diff --git a/.changeset/config.json b/.changeset/config.json
index 8292fbe078..7273a3a59c 100644
--- a/.changeset/config.json
+++ b/.changeset/config.json
@@ -2,7 +2,7 @@
   "$schema": "https://unpkg.com/@changesets/config@1.7.0/schema.json",
   "changelog": ["@changesets/changelog-github", { "repo": "withastro/astro" }],
   "commit": false,
-  "linked": [],
+  "linked": [["astro", "astro-check"]],
   "access": "public",
   "baseBranch": "main",
   "updateInternalDependencies": "patch",
diff --git a/packages/astro-check/package.json b/packages/astro-check/package.json
new file mode 100644
index 0000000000..f8490c25b0
--- /dev/null
+++ b/packages/astro-check/package.json
@@ -0,0 +1,40 @@
+{
+  "name": "astro-check",
+  "description": "Validate your Astro project",
+  "version": "0.25.0-next.2",
+  "type": "module",
+  "types": "./dist/index.d.ts",
+  "author": "withastro",
+  "license": "MIT",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/withastro/astro.git",
+    "directory": "packages/astro-check"
+  },
+  "bugs": "https://github.com/withastro/astro/issues",
+  "homepage": "https://astro.build",
+  "bin": {
+    "astro-check": "./dist/index.js"
+  },
+  "exports": {
+    ".": "./dist/index.js",
+    "./package.json": "./package.json"
+  },
+  "scripts": {
+    "build": "astro-scripts build \"src/**/*.ts\"",
+    "dev": "astro-scripts dev \"src/**/*.ts\""
+  },
+  "dependencies": {
+    "@astrojs/language-server": "^0.12.1",
+    "astro": "0.25.0-next.2",
+    "kleur": "^4.1.4",
+    "yargs-parser": "^21.0.1",
+    "zod": "^3.14.2"
+  },
+  "devDependencies": {
+    "astro-scripts": "workspace:*"
+  },
+  "engines": {
+    "node": "^14.15.0 || >=16.0.0"
+  }
+}
diff --git a/packages/astro-check/src/check.ts b/packages/astro-check/src/check.ts
new file mode 100644
index 0000000000..8deccffb57
--- /dev/null
+++ b/packages/astro-check/src/check.ts
@@ -0,0 +1,109 @@
+/* eslint-disable no-console */
+import { AstroCheck, DiagnosticSeverity } from '@astrojs/language-server';
+import type { AstroConfig } from 'astro';
+
+import { bold, black, bgWhite, red, cyan, yellow } from 'kleur/colors';
+import glob from 'fast-glob';
+import * as path from 'path';
+import { pathToFileURL } from 'url';
+import * as fs from 'fs';
+
+async function openAllDocuments(workspaceUri: URL, filePathsToIgnore: string[], checker: AstroCheck) {
+	const files = await glob('**/*.astro', {
+		cwd: workspaceUri.pathname,
+		ignore: ['node_modules/**'].concat(filePathsToIgnore.map((ignore) => `${ignore}/**`)),
+	});
+	const absFilePaths = files.map((f) => path.resolve(workspaceUri.pathname, f));
+
+	for (const absFilePath of absFilePaths) {
+		const text = fs.readFileSync(absFilePath, 'utf-8');
+		checker.upsertDocument({
+			uri: pathToFileURL(absFilePath).toString(),
+			text,
+		});
+	}
+}
+
+interface Result {
+	errors: number;
+	warnings: number;
+}
+
+function offsetAt({ line, character }: { line: number; character: number }, text: string) {
+	let i = 0;
+	let l = 0;
+	let c = 0;
+	while (i < text.length) {
+		if (l === line && c === character) {
+			break;
+		}
+
+		let char = text[i];
+		switch (char) {
+			case '\n': {
+				l++;
+				c = 0;
+				break;
+			}
+			default: {
+				c++;
+				break;
+			}
+		}
+
+		i++;
+	}
+
+	return i;
+}
+
+function pad(str: string, len: number) {
+	return Array.from({ length: len }, () => str).join('');
+}
+
+export async function run() {}
+
+export async function check(astroConfig: AstroConfig) {
+	const root = astroConfig.projectRoot;
+	let checker = new AstroCheck(root.toString());
+	await openAllDocuments(root, [], checker);
+
+	let diagnostics = await checker.getDiagnostics();
+
+	let result: Result = {
+		errors: 0,
+		warnings: 0,
+	};
+
+	diagnostics.forEach((diag) => {
+		diag.diagnostics.forEach((d) => {
+			switch (d.severity) {
+				case DiagnosticSeverity.Error: {
+					console.error(`${bold(cyan(path.relative(root.pathname, diag.filePath)))}:${bold(yellow(d.range.start.line))}:${bold(yellow(d.range.start.character))} - ${d.message}`);
+					let startOffset = offsetAt({ line: d.range.start.line, character: 0 }, diag.text);
+					let endOffset = offsetAt({ line: d.range.start.line + 1, character: 0 }, diag.text);
+					let str = diag.text.substring(startOffset, endOffset - 1);
+					const lineNumStr = d.range.start.line.toString();
+					const lineNumLen = lineNumStr.length;
+					console.error(`${bgWhite(black(lineNumStr))}  ${str}`);
+					let tildes = pad('~', d.range.end.character - d.range.start.character);
+					let spaces = pad(' ', d.range.start.character + lineNumLen - 1);
+					console.error(`   ${spaces}${bold(red(tildes))}\n`);
+					result.errors++;
+					break;
+				}
+				case DiagnosticSeverity.Warning: {
+					result.warnings++;
+					break;
+				}
+			}
+		});
+	});
+
+	if (result.errors) {
+		console.error(`Found ${result.errors} errors.`);
+	}
+
+	const exitCode = result.errors ? 1 : 0;
+	return exitCode;
+}
diff --git a/packages/astro-check/src/index.ts b/packages/astro-check/src/index.ts
new file mode 100644
index 0000000000..16505cf3dc
--- /dev/null
+++ b/packages/astro-check/src/index.ts
@@ -0,0 +1,40 @@
+/* eslint-disable no-console */
+
+import type { AstroConfig } from 'astro';
+
+import * as colors from 'kleur/colors';
+import yargs from 'yargs-parser';
+import { z } from 'zod';
+import { check } from './check.js';
+import { formatConfigError, loadConfig } from 'astro/core/config';
+
+
+/** The primary CLI action */
+export async function cli(args: string[]) {
+	const flags = yargs(args);
+	const projectRoot = flags.projectRoot || flags._[3];
+
+	let config: AstroConfig;
+	try {
+		config = await loadConfig({ cwd: projectRoot, flags });
+	} catch (err) {
+		throwAndExit(err);
+		return;
+	}
+
+	const ret = await check(config);
+	return process.exit(ret);
+}
+
+/** Display error and exit */
+function throwAndExit(err: any) {
+	if (err instanceof z.ZodError) {
+		console.error(formatConfigError(err));
+	} else if (err.stack) {
+		const [mainMsg, ...stackMsg] = err.stack.split('\n');
+		console.error(colors.red(mainMsg) + '\n' + colors.dim(stackMsg.join('\n')));
+	} else {
+		console.error(colors.red(err.toString() || err));
+	}
+	process.exit(1);
+}
diff --git a/packages/astro/package.json b/packages/astro/package.json
index 54efee8de6..d81ad340f8 100644
--- a/packages/astro/package.json
+++ b/packages/astro/package.json
@@ -19,6 +19,7 @@
     "./config": "./config.mjs",
     "./internal": "./internal.js",
     "./app/node": "./dist/core/app/node.js",
+    "./core/config": "./dist/core/config.js",
     "./client/*": "./dist/runtime/client/*",
     "./components": "./components/index.js",
     "./components/*": "./components/*",
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 865ae49b46..175a9870a3 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -585,6 +585,23 @@ importers:
       mocha: 9.2.2
       sass: 1.49.9
 
+  packages/astro-check:
+    specifiers:
+      '@astrojs/language-server': ^0.12.1
+      astro: 0.25.0-next.2
+      astro-scripts: workspace:*
+      kleur: ^4.1.4
+      yargs-parser: ^21.0.1
+      zod: ^3.14.2
+    dependencies:
+      '@astrojs/language-server': 0.12.1
+      astro: link:../astro
+      kleur: 4.1.4
+      yargs-parser: 21.0.1
+      zod: 3.14.2
+    devDependencies:
+      astro-scripts: link:../../scripts
+
   packages/astro-prism:
     specifiers:
       prismjs: ^1.27.0
@@ -1636,6 +1653,24 @@ packages:
       uvu: 0.5.3
     dev: false
 
+  /@astrojs/language-server/0.12.1:
+    resolution: {integrity: sha512-LgU0pORDTYzAbxXS85ZyLs1MR5txF2Uj9wZZv4PyoHU5K2QIPhyghYn9Rh6NmlDMI7Q2aWotB8c/UbuNy9e8pA==}
+    hasBin: true
+    dependencies:
+      '@astrojs/svelte-language-integration': 0.1.1_typescript@4.6.2
+      '@vscode/emmet-helper': 2.8.4
+      lodash: 4.17.21
+      source-map: 0.7.3
+      typescript: 4.6.2
+      vscode-css-languageservice: 5.2.0
+      vscode-html-languageservice: 4.2.4
+      vscode-languageserver: 7.0.0
+      vscode-languageserver-protocol: 3.16.0
+      vscode-languageserver-textdocument: 1.0.4
+      vscode-languageserver-types: 3.16.0
+      vscode-uri: 3.0.3
+    dev: false
+
   /@astrojs/language-server/0.8.10:
     resolution: {integrity: sha512-F3ceZrBKywnNkDq9mK/6RgRDAGUAv9Z45oljpBx9dlMQHnWOnPdJFWncw1jVItAT57SEflLJqTuFaDphKQAFtQ==}
     hasBin: true
@@ -1654,6 +1689,15 @@ packages:
       vscode-uri: 3.0.3
     dev: false
 
+  /@astrojs/svelte-language-integration/0.1.1_typescript@4.6.2:
+    resolution: {integrity: sha512-npUDO0bitzUC9oTDqVuup0yZObOF45GQ0IkaMf5wxe6XW30SIeyl1j8mdyjOv90vlJeothCKqnQ91qMudpq3Vg==}
+    dependencies:
+      svelte: 3.46.4
+      svelte2tsx: 0.5.6_svelte@3.46.4+typescript@4.6.2
+    transitivePeerDependencies:
+      - typescript
+    dev: false
+
   /@babel/code-frame/7.16.7:
     resolution: {integrity: sha512-iAXqUn8IIeBTNd72xsFlgaXHkMBMt6y4HJp1tIaK465CWLT/fG1aqB7ykr95gHHmlBdGbFeWWfyB4NJJ0nmeIg==}
     engines: {node: '>=6.9.0'}
@@ -4237,6 +4281,17 @@ packages:
       vue: 3.2.31
     dev: false
 
+  /@vscode/emmet-helper/2.8.4:
+    resolution: {integrity: sha512-lUki5QLS47bz/U8IlG9VQ+1lfxMtxMZENmU5nu4Z71eOD5j9FK0SmYGL5NiVJg9WBWeAU0VxRADMY2Qpq7BfVg==}
+    dependencies:
+      emmet: 2.3.6
+      jsonc-parser: 2.3.1
+      vscode-languageserver-textdocument: 1.0.4
+      vscode-languageserver-types: 3.16.0
+      vscode-nls: 5.0.0
+      vscode-uri: 2.1.2
+    dev: false
+
   /@vue/compiler-core/3.2.31:
     resolution: {integrity: sha512-aKno00qoA4o+V/kR6i/pE+aP+esng5siNAVQ422TkBNM6qA4veXiZbSe8OTXHXquEi/f6Akc+nLfB4JGfe4/WQ==}
     dependencies:
@@ -5194,6 +5249,10 @@ packages:
       mimic-response: 3.1.0
     dev: true
 
+  /dedent-js/1.0.1:
+    resolution: {integrity: sha1-vuX7fJ5yfYXf+iRZDRDsGrElUwU=}
+    dev: false
+
   /deep-eql/3.0.1:
     resolution: {integrity: sha512-+QeIQyN5ZuO+3Uk5DYh6/1eKO0m0YmJFGNmFHGACpf1ClL1nmlV/p4gNgbl2pJGxgXb4faqo6UE+M5ACEMyVcw==}
     engines: {node: '>=0.12'}
@@ -7327,6 +7386,12 @@ packages:
       get-func-name: 2.0.0
     dev: true
 
+  /lower-case/2.0.2:
+    resolution: {integrity: sha512-7fm3l3NAF9WfN6W3JOmf5drwpVqX78JtoGJ3A6W0a6ZnldM41w2fV5D490psKFTpMds8TJse/eHLFFsNHHjHgg==}
+    dependencies:
+      tslib: 2.3.1
+    dev: false
+
   /lru-cache/4.1.5:
     resolution: {integrity: sha512-sWZlbEP2OsHNkXrMl5GYk/jKk70MBng6UU4YI/qGDYbgf6YbP4EvmqISbXCoJiRKs+1bSpFHVgQxvJ17F2li5g==}
     dependencies:
@@ -8020,6 +8085,13 @@ packages:
       '@types/nlcst': 1.0.0
     dev: false
 
+  /no-case/3.0.4:
+    resolution: {integrity: sha512-fgAN3jGAh+RoxUGZHTSOLJIqUc2wmoBwGR4tbpNAKmmovFoWq0OdRkb0VkldReO2a2iBT/OEulG9XSUc10r3zg==}
+    dependencies:
+      lower-case: 2.0.2
+      tslib: 2.3.1
+    dev: false
+
   /node-abi/3.8.0:
     resolution: {integrity: sha512-tzua9qWWi7iW4I42vUPKM+SfaF0vQSLAm4yO5J83mSwB7GeoWrDKC/K+8YCnYNwqP5duwazbw2X9l4m8SC2cUw==}
     engines: {node: '>=10'}
@@ -8331,6 +8403,13 @@ packages:
   /parse5/6.0.1:
     resolution: {integrity: sha512-Ofn/CTFzRGTTxwpNEs9PP93gXShHcTq255nzRYSKe8AkVpZY7e1fpmTfOyoIvjP5HG7Z2ZM7VS9PPhQGW2pOpw==}
 
+  /pascal-case/3.1.2:
+    resolution: {integrity: sha512-uWlGT3YSnK9x3BQJaOdcZwrnV6hPpd8jFH1/ucpiLRPh/2zCVJKS19E4GvYHvaCcACn3foXZ0cLB9Wrx1KGe5g==}
+    dependencies:
+      no-case: 3.0.4
+      tslib: 2.3.1
+    dev: false
+
   /path-browserify/1.0.1:
     resolution: {integrity: sha512-b7uo2UCUOYZcnF/3ID0lulOJi/bafxa1xPe7ZPsammBSpjSWQkjNxlt635YGS2MiR9GjvuXCtz2emr3jbsz98g==}
     dev: false
@@ -9640,6 +9719,18 @@ packages:
     resolution: {integrity: sha512-qKJzw6DpA33CIa+C/rGp4AUdSfii0DOTCzj/2YpSKKayw5WGSS624Et9L1nU1k2OVRS9vaENQXp2CVZNU+xvIg==}
     engines: {node: '>= 8'}
 
+  /svelte2tsx/0.5.6_svelte@3.46.4+typescript@4.6.2:
+    resolution: {integrity: sha512-B4WZUtoTdVD+F73H1RQEH3Hrv7m2/ahThmAUkjT5CTWRigQaJqYQpSjisCH1Pzfi9B37YikDnAi4u4uxwYM+iw==}
+    peerDependencies:
+      svelte: ^3.24
+      typescript: ^4.1.2
+    dependencies:
+      dedent-js: 1.0.1
+      pascal-case: 3.1.2
+      svelte: 3.46.4
+      typescript: 4.6.2
+    dev: false
+
   /tailwindcss/3.0.23_autoprefixer@10.4.4:
     resolution: {integrity: sha512-+OZOV9ubyQ6oI2BXEhzw4HrqvgcARY38xv3zKcjnWtMIZstEsXdI9xftd1iB7+RbOnj2HOEzkA0OyB5BaSxPQA==}
     engines: {node: '>=12.13.0'}
@@ -9824,7 +9915,6 @@ packages:
 
   /tslib/2.3.1:
     resolution: {integrity: sha512-77EbyPPpMz+FRFRuAFlWMtmgUWGe9UOG2Z25NqCwiIjRhOf5iKGuzSe5P2w1laq+FkRy4p+PCuVkJSGkzTEKVw==}
-    dev: true
 
   /tsm/2.2.1:
     resolution: {integrity: sha512-qvJB0baPnxQJolZru11mRgGTdNlx17WqgJnle7eht3Vhb+VUR4/zFA5hFl6NqRe7m8BD9w/6yu0B2XciRrdoJA==}
@@ -10409,6 +10499,15 @@ packages:
       vscode-uri: 2.1.2
     dev: false
 
+  /vscode-html-languageservice/4.2.4:
+    resolution: {integrity: sha512-1HqvXKOq9WlZyW4HTD+0XzrjZoZ/YFrgQY2PZqktbRloHXVAUKm6+cAcvZi4YqKPVn05/CK7do+KBHfuSaEdbg==}
+    dependencies:
+      vscode-languageserver-textdocument: 1.0.4
+      vscode-languageserver-types: 3.16.0
+      vscode-nls: 5.0.0
+      vscode-uri: 3.0.3
+    dev: false
+
   /vscode-jsonrpc/6.0.0:
     resolution: {integrity: sha512-wnJA4BnEjOSyFMvjZdpiOwhSq9uDoK8e/kpRJDTaMYzwlkrhG1fwDIZI94CLsLzlCK5cIbMMtFlJlfR57Lavmg==}
     engines: {node: '>=8.0.0 || >=10.0.0'}
@@ -10440,6 +10539,13 @@ packages:
       vscode-languageserver-protocol: 3.16.0
     dev: false
 
+  /vscode-languageserver/7.0.0:
+    resolution: {integrity: sha512-60HTx5ID+fLRcgdHfmz0LDZAXYEV68fzwG0JWwEPBode9NuMYTIxuYXPg4ngO8i8+Ou0lM7y6GzaYWbiDL0drw==}
+    hasBin: true
+    dependencies:
+      vscode-languageserver-protocol: 3.16.0
+    dev: false
+
   /vscode-nls/5.0.0:
     resolution: {integrity: sha512-u0Lw+IYlgbEJFF6/qAqG2d1jQmJl0eyAGJHoAJqr2HT4M2BNuQYSEiSE75f52pXHSJm8AlTjnLLbBFPrdz2hpA==}
     dev: false