diff --git a/.changeset/chatty-mammals-find.md b/.changeset/chatty-mammals-find.md
deleted file mode 100644
index 373dc0059a..0000000000
--- a/.changeset/chatty-mammals-find.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-fix: ensure infinite effect loops are cleared after flushing
diff --git a/.changeset/clear-olives-share.md b/.changeset/clear-olives-share.md
deleted file mode 100644
index 975b2b21b6..0000000000
--- a/.changeset/clear-olives-share.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-fix: allow `{#key NaN}`
diff --git a/.changeset/fix-each-bind-store-logical.md b/.changeset/fix-each-bind-store-logical.md
deleted file mode 100644
index 1327015124..0000000000
--- a/.changeset/fix-each-bind-store-logical.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-fix: detect store in each block expression regardless of AST shape
diff --git a/.changeset/fix-menu-element-a11y-roles.md b/.changeset/fix-menu-element-a11y-roles.md
deleted file mode 100644
index 75cfe8d310..0000000000
--- a/.changeset/fix-menu-element-a11y-roles.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-fix: treat `<menu>` like `<ul>`/`<ol>` for a11y role checks
diff --git a/.changeset/forty-worlds-attack.md b/.changeset/forty-worlds-attack.md
deleted file mode 100644
index 52bb3644c0..0000000000
--- a/.changeset/forty-worlds-attack.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-fix: add vite-ignore comment inside dynamic crypto import
diff --git a/.changeset/loud-bottles-own.md b/.changeset/loud-bottles-own.md
deleted file mode 100644
index 493dc6c47f..0000000000
--- a/.changeset/loud-bottles-own.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-chore: wrap JSDoc URLs in `@see` and `@link` tags
diff --git a/.changeset/orange-ants-greet.md b/.changeset/orange-ants-greet.md
deleted file mode 100644
index 6f7c684fee..0000000000
--- a/.changeset/orange-ants-greet.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': minor
----
-
-feat: allow use of createContext when instantiating components programmatically
diff --git a/.changeset/poor-students-nail.md b/.changeset/poor-students-nail.md
deleted file mode 100644
index cee650c002..0000000000
--- a/.changeset/poor-students-nail.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-"svelte": patch
----
-
-fix: properly hydrate already-resolved async blocks
diff --git a/.changeset/sharp-snakes-poke.md b/.changeset/sharp-snakes-poke.md
deleted file mode 100644
index 7f7f8aa7b2..0000000000
--- a/.changeset/sharp-snakes-poke.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-fix: emit `each_key_duplicate` error in production
diff --git a/.changeset/tiny-owls-pay.md b/.changeset/tiny-owls-pay.md
deleted file mode 100644
index ac25500258..0000000000
--- a/.changeset/tiny-owls-pay.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-fix: exit resolved async blocks on correct node when hydrating
diff --git a/.oxlintrc.json b/.oxlintrc.json
index f3cf53d67d..debe49a196 100644
--- a/.oxlintrc.json
+++ b/.oxlintrc.json
@@ -120,6 +120,7 @@
 		"coverage/**",
 		"playgrounds/sandbox/**",
 		"*.config.js",
+		"vitest-xhtml-environment.ts",
 		"documentation",
 		"tmp/**"
 	],
diff --git a/documentation/docs/03-template-syntax/09-@attach.md b/documentation/docs/03-template-syntax/09-@attach.md
index b25fbb32a6..8814ead487 100644
--- a/documentation/docs/03-template-syntax/09-@attach.md
+++ b/documentation/docs/03-template-syntax/09-@attach.md
@@ -82,6 +82,14 @@ Attachments can also be created inline ([demo](/playground/untitled#H4sIAAAAAAAA
 > [!NOTE]
 > The nested effect runs whenever `color` changes, while the outer effect (where `canvas.getContext(...)` is called) only runs once, since it doesn't read any reactive state.
 
+## Conditional attachments
+
+Falsy values like `false` or `undefined` are treated as no attachment, enabling conditional usage:
+
+```svelte
+<div {@attach enabled && myAttachment}>...</div>
+```
+
 ## Passing attachments to components
 
 When used on a component, `{@attach ...}` will create a prop whose key is a [`Symbol`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Symbol). If the component then [spreads](/tutorial/svelte/spread-props) props onto an element, the element will receive those attachments.
diff --git a/packages/svelte/CHANGELOG.md b/packages/svelte/CHANGELOG.md
index a71effd5dd..b251e778ef 100644
--- a/packages/svelte/CHANGELOG.md
+++ b/packages/svelte/CHANGELOG.md
@@ -1,5 +1,31 @@
 # svelte
 
+## 5.50.0
+
+### Minor Changes
+
+- feat: allow use of createContext when instantiating components programmatically ([#17575](https://github.com/sveltejs/svelte/pull/17575))
+
+### Patch Changes
+
+- fix: ensure infinite effect loops are cleared after flushing ([#17601](https://github.com/sveltejs/svelte/pull/17601))
+
+- fix: allow `{#key NaN}` ([#17642](https://github.com/sveltejs/svelte/pull/17642))
+
+- fix: detect store in each block expression regardless of AST shape ([#17636](https://github.com/sveltejs/svelte/pull/17636))
+
+- fix: treat `<menu>` like `<ul>`/`<ol>` for a11y role checks ([#17638](https://github.com/sveltejs/svelte/pull/17638))
+
+- fix: add vite-ignore comment inside dynamic crypto import ([#17623](https://github.com/sveltejs/svelte/pull/17623))
+
+- chore: wrap JSDoc URLs in `@see` and `@link` tags ([#17617](https://github.com/sveltejs/svelte/pull/17617))
+
+- fix: properly hydrate already-resolved async blocks ([#17641](https://github.com/sveltejs/svelte/pull/17641))
+
+- fix: emit `each_key_duplicate` error in production ([#16724](https://github.com/sveltejs/svelte/pull/16724))
+
+- fix: exit resolved async blocks on correct node when hydrating ([#17640](https://github.com/sveltejs/svelte/pull/17640))
+
 ## 5.49.2
 
 ### Patch Changes
diff --git a/packages/svelte/package.json b/packages/svelte/package.json
index 48f492783f..82d0d1a8ed 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": "5.49.2",
+  "version": "5.50.0",
   "type": "module",
   "types": "./types/index.d.ts",
   "engines": {
diff --git a/packages/svelte/src/version.js b/packages/svelte/src/version.js
index 31538c3fe7..3aefb2e1f6 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 = '5.49.2';
+export const VERSION = '5.50.0';
 export const PUBLIC_VERSION = '5';
diff --git a/packages/svelte/tests/html_equal.js b/packages/svelte/tests/html_equal.js
index 76a4a957a5..cdb8f52e37 100644
--- a/packages/svelte/tests/html_equal.js
+++ b/packages/svelte/tests/html_equal.js
@@ -9,7 +9,9 @@ function clean_children(node, opts) {
 	let previous = null;
 	let has_element_children = false;
 	let template =
-		node.nodeName === 'TEMPLATE' ? /** @type {HTMLTemplateElement} */ (node) : undefined;
+		node.nodeName.toUpperCase() === 'TEMPLATE'
+			? /** @type {HTMLTemplateElement} */ (node)
+			: undefined;
 
 	if (template) {
 		const div = document.createElement('div');
@@ -23,22 +25,20 @@ function clean_children(node, opts) {
 	});
 
 	attributes.forEach((attr) => {
-		node.removeAttribute(attr.name);
+		if (attr.name !== 'xmlns') node.removeAttribute(attr.name);
 	});
 
-	attributes.forEach((attr) => {
+	attributes.forEach(({ name, value }) => {
 		// Strip out the special onload/onerror hydration events from the test output
-		if ((attr.name === 'onload' || attr.name === 'onerror') && attr.value === 'this.__e=event') {
+		if (['onload', 'onerror', 'xmlns'].includes(name) && value === 'this.__e=event') {
 			return;
 		}
 
-		let value = attr.value;
-
-		if (attr.name === 'class') {
+		if (name === 'class') {
 			value = value.replace(/svelte-\w+/, 'svelte-xyz123');
 		}
 
-		node.setAttribute(attr.name, value);
+		node.setAttribute(name, value);
 	});
 
 	for (let child of [...node.childNodes]) {
diff --git a/packages/svelte/tests/runtime-xhtml/samples/attribute-quotes/_config.js b/packages/svelte/tests/runtime-xhtml/samples/attribute-quotes/_config.js
new file mode 100644
index 0000000000..f47bee71df
--- /dev/null
+++ b/packages/svelte/tests/runtime-xhtml/samples/attribute-quotes/_config.js
@@ -0,0 +1,3 @@
+import { test } from '../../test';
+
+export default test({});
diff --git a/packages/svelte/tests/runtime-xhtml/samples/attribute-quotes/main.svelte b/packages/svelte/tests/runtime-xhtml/samples/attribute-quotes/main.svelte
new file mode 100644
index 0000000000..82db611c12
--- /dev/null
+++ b/packages/svelte/tests/runtime-xhtml/samples/attribute-quotes/main.svelte
@@ -0,0 +1,2 @@
+<div foo=bar></div>
+<div foo='bar baz'></div>
diff --git a/packages/svelte/tests/runtime-xhtml/samples/autoclosed-tags/_config.js b/packages/svelte/tests/runtime-xhtml/samples/autoclosed-tags/_config.js
new file mode 100644
index 0000000000..f47bee71df
--- /dev/null
+++ b/packages/svelte/tests/runtime-xhtml/samples/autoclosed-tags/_config.js
@@ -0,0 +1,3 @@
+import { test } from '../../test';
+
+export default test({});
diff --git a/packages/svelte/tests/runtime-xhtml/samples/autoclosed-tags/main.svelte b/packages/svelte/tests/runtime-xhtml/samples/autoclosed-tags/main.svelte
new file mode 100644
index 0000000000..18a4463ce1
--- /dev/null
+++ b/packages/svelte/tests/runtime-xhtml/samples/autoclosed-tags/main.svelte
@@ -0,0 +1,6 @@
+<ul><li><li></ul>
+<dl><dt><dd><dd></dl>
+<p><p><div></div>
+<ruby><rp><rt><rt></ruby>
+<select><option><optgroup><optgroup></select>
+<table><thead><tbody><tfoot><tbody><tr><td><th></tr><tr></table>
diff --git a/packages/svelte/tests/runtime-xhtml/samples/boolean-attributes/_config.js b/packages/svelte/tests/runtime-xhtml/samples/boolean-attributes/_config.js
new file mode 100644
index 0000000000..f965e04b02
--- /dev/null
+++ b/packages/svelte/tests/runtime-xhtml/samples/boolean-attributes/_config.js
@@ -0,0 +1,5 @@
+import { test } from '../../test';
+
+export default test({
+	skip: true
+});
diff --git a/packages/svelte/tests/runtime-xhtml/samples/boolean-attributes/main.svelte b/packages/svelte/tests/runtime-xhtml/samples/boolean-attributes/main.svelte
new file mode 100644
index 0000000000..3d2fc88d10
--- /dev/null
+++ b/packages/svelte/tests/runtime-xhtml/samples/boolean-attributes/main.svelte
@@ -0,0 +1 @@
+<input disabled hidden>
diff --git a/packages/svelte/tests/runtime-xhtml/samples/comment-marker/_config.js b/packages/svelte/tests/runtime-xhtml/samples/comment-marker/_config.js
new file mode 100644
index 0000000000..f47bee71df
--- /dev/null
+++ b/packages/svelte/tests/runtime-xhtml/samples/comment-marker/_config.js
@@ -0,0 +1,3 @@
+import { test } from '../../test';
+
+export default test({});
diff --git a/packages/svelte/tests/runtime-xhtml/samples/comment-marker/main.svelte b/packages/svelte/tests/runtime-xhtml/samples/comment-marker/main.svelte
new file mode 100644
index 0000000000..8dd87ce81e
--- /dev/null
+++ b/packages/svelte/tests/runtime-xhtml/samples/comment-marker/main.svelte
@@ -0,0 +1 @@
+{#each [1,2] as i}{i}{/each}
diff --git a/packages/svelte/tests/runtime-xhtml/samples/is-xhtml/_config.js b/packages/svelte/tests/runtime-xhtml/samples/is-xhtml/_config.js
new file mode 100644
index 0000000000..52dddb4ad7
--- /dev/null
+++ b/packages/svelte/tests/runtime-xhtml/samples/is-xhtml/_config.js
@@ -0,0 +1,8 @@
+import { test } from '../../test';
+
+export default test({
+	mode: ['client'],
+	test({ assert, target }) {
+		assert.htmlEqual(target.innerHTML, `<div>div</div>`);
+	}
+});
diff --git a/packages/svelte/tests/runtime-xhtml/samples/is-xhtml/main.svelte b/packages/svelte/tests/runtime-xhtml/samples/is-xhtml/main.svelte
new file mode 100644
index 0000000000..27a4378d0f
--- /dev/null
+++ b/packages/svelte/tests/runtime-xhtml/samples/is-xhtml/main.svelte
@@ -0,0 +1,5 @@
+<script>
+	let elem = $state();
+	let nodeName = $derived(elem?.nodeName);
+</script>
+<div bind:this={elem}>{nodeName}</div>
diff --git a/packages/svelte/tests/runtime-xhtml/samples/void-tags/_config.js b/packages/svelte/tests/runtime-xhtml/samples/void-tags/_config.js
new file mode 100644
index 0000000000..f47bee71df
--- /dev/null
+++ b/packages/svelte/tests/runtime-xhtml/samples/void-tags/_config.js
@@ -0,0 +1,3 @@
+import { test } from '../../test';
+
+export default test({});
diff --git a/packages/svelte/tests/runtime-xhtml/samples/void-tags/main.svelte b/packages/svelte/tests/runtime-xhtml/samples/void-tags/main.svelte
new file mode 100644
index 0000000000..08ea2838b3
--- /dev/null
+++ b/packages/svelte/tests/runtime-xhtml/samples/void-tags/main.svelte
@@ -0,0 +1,15 @@
+<area alt="">
+<base>
+<br>
+<col>
+<embed>
+<hr>
+<img alt="">
+<input>
+<keygen>
+<link>
+<meta>
+<param>
+<source>
+<track>
+<wbr>
diff --git a/packages/svelte/tests/runtime-xhtml/test.ts b/packages/svelte/tests/runtime-xhtml/test.ts
new file mode 100644
index 0000000000..416300dc58
--- /dev/null
+++ b/packages/svelte/tests/runtime-xhtml/test.ts
@@ -0,0 +1,9 @@
+// @vitest-environment vitest-xhtml-environment.ts
+
+import { runtime_suite, ok } from '../runtime-legacy/shared';
+
+const { test, run } = runtime_suite(true);
+
+export { test, ok };
+
+await run(__dirname);
diff --git a/vitest-xhtml-environment.ts b/vitest-xhtml-environment.ts
new file mode 100644
index 0000000000..dc8b271440
--- /dev/null
+++ b/vitest-xhtml-environment.ts
@@ -0,0 +1,19 @@
+import { type Environment, builtinEnvironments } from 'vitest/environments';
+
+const xhtml_page = `<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN" "http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd">
+<html xmlns="http://www.w3.org/1999/xhtml"><head></head><body></body></html>`;
+
+export default <Environment>{
+	name: 'jsdom-xhtml',
+	transformMode: 'web',
+	setup(global, { jsdom = {} }) {
+		return builtinEnvironments.jsdom.setup(global, {
+			jsdom: {
+				...jsdom,
+				html: xhtml_page,
+				contentType: 'application/xhtml+xml'
+			}
+		});
+	}
+};