diff --git a/.changeset/fix-db-cloudflare-build.md b/.changeset/fix-db-cloudflare-build.md
new file mode 100644
index 000000000000..f5958a1eea30
--- /dev/null
+++ b/.changeset/fix-db-cloudflare-build.md
@@ -0,0 +1,5 @@
+---
+'@astrojs/db': patch
+---
+
+Fixes `astro build --remote` failing with "Invalid URL string" when using `@astrojs/db` with `@astrojs/cloudflare`. The temporary Vite server created during build now filters out Cloudflare's environment-replacing plugins, preventing the workerd runtime from eagerly loading the manifest placeholder.
diff --git a/packages/db/src/core/integration/index.ts b/packages/db/src/core/integration/index.ts
index 6449e6044e4e..ca06bb3702b5 100644
--- a/packages/db/src/core/integration/index.ts
+++ b/packages/db/src/core/integration/index.ts
@@ -242,17 +242,41 @@ async function executeSeedFile({
 	}
 }
 
+/**
+ * Filter out adapter plugins that replace the SSR environment with a non-Node.js
+ * runtime (e.g. @cloudflare/vite-plugin creates a workerd-based environment).
+ * The temp server only needs a standard Node.js SSR environment for seed execution.
+ */
+export function filterPluginsForTempServer(plugins: UserConfig['plugins']): UserConfig['plugins'] {
+	return (plugins ?? []).flat().filter((plugin) => {
+		if (
+			plugin &&
+			typeof plugin === 'object' &&
+			'name' in plugin &&
+			typeof plugin.name === 'string'
+		) {
+			if (plugin.name.startsWith('vite-plugin-cloudflare')) return false;
+		}
+		return true;
+	});
+}
+
 /**
  * Inspired by Astro content collection config loader.
  */
 async function getTempViteServer({ viteConfig }: { viteConfig: UserConfig }) {
+	const filteredPlugins = filterPluginsForTempServer(viteConfig.plugins);
+
 	const tempViteServer = await createServer(
-		mergeConfig(viteConfig, {
-			server: { middlewareMode: true, hmr: false, watch: null, ws: false },
-			optimizeDeps: { noDiscovery: true },
-			ssr: { external: [] },
-			logLevel: 'silent',
-		}),
+		mergeConfig(
+			{ ...viteConfig, plugins: filteredPlugins },
+			{
+				server: { middlewareMode: true, hmr: false, watch: null, ws: false },
+				optimizeDeps: { noDiscovery: true },
+				ssr: { external: [] },
+				logLevel: 'silent',
+			},
+		),
 	);
 
 	const hotSend = tempViteServer.environments.client.hot.send;
diff --git a/packages/db/test/unit/filter-plugins.test.ts b/packages/db/test/unit/filter-plugins.test.ts
new file mode 100644
index 000000000000..1ed19da26ec1
--- /dev/null
+++ b/packages/db/test/unit/filter-plugins.test.ts
@@ -0,0 +1,79 @@
+import assert from 'node:assert';
+import test, { describe } from 'node:test';
+import { filterPluginsForTempServer } from '../../dist/core/integration/index.js';
+
+describe('filterPluginsForTempServer', () => {
+	test('removes vite-plugin-cloudflare plugins', () => {
+		const plugins = [
+			{ name: 'astro:build' },
+			{ name: 'vite-plugin-cloudflare' },
+			{ name: 'vite-plugin-cloudflare:dev' },
+			{ name: 'vite-plugin-cloudflare:config' },
+			{ name: 'astro:assets' },
+		];
+		const filtered = filterPluginsForTempServer(plugins);
+		const names = (filtered ?? []).flatMap((p) =>
+			p && typeof p === 'object' && 'name' in p ? [p.name] : [],
+		);
+		assert.deepStrictEqual(names, ['astro:build', 'astro:assets']);
+	});
+
+	test('preserves all plugins when no cloudflare plugins present', () => {
+		const plugins = [
+			{ name: 'astro:build' },
+			{ name: 'astro:assets' },
+			{ name: '@astrojs/react' },
+		];
+		const filtered = filterPluginsForTempServer(plugins);
+		const names = (filtered ?? []).flatMap((p) =>
+			p && typeof p === 'object' && 'name' in p ? [p.name] : [],
+		);
+		assert.deepStrictEqual(names, ['astro:build', 'astro:assets', '@astrojs/react']);
+	});
+
+	test('handles undefined plugins', () => {
+		const filtered = filterPluginsForTempServer(undefined);
+		assert.deepStrictEqual(filtered, []);
+	});
+
+	test('handles empty plugins array', () => {
+		const filtered = filterPluginsForTempServer([]);
+		assert.deepStrictEqual(filtered, []);
+	});
+
+	test('handles nested plugin arrays (flattens)', () => {
+		const plugins = [
+			[{ name: 'astro:build' }, { name: 'vite-plugin-cloudflare:rsc' }],
+			{ name: 'astro:assets' },
+		];
+		const filtered = filterPluginsForTempServer(plugins);
+		const names = (filtered ?? []).flatMap((p) =>
+			p && typeof p === 'object' && 'name' in p ? [p.name] : [],
+		);
+		assert.deepStrictEqual(names, ['astro:build', 'astro:assets']);
+	});
+
+	test('handles null/falsy entries in plugins array', () => {
+		const plugins = [null, undefined, false, { name: 'astro:build' }] as const;
+		const filtered = filterPluginsForTempServer(plugins as any);
+		assert.strictEqual((filtered ?? []).length, 4); // null, undefined, false pass the name check
+	});
+
+	test('preserves non-cloudflare adapter plugins', () => {
+		const plugins = [
+			{ name: '@astrojs/cloudflare:cf-imports' },
+			{ name: '@astrojs/cloudflare:environment' },
+			{ name: 'vite-plugin-cloudflare' },
+			{ name: 'vite-plugin-cloudflare:dev' },
+		];
+		const filtered = filterPluginsForTempServer(plugins);
+		const names = (filtered ?? []).flatMap((p) =>
+			p && typeof p === 'object' && 'name' in p ? [p.name] : [],
+		);
+		// Only vite-plugin-cloudflare* are removed; @astrojs/cloudflare:* are kept
+		assert.deepStrictEqual(names, [
+			'@astrojs/cloudflare:cf-imports',
+			'@astrojs/cloudflare:environment',
+		]);
+	});
+});