diff --git a/packages/svelte/package.json b/packages/svelte/package.json
index ee35cda2bd..e0f6afe6fc 100644
--- a/packages/svelte/package.json
+++ b/packages/svelte/package.json
@@ -136,7 +136,7 @@
   ],
   "scripts": {
     "build": "node scripts/process-messages && rollup -c && pnpm generate:types && node scripts/check-treeshakeability.js",
-    "dev": "node scripts/process-messages && rollup -cw",
+    "dev": "node scripts/process-messages -w & rollup -cw",
     "check": "tsc --project tsconfig.runtime.json && tsc && cd ./tests/types && tsc",
     "check:watch": "tsc --watch",
     "generate:version": "node ./scripts/generate-version.js",
diff --git a/packages/svelte/scripts/process-messages/index.js b/packages/svelte/scripts/process-messages/index.js
index 80619acfa7..81c59271de 100644
--- a/packages/svelte/scripts/process-messages/index.js
+++ b/packages/svelte/scripts/process-messages/index.js
@@ -1,409 +1,441 @@
 // @ts-check
+import process from 'node:process';
 import fs from 'node:fs';
 import * as acorn from 'acorn';
 import { walk } from 'zimmerframe';
 import * as esrap from 'esrap';
 
-/** @type {Record<string, Record<string, { messages: string[], details: string | null }>>} */
-const messages = {};
-const seen = new Set();
-
 const DIR = '../../documentation/docs/98-reference/.generated';
-fs.rmSync(DIR, { force: true, recursive: true });
-fs.mkdirSync(DIR);
 
-for (const category of fs.readdirSync('messages')) {
-	if (category.startsWith('.')) continue;
+const watch = process.argv.includes('-w');
 
-	messages[category] = {};
+function run() {
+	/** @type {Record<string, Record<string, { messages: string[], details: string | null }>>} */
+	const messages = {};
+	const seen = new Set();
 
-	for (const file of fs.readdirSync(`messages/${category}`)) {
-		if (!file.endsWith('.md')) continue;
+	fs.rmSync(DIR, { force: true, recursive: true });
+	fs.mkdirSync(DIR);
 
-		const markdown = fs
-			.readFileSync(`messages/${category}/${file}`, 'utf-8')
-			.replace(/\r\n/g, '\n');
+	for (const category of fs.readdirSync('messages')) {
+		if (category.startsWith('.')) continue;
 
-		const sorted = [];
+		messages[category] = {};
 
-		for (const match of markdown.matchAll(/## ([\w]+)\n\n([^]+?)(?=$|\n\n## )/g)) {
-			const [_, code, text] = match;
+		for (const file of fs.readdirSync(`messages/${category}`)) {
+			if (!file.endsWith('.md')) continue;
 
-			if (seen.has(code)) {
-				throw new Error(`Duplicate message code ${category}/${code}`);
-			}
+			const markdown = fs
+				.readFileSync(`messages/${category}/${file}`, 'utf-8')
+				.replace(/\r\n/g, '\n');
 
-			sorted.push({ code, _ });
+			const sorted = [];
 
-			const sections = text.trim().split('\n\n');
-			const details = [];
+			for (const match of markdown.matchAll(/## ([\w]+)\n\n([^]+?)(?=$|\n\n## )/g)) {
+				const [_, code, text] = match;
 
-			while (!sections[sections.length - 1].startsWith('> ')) {
-				details.unshift(/** @type {string} */ (sections.pop()));
-			}
+				if (seen.has(code)) {
+					throw new Error(`Duplicate message code ${category}/${code}`);
+				}
+
+				sorted.push({ code, _ });
 
-			if (sections.length === 0) {
-				throw new Error('No message text');
+				const sections = text.trim().split('\n\n');
+				const details = [];
+
+				while (!sections[sections.length - 1].startsWith('> ')) {
+					details.unshift(/** @type {string} */ (sections.pop()));
+				}
+
+				if (sections.length === 0) {
+					throw new Error('No message text');
+				}
+
+				seen.add(code);
+				messages[category][code] = {
+					messages: sections.map((section) => section.replace(/^> /gm, '').replace(/^>\n/gm, '\n')),
+					details: details.join('\n\n')
+				};
 			}
 
-			seen.add(code);
-			messages[category][code] = {
-				messages: sections.map((section) => section.replace(/^> /gm, '').replace(/^>\n/gm, '\n')),
-				details: details.join('\n\n')
-			};
+			sorted.sort((a, b) => (a.code < b.code ? -1 : 1));
+
+			fs.writeFileSync(
+				`messages/${category}/${file}`,
+				sorted.map((x) => x._.trim()).join('\n\n') + '\n'
+			);
 		}
 
-		sorted.sort((a, b) => (a.code < b.code ? -1 : 1));
 		fs.writeFileSync(
-			`messages/${category}/${file}`,
-			sorted.map((x) => x._.trim()).join('\n\n') + '\n'
+			`${DIR}/${category}.md`,
+			'<!-- This file is generated by scripts/process-messages/index.js. Do not edit! -->\n\n' +
+				Object.entries(messages[category])
+					.map(([code, { messages, details }]) => {
+						const chunks = [
+							`### ${code}`,
+							...messages.map((message) => '```\n' + message + '\n```')
+						];
+
+						if (details) {
+							chunks.push(details);
+						}
+
+						return chunks.join('\n\n');
+					})
+					.sort()
+					.join('\n\n') +
+				'\n'
 		);
 	}
 
-	fs.writeFileSync(
-		`${DIR}/${category}.md`,
-		'<!-- This file is generated by scripts/process-messages/index.js. Do not edit! -->\n\n' +
-			Object.entries(messages[category])
-				.map(([code, { messages, details }]) => {
-					const chunks = [`### ${code}`, ...messages.map((message) => '```\n' + message + '\n```')];
-
-					if (details) {
-						chunks.push(details);
-					}
-
-					return chunks.join('\n\n');
-				})
-				.sort()
-				.join('\n\n') +
-			'\n'
-	);
-}
-
-/**
- * @param {string} name
- * @param {string} dest
- */
-function transform(name, dest) {
-	const source = fs
-		.readFileSync(new URL(`./templates/${name}.js`, import.meta.url), 'utf-8')
-		.replace(/\r\n/g, '\n');
-
 	/**
-	 * @type {Array<{
-	 * 	type: string;
-	 * 	value: string;
-	 * 	start: number;
-	 * 	end: number
-	 * }>}
+	 * @param {string} name
+	 * @param {string} dest
 	 */
-	const comments = [];
-
-	let ast = acorn.parse(source, {
-		ecmaVersion: 'latest',
-		sourceType: 'module',
-		onComment: (block, value, start, end) => {
-			if (block && /\n/.test(value)) {
-				let a = start;
-				while (a > 0 && source[a - 1] !== '\n') a -= 1;
-
-				let b = a;
-				while (/[ \t]/.test(source[b])) b += 1;
-
-				const indentation = source.slice(a, b);
-				value = value.replace(new RegExp(`^${indentation}`, 'gm'), '');
-			}
-
-			comments.push({ type: block ? 'Block' : 'Line', value, start, end });
-		}
-	});
+	function transform(name, dest) {
+		const source = fs
+			.readFileSync(new URL(`./templates/${name}.js`, import.meta.url), 'utf-8')
+			.replace(/\r\n/g, '\n');
 
-	ast = walk(ast, null, {
-		_(node, { next }) {
-			let comment;
+		/**
+		 * @type {Array<{
+		 * 	type: string;
+		 * 	value: string;
+		 * 	start: number;
+		 * 	end: number
+		 * }>}
+		 */
+		const comments = [];
+
+		let ast = acorn.parse(source, {
+			ecmaVersion: 'latest',
+			sourceType: 'module',
+			onComment: (block, value, start, end) => {
+				if (block && /\n/.test(value)) {
+					let a = start;
+					while (a > 0 && source[a - 1] !== '\n') a -= 1;
+
+					let b = a;
+					while (/[ \t]/.test(source[b])) b += 1;
+
+					const indentation = source.slice(a, b);
+					value = value.replace(new RegExp(`^${indentation}`, 'gm'), '');
+				}
 
-			while (comments[0] && comments[0].start < node.start) {
-				comment = comments.shift();
-				// @ts-expect-error
-				(node.leadingComments ||= []).push(comment);
+				comments.push({ type: block ? 'Block' : 'Line', value, start, end });
 			}
+		});
 
-			next();
-
-			if (comments[0]) {
-				const slice = source.slice(node.end, comments[0].start);
+		ast = walk(ast, null, {
+			_(node, { next }) {
+				let comment;
 
-				if (/^[,) \t]*$/.test(slice)) {
+				while (comments[0] && comments[0].start < node.start) {
+					comment = comments.shift();
 					// @ts-expect-error
-					node.trailingComments = [comments.shift()];
+					(node.leadingComments ||= []).push(comment);
 				}
-			}
-		},
-		// @ts-expect-error
-		Identifier(node, context) {
-			if (node.name === 'CODES') {
-				return {
-					type: 'ArrayExpression',
-					elements: Object.keys(messages[name]).map((code) => ({
-						type: 'Literal',
-						value: code
-					}))
-				};
-			}
-		}
-	});
-
-	if (comments.length > 0) {
-		// @ts-expect-error
-		(ast.trailingComments ||= []).push(...comments);
-	}
-
-	const category = messages[name];
-
-	// find the `export function CODE` node
-	const index = ast.body.findIndex((node) => {
-		if (
-			node.type === 'ExportNamedDeclaration' &&
-			node.declaration &&
-			node.declaration.type === 'FunctionDeclaration'
-		) {
-			return node.declaration.id.name === 'CODE';
-		}
-	});
-
-	if (index === -1) throw new Error(`missing export function CODE in ${name}.js`);
 
-	const template_node = ast.body[index];
-	ast.body.splice(index, 1);
+				next();
 
-	for (const code in category) {
-		const { messages } = category[code];
-		/** @type {string[]} */
-		const vars = [];
+				if (comments[0]) {
+					const slice = source.slice(node.end, comments[0].start);
 
-		const group = messages.map((text, i) => {
-			for (const match of text.matchAll(/%(\w+)%/g)) {
-				const name = match[1];
-				if (!vars.includes(name)) {
-					vars.push(match[1]);
+					if (/^[,) \t]*$/.test(slice)) {
+						// @ts-expect-error
+						node.trailingComments = [comments.shift()];
+					}
+				}
+			},
+			// @ts-expect-error
+			Identifier(node, context) {
+				if (node.name === 'CODES') {
+					return {
+						type: 'ArrayExpression',
+						elements: Object.keys(messages[name]).map((code) => ({
+							type: 'Literal',
+							value: code
+						}))
+					};
 				}
 			}
-
-			return {
-				text,
-				vars: vars.slice()
-			};
 		});
 
-		/** @type {import('estree').Expression} */
-		let message = { type: 'Literal', value: '' };
-		let prev_vars;
+		if (comments.length > 0) {
+			// @ts-expect-error
+			(ast.trailingComments ||= []).push(...comments);
+		}
 
-		for (let i = 0; i < group.length; i += 1) {
-			const { text, vars } = group[i];
+		const category = messages[name];
 
-			if (vars.length === 0) {
-				message = {
-					type: 'Literal',
-					value: text
-				};
-				prev_vars = vars;
-				continue;
+		// find the `export function CODE` node
+		const index = ast.body.findIndex((node) => {
+			if (
+				node.type === 'ExportNamedDeclaration' &&
+				node.declaration &&
+				node.declaration.type === 'FunctionDeclaration'
+			) {
+				return node.declaration.id.name === 'CODE';
 			}
+		});
 
-			const parts = text.split(/(%\w+%)/);
+		if (index === -1) throw new Error(`missing export function CODE in ${name}.js`);
 
-			/** @type {import('estree').Expression[]} */
-			const expressions = [];
+		const template_node = ast.body[index];
+		ast.body.splice(index, 1);
 
-			/** @type {import('estree').TemplateElement[]} */
-			const quasis = [];
+		for (const code in category) {
+			const { messages } = category[code];
+			/** @type {string[]} */
+			const vars = [];
 
-			for (let i = 0; i < parts.length; i += 1) {
-				const part = parts[i];
-				if (i % 2 === 0) {
-					const str = part.replace(/(`|\${)/g, '\\$1');
-					quasis.push({
-						type: 'TemplateElement',
-						value: { raw: str, cooked: str },
-						tail: i === parts.length - 1
-					});
-				} else {
-					expressions.push({
-						type: 'Identifier',
-						name: part.slice(1, -1)
-					});
+			const group = messages.map((text, i) => {
+				for (const match of text.matchAll(/%(\w+)%/g)) {
+					const name = match[1];
+					if (!vars.includes(name)) {
+						vars.push(match[1]);
+					}
 				}
-			}
+
+				return {
+					text,
+					vars: vars.slice()
+				};
+			});
 
 			/** @type {import('estree').Expression} */
-			const expression = {
-				type: 'TemplateLiteral',
-				expressions,
-				quasis
-			};
-
-			if (prev_vars) {
-				if (vars.length === prev_vars.length) {
-					throw new Error('Message overloads must have new parameters');
+			let message = { type: 'Literal', value: '' };
+			let prev_vars;
+
+			for (let i = 0; i < group.length; i += 1) {
+				const { text, vars } = group[i];
+
+				if (vars.length === 0) {
+					message = {
+						type: 'Literal',
+						value: text
+					};
+					prev_vars = vars;
+					continue;
 				}
 
-				message = {
-					type: 'ConditionalExpression',
-					test: {
-						type: 'Identifier',
-						name: vars[prev_vars.length]
-					},
-					consequent: expression,
-					alternate: message
-				};
-			} else {
-				message = expression;
-			}
+				const parts = text.split(/(%\w+%)/);
 
-			prev_vars = vars;
-		}
+				/** @type {import('estree').Expression[]} */
+				const expressions = [];
 
-		const clone = walk(/** @type {import('estree').Node} */ (template_node), null, {
-			// @ts-expect-error Block is a block comment, which is not recognised
-			Block(node, context) {
-				if (!node.value.includes('PARAMETER')) return;
-
-				const value = /** @type {string} */ (node.value)
-					.split('\n')
-					.map((line) => {
-						if (line === ' * MESSAGE') {
-							return messages[messages.length - 1]
-								.split('\n')
-								.map((line) => ` * ${line}`)
-								.join('\n');
-						}
+				/** @type {import('estree').TemplateElement[]} */
+				const quasis = [];
 
-						if (line.includes('PARAMETER')) {
-							return vars
-								.map((name, i) => {
-									const optional = i >= group[0].vars.length;
+				for (let i = 0; i < parts.length; i += 1) {
+					const part = parts[i];
+					if (i % 2 === 0) {
+						const str = part.replace(/(`|\${)/g, '\\$1');
+						quasis.push({
+							type: 'TemplateElement',
+							value: { raw: str, cooked: str },
+							tail: i === parts.length - 1
+						});
+					} else {
+						expressions.push({
+							type: 'Identifier',
+							name: part.slice(1, -1)
+						});
+					}
+				}
 
-									return optional
-										? ` * @param {string | undefined | null} [${name}]`
-										: ` * @param {string} ${name}`;
-								})
-								.join('\n');
-						}
+				/** @type {import('estree').Expression} */
+				const expression = {
+					type: 'TemplateLiteral',
+					expressions,
+					quasis
+				};
 
-						return line;
-					})
-					.filter((x) => x !== '')
-					.join('\n');
+				if (prev_vars) {
+					if (vars.length === prev_vars.length) {
+						throw new Error('Message overloads must have new parameters');
+					}
 
-				if (value !== node.value) {
-					return { ...node, value };
+					message = {
+						type: 'ConditionalExpression',
+						test: {
+							type: 'Identifier',
+							name: vars[prev_vars.length]
+						},
+						consequent: expression,
+						alternate: message
+					};
+				} else {
+					message = expression;
 				}
-			},
-			FunctionDeclaration(node, context) {
-				if (node.id.name !== 'CODE') return;
 
-				const params = [];
+				prev_vars = vars;
+			}
 
-				for (const param of node.params) {
-					if (param.type === 'Identifier' && param.name === 'PARAMETER') {
-						params.push(...vars.map((name) => ({ type: 'Identifier', name })));
-					} else {
-						params.push(param);
+			const clone = walk(/** @type {import('estree').Node} */ (template_node), null, {
+				// @ts-expect-error Block is a block comment, which is not recognised
+				Block(node, context) {
+					if (!node.value.includes('PARAMETER')) return;
+
+					const value = /** @type {string} */ (node.value)
+						.split('\n')
+						.map((line) => {
+							if (line === ' * MESSAGE') {
+								return messages[messages.length - 1]
+									.split('\n')
+									.map((line) => ` * ${line}`)
+									.join('\n');
+							}
+
+							if (line.includes('PARAMETER')) {
+								return vars
+									.map((name, i) => {
+										const optional = i >= group[0].vars.length;
+
+										return optional
+											? ` * @param {string | undefined | null} [${name}]`
+											: ` * @param {string} ${name}`;
+									})
+									.join('\n');
+							}
+
+							return line;
+						})
+						.filter((x) => x !== '')
+						.join('\n');
+
+					if (value !== node.value) {
+						return { ...node, value };
 					}
-				}
+				},
+				FunctionDeclaration(node, context) {
+					if (node.id.name !== 'CODE') return;
+
+					const params = [];
 
-				return /** @type {import('estree').FunctionDeclaration} */ ({
-					.../** @type {import('estree').FunctionDeclaration} */ (context.next()),
-					params,
-					id: {
-						...node.id,
-						name: code
+					for (const param of node.params) {
+						if (param.type === 'Identifier' && param.name === 'PARAMETER') {
+							params.push(...vars.map((name) => ({ type: 'Identifier', name })));
+						} else {
+							params.push(param);
+						}
 					}
-				});
-			},
-			TemplateLiteral(node, context) {
-				/** @type {import('estree').TemplateElement} */
-				let quasi = {
-					type: 'TemplateElement',
-					value: {
-						...node.quasis[0].value
-					},
-					tail: node.quasis[0].tail
-				};
 
-				/** @type {import('estree').TemplateLiteral} */
-				let out = {
-					type: 'TemplateLiteral',
-					quasis: [quasi],
-					expressions: []
-				};
+					return /** @type {import('estree').FunctionDeclaration} */ ({
+						.../** @type {import('estree').FunctionDeclaration} */ (context.next()),
+						params,
+						id: {
+							...node.id,
+							name: code
+						}
+					});
+				},
+				TemplateLiteral(node, context) {
+					/** @type {import('estree').TemplateElement} */
+					let quasi = {
+						type: 'TemplateElement',
+						value: {
+							...node.quasis[0].value
+						},
+						tail: node.quasis[0].tail
+					};
 
-				for (let i = 0; i < node.expressions.length; i += 1) {
-					const q = structuredClone(node.quasis[i + 1]);
-					const e = node.expressions[i];
+					/** @type {import('estree').TemplateLiteral} */
+					let out = {
+						type: 'TemplateLiteral',
+						quasis: [quasi],
+						expressions: []
+					};
 
-					if (e.type === 'Literal' && e.value === 'CODE') {
-						quasi.value.raw += code + q.value.raw;
-						continue;
-					}
+					for (let i = 0; i < node.expressions.length; i += 1) {
+						const q = structuredClone(node.quasis[i + 1]);
+						const e = node.expressions[i];
 
-					if (e.type === 'Identifier' && e.name === 'MESSAGE') {
-						if (message.type === 'Literal') {
-							const str = /** @type {string} */ (message.value).replace(/(`|\${)/g, '\\$1');
-							quasi.value.raw += str + q.value.raw;
+						if (e.type === 'Literal' && e.value === 'CODE') {
+							quasi.value.raw += code + q.value.raw;
 							continue;
 						}
 
-						if (message.type === 'TemplateLiteral') {
-							const m = structuredClone(message);
-							quasi.value.raw += m.quasis[0].value.raw;
-							out.quasis.push(...m.quasis.slice(1));
-							out.expressions.push(...m.expressions);
-							quasi = m.quasis[m.quasis.length - 1];
-							quasi.value.raw += q.value.raw;
-							continue;
+						if (e.type === 'Identifier' && e.name === 'MESSAGE') {
+							if (message.type === 'Literal') {
+								const str = /** @type {string} */ (message.value).replace(/(`|\${)/g, '\\$1');
+								quasi.value.raw += str + q.value.raw;
+								continue;
+							}
+
+							if (message.type === 'TemplateLiteral') {
+								const m = structuredClone(message);
+								quasi.value.raw += m.quasis[0].value.raw;
+								out.quasis.push(...m.quasis.slice(1));
+								out.expressions.push(...m.expressions);
+								quasi = m.quasis[m.quasis.length - 1];
+								quasi.value.raw += q.value.raw;
+								continue;
+							}
 						}
+
+						out.quasis.push((quasi = q));
+						out.expressions.push(/** @type {import('estree').Expression} */ (context.visit(e)));
 					}
 
-					out.quasis.push((quasi = q));
-					out.expressions.push(/** @type {import('estree').Expression} */ (context.visit(e)));
+					return out;
+				},
+				Literal(node) {
+					if (node.value === 'CODE') {
+						return {
+							type: 'Literal',
+							value: code
+						};
+					}
+				},
+				Identifier(node) {
+					if (node.name !== 'MESSAGE') return;
+					return message;
 				}
+			});
 
-				return out;
-			},
-			Literal(node) {
-				if (node.value === 'CODE') {
-					return {
-						type: 'Literal',
-						value: code
-					};
-				}
-			},
-			Identifier(node) {
-				if (node.name !== 'MESSAGE') return;
-				return message;
-			}
-		});
+			// @ts-expect-error
+			ast.body.push(clone);
+		}
+
+		const module = esrap.print(ast);
 
-		// @ts-expect-error
-		ast.body.push(clone);
+		fs.writeFileSync(
+			dest,
+			`/* This file is generated by scripts/process-messages/index.js. Do not edit! */\n\n` +
+				module.code,
+			'utf-8'
+		);
 	}
 
-	const module = esrap.print(ast);
+	transform('compile-errors', 'src/compiler/errors.js');
+	transform('compile-warnings', 'src/compiler/warnings.js');
 
-	fs.writeFileSync(
-		dest,
-		`/* This file is generated by scripts/process-messages/index.js. Do not edit! */\n\n` +
-			module.code,
-		'utf-8'
-	);
+	transform('client-warnings', 'src/internal/client/warnings.js');
+	transform('client-errors', 'src/internal/client/errors.js');
+	transform('server-errors', 'src/internal/server/errors.js');
+	transform('shared-errors', 'src/internal/shared/errors.js');
+	transform('shared-warnings', 'src/internal/shared/warnings.js');
 }
 
-transform('compile-errors', 'src/compiler/errors.js');
-transform('compile-warnings', 'src/compiler/warnings.js');
+if (watch) {
+	let running = false;
+	let timeout;
+
+	fs.watch('messages', { recursive: true }, (type, file) => {
+		if (running) {
+			timeout ??= setTimeout(() => {
+				running = false;
+				timeout = null;
+			});
+		} else {
+			running = true;
+
+			// eslint-disable-next-line no-console
+			console.log('Regenerating messages...');
+			run();
+		}
+	});
+}
 
-transform('client-warnings', 'src/internal/client/warnings.js');
-transform('client-errors', 'src/internal/client/errors.js');
-transform('server-errors', 'src/internal/server/errors.js');
-transform('shared-errors', 'src/internal/shared/errors.js');
-transform('shared-warnings', 'src/internal/shared/warnings.js');
+run();