@ -48,6 +48,8 @@ import { Batch, schedule_effect } from './batch.js';
 import { flatten } from './async.js';
 
 /**
+ * If an effect can be created in the current context, `VALID_EFFECT_PARENT` is returned. 
+ * If not, a value indicating why is returned. 
  * @returns {number}
  */
 function active_root_effect() {

From c61f2a9bae8176b9e9aa74e4206c17720a82d8c9 Mon Sep 17 00:00:00 2001
From: ComputerGuy <63362464+Ocean-OS@users.noreply.github.com>
Date: Sat, 19 Jul 2025 10:27:25 -0700
Subject: [PATCH 04/10] changeset

---
 .changeset/two-dancers-speak.md | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 .changeset/two-dancers-speak.md

diff --git a/.changeset/two-dancers-speak.md b/.changeset/two-dancers-speak.md
new file mode 100644
index 000000000000..7044eaa329d3
--- /dev/null
+++ b/.changeset/two-dancers-speak.md
@@ -0,0 +1,5 @@
+---
+'svelte': minor
+---
+
+feat: add `$effect.active` rune

From 9c1de633c0812f47eca2e8c9c5c1366eb9f2212b Mon Sep 17 00:00:00 2001
From: ComputerGuy <63362464+Ocean-OS@users.noreply.github.com>
Date: Sat, 19 Jul 2025 10:41:47 -0700
Subject: [PATCH 05/10] add test

---
 packages/svelte/tests/signals/test.ts | 38 +++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/packages/svelte/tests/signals/test.ts b/packages/svelte/tests/signals/test.ts
index 937324727b16..261198fc1c87 100644
--- a/packages/svelte/tests/signals/test.ts
+++ b/packages/svelte/tests/signals/test.ts
@@ -4,6 +4,7 @@ import * as $ from '../../src/internal/client/runtime';
 import { push, pop } from '../../src/internal/client/context';
 import {
 	effect,
+	effect_active,
 	effect_root,
 	render_effect,
 	user_effect,
@@ -1390,4 +1391,41 @@ describe('signals', () => {
 			destroy();
 		};
 	});
+
+	test('$effect.active()', () => {
+		const log: Array<string | boolean> = [];
+
+		return () => {
+			log.push('effect orphan', effect_active());
+			const destroy = effect_root(() => {
+				log.push('effect root', effect_active());
+				effect(() => {
+					log.push('effect', effect_active());
+				});
+				$.get(
+					derived(() => {
+						log.push('derived', effect_active());
+						return 1;
+					})
+				);
+				return () => {
+					log.push('effect teardown', effect_active());
+				};
+			});
+			flushSync();
+			destroy();
+			assert.deepEqual(log, [
+				'effect orphan',
+				false,
+				'effect root',
+				true,
+				'derived',
+				true,
+				'effect',
+				true,
+				'effect teardown',
+				false
+			]);
+		};
+	});
 });

From c82fb3a0c83b7aed53183c61b26ab7a699089dfa Mon Sep 17 00:00:00 2001
From: ComputerGuy <63362464+Ocean-OS@users.noreply.github.com>
Date: Sun, 20 Jul 2025 13:57:48 -0700
Subject: [PATCH 06/10] remove obsolete test

---
 .../compiler-errors/samples/effect-active-rune/_config.js | 8 --------
 .../samples/effect-active-rune/main.svelte.js             | 1 -
 2 files changed, 9 deletions(-)
 delete mode 100644 packages/svelte/tests/compiler-errors/samples/effect-active-rune/_config.js
 delete mode 100644 packages/svelte/tests/compiler-errors/samples/effect-active-rune/main.svelte.js

diff --git a/packages/svelte/tests/compiler-errors/samples/effect-active-rune/_config.js b/packages/svelte/tests/compiler-errors/samples/effect-active-rune/_config.js
deleted file mode 100644
index e12e4046f36d..000000000000
--- a/packages/svelte/tests/compiler-errors/samples/effect-active-rune/_config.js
+++ /dev/null
@@ -1,8 +0,0 @@
-import { test } from '../../test';
-
-export default test({
-	error: {
-		code: 'rune_renamed',
-		message: '`$effect.active` is now `$effect.tracking`'
-	}
-});
diff --git a/packages/svelte/tests/compiler-errors/samples/effect-active-rune/main.svelte.js b/packages/svelte/tests/compiler-errors/samples/effect-active-rune/main.svelte.js
deleted file mode 100644
index c33c104aac31..000000000000
--- a/packages/svelte/tests/compiler-errors/samples/effect-active-rune/main.svelte.js
+++ /dev/null
@@ -1 +0,0 @@
-$effect.active();

From 7b33b2ab54ce4e1710e89e1120a100e00ceaefc4 Mon Sep 17 00:00:00 2001
From: ComputerGuy <63362464+Ocean-OS@users.noreply.github.com>
Date: Sun, 20 Jul 2025 14:04:46 -0700
Subject: [PATCH 07/10] fix lint

---
 .../svelte/src/internal/client/reactivity/effects.js     | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/packages/svelte/src/internal/client/reactivity/effects.js b/packages/svelte/src/internal/client/reactivity/effects.js
index 75f8aa22f3d3..5d0b24e33d4e 100644
--- a/packages/svelte/src/internal/client/reactivity/effects.js
+++ b/packages/svelte/src/internal/client/reactivity/effects.js
@@ -48,8 +48,8 @@ import { Batch, schedule_effect } from './batch.js';
 import { flatten } from './async.js';
 
 /**
- * If an effect can be created in the current context, `VALID_EFFECT_PARENT` is returned. 
- * If not, a value indicating why is returned. 
+ * If an effect can be created in the current context, `VALID_EFFECT_PARENT` is returned.
+ * If not, a value indicating why is returned.
  * @returns {number}
  */
 function active_root_effect() {
@@ -73,15 +73,18 @@ function active_root_effect() {
  */
 export function validate_effect(rune) {
 	const valid_effect_parent = active_root_effect();
-	switch(valid_effect_parent) {
+	switch (valid_effect_parent) {
 		case VALID_EFFECT_PARENT:
 			return;
 		case EFFECT_ORPHAN:
 			e.effect_orphan(rune);
+			break;
 		case UNOWNED_DERIVED_PARENT:
 			e.effect_in_unowned_derived();
+			break;
 		case EFFECT_TEARDOWN:
 			e.effect_in_teardown(rune);
+			break;
 	}
 }
 

From ab91795ac8b2bfefac3e72e2f24b6a0e40d16f91 Mon Sep 17 00:00:00 2001
From: ComputerGuy <63362464+Ocean-OS@users.noreply.github.com>
Date: Sun, 20 Jul 2025 14:13:23 -0700
Subject: [PATCH 08/10] lint

---
 packages/svelte/src/ambient.d.ts                 | 6 +++---
 packages/svelte/src/internal/client/constants.js | 2 +-
 packages/svelte/types/index.d.ts                 | 6 +++---
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/packages/svelte/src/ambient.d.ts b/packages/svelte/src/ambient.d.ts
index 5bf69a157fe2..cc395995cc3c 100644
--- a/packages/svelte/src/ambient.d.ts
+++ b/packages/svelte/src/ambient.d.ts
@@ -240,12 +240,12 @@ declare namespace $effect {
 	/**
 	 * The `$effect.active` rune is an advanced feature that indicates whether an effect or async `$derived` can be created in the current context.
 	 * Effects and async deriveds can only be created in root effects, which are created during component setup, or can be programmatically created via `$effect.root`.
-	 * 
+	 *
 	 * Example:
 	 * ```svelte
 	 * <script>
 	 *   console.log('in component setup', $effect.active()); // true
-	 * 
+	 *
 	 *   function onclick() {
 	 *     console.log('after component setup', $effect.active()); // false
 	 *   }
@@ -261,7 +261,7 @@ declare namespace $effect {
 	 * <button {onclick}>Click me!</button>
 	 * <button {ondblclick}>Click me twice!</button>
 	 * ```
-	 * 
+	 *
 	 * https://svelte.dev/docs/svelte/$effect#$effect.active
 	 */
 	export function active(): boolean;
diff --git a/packages/svelte/src/internal/client/constants.js b/packages/svelte/src/internal/client/constants.js
index de0ca92f1289..32dc23df3be1 100644
--- a/packages/svelte/src/internal/client/constants.js
+++ b/packages/svelte/src/internal/client/constants.js
@@ -45,4 +45,4 @@ export const DOCUMENT_FRAGMENT_NODE = 11;
 export const VALID_EFFECT_PARENT = 0;
 export const EFFECT_ORPHAN = 1;
 export const UNOWNED_DERIVED_PARENT = 2;
-export const EFFECT_TEARDOWN = 3;
\ No newline at end of file
+export const EFFECT_TEARDOWN = 3;
diff --git a/packages/svelte/types/index.d.ts b/packages/svelte/types/index.d.ts
index c59633e7e63c..39e1c54d4c75 100644
--- a/packages/svelte/types/index.d.ts
+++ b/packages/svelte/types/index.d.ts
@@ -3314,12 +3314,12 @@ declare namespace $effect {
 	/**
 	 * The `$effect.active` rune is an advanced feature that indicates whether an effect or async `$derived` can be created in the current context.
 	 * Effects and async deriveds can only be created in root effects, which are created during component setup, or can be programmatically created via `$effect.root`.
-	 * 
+	 *
 	 * Example:
 	 * ```svelte
 	 * <script>
 	 *   console.log('in component setup', $effect.active()); // true
-	 * 
+	 *
 	 *   function onclick() {
 	 *     console.log('after component setup', $effect.active()); // false
 	 *   }
@@ -3335,7 +3335,7 @@ declare namespace $effect {
 	 * <button {onclick}>Click me!</button>
 	 * <button {ondblclick}>Click me twice!</button>
 	 * ```
-	 * 
+	 *
 	 * https://svelte.dev/docs/svelte/$effect#$effect.active
 	 */
 	export function active(): boolean;

From 3345ed078254accf293e5278af12fe6dd3e11cc5 Mon Sep 17 00:00:00 2001
From: ComputerGuy <63362464+Ocean-OS@users.noreply.github.com>
Date: Sun, 20 Jul 2025 15:55:23 -0700
Subject: [PATCH 09/10] apply suggestion from review

---
 packages/svelte/src/internal/client/constants.js      |  5 -----
 .../svelte/src/internal/client/reactivity/effects.js  | 11 ++++++-----
 2 files changed, 6 insertions(+), 10 deletions(-)

diff --git a/packages/svelte/src/internal/client/constants.js b/packages/svelte/src/internal/client/constants.js
index 32dc23df3be1..50a7a21ae80f 100644
--- a/packages/svelte/src/internal/client/constants.js
+++ b/packages/svelte/src/internal/client/constants.js
@@ -41,8 +41,3 @@ export const ELEMENT_NODE = 1;
 export const TEXT_NODE = 3;
 export const COMMENT_NODE = 8;
 export const DOCUMENT_FRAGMENT_NODE = 11;
-
-export const VALID_EFFECT_PARENT = 0;
-export const EFFECT_ORPHAN = 1;
-export const UNOWNED_DERIVED_PARENT = 2;
-export const EFFECT_TEARDOWN = 3;
diff --git a/packages/svelte/src/internal/client/reactivity/effects.js b/packages/svelte/src/internal/client/reactivity/effects.js
index 5d0b24e33d4e..5eb98c8de710 100644
--- a/packages/svelte/src/internal/client/reactivity/effects.js
+++ b/packages/svelte/src/internal/client/reactivity/effects.js
@@ -33,11 +33,7 @@ import {
 	EFFECT_PRESERVED,
 	STALE_REACTION,
 	USER_EFFECT,
-	ASYNC,
-	EFFECT_ORPHAN,
-	EFFECT_TEARDOWN,
-	UNOWNED_DERIVED_PARENT,
-	VALID_EFFECT_PARENT
+	ASYNC
 } from '#client/constants';
 import * as e from '../errors.js';
 import { DEV } from 'esm-env';
@@ -47,6 +43,11 @@ import { component_context, dev_current_component_function, dev_stack } from '..
 import { Batch, schedule_effect } from './batch.js';
 import { flatten } from './async.js';
 
+const VALID_EFFECT_PARENT = 0;
+const EFFECT_ORPHAN = 1;
+const UNOWNED_DERIVED_PARENT = 2;
+const EFFECT_TEARDOWN = 3;
+
 /**
  * If an effect can be created in the current context, `VALID_EFFECT_PARENT` is returned.
  * If not, a value indicating why is returned.

From 5aff44a83fde800631d73737384c839bbfcee80a Mon Sep 17 00:00:00 2001
From: ComputerGuy <63362464+Ocean-OS@users.noreply.github.com>
Date: Mon, 21 Jul 2025 02:20:33 -0700
Subject: [PATCH 10/10] rename to `$effect.allowed`

---
 .changeset/two-dancers-speak.md                    |  2 +-
 documentation/docs/02-runes/04-$effect.md          | 12 ++++++------
 packages/svelte/src/ambient.d.ts                   | 14 +++++++-------
 .../phases/2-analyze/visitors/CallExpression.js    |  2 +-
 .../3-transform/client/visitors/CallExpression.js  |  4 ++--
 .../3-transform/server/visitors/CallExpression.js  |  2 +-
 packages/svelte/src/internal/client/index.js       |  2 +-
 .../src/internal/client/reactivity/effects.js      | 10 +++++-----
 packages/svelte/src/utils.js                       |  2 +-
 .../samples/effect-active-rune/_config.js          |  8 ++++++++
 .../samples/effect-active-rune/main.svelte.js      |  1 +
 packages/svelte/tests/signals/test.ts              | 14 +++++++-------
 packages/svelte/types/index.d.ts                   | 14 +++++++-------
 13 files changed, 48 insertions(+), 39 deletions(-)
 create mode 100644 packages/svelte/tests/compiler-errors/samples/effect-active-rune/_config.js
 create mode 100644 packages/svelte/tests/compiler-errors/samples/effect-active-rune/main.svelte.js

diff --git a/.changeset/two-dancers-speak.md b/.changeset/two-dancers-speak.md
index 7044eaa329d3..b0d8d394d0dd 100644
--- a/.changeset/two-dancers-speak.md
+++ b/.changeset/two-dancers-speak.md
@@ -2,4 +2,4 @@
 'svelte': minor
 ---
 
-feat: add `$effect.active` rune
+feat: add `$effect.allowed` rune
diff --git a/documentation/docs/02-runes/04-$effect.md b/documentation/docs/02-runes/04-$effect.md
index 4a27a7277851..59010c981fca 100644
--- a/documentation/docs/02-runes/04-$effect.md
+++ b/documentation/docs/02-runes/04-$effect.md
@@ -255,22 +255,22 @@ const destroy = $effect.root(() => {
 destroy();
 ```
 
-## `$effect.active`
+## `$effect.allowed`
 
-The `$effect.active` rune is an advanced feature that indicates whether or not an effect or [async `$derived`](await-expressions) can be created in the current context. To improve performance and memory efficiency, effects and async deriveds can only be created when a root effect is active. Root effects are created during component setup, but they can also be programmatically created via `$effect.root`. 
+The `$effect.allowed` rune is an advanced feature that indicates whether or not an effect or [async `$derived`](await-expressions) can be created in the current context. To improve performance and memory efficiency, effects and async deriveds can only be created when a root effect is active. Root effects are created during component setup, but they can also be programmatically created via `$effect.root`. 
 
 ```svelte
 <script>
-	console.log('in component setup', $effect.active()); // true
+	console.log('in component setup', $effect.allowed()); // true
 
 	function onclick() {
-		console.log('after component setup', $effect.active()); // false
+		console.log('after component setup', $effect.allowed()); // false
 	}
 	function ondblclick() {
 		$effect.root(() => {
-			console.log('in root effect', $effect.active()); // true
+			console.log('in root effect', $effect.allowed()); // true
 			return () => {
-				console.log('in effect teardown', $effect.active()); // false
+				console.log('in effect teardown', $effect.allowed()); // false
 			}
 		})();
 	}
diff --git a/packages/svelte/src/ambient.d.ts b/packages/svelte/src/ambient.d.ts
index cc395995cc3c..5245626d53b4 100644
--- a/packages/svelte/src/ambient.d.ts
+++ b/packages/svelte/src/ambient.d.ts
@@ -238,22 +238,22 @@ declare function $effect(fn: () => void | (() => void)): void;
 
 declare namespace $effect {
 	/**
-	 * The `$effect.active` rune is an advanced feature that indicates whether an effect or async `$derived` can be created in the current context.
+	 * The `$effect.allowed` rune is an advanced feature that indicates whether an effect or async `$derived` can be created in the current context.
 	 * Effects and async deriveds can only be created in root effects, which are created during component setup, or can be programmatically created via `$effect.root`.
 	 *
 	 * Example:
 	 * ```svelte
 	 * <script>
-	 *   console.log('in component setup', $effect.active()); // true
+	 *   console.log('in component setup', $effect.allowed()); // true
 	 *
 	 *   function onclick() {
-	 *     console.log('after component setup', $effect.active()); // false
+	 *     console.log('after component setup', $effect.allowed()); // false
 	 *   }
 	 *   function ondblclick() {
 	 *     $effect.root(() => {
-	 *       console.log('in root effect', $effect.active()); // true
+	 *       console.log('in root effect', $effect.allowed()); // true
 	 *       return () => {
-	 *         console.log('in effect teardown', $effect.active()); // false
+	 *         console.log('in effect teardown', $effect.allowed()); // false
 	 *       }
 	 *     })();
 	 *   }
@@ -262,9 +262,9 @@ declare namespace $effect {
 	 * <button {ondblclick}>Click me twice!</button>
 	 * ```
 	 *
-	 * https://svelte.dev/docs/svelte/$effect#$effect.active
+	 * https://svelte.dev/docs/svelte/$effect#$effect.allowed
 	 */
-	export function active(): boolean;
+	export function allowed(): boolean;
 	/**
 	 * Runs code right before a component is mounted to the DOM, and then whenever its dependencies change, i.e. `$state` or `$derived` values.
 	 * The timing of the execution is right before the DOM is updated.
diff --git a/packages/svelte/src/compiler/phases/2-analyze/visitors/CallExpression.js b/packages/svelte/src/compiler/phases/2-analyze/visitors/CallExpression.js
index 25cff4bfe093..b4c5d4fdc400 100644
--- a/packages/svelte/src/compiler/phases/2-analyze/visitors/CallExpression.js
+++ b/packages/svelte/src/compiler/phases/2-analyze/visitors/CallExpression.js
@@ -150,7 +150,7 @@ export function CallExpression(node, context) {
 
 			break;
 
-		case '$effect.active':
+		case '$effect.allowed':
 		case '$effect.tracking':
 			if (node.arguments.length !== 0) {
 				e.rune_invalid_arguments(node, rune);
diff --git a/packages/svelte/src/compiler/phases/3-transform/client/visitors/CallExpression.js b/packages/svelte/src/compiler/phases/3-transform/client/visitors/CallExpression.js
index 746c051e3f30..1b5c2fa2dae5 100644
--- a/packages/svelte/src/compiler/phases/3-transform/client/visitors/CallExpression.js
+++ b/packages/svelte/src/compiler/phases/3-transform/client/visitors/CallExpression.js
@@ -17,8 +17,8 @@ export function CallExpression(node, context) {
 		case '$host':
 			return b.id('$$props.$$host');
 
-		case '$effect.active':
-			return b.call('$.effect_active');
+		case '$effect.allowed':
+			return b.call('$.effect_allowed');
 
 		case '$effect.tracking':
 			return b.call('$.effect_tracking');
diff --git a/packages/svelte/src/compiler/phases/3-transform/server/visitors/CallExpression.js b/packages/svelte/src/compiler/phases/3-transform/server/visitors/CallExpression.js
index 64d4f573c586..e4c6fc66ab54 100644
--- a/packages/svelte/src/compiler/phases/3-transform/server/visitors/CallExpression.js
+++ b/packages/svelte/src/compiler/phases/3-transform/server/visitors/CallExpression.js
@@ -16,7 +16,7 @@ export function CallExpression(node, context) {
 		return b.void0;
 	}
 
-	if (rune === '$effect.tracking' || rune === '$effect.active') {
+	if (rune === '$effect.tracking' || rune === '$effect.allowed') {
 		return b.false;
 	}
 
diff --git a/packages/svelte/src/internal/client/index.js b/packages/svelte/src/internal/client/index.js
index a186cdd86bbf..a38f2f4173f8 100644
--- a/packages/svelte/src/internal/client/index.js
+++ b/packages/svelte/src/internal/client/index.js
@@ -107,7 +107,7 @@ export {
 } from './reactivity/deriveds.js';
 export {
 	aborted,
-	effect_active,
+	effect_allowed,
 	effect_tracking,
 	effect_root,
 	legacy_pre_effect,
diff --git a/packages/svelte/src/internal/client/reactivity/effects.js b/packages/svelte/src/internal/client/reactivity/effects.js
index 5eb98c8de710..18167d6bf5e8 100644
--- a/packages/svelte/src/internal/client/reactivity/effects.js
+++ b/packages/svelte/src/internal/client/reactivity/effects.js
@@ -53,7 +53,7 @@ const EFFECT_TEARDOWN = 3;
  * If not, a value indicating why is returned.
  * @returns {number}
  */
-function active_root_effect() {
+function valid_effect_creation_context() {
 	if (active_effect === null && active_reaction === null) {
 		return EFFECT_ORPHAN;
 	}
@@ -73,7 +73,7 @@ function active_root_effect() {
  * @param {'$effect' | '$effect.pre' | '$inspect'} rune
  */
 export function validate_effect(rune) {
-	const valid_effect_parent = active_root_effect();
+	const valid_effect_parent = valid_effect_creation_context();
 	switch (valid_effect_parent) {
 		case VALID_EFFECT_PARENT:
 			return;
@@ -195,11 +195,11 @@ export function effect_tracking() {
 }
 
 /**
- * Internal representation of `$effect.active()`
+ * Internal representation of `$effect.allowed()`
  * @returns {boolean}
  */
-export function effect_active() {
-	return active_root_effect() === VALID_EFFECT_PARENT;
+export function effect_allowed() {
+	return valid_effect_creation_context() === VALID_EFFECT_PARENT;
 }
 
 /**
diff --git a/packages/svelte/src/utils.js b/packages/svelte/src/utils.js
index f49382921a5b..231c10c7cf5b 100644
--- a/packages/svelte/src/utils.js
+++ b/packages/svelte/src/utils.js
@@ -442,7 +442,7 @@ const RUNES = /** @type {const} */ ([
 	'$props.id',
 	'$bindable',
 	'$effect',
-	'$effect.active',
+	'$effect.allowed',
 	'$effect.pre',
 	'$effect.tracking',
 	'$effect.root',
diff --git a/packages/svelte/tests/compiler-errors/samples/effect-active-rune/_config.js b/packages/svelte/tests/compiler-errors/samples/effect-active-rune/_config.js
new file mode 100644
index 000000000000..e12e4046f36d
--- /dev/null
+++ b/packages/svelte/tests/compiler-errors/samples/effect-active-rune/_config.js
@@ -0,0 +1,8 @@
+import { test } from '../../test';
+
+export default test({
+	error: {
+		code: 'rune_renamed',
+		message: '`$effect.active` is now `$effect.tracking`'
+	}
+});
diff --git a/packages/svelte/tests/compiler-errors/samples/effect-active-rune/main.svelte.js b/packages/svelte/tests/compiler-errors/samples/effect-active-rune/main.svelte.js
new file mode 100644
index 000000000000..c33c104aac31
--- /dev/null
+++ b/packages/svelte/tests/compiler-errors/samples/effect-active-rune/main.svelte.js
@@ -0,0 +1 @@
+$effect.active();
diff --git a/packages/svelte/tests/signals/test.ts b/packages/svelte/tests/signals/test.ts
index 261198fc1c87..32aed75b658f 100644
--- a/packages/svelte/tests/signals/test.ts
+++ b/packages/svelte/tests/signals/test.ts
@@ -4,7 +4,7 @@ import * as $ from '../../src/internal/client/runtime';
 import { push, pop } from '../../src/internal/client/context';
 import {
 	effect,
-	effect_active,
+	effect_allowed,
 	effect_root,
 	render_effect,
 	user_effect,
@@ -1392,24 +1392,24 @@ describe('signals', () => {
 		};
 	});
 
-	test('$effect.active()', () => {
+	test('$effect.allowed()', () => {
 		const log: Array<string | boolean> = [];
 
 		return () => {
-			log.push('effect orphan', effect_active());
+			log.push('effect orphan', effect_allowed());
 			const destroy = effect_root(() => {
-				log.push('effect root', effect_active());
+				log.push('effect root', effect_allowed());
 				effect(() => {
-					log.push('effect', effect_active());
+					log.push('effect', effect_allowed());
 				});
 				$.get(
 					derived(() => {
-						log.push('derived', effect_active());
+						log.push('derived', effect_allowed());
 						return 1;
 					})
 				);
 				return () => {
-					log.push('effect teardown', effect_active());
+					log.push('effect teardown', effect_allowed());
 				};
 			});
 			flushSync();
diff --git a/packages/svelte/types/index.d.ts b/packages/svelte/types/index.d.ts
index 39e1c54d4c75..e1ac8031985a 100644
--- a/packages/svelte/types/index.d.ts
+++ b/packages/svelte/types/index.d.ts
@@ -3312,22 +3312,22 @@ declare function $effect(fn: () => void | (() => void)): void;
 
 declare namespace $effect {
 	/**
-	 * The `$effect.active` rune is an advanced feature that indicates whether an effect or async `$derived` can be created in the current context.
+	 * The `$effect.allowed` rune is an advanced feature that indicates whether an effect or async `$derived` can be created in the current context.
 	 * Effects and async deriveds can only be created in root effects, which are created during component setup, or can be programmatically created via `$effect.root`.
 	 *
 	 * Example:
 	 * ```svelte
 	 * <script>
-	 *   console.log('in component setup', $effect.active()); // true
+	 *   console.log('in component setup', $effect.allowed()); // true
 	 *
 	 *   function onclick() {
-	 *     console.log('after component setup', $effect.active()); // false
+	 *     console.log('after component setup', $effect.allowed()); // false
 	 *   }
 	 *   function ondblclick() {
 	 *     $effect.root(() => {
-	 *       console.log('in root effect', $effect.active()); // true
+	 *       console.log('in root effect', $effect.allowed()); // true
 	 *       return () => {
-	 *         console.log('in effect teardown', $effect.active()); // false
+	 *         console.log('in effect teardown', $effect.allowed()); // false
 	 *       }
 	 *     })();
 	 *   }
@@ -3336,9 +3336,9 @@ declare namespace $effect {
 	 * <button {ondblclick}>Click me twice!</button>
 	 * ```
 	 *
-	 * https://svelte.dev/docs/svelte/$effect#$effect.active
+	 * https://svelte.dev/docs/svelte/$effect#$effect.allowed
 	 */
-	export function active(): boolean;
+	export function allowed(): boolean;
 	/**
 	 * Runs code right before a component is mounted to the DOM, and then whenever its dependencies change, i.e. `$state` or `$derived` values.
 	 * The timing of the execution is right before the DOM is updated.