diff --git a/packages/void/src/plugin-env-schema.ts b/packages/void/src/plugin-env-schema.ts
index 7625d9702..a4ca70308 100644
--- a/packages/void/src/plugin-env-schema.ts
+++ b/packages/void/src/plugin-env-schema.ts
@@ -1,7 +1,7 @@
 import { existsSync, mkdirSync, readFileSync, realpathSync } from 'node:fs';
 import { parseEnv } from 'node:util';
 import { join, resolve } from 'pathslash';
-import { loadEnv, resolveEnvPrefix, type Plugin, type ResolvedConfig } from 'vite';
+import { loadEnv, normalizePath, resolveEnvPrefix, type Plugin, type ResolvedConfig } from 'vite';
 import { findEnvFile, generateEnvTypes } from './codegen/env-types.ts';
 import { writeFileIfChanged } from './codegen/write-if-changed.ts';
 import { loadUserEnvFile } from './host/load-user-env.ts';
@@ -72,7 +72,7 @@ function stripLocalClientEnv(
   config: ResolvedConfig,
   before: ProcessEnvCopies | undefined,
 ): void {
-  if (config.envDir === false || realDir(config.envDir) !== realDir(root)) {
+  if (config.envDir === false || realPath(config.envDir) !== realPath(root)) {
     return;
   }
   const file = join(root, LOCAL_ENV_FILE);
@@ -107,14 +107,24 @@ function stripLocalClientEnv(
 }
 
 /** Match Vite's canonical paths, including Windows short names and filesystem casing. */
-function realDir(dir: string): string {
+function realPath(path: string): string {
   try {
-    return realpathSync.native(dir);
+    return realpathSync.native(path);
   } catch {
-    return resolve(dir);
+    return resolve(path);
   }
 }
 
+/** Module ids that name an env file: its path as found, and as Vite resolves it. */
+function envFileIdsFor(envFile: string | null): Set<string> {
+  return new Set(envFile ? [normalizePath(envFile), normalizePath(realPath(envFile))] : []);
+}
+
+/** A hook filter pattern that matches exactly `id`. */
+function exactId(id: string): RegExp {
+  return new RegExp(`^${id.replace(/[.*+?^${}()|[\]\\]/g, '\\$&')}$`);
+}
+
 /** Patterns Vite's `define` typically uses for env-shaped constants. */
 const DEFINE_ENV_PATTERN =
   /^(?:globalThis\.)?(?:process\.env|import\.meta\.env)\.([A-Z_][A-Z0-9_]*)$/;
@@ -133,6 +143,22 @@ const DEFINE_ENV_PATTERN =
 export function envSchemaPlugin(root: string, options: EnvSchemaPluginOptions = {}): Plugin {
   const outDir = join(root, '.void');
   let envFile: string | null = null;
+  // `config` finds the file again. The transform filter below keeps the ids found here: a hook
+  // filter is fixed when the plugin is created.
+  let envFileIds = envFileIdsFor(findEnvFile(root));
+  // Generated server entries import env.ts only to register its schema. Keep that import when
+  // the app's package.json declares `"sideEffects": false`, which would let the bundler drop it.
+  // The filter matches the resolved id, which for a symlink is the target's path, whatever its
+  // file name.
+  const keepEnvFileImport: Plugin['transform'] = {
+    filter: { id: [...envFileIds].map(exactId) },
+    handler(code, id) {
+      if (this.environment.config.consumer === 'client' || !envFileIds.has(id)) {
+        return;
+      }
+      return { code, map: null, moduleSideEffects: true };
+    },
+  };
   let command: 'serve' | 'build' = 'serve';
   let processEnvCopiesBefore: ProcessEnvCopies | undefined;
   const appliedClientDefaults = new Map<string, string>();
@@ -317,6 +343,7 @@ export function envSchemaPlugin(root: string, options: EnvSchemaPluginOptions =
         throw new Error(reservedEnvKeysMessage('.env', reservedInDotenv));
       }
       envFile = findEnvFile(root);
+      envFileIds = envFileIdsFor(envFile);
       if (!envFile) {
         return;
       }
@@ -392,5 +419,6 @@ export function envSchemaPlugin(root: string, options: EnvSchemaPluginOptions =
         await importUserEnv();
       }
     },
+    ...(envFileIds.size > 0 && { transform: keepEnvFileImport }),
   };
 }
diff --git a/packages/void/test/integration/plugin-env-schema.test.ts b/packages/void/test/integration/plugin-env-schema.test.ts
index 08cb08702..b2b448a11 100644
--- a/packages/void/test/integration/plugin-env-schema.test.ts
+++ b/packages/void/test/integration/plugin-env-schema.test.ts
@@ -1,6 +1,15 @@
-import { existsSync, mkdirSync, mkdtempSync, readFileSync, rmSync, writeFileSync } from 'node:fs';
+import {
+  existsSync,
+  mkdirSync,
+  mkdtempSync,
+  readFileSync,
+  rmSync,
+  symlinkSync,
+  writeFileSync,
+} from 'node:fs';
 import { tmpdir } from 'node:os';
 import { basename, dirname, join } from 'node:path';
+import { pathToFileURL } from 'node:url';
 import { build, createBuilder, resolveConfig, type InlineConfig } from 'vite';
 import { afterEach, describe, expect, it, vi } from 'vite-plus/test';
 import { envClientFoldPlugin } from '../../src/plugin-env-client-fold.ts';
@@ -558,3 +567,72 @@ describe('envSchemaPlugin reserved __VOID_ names', () => {
     },
   );
 });
+
+describe('envSchemaPlugin with "sideEffects": false', () => {
+  const publicEnvUrl = pathToFileURL(
+    join(import.meta.dirname, '../../src/runtime/env-public.ts'),
+  ).href;
+
+  /** Build an app that declares no side effects, with an entry that imports env.ts for its side effect. */
+  async function buildEntryImportingEnv(
+    consumer: 'server' | 'client',
+    options: { symlinkTo?: string } = {},
+  ): Promise<string> {
+    const root = createTempRoot();
+    writeFileSync(
+      join(root, 'package.json'),
+      JSON.stringify({ type: 'module', sideEffects: false }),
+    );
+    const schemaFile = join(root, options.symlinkTo ?? 'env.ts');
+    writeFileSync(
+      schemaFile,
+      `import { defineEnv, number } from ${JSON.stringify(publicEnvUrl)};\n` +
+        'export default defineEnv({ SCHEMA_DEFAULT: number().default(48213) });\n',
+    );
+    if (options.symlinkTo) {
+      symlinkSync(schemaFile, join(root, 'env.ts'));
+    }
+    writeFileSync(join(root, 'entry.js'), 'import "./env.ts";\nexport const ready = true;\n');
+    const entry = join(root, 'entry.js');
+    const output = await build({
+      root,
+      configFile: false,
+      logLevel: 'silent',
+      plugins: [envSchemaPlugin(root)],
+      build: {
+        ssr: consumer === 'server' ? entry : false,
+        write: false,
+        minify: false,
+        rollupOptions: {
+          ...(consumer === 'client' && { input: entry }),
+          external: ['cloudflare:workers'],
+        },
+      },
+    });
+    return [output]
+      .flat()
+      .flatMap((result) => ('output' in result ? result.output : []))
+      .map((chunk) => ('code' in chunk ? chunk.code : ''))
+      .join('\n');
+  }
+
+  // Void's server entries import env.ts to register its schema.
+  it('keeps env.ts in a server build', async () => {
+    expect(await buildEntryImportingEnv('server')).toContain('48213');
+  });
+
+  // Vite loads a symlinked env.ts under its target's path. Windows needs privileges for a file
+  // symlink.
+  it.skipIf(process.platform === 'win32')(
+    'keeps a symlinked env.ts whose target has another name',
+    async () => {
+      expect(await buildEntryImportingEnv('server', { symlinkTo: 'shared-schema.ts' })).toContain(
+        '48213',
+      );
+    },
+  );
+
+  it('leaves client builds to the side effects that the app declares', async () => {
+    expect(await buildEntryImportingEnv('client')).not.toContain('48213');
+  });
+});