diff --git a/documentation/docs/02-runes/05-$props.md b/documentation/docs/02-runes/05-$props.md
index f300fb239d77..222b4831b65a 100644
--- a/documentation/docs/02-runes/05-$props.md
+++ b/documentation/docs/02-runes/05-$props.md
@@ -37,7 +37,7 @@ On the other side, inside `MyComponent.svelte`, we can receive props with the `$
 
 ## Fallback values
 
-Destructuring allows us to declare fallback values, which are used if the parent component does not set a given prop:
+Destructuring allows us to declare fallback values, which are used if the parent component does not set a given prop (or the value is `undefined`):
 
 ```js
 let { adjective = 'happy' } = $props();
@@ -219,4 +219,4 @@ This is useful for linking elements via attributes like `for` and `aria-labelled
 	<label for="{uid}-lastname">Last Name: </label>
 	<input id="{uid}-lastname" type="text" />
 </form>
-```
\ No newline at end of file
+```
diff --git a/documentation/docs/03-template-syntax/01-basic-markup.md b/documentation/docs/03-template-syntax/01-basic-markup.md
index 5e8b4342d3c5..fe5f8b02aae0 100644
--- a/documentation/docs/03-template-syntax/01-basic-markup.md
+++ b/documentation/docs/03-template-syntax/01-basic-markup.md
@@ -154,6 +154,8 @@ A JavaScript expression can be included as text by surrounding it with curly bra
 {expression}
 ```
 
+Expressions that are `null` or `undefined` will be omitted; all others are [coerced to strings](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String#string_coercion).
+
 Curly braces can be included in a Svelte template by using their [HTML entity](https://developer.mozilla.org/docs/Glossary/Entity) strings: `&lbrace;`, `&lcub;`, or `&#123;` for `{` and `&rbrace;`, `&rcub;`, or `&#125;` for `}`.
 
 If you're using a regular expression (`RegExp`) [literal notation](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp#literal_notation_and_constructor), you'll need to wrap it in parentheses.
diff --git a/documentation/docs/03-template-syntax/06-snippet.md b/documentation/docs/03-template-syntax/06-snippet.md
index c9951d3f3414..ab536c6e5ced 100644
--- a/documentation/docs/03-template-syntax/06-snippet.md
+++ b/documentation/docs/03-template-syntax/06-snippet.md
@@ -112,6 +112,8 @@ Snippets can reference themselves and each other ([demo](/playground/untitled#H4
 
 ## Passing snippets to components
 
+### Explicit props
+
 Within the template, snippets are values just like any other. As such, they can be passed to components as props ([demo](/playground/untitled#H4sIAAAAAAAAE3VS247aMBD9lZGpBGwDASRegonaPvQL2qdlH5zYEKvBNvbQLbL875VzAcKyj3PmzJnLGU8UOwqSkd8KJdaCk4TsZS0cyV49wYuJuQiQpGd-N2bu_ooaI1YwJ57hpVYoFDqSEepKKw3mO7VDeTTaIvxiRS1gb_URxvO0ibrS8WanIrHUyiHs7Vmigy28RmyHHmKvDMbMmFq4cQInvGSwTsBYWYoMVhCSB2rBFFPsyl0uruTlR3JZCWvlTXl1Yy_mawiR_rbZKZrellJ-5JQ0RiBUgnFhJ9OGR7HKmwVoilXeIye8DOJGfYCgRlZ3iE876TBsZPX7hPdteO75PC4QaIo8vwNPePmANQ2fMeEFHrLD7rR1jTNkW986E8C3KwfwVr8HSHOSEBT_kGRozyIkn_zQveXDL3rIfPJHtUDwzShJd_Qk3gQCbOGLsdq4yfTRJopRuin3I7nv6kL7ARRjmLdBDG3uv1mhuLA3V2mKtqNEf_oCn8p9aN-WYqH5peP4kWBl1UwJzAEPT9U7K--0fRrrWnPTXpCm1_EVdXjpNmlA8G1hPPyM1fKgMqjFHjctXGjLhZ05w0qpDhksGrybuNEHtJnCalZWsuaTlfq6nPaaBSv_HKw-K57BjzOiVj9ZKQYKzQjZodYFqydYTRN4gPhVzTDO2xnma3HsVWjaLjT8nbfwHy7Q5f2dBAAA)):
 
 ```svelte
@@ -144,6 +146,8 @@ Within the template, snippets are values just like any other. As such, they can
 
 Think about it like passing content instead of data to a component. The concept is similar to slots in web components.
 
+### Implicit props
+
 As an authoring convenience, snippets declared directly _inside_ a component implicitly become props _on_ the component ([demo](/playground/untitled#H4sIAAAAAAAAE3VSTa_aMBD8Kyu_SkAbCA-JSzBR20N_QXt6vIMTO8SqsY29tI2s_PcqTiB8vaPHs7MzuxuIZgdBMvJLo0QlOElIJZXwJHsLBBvb_XUASc7Mb9Yu_B-hsMMK5sUzvDQahUZPMkJ96aTFfKd3KA_WOISfrFACKmcOMFmk8TWUTjY73RFLoz1C5U4SPWzhrcN2GKDrlcGEWauEnyRwxCaDdQLWyVJksII2uaMWTDPNLtzX5YX8-kgua-GcHJVXI3u5WEPb0d83O03TMZSmfRzOkG1Db7mNacOL19JagVALxoWbztq-H8U6j0SaYp2P2BGbOyQ2v8PQIFMXLKRDk177pq0zf6d8bMrzwBdd0pamyPMb-IjNEzS2f86Gz_Dwf-2F9nvNSUJQ_EOSoTuJNvngqK5v4Pas7n4-OCwlEEJcQTIMO-nSQwtb-GSdsX46e9gbRoP9yGQ11I0rEuycunu6PHx1QnPhxm3SFN15MOlYEFJZtf0dUywMbwZOeBGsrKNLYB54-1R9WNqVdki7usim6VmQphf7mnpshiQRhNAXdoOfMyX3OgMlKtz0cGEcF27uLSul3mewjPjgOOoDukxjPS9rqfh0pb-8zs6aBSt_7505aZ7B9xOi0T9YKW4UooVsr0zB1BTrWQJ3EL-oWcZ572GxFoezCk37QLe3897-B2i2U62uBAAA)):
 
 ```svelte
@@ -165,6 +169,8 @@ As an authoring convenience, snippets declared directly _inside_ a component imp
 </Table>
 ```
 
+### Implicit `children` snippet
+
 Any content inside the component tags that is _not_ a snippet declaration implicitly becomes part of the `children` snippet ([demo](/playground/untitled#H4sIAAAAAAAAE3WOQQrCMBBFrzIMggql3ddY1Du4si5sOmIwnYRkFKX07lKqglqX8_7_w2uRDw1hjlsWI5ZqTPBoLEXMdy3K3fdZDzB5Ndfep_FKVnpWHSKNce1YiCVijirqYLwUJQOYxrsgsLmIOIZjcA1M02w4n-PpomSVvTclqyEutDX6DA2pZ7_ABIVugrmEC3XJH92P55_G39GodCmWBFrQJ2PrQAwdLGHig_NxNv9xrQa1dhWIawrv1Wzeqawa8953D-8QOmaEAQAA)):
 
 ```svelte
@@ -184,6 +190,8 @@ Any content inside the component tags that is _not_ a snippet declaration implic
 
 > [!NOTE] Note that you cannot have a prop called `children` if you also have content inside the component — for this reason, you should avoid having props with that name
 
+### Optional snippet props
+
 You can declare snippet props as being optional. You can either use optional chaining to not render anything if the snippet isn't set...
 
 ```svelte
diff --git a/packages/svelte/CHANGELOG.md b/packages/svelte/CHANGELOG.md
index 3c876880b8e2..58f2317796c8 100644
--- a/packages/svelte/CHANGELOG.md
+++ b/packages/svelte/CHANGELOG.md
@@ -1,5 +1,15 @@
 # svelte
 
+## 5.26.3
+
+### Patch Changes
+
+- fix: correctly validate head snippets on the server ([#15755](https://github.com/sveltejs/svelte/pull/15755))
+
+- fix: ignore mutation validation for props that are not proxies in more cases ([#15759](https://github.com/sveltejs/svelte/pull/15759))
+
+- fix: allow self-closing tags within math namespace ([#15761](https://github.com/sveltejs/svelte/pull/15761))
+
 ## 5.26.2
 
 ### Patch Changes
diff --git a/packages/svelte/package.json b/packages/svelte/package.json
index 75568f4a7723..b8654671ec97 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": "5.26.2",
+  "version": "5.26.3",
   "type": "module",
   "types": "./types/index.d.ts",
   "engines": {
diff --git a/packages/svelte/src/compiler/phases/2-analyze/visitors/RegularElement.js b/packages/svelte/src/compiler/phases/2-analyze/visitors/RegularElement.js
index 03dfaebcb793..d5689e5d5592 100644
--- a/packages/svelte/src/compiler/phases/2-analyze/visitors/RegularElement.js
+++ b/packages/svelte/src/compiler/phases/2-analyze/visitors/RegularElement.js
@@ -173,7 +173,8 @@ export function RegularElement(node, context) {
 	if (
 		context.state.analysis.source[node.end - 2] === '/' &&
 		!is_void(node_name) &&
-		!is_svg(node_name)
+		!is_svg(node_name) &&
+		!is_mathml(node_name)
 	) {
 		w.element_invalid_self_closing_tag(node, node.name);
 	}
diff --git a/packages/svelte/src/internal/client/dev/ownership.js b/packages/svelte/src/internal/client/dev/ownership.js
index 108c7adf9282..5a8af6d52299 100644
--- a/packages/svelte/src/internal/client/dev/ownership.js
+++ b/packages/svelte/src/internal/client/dev/ownership.js
@@ -31,13 +31,14 @@ export function create_ownership_validator(props) {
 				return result;
 			}
 
-			let value = props[name];
+			/** @type {any} */
+			let value = props;
 
-			for (let i = 1; i < path.length - 1; i++) {
+			for (let i = 0; i < path.length - 1; i++) {
+				value = value[path[i]];
 				if (!value?.[STATE_SYMBOL]) {
 					return result;
 				}
-				value = value[path[i]];
 			}
 
 			const location = sanitize_location(`${component[FILENAME]}:${line}:${column}`);
diff --git a/packages/svelte/src/internal/server/dev.js b/packages/svelte/src/internal/server/dev.js
index 34849196b7b6..157f22f929c9 100644
--- a/packages/svelte/src/internal/server/dev.js
+++ b/packages/svelte/src/internal/server/dev.js
@@ -6,7 +6,7 @@ import {
 } from '../../html-tree-validation.js';
 import { current_component } from './context.js';
 import { invalid_snippet_arguments } from '../shared/errors.js';
-import { Payload } from './payload.js';
+import { HeadPayload, Payload } from './payload.js';
 
 /**
  * @typedef {{
@@ -105,7 +105,11 @@ export function pop_element() {
  * @param {Payload} payload
  */
 export function validate_snippet_args(payload) {
-	if (typeof payload !== 'object' || !(payload instanceof Payload)) {
+	if (
+		typeof payload !== 'object' ||
+		// for some reason typescript consider the type of payload as never after the first instanceof
+		!(payload instanceof Payload || /** @type {any} */ (payload) instanceof HeadPayload)
+	) {
 		invalid_snippet_arguments();
 	}
 }
diff --git a/packages/svelte/src/internal/server/payload.js b/packages/svelte/src/internal/server/payload.js
index 03bcaf492ea9..8df5787ba4a7 100644
--- a/packages/svelte/src/internal/server/payload.js
+++ b/packages/svelte/src/internal/server/payload.js
@@ -1,16 +1,25 @@
+export class HeadPayload {
+	/** @type {Set<{ hash: string; code: string }>} */
+	css = new Set();
+	out = '';
+	uid = () => '';
+	title = '';
+
+	constructor(css = new Set(), out = '', title = '', uid = () => '') {
+		this.css = css;
+		this.out = out;
+		this.title = title;
+		this.uid = uid;
+	}
+}
+
 export class Payload {
 	/** @type {Set<{ hash: string; code: string }>} */
 	css = new Set();
 	out = '';
 	uid = () => '';
 
-	head = {
-		/** @type {Set<{ hash: string; code: string }>} */
-		css: new Set(),
-		title: '',
-		out: '',
-		uid: () => ''
-	};
+	head = new HeadPayload();
 
 	constructor(id_prefix = '') {
 		this.uid = props_id_generator(id_prefix);
@@ -30,12 +39,11 @@ export function copy_payload({ out, css, head, uid }) {
 	payload.css = new Set(css);
 	payload.uid = uid;
 
-	payload.head = {
-		title: head.title,
-		out: head.out,
-		css: new Set(head.css),
-		uid: head.uid
-	};
+	payload.head = new HeadPayload();
+	payload.head.out = head.out;
+	payload.head.css = new Set(head.css);
+	payload.head.title = head.title;
+	payload.head.uid = head.uid;
 
 	return payload;
 }
diff --git a/packages/svelte/src/version.js b/packages/svelte/src/version.js
index 2dc75f7e595b..190958814669 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 = '5.26.2';
+export const VERSION = '5.26.3';
 export const PUBLIC_VERSION = '5';
diff --git a/packages/svelte/tests/runtime-runes/samples/head-payload-validation/_config.js b/packages/svelte/tests/runtime-runes/samples/head-payload-validation/_config.js
new file mode 100644
index 000000000000..7c609205df9b
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/head-payload-validation/_config.js
@@ -0,0 +1,11 @@
+import { test } from '../../test';
+
+export default test({
+	compileOptions: {
+		dev: true
+	},
+	mode: ['server'],
+	async test({ errors, assert }) {
+		assert.equal(errors, []);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/head-payload-validation/main.svelte b/packages/svelte/tests/runtime-runes/samples/head-payload-validation/main.svelte
new file mode 100644
index 000000000000..7eb31d3a9ee9
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/head-payload-validation/main.svelte
@@ -0,0 +1,7 @@
+{#snippet head()}
+	<title>Cool</title>
+{/snippet}
+
+<svelte:head>
+	{@render head()}
+</svelte:head>
\ No newline at end of file
diff --git a/packages/svelte/tests/runtime-runes/samples/non-local-mutation-ok/_config.js b/packages/svelte/tests/runtime-runes/samples/non-local-mutation-ok/_config.js
new file mode 100644
index 000000000000..437385e185c8
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/non-local-mutation-ok/_config.js
@@ -0,0 +1,18 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	compileOptions: {
+		dev: true
+	},
+
+	test({ assert, target, warnings }) {
+		const btn = target.querySelector('button');
+		btn?.click();
+		flushSync();
+
+		assert.deepEqual(warnings, []);
+	},
+
+	warnings: []
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/non-local-mutation-ok/child.svelte b/packages/svelte/tests/runtime-runes/samples/non-local-mutation-ok/child.svelte
new file mode 100644
index 000000000000..0243a6c7d1fa
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/non-local-mutation-ok/child.svelte
@@ -0,0 +1,8 @@
+<script>
+	let { klass, getter_setter } = $props();
+</script>
+
+<button onclick={() => {
+	klass.y = 2;
+	getter_setter.y = 2;
+}}>mutate</button>
diff --git a/packages/svelte/tests/runtime-runes/samples/non-local-mutation-ok/main.svelte b/packages/svelte/tests/runtime-runes/samples/non-local-mutation-ok/main.svelte
new file mode 100644
index 000000000000..8685664ab164
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/non-local-mutation-ok/main.svelte
@@ -0,0 +1,21 @@
+<script>
+	import Child from './child.svelte';
+
+	class X {
+		y = $state(1);
+	}
+
+	const klass = new X();
+
+	let y = $state(1);
+	const getter_setter = {
+		get y() {
+			return y;
+		},
+		set y(value) {
+			y = value;
+		}
+	}
+</script>
+
+<Child {klass}  {getter_setter} />
diff --git a/packages/svelte/tests/validator/samples/invalid-self-closing-tag/input.svelte b/packages/svelte/tests/validator/samples/invalid-self-closing-tag/input.svelte
index 376c9f79bd84..07582e834341 100644
--- a/packages/svelte/tests/validator/samples/invalid-self-closing-tag/input.svelte
+++ b/packages/svelte/tests/validator/samples/invalid-self-closing-tag/input.svelte
@@ -1,6 +1,7 @@
 <!-- valid -->
 <link />
 <svg><g /></svg>
+<math><mspace /></math>
 <enhanced:img />
 
 
diff --git a/packages/svelte/tests/validator/samples/invalid-self-closing-tag/warnings.json b/packages/svelte/tests/validator/samples/invalid-self-closing-tag/warnings.json
index 40b87ec7c8f4..3e45bca5ad15 100644
--- a/packages/svelte/tests/validator/samples/invalid-self-closing-tag/warnings.json
+++ b/packages/svelte/tests/validator/samples/invalid-self-closing-tag/warnings.json
@@ -3,11 +3,11 @@
 		"code": "element_invalid_self_closing_tag",
 		"message": "Self-closing HTML tags for non-void elements are ambiguous — use `<div ...></div>` rather than `<div ... />`",
 		"start": {
-			"line": 8,
+			"line": 9,
 			"column": 0
 		},
 		"end": {
-			"line": 8,
+			"line": 9,
 			"column": 7
 		}
 	},
@@ -15,11 +15,11 @@
 		"code": "element_invalid_self_closing_tag",
 		"message": "Self-closing HTML tags for non-void elements are ambiguous — use `<my-thing ...></my-thing>` rather than `<my-thing ... />`",
 		"start": {
-			"line": 9,
+			"line": 10,
 			"column": 0
 		},
 		"end": {
-			"line": 9,
+			"line": 10,
 			"column": 12
 		}
 	}

<!DOCTYPE html PUBLIC '-//W3C//DTD XHTML 1.0 Transitional//EN' 'http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd'>
<html xmlns='http://www.w3.org/1999/xhtml'>
<head>
<title>pFad - Phonifier reborn</title>
<meta http-equiv='Content-Type' content='text/html; charset=utf-8' />
</head>
<body>
<h1>Pfad - The Proxy pFad of &#169; 2024 Garber Painting. All rights reserved.</h1>


<!-- Disclaimer -->
<p>Note: This service is not intended for secure transactions such as banking, social media, email, or purchasing. Use at your own risk. We assume no liability whatsoever for broken pages.</p>
<br>
<p>Alternative Proxies:</p><p><a href="http://rainy.clevelandohioweatherforecast.com/php-proxy/index.php?q=https://github.com/sveltejs/svelte/compare/svelte@5.26.2...svelte@5.26.3.diff" target="_blank">Alternative Proxy</a></p><p><a href="http://rainy.clevelandohioweatherforecast.com/pFad/index.php?u=https://github.com/sveltejs/svelte/compare/svelte@5.26.2...svelte@5.26.3.diff" target="_blank">pFad Proxy</a></p><p><a href="http://rainy.clevelandohioweatherforecast.com/pFad/v3index.php?u=https://github.com/sveltejs/svelte/compare/svelte@5.26.2...svelte@5.26.3.diff" target="_blank">pFad v3 Proxy</a></p><p><a href="http://rainy.clevelandohioweatherforecast.com/pFad/v4index.php?u=https://github.com/sveltejs/svelte/compare/svelte@5.26.2...svelte@5.26.3.diff" target="_blank">pFad v4 Proxy</a></p></body>
</html>