diff --git a/packages/plugins/apps/package.json b/packages/plugins/apps/package.json
index 2a737b1e2..8228aa9c4 100644
--- a/packages/plugins/apps/package.json
+++ b/packages/plugins/apps/package.json
@@ -15,8 +15,14 @@
         "hideFromRootReadme": true
     },
     "toBuild": {
-        "apps-runtime": {
-            "entry": "./src/built/apps-runtime.ts",
+        "apps-runtime-dev": {
+            "entry": "./src/built/apps-runtime-dev.ts",
+            "format": [
+                "esm"
+            ]
+        },
+        "apps-runtime-prod": {
+            "entry": "./src/built/apps-runtime-prod.ts",
             "format": [
                 "esm"
             ]
diff --git a/packages/plugins/apps/src/backend/client/execute-backend-function.ts b/packages/plugins/apps/src/backend/client/execute-backend-function.ts
deleted file mode 100644
index 666f1da81..000000000
--- a/packages/plugins/apps/src/backend/client/execute-backend-function.ts
+++ /dev/null
@@ -1,54 +0,0 @@
-// Unless explicitly stated otherwise all files in this repository are licensed under the MIT License.
-// This product includes software developed at Datadog (https://www.datadoghq.com/).
-// Copyright 2019-Present Datadog, Inc.
-
-/* eslint-env browser */
-
-import { devServerTransport } from './transports/dev-server-transport';
-import { postMessageTransport } from './transports/post-message-transport/post-message-transport';
-import type { BackendFunctionTransport } from './types';
-
-function isInIframe(): boolean {
-    try {
-        return typeof window !== 'undefined' && window.parent !== window;
-    } catch {
-        // Accessing window.parent can throw if cross-origin
-        return true;
-    }
-}
-
-function resolveTransport(): BackendFunctionTransport {
-    if (isInIframe()) {
-        return postMessageTransport;
-    }
-    return devServerTransport;
-}
-
-/**
- * Executes a backend function by name with the provided arguments.
- *
- * When running inside an iframe embedded in App Builder, automatically
- * uses postMessage to communicate with the parent window. Otherwise,
- * uses HTTP fetch to the backend endpoint.
- *
- * @param functionName - The name of the backend function to execute
- * @param args - Array of arguments to pass to the function
- * @returns Promise that resolves to the function's return value
- * @throws {BackendFunctionError} If the request fails or the function throws an error
- *
- * @example
- * ```typescript
- * const result = await executeBackendFunction<{ sum: number }, [number, number]>(
- *   'testWithImport',
- *   [5, 7]
- * );
- * console.log(result.sum); // 12
- * ```
- */
-export async function executeBackendFunction<TData = unknown, TArgs extends unknown[] = unknown[]>(
-    functionName: string,
-    args: TArgs,
-): Promise<TData> {
-    const transport = resolveTransport();
-    return transport<TData>(functionName, args);
-}
diff --git a/packages/plugins/apps/src/backend/client/execute-backend-function.test.ts b/packages/plugins/apps/src/backend/client/transports/dev-server-transport.test.ts
similarity index 73%
rename from packages/plugins/apps/src/backend/client/execute-backend-function.test.ts
rename to packages/plugins/apps/src/backend/client/transports/dev-server-transport.test.ts
index be1504dde..a4f40797c 100644
--- a/packages/plugins/apps/src/backend/client/execute-backend-function.test.ts
+++ b/packages/plugins/apps/src/backend/client/transports/dev-server-transport.test.ts
@@ -9,10 +9,11 @@
 // lives with the original tests in web-ui's @datadog/apps-function-query
 // until a DOM-enabled harness is introduced.
 
-import { executeBackendFunction } from './execute-backend-function';
-import { BackendFunctionError } from './types';
+import { BackendFunctionError } from '../types';
 
-describe('executeBackendFunction', () => {
+import { devServerTransport } from './dev-server-transport';
+
+describe('devServerTransport', () => {
     let originalFetch: typeof fetch;
 
     beforeEach(() => {
@@ -30,7 +31,7 @@ describe('executeBackendFunction', () => {
             json: async () => mockResponse,
         });
 
-        const result = await executeBackendFunction<{ sum: number }>('testWithImport', [5, 7]);
+        const result = await devServerTransport<{ sum: number }>('testWithImport', [5, 7]);
 
         expect(result).toEqual({ sum: 12 });
         expect(global.fetch).toHaveBeenCalledWith('/__dd/executeAction', {
@@ -48,11 +49,9 @@ describe('executeBackendFunction', () => {
     it('should throw BackendFunctionError on network error', async () => {
         global.fetch = jest.fn().mockRejectedValue(new Error('Network failed'));
 
-        await expect(executeBackendFunction('testFunction', [])).rejects.toThrow(
-            BackendFunctionError,
-        );
+        await expect(devServerTransport('testFunction', [])).rejects.toThrow(BackendFunctionError);
 
-        await expect(executeBackendFunction('testFunction', [])).rejects.toThrow(
+        await expect(devServerTransport('testFunction', [])).rejects.toThrow(
             'Network error while executing backend function "testFunction"',
         );
     });
@@ -64,11 +63,9 @@ describe('executeBackendFunction', () => {
             text: async () => 'Internal Server Error',
         });
 
-        await expect(executeBackendFunction('testFunction', [])).rejects.toThrow(
-            BackendFunctionError,
-        );
+        await expect(devServerTransport('testFunction', [])).rejects.toThrow(BackendFunctionError);
 
-        await expect(executeBackendFunction('testFunction', [])).rejects.toThrow(
+        await expect(devServerTransport('testFunction', [])).rejects.toThrow(
             'Backend function "testFunction" failed with status 500',
         );
     });
@@ -83,11 +80,9 @@ describe('executeBackendFunction', () => {
             json: async () => mockResponse,
         });
 
-        await expect(executeBackendFunction('testFunction', [])).rejects.toThrow(
-            BackendFunctionError,
-        );
+        await expect(devServerTransport('testFunction', [])).rejects.toThrow(BackendFunctionError);
 
-        await expect(executeBackendFunction('testFunction', [])).rejects.toThrow(
+        await expect(devServerTransport('testFunction', [])).rejects.toThrow(
             'Backend function "testFunction" returned an error',
         );
     });
@@ -101,11 +96,9 @@ describe('executeBackendFunction', () => {
             },
         });
 
-        await expect(executeBackendFunction('testFunction', [])).rejects.toThrow(
-            BackendFunctionError,
-        );
+        await expect(devServerTransport('testFunction', [])).rejects.toThrow(BackendFunctionError);
 
-        await expect(executeBackendFunction('testFunction', [])).rejects.toThrow(
+        await expect(devServerTransport('testFunction', [])).rejects.toThrow(
             'Failed to parse response from backend function',
         );
     });
@@ -117,7 +110,7 @@ describe('executeBackendFunction', () => {
             text: async () => 'Not Found',
         });
 
-        await expect(executeBackendFunction('testFunction', [])).rejects.toMatchObject({
+        await expect(devServerTransport('testFunction', [])).rejects.toMatchObject({
             name: 'BackendFunctionError',
             functionName: 'testFunction',
             statusCode: 404,
diff --git a/packages/plugins/apps/src/built/apps-runtime-dev.ts b/packages/plugins/apps/src/built/apps-runtime-dev.ts
new file mode 100644
index 000000000..5fe07491b
--- /dev/null
+++ b/packages/plugins/apps/src/built/apps-runtime-dev.ts
@@ -0,0 +1,10 @@
+// Unless explicitly stated otherwise all files in this repository are licensed under the MIT License.
+// This product includes software developed at Datadog (https://www.datadoghq.com/).
+// Copyright 2019-Present Datadog, Inc.
+
+/* eslint-env browser */
+/* global globalThis */
+import { devServerTransport } from '../backend/client/transports/dev-server-transport';
+
+const globalAny: any = globalThis;
+globalAny.DD_APPS_RUNTIME = { executeBackendFunction: devServerTransport };
diff --git a/packages/plugins/apps/src/built/apps-runtime-prod.ts b/packages/plugins/apps/src/built/apps-runtime-prod.ts
new file mode 100644
index 000000000..1df4a3516
--- /dev/null
+++ b/packages/plugins/apps/src/built/apps-runtime-prod.ts
@@ -0,0 +1,10 @@
+// Unless explicitly stated otherwise all files in this repository are licensed under the MIT License.
+// This product includes software developed at Datadog (https://www.datadoghq.com/).
+// Copyright 2019-Present Datadog, Inc.
+
+/* eslint-env browser */
+/* global globalThis */
+import { postMessageTransport } from '../backend/client/transports/post-message-transport/post-message-transport';
+
+const globalAny: any = globalThis;
+globalAny.DD_APPS_RUNTIME = { executeBackendFunction: postMessageTransport };
diff --git a/packages/plugins/apps/src/built/apps-runtime.ts b/packages/plugins/apps/src/built/apps-runtime.ts
deleted file mode 100644
index 4dd7c2b8d..000000000
--- a/packages/plugins/apps/src/built/apps-runtime.ts
+++ /dev/null
@@ -1,14 +0,0 @@
-// Unless explicitly stated otherwise all files in this repository are licensed under the MIT License.
-// This product includes software developed at Datadog (https://www.datadoghq.com/).
-// Copyright 2019-Present Datadog, Inc.
-
-/* eslint-env browser */
-/* global globalThis */
-import { executeBackendFunction } from '../backend/client/execute-backend-function';
-
-// Exposed on `globalThis.DD_APPS_RUNTIME` by the apps plugin injection so
-// generated proxy modules can call `executeBackendFunction` without importing
-// a runtime package. Internal API — consumers (generated .backend.ts proxy
-// modules) are produced by the apps plugin itself, not authored by users.
-const globalAny: any = globalThis;
-globalAny.DD_APPS_RUNTIME = { executeBackendFunction };
diff --git a/packages/plugins/apps/src/index.test.ts b/packages/plugins/apps/src/index.test.ts
index 553f29c2a..11c60983a 100644
--- a/packages/plugins/apps/src/index.test.ts
+++ b/packages/plugins/apps/src/index.test.ts
@@ -59,21 +59,37 @@ describe('Apps Plugin - getPlugins', () => {
         expect(getPlugins(getArgs())).toHaveLength(1);
     });
 
-    test('Should inject the apps runtime at the top of the user bundle when enabled', () => {
-        const injectMock = jest.fn();
-        getPlugins(
-            getGetPluginsArg(
-                { apps: {} },
-                { bundler: { ...getMockBundler({ name: 'vite' }), outDir }, inject: injectMock },
-            ),
-        );
-
-        expect(injectMock).toHaveBeenCalledWith({
-            type: 'file',
-            position: InjectPosition.MIDDLE,
-            value: expect.stringContaining('apps-runtime.mjs'),
-        });
-    });
+    const runtimeInjectionCases = [
+        { command: 'serve' as const, runtime: 'apps-runtime-dev.mjs' },
+        { command: 'build' as const, runtime: 'apps-runtime-prod.mjs' },
+    ];
+
+    test.each(runtimeInjectionCases)(
+        'Should inject the $runtime runtime when vite command is "$command"',
+        ({ command, runtime }) => {
+            const injectMock = jest.fn();
+            const plugins = getPlugins(
+                getGetPluginsArg(
+                    { apps: {} },
+                    {
+                        bundler: { ...getMockBundler({ name: 'vite' }), outDir },
+                        inject: injectMock,
+                    },
+                ),
+            );
+            const configHook = plugins[0].vite!.config as (
+                userConfig: object,
+                env: { command: 'serve' | 'build' },
+            ) => void;
+            configHook({}, { command });
+
+            expect(injectMock).toHaveBeenCalledWith({
+                type: 'file',
+                position: InjectPosition.MIDDLE,
+                value: expect.stringContaining(runtime),
+            });
+        },
+    );
 
     test('Should not inject the runtime when disabled', () => {
         const injectMock = jest.fn();
diff --git a/packages/plugins/apps/src/index.ts b/packages/plugins/apps/src/index.ts
index 13af8ff23..be26321ee 100644
--- a/packages/plugins/apps/src/index.ts
+++ b/packages/plugins/apps/src/index.ts
@@ -4,7 +4,6 @@
 
 import { rm } from '@dd/core/helpers/fs';
 import type { GetPlugins } from '@dd/core/types';
-import { InjectPosition } from '@dd/core/types';
 import chalk from 'chalk';
 import path from 'path';
 
@@ -89,21 +88,6 @@ export const getPlugins: GetPlugins = ({ options, context, bundler }) => {
         return [];
     }
 
-    // Inject the runtime that `globalThis.DD_APPS_RUNTIME.executeBackendFunction`
-    // is read from. The generated proxy modules (emitted by the transform hook
-    // below) reference that global. NOTE: This file is built alongside the
-    // bundler plugin via the `toBuild` entry in @dd/apps-plugin's package.json.
-    //
-    // Position MIDDLE is used instead of BEFORE so Vite's dev server injects
-    // the runtime as a <script type="module"> via `transformIndexHtml` — BEFORE
-    // is served via Rollup's `banner()` output hook which only fires at build
-    // time, leaving the runtime undefined during `vite` (dev).
-    context.inject({
-        type: 'file',
-        position: InjectPosition.MIDDLE,
-        value: path.join(__dirname, './apps-runtime.mjs'),
-    });
-
     const { setBackendFunctions, getBackendFunctions } = createBackendFunctionRegistry();
 
     const handleUpload = async (backendOutputs: Map<string, string>) => {
@@ -257,6 +241,8 @@ Either:
                 handleUpload,
                 log,
                 auth: context.auth,
+                inject: context.inject,
+                pluginDir: __dirname,
             }),
         },
     ];
diff --git a/packages/plugins/apps/src/vite/index.test.ts b/packages/plugins/apps/src/vite/index.test.ts
index 5d923f8a7..088bb4752 100644
--- a/packages/plugins/apps/src/vite/index.test.ts
+++ b/packages/plugins/apps/src/vite/index.test.ts
@@ -41,6 +41,8 @@ const defaultOptions = {
     handleUpload: mockHandleUpload,
     log,
     auth: { site: 'datadoghq.com' },
+    inject: jest.fn(),
+    pluginDir: '/plugin',
 };
 
 describe('Backend Functions - getVitePlugin', () => {
diff --git a/packages/plugins/apps/src/vite/index.ts b/packages/plugins/apps/src/vite/index.ts
index b35658349..063f93e6d 100644
--- a/packages/plugins/apps/src/vite/index.ts
+++ b/packages/plugins/apps/src/vite/index.ts
@@ -3,7 +3,9 @@
 // Copyright 2019-Present Datadog, Inc.
 
 import { rm } from '@dd/core/helpers/fs';
-import type { AuthOptionsWithDefaults, Logger, PluginOptions } from '@dd/core/types';
+import type { AuthOptionsWithDefaults, GlobalContext, Logger, PluginOptions } from '@dd/core/types';
+import { InjectPosition } from '@dd/core/types';
+import path from 'path';
 import type { build } from 'vite';
 
 import type { BackendFunction } from '../backend/discovery';
@@ -18,11 +20,17 @@ export interface VitePluginOptions {
     handleUpload: (backendOutputs: Map<string, string>) => Promise<void>;
     log: Logger;
     auth: AuthOptionsWithDefaults;
+    inject: GlobalContext['inject'];
+    pluginDir: string;
 }
 
 /**
  * Returns the Vite-specific plugin hooks for the apps plugin.
  *
+ * Config: injects either the dev-server or postMessage runtime depending on
+ * whether Vite is running in `serve` (dev) or `build` (production) mode, so
+ * each bundle ships only the transport it needs.
+ *
  * Production (closeBundle): builds backend functions (if any) then uploads
  * all assets sequentially.
  *
@@ -36,7 +44,20 @@ export const getVitePlugin = ({
     handleUpload,
     log,
     auth,
+    inject,
+    pluginDir,
 }: VitePluginOptions): PluginOptions['vite'] => ({
+    config(_userConfig, { command }) {
+        // Position MIDDLE so the runtime is injected via Vite's
+        // `transformIndexHtml` in dev — BEFORE goes through Rollup's
+        // `banner()` which only fires at build time.
+        const runtime = command === 'serve' ? 'apps-runtime-dev.mjs' : 'apps-runtime-prod.mjs';
+        inject({
+            type: 'file',
+            position: InjectPosition.MIDDLE,
+            value: path.join(pluginDir, runtime),
+        });
+    },
     async closeBundle() {
         let backendOutDir: string | undefined;
         let backendOutputs = new Map<string, string>();