diff --git a/packages/app/src/cli/models/extensions/specifications/admin.test.ts b/packages/app/src/cli/models/extensions/specifications/admin.test.ts
new file mode 100644
index 00000000000..f9af0bba308
--- /dev/null
+++ b/packages/app/src/cli/models/extensions/specifications/admin.test.ts
@@ -0,0 +1,83 @@
+import adminSpec, {AdminConfigType} from './admin.js'
+import {ExtensionInstance} from '../extension-instance.js'
+import {inTemporaryDirectory, mkdir, touchFile} from '@shopify/cli-kit/node/fs'
+import {joinPath} from '@shopify/cli-kit/node/path'
+import {describe, expect, test} from 'vitest'
+
+function createAdminExtensionInstance(directory: string, staticRoot?: string): ExtensionInstance<AdminConfigType> {
+  return {
+    directory,
+    configuration: {
+      name: 'test-admin',
+      type: 'admin',
+      admin: staticRoot ? {static_root: staticRoot} : undefined,
+    },
+  } as unknown as ExtensionInstance<AdminConfigType>
+}
+
+describe('admin buildValidation', () => {
+  test('passes when static_root is not configured', async () => {
+    await inTemporaryDirectory(async (tmpDir) => {
+      const extension = createAdminExtensionInstance(tmpDir, undefined)
+
+      // Should not throw
+      await expect(adminSpec.buildValidation!(extension)).resolves.toBeUndefined()
+    })
+  })
+
+  test('passes when static_root exists and contains index.html', async () => {
+    await inTemporaryDirectory(async (tmpDir) => {
+      const distDir = joinPath(tmpDir, 'dist')
+      await mkdir(distDir)
+      await touchFile(joinPath(distDir, 'index.html'))
+
+      const extension = createAdminExtensionInstance(tmpDir, './dist')
+
+      // Should not throw
+      await expect(adminSpec.buildValidation!(extension)).resolves.toBeUndefined()
+    })
+  })
+
+  test('throws when static_root is configured but index.html is missing', async () => {
+    await inTemporaryDirectory(async (tmpDir) => {
+      // Create the dist directory but without index.html
+      const distDir = joinPath(tmpDir, 'dist')
+      await mkdir(distDir)
+
+      const extension = createAdminExtensionInstance(tmpDir, './dist')
+
+      await expect(adminSpec.buildValidation!(extension)).rejects.toThrow(
+        'The admin extension requires an index.html file in the static_root directory (./dist), but it was not found.',
+      )
+    })
+  })
+
+  test('throws when static_root directory does not exist', async () => {
+    await inTemporaryDirectory(async (tmpDir) => {
+      const extension = createAdminExtensionInstance(tmpDir, './dist')
+
+      await expect(adminSpec.buildValidation!(extension)).rejects.toThrow(
+        'The admin extension requires an index.html file in the static_root directory (./dist), but it was not found.',
+      )
+    })
+  })
+})
+
+describe('admin devSessionWatchConfig', () => {
+  test('returns empty paths when static_root is not configured', () => {
+    const extension = createAdminExtensionInstance('/tmp/test', undefined)
+    const watchConfig = adminSpec.devSessionWatchConfig!(extension)
+
+    expect(watchConfig).toEqual({paths: []})
+  })
+
+  test('returns watch paths when static_root is configured', () => {
+    const extension = createAdminExtensionInstance('/tmp/test', './dist')
+    const watchConfig = adminSpec.devSessionWatchConfig!(extension)
+
+    expect(watchConfig).toBeDefined()
+    expect(watchConfig!.paths).toHaveLength(1)
+    expect(watchConfig!.paths[0]).toContain('dist')
+    expect(watchConfig!.paths[0]).toContain('**/*')
+  })
+})
diff --git a/packages/app/src/cli/models/extensions/specifications/admin.ts b/packages/app/src/cli/models/extensions/specifications/admin.ts
index bdd20cb2131..515cfa6706c 100644
--- a/packages/app/src/cli/models/extensions/specifications/admin.ts
+++ b/packages/app/src/cli/models/extensions/specifications/admin.ts
@@ -2,6 +2,8 @@ import {createExtensionSpecification} from '../specification.js'
 import {BaseConfigType, ZodSchemaType} from '../schemas.js'
 import {zod} from '@shopify/cli-kit/node/schema'
 import {joinPath} from '@shopify/cli-kit/node/path'
+import {fileExists} from '@shopify/cli-kit/node/fs'
+import {AbortError} from '@shopify/cli-kit/node/error'
 
 export const AdminSpecIdentifier = 'admin'
 
@@ -31,6 +33,20 @@ const adminSpecificationSpec = createExtensionSpecification<AdminConfigType>({
     const path = joinPath(extension.directory, staticRoot, '**/*')
     return {paths: [path], ignore: []}
   },
+  buildValidation: async (extension) => {
+    const staticRoot = extension.configuration.admin?.static_root
+    if (!staticRoot) return
+
+    const indexHtmlPath = joinPath(extension.directory, staticRoot, 'index.html')
+    const indexExists = await fileExists(indexHtmlPath)
+
+    if (!indexExists) {
+      throw new AbortError(
+        `The admin extension requires an index.html file in the static_root directory (${staticRoot}), but it was not found.`,
+        `This usually means the build step has not completed yet. Make sure your app runs a build command (e.g., via a predev hook in your web configuration) before starting the dev server.`,
+      )
+    }
+  },
   transformRemoteToLocal: (remoteContent) => {
     return {
       admin: {