diff --git a/.changeset/pr-1143.md b/.changeset/pr-1143.md
new file mode 100644
index 000000000..75890513e
--- /dev/null
+++ b/.changeset/pr-1143.md
@@ -0,0 +1,6 @@
+---
+'@sanity/cli-core': minor
+'@sanity/cli': minor
+---
+
+Add `unstable_defineApp`, exported from `sanity/cli`, as the opt-in for workbench apps. Calling it in `sanity.cli.ts` enables workbench for a studio or SDK app — the previous experimental `federation: { enabled }` config flag is removed.
diff --git a/fixtures/federated-studio/package.json b/fixtures/federated-studio/package.json
index d3d18cb18..58c615976 100644
--- a/fixtures/federated-studio/package.json
+++ b/fixtures/federated-studio/package.json
@@ -12,6 +12,7 @@
     "build:fixture": "sanity build"
   },
   "dependencies": {
+    "@sanity/federation": "0.1.0-alpha.9",
     "react": "^19.2.5",
     "react-dom": "^19.2.5",
     "sanity": "catalog:",
diff --git a/fixtures/federated-studio/sanity.cli.ts b/fixtures/federated-studio/sanity.cli.ts
index 2ab1cd728..d9bccb303 100644
--- a/fixtures/federated-studio/sanity.cli.ts
+++ b/fixtures/federated-studio/sanity.cli.ts
@@ -1,3 +1,4 @@
+import {unstable_defineApp} from '@sanity/federation'
 import {defineCliConfig} from 'sanity/cli'
 
 export default defineCliConfig({
@@ -5,10 +6,12 @@ export default defineCliConfig({
     dataset: 'test',
     projectId: 'ppsg7ml5',
   },
+  // Calling `unstable_defineApp` opts this studio into workbench (a
+  // `sanity.config.ts` is present, so it resolves to `applicationType: 'studio'`).
+  app: unstable_defineApp({
+    name: 'federated-studio',
+  }),
   deployment: {
     autoUpdates: true,
   },
-  federation: {
-    enabled: true,
-  },
 })
diff --git a/packages/@sanity/cli-core/package.json b/packages/@sanity/cli-core/package.json
index 91d2fdca1..dea754b58 100644
--- a/packages/@sanity/cli-core/package.json
+++ b/packages/@sanity/cli-core/package.json
@@ -66,6 +66,7 @@
     "@inquirer/prompts": "^8.3.0",
     "@oclif/core": "catalog:",
     "@sanity/client": "catalog:",
+    "@sanity/federation": "0.1.0-alpha.9",
     "babel-plugin-react-compiler": "^1.0.0",
     "boxen": "^8.0.1",
     "debug": "catalog:",
diff --git a/packages/@sanity/cli-core/src/config/__tests__/getCliConfig.test.ts b/packages/@sanity/cli-core/src/config/__tests__/getCliConfig.test.ts
index 0dcb347cb..a757dd906 100644
--- a/packages/@sanity/cli-core/src/config/__tests__/getCliConfig.test.ts
+++ b/packages/@sanity/cli-core/src/config/__tests__/getCliConfig.test.ts
@@ -12,6 +12,12 @@ vi.mock('../util/findConfigsPaths.js', () => ({
 }))
 
 const ROOT = '/mock/project'
+const BRAND = Symbol.for('sanity.workbench.defineApp')
+
+/** Mimics what `unstable_defineApp` returns: the input plus the brand. */
+function brandedApp(input: Record<string, unknown>) {
+  return Object.defineProperty({...input}, BRAND, {enumerable: false, value: true})
+}
 
 function setupSingleConfig(configPath = `${ROOT}/sanity.cli.ts`) {
   mockFindPathForFiles.mockResolvedValue([
@@ -70,6 +76,21 @@ describe('getCliConfig', () => {
     await expect(getCliConfig(ROOT)).rejects.toThrow('CLI config cannot be loaded')
   })
 
+  test('routes a branded app through the workbench loader', async () => {
+    const getCliConfig = await freshImport()
+    setupSingleConfig()
+    const app = brandedApp({name: 'drop-desk', title: 'Drop Desk'})
+    mockImportModule.mockResolvedValue({api: {projectId: 'abc'}, app})
+
+    const config = await getCliConfig(ROOT)
+
+    // `/mock/project` has no `sanity.config.*`, so it resolves to a core app —
+    // proving the branch ran parseWorkbenchCliConfig and kept the brand.
+    expect((config.app as {applicationType?: string}).applicationType).toBe('coreApp')
+    expect(BRAND in (config.app as object)).toBe(true)
+    expect('applicationType' in app).toBe(false)
+  })
+
   test('throws on schema validation failure', async () => {
     const getCliConfig = await freshImport()
     setupSingleConfig()
diff --git a/packages/@sanity/cli-core/src/config/__tests__/getCliConfigSync.test.ts b/packages/@sanity/cli-core/src/config/__tests__/getCliConfigSync.test.ts
index 97115c6e8..29840bc63 100644
--- a/packages/@sanity/cli-core/src/config/__tests__/getCliConfigSync.test.ts
+++ b/packages/@sanity/cli-core/src/config/__tests__/getCliConfigSync.test.ts
@@ -1,3 +1,7 @@
+import {mkdtempSync, rmSync, writeFileSync} from 'node:fs'
+import {tmpdir} from 'node:os'
+import {join} from 'node:path'
+
 import {afterEach, beforeEach, describe, expect, test, vi} from 'vitest'
 
 import {getCliConfigSync} from '../cli/getCliConfigSync'
@@ -37,4 +41,35 @@ describe('getCliConfigSync', () => {
 
     expect(() => getCliConfigSync(mockRootPath)).toThrow('Multiple CLI config files found')
   })
+
+  test('routes a branded app through the workbench loader', async () => {
+    const {existsSync} = await import('node:fs')
+    const realFs = await vi.importActual<typeof import('node:fs')>('node:fs')
+    vi.mocked(existsSync).mockImplementation((path) => realFs.existsSync(path))
+
+    // A self-contained config: brand the app via the global `Symbol.for` the
+    // same way `unstable_defineApp` does, so it needs no external import.
+    const dir = mkdtempSync(join(tmpdir(), 'cli-sync-cfg-'))
+    writeFileSync(
+      join(dir, 'sanity.cli.ts'),
+      [
+        `const app = {name: 'drop-desk', title: 'Drop Desk'}`,
+        `Object.defineProperty(app, Symbol.for('sanity.workbench.defineApp'), {`,
+        `  enumerable: false, value: true,`,
+        `})`,
+        `export default {api: {projectId: 'abc'}, app}`,
+      ].join('\n'),
+    )
+
+    try {
+      const config = getCliConfigSync(dir)
+
+      // No `sanity.config.*` in the temp dir, so it resolves to a core app —
+      // proving the branch ran parseWorkbenchCliConfig and kept the brand.
+      expect((config.app as {applicationType?: string}).applicationType).toBe('coreApp')
+      expect(Symbol.for('sanity.workbench.defineApp') in (config.app as object)).toBe(true)
+    } finally {
+      rmSync(dir, {force: true, recursive: true})
+    }
+  })
 })
diff --git a/packages/@sanity/cli-core/src/config/cli/__tests__/workbenchApp.test.ts b/packages/@sanity/cli-core/src/config/cli/__tests__/workbenchApp.test.ts
new file mode 100644
index 000000000..8b0decc88
--- /dev/null
+++ b/packages/@sanity/cli-core/src/config/cli/__tests__/workbenchApp.test.ts
@@ -0,0 +1,64 @@
+import {tmpdir} from 'node:os'
+import {join} from 'node:path'
+
+import {describe, expect, test} from 'vitest'
+
+import {parseWorkbenchCliConfig} from '../workbenchApp'
+
+const BRAND = Symbol.for('sanity.workbench.defineApp')
+// A dir with no `sanity.config.*`, so detection resolves to a core app.
+const APP_DIR = tmpdir()
+
+/** Mimics what `unstable_defineApp` returns: the input plus the brand. */
+function brandedApp(input: Record<string, unknown>) {
+  return Object.defineProperty({...input}, BRAND, {enumerable: false, value: true})
+}
+
+describe('parseWorkbenchCliConfig', () => {
+  test('keeps the identity fields and the brand on the resolved app', () => {
+    const app = brandedApp({
+      entry: './src/App.tsx',
+      name: 'drop-desk',
+      organizationId: 'o1',
+      title: 'Drop Desk',
+    })
+
+    const config = parseWorkbenchCliConfig({app, server: {port: 3333}}, APP_DIR)
+
+    expect((config.app as {name?: string}).name).toBe('drop-desk')
+    expect(BRAND in (config.app as object)).toBe(true)
+  })
+
+  test('resolves applicationType onto a clone without mutating the caller', () => {
+    const app = brandedApp({name: 'drop-desk', title: 'Drop Desk'})
+
+    const config = parseWorkbenchCliConfig({app}, APP_DIR)
+
+    // Caller's object is untouched; the resolved value lives on the returned clone.
+    expect('applicationType' in app).toBe(false)
+    expect(config.app).not.toBe(app)
+    expect((config.app as {applicationType?: string}).applicationType).toBe('coreApp')
+  })
+
+  test('keeps an explicit applicationType (no detection)', () => {
+    const app = brandedApp({applicationType: 'media-library', name: 'media', title: 'Media'})
+
+    const config = parseWorkbenchCliConfig({app}, join(APP_DIR, 'nope'))
+
+    expect((config.app as {applicationType?: string}).applicationType).toBe('media-library')
+  })
+
+  test('rejects an unknown applicationType', () => {
+    const app = brandedApp({applicationType: 'Studio', name: 'typo', title: 'Typo'})
+
+    expect(() => parseWorkbenchCliConfig({app}, APP_DIR)).toThrow(/Invalid `applicationType`/)
+  })
+
+  test('still validates the non-app fields', () => {
+    const app = brandedApp({name: 'drop-desk', title: 'Drop Desk'})
+
+    expect(() => parseWorkbenchCliConfig({app, server: {port: 'nope'}}, APP_DIR)).toThrow(
+      /Invalid CLI config/,
+    )
+  })
+})
diff --git a/packages/@sanity/cli-core/src/config/cli/getCliConfig.ts b/packages/@sanity/cli-core/src/config/cli/getCliConfig.ts
index 40339da6e..75e4cc64a 100644
--- a/packages/@sanity/cli-core/src/config/cli/getCliConfig.ts
+++ b/packages/@sanity/cli-core/src/config/cli/getCliConfig.ts
@@ -1,4 +1,7 @@
 import {createRequire} from 'node:module'
+import {dirname} from 'node:path'
+
+import {isWorkbenchApp} from '@sanity/federation'
 
 import {debug} from '../../debug.js'
 import {NotFoundError} from '../../errors/NotFoundError.js'
@@ -6,6 +9,7 @@ import {importModule} from '../../util/importModule.js'
 import {findPathForFiles} from '../util/findConfigsPaths.js'
 import {cliConfigSchema} from './schemas.js'
 import {type CliConfig} from './types/cliConfig.js'
+import {parseWorkbenchCliConfig} from './workbenchApp.js'
 
 const cache = new Map<string, Promise<CliConfig>>()
 
@@ -97,6 +101,12 @@ export async function getCliConfigUncached(rootPath: string): Promise<CliConfig>
     throw new Error('CLI config cannot be loaded', {cause: err})
   }
 
+  // Branch as early as possible: a branded `unstable_defineApp(...)` opts into
+  // workbench behavior, so its `app` skips the legacy `app` schema entirely.
+  if (isWorkbenchApp(cliConfig?.app)) {
+    return parseWorkbenchCliConfig(cliConfig, dirname(configPath))
+  }
+
   const {data, error, success} = cliConfigSchema.safeParse(cliConfig)
   if (!success) {
     debug(`Invalid CLI config: ${error.message}`)
diff --git a/packages/@sanity/cli-core/src/config/cli/getCliConfigSync.ts b/packages/@sanity/cli-core/src/config/cli/getCliConfigSync.ts
index d5f02e1a5..967c12f31 100644
--- a/packages/@sanity/cli-core/src/config/cli/getCliConfigSync.ts
+++ b/packages/@sanity/cli-core/src/config/cli/getCliConfigSync.ts
@@ -2,12 +2,14 @@ import {existsSync} from 'node:fs'
 import {createRequire} from 'node:module'
 import {join} from 'node:path'
 
+import {isWorkbenchApp} from '@sanity/federation'
 import {register} from 'tsx/esm/api'
 
 import {NotFoundError} from '../../errors/NotFoundError.js'
 import {tryGetDefaultExport} from '../../util/tryGetDefaultExport.js'
 import {cliConfigSchema} from './schemas.js'
 import {type CliConfig} from './types/cliConfig.js'
+import {parseWorkbenchCliConfig} from './workbenchApp.js'
 
 /**
  * Get the CLI config for a project synchronously, given the root path.
@@ -47,6 +49,12 @@ export function getCliConfigSync(rootPath: string): CliConfig {
     unregister()
   }
 
+  // Branch as early as possible: a branded `unstable_defineApp(...)` opts into
+  // workbench behavior, so its `app` skips the legacy `app` schema entirely.
+  if (isWorkbenchApp(cliConfig?.app)) {
+    return parseWorkbenchCliConfig(cliConfig, rootPath)
+  }
+
   const {data, error, success} = cliConfigSchema.safeParse(cliConfig)
   if (!success) {
     throw new Error(`Invalid CLI config: ${error.message}`)
diff --git a/packages/@sanity/cli-core/src/config/cli/schemas.ts b/packages/@sanity/cli-core/src/config/cli/schemas.ts
index bf2b9d43e..f9bfb031a 100644
--- a/packages/@sanity/cli-core/src/config/cli/schemas.ts
+++ b/packages/@sanity/cli-core/src/config/cli/schemas.ts
@@ -34,12 +34,6 @@ export const cliConfigSchema = z.object({
     }),
   ),
 
-  federation: z.optional(
-    z.object({
-      enabled: z.boolean(),
-    }),
-  ),
-
   graphql: z.optional(
     z.array(
       z.object({
diff --git a/packages/@sanity/cli-core/src/config/cli/types/cliConfig.ts b/packages/@sanity/cli-core/src/config/cli/types/cliConfig.ts
index 3a76c4389..b823c078e 100644
--- a/packages/@sanity/cli-core/src/config/cli/types/cliConfig.ts
+++ b/packages/@sanity/cli-core/src/config/cli/types/cliConfig.ts
@@ -59,14 +59,6 @@ export interface CliConfig {
     autoUpdates?: boolean
   }
 
-  /**
-   * Enable federated builds & dev environments for your studio or application.
-   * @experimental
-   */
-  federation?: {
-    enabled: boolean
-  }
-
   /** Define the GraphQL APIs that the CLI can deploy and interact with */
   graphql?: Array<{
     filterSuffix?: string
diff --git a/packages/@sanity/cli-core/src/config/cli/workbenchApp.ts b/packages/@sanity/cli-core/src/config/cli/workbenchApp.ts
new file mode 100644
index 000000000..29e26f41d
--- /dev/null
+++ b/packages/@sanity/cli-core/src/config/cli/workbenchApp.ts
@@ -0,0 +1,83 @@
+import {existsSync} from 'node:fs'
+import {join} from 'node:path'
+
+import {cliConfigSchema} from './schemas.js'
+import {type CliConfig} from './types/cliConfig.js'
+
+const STUDIO_CONFIG_FILES = [
+  'sanity.config.ts',
+  'sanity.config.tsx',
+  'sanity.config.js',
+  'sanity.config.jsx',
+  'sanity.config.mjs',
+  'sanity.config.cjs',
+]
+
+// Mirrors `@sanity/federation`'s `ApplicationType` enum. `unstable_defineApp`
+// is a pure identity wrapper that doesn't validate its input, so the loader is
+// the first place an explicit `applicationType` can be checked.
+const APPLICATION_TYPES = [
+  'coreApp',
+  'studio',
+  'canvas',
+  'dashboard',
+  'media-library',
+  'system',
+] as const
+type ApplicationType = (typeof APPLICATION_TYPES)[number]
+
+function isApplicationType(value: unknown): value is ApplicationType {
+  return typeof value === 'string' && (APPLICATION_TYPES as readonly string[]).includes(value)
+}
+
+/**
+ * Infer the application type for a workbench app when `unstable_defineApp`
+ * didn't set one: a project with a `sanity.config.*` is a studio, otherwise a
+ * core (SDK) app. An explicit `applicationType` always wins.
+ */
+function detectApplicationType(projectDir: string): ApplicationType {
+  return STUDIO_CONFIG_FILES.some((file) => existsSync(join(projectDir, file)))
+    ? 'studio'
+    : 'coreApp'
+}
+
+/**
+ * Parse a config whose `app` is a branded `unstable_defineApp(...)` result.
+ * The branded `app` bypasses the legacy `app` object schema (which would strip
+ * its identity fields and the brand symbol); every other field is still
+ * validated. The brand is preserved so downstream code relies on the
+ * `isWorkbenchApp` identity (from `@sanity/federation`) instead of a flag.
+ *
+ * Resolves `applicationType` here — as early as possible — so studio-vs-app
+ * classification is settled once and read off the app everywhere else. The
+ * resolved value lands on a clone, never the caller's object, so re-parsing the
+ * same `app` for a different directory can't inherit a stale inference.
+ */
+export function parseWorkbenchCliConfig(cliConfig: unknown, projectDir: string): CliConfig {
+  const {app, ...rest} = cliConfig as Record<string, unknown> & {
+    app: Record<string, unknown> & {applicationType?: string}
+  }
+  const {data, error, success} = cliConfigSchema.safeParse(rest)
+  if (!success) {
+    throw new Error(`Invalid CLI config: ${error.message}`, {cause: error})
+  }
+
+  const explicit = app.applicationType
+  if (explicit !== undefined && !isApplicationType(explicit)) {
+    throw new Error(
+      `Invalid \`applicationType\` "${explicit}" in \`unstable_defineApp\` — expected one of: ${APPLICATION_TYPES.join(', ')}`,
+    )
+  }
+  const applicationType = explicit ?? detectApplicationType(projectDir)
+
+  // Clone the branded app rather than mutating the caller's object. Copying own
+  // property descriptors carries over the non-enumerable `unstable_defineApp`
+  // brand, which a spread would drop.
+  const resolvedApp = Object.defineProperties({}, Object.getOwnPropertyDescriptors(app)) as Record<
+    string,
+    unknown
+  >
+  resolvedApp.applicationType = applicationType
+
+  return {...data, app: resolvedApp} as CliConfig
+}
diff --git a/packages/@sanity/cli-e2e/__tests__/init/init.app.test.ts b/packages/@sanity/cli-e2e/__tests__/init/init.app.test.ts
index 601e8de78..15c24928f 100644
--- a/packages/@sanity/cli-e2e/__tests__/init/init.app.test.ts
+++ b/packages/@sanity/cli-e2e/__tests__/init/init.app.test.ts
@@ -100,7 +100,6 @@ describe('sanity init - app', {timeout: 120_000}, () => {
         tmp.path,
         '--no-git',
         '--no-mcp',
-        '--no-federation',
       ],
       interactive: true,
     })
diff --git a/packages/@sanity/cli-e2e/__tests__/init/init.studio-interactive.test.ts b/packages/@sanity/cli-e2e/__tests__/init/init.studio-interactive.test.ts
index c8999164a..a8425574b 100644
--- a/packages/@sanity/cli-e2e/__tests__/init/init.studio-interactive.test.ts
+++ b/packages/@sanity/cli-e2e/__tests__/init/init.studio-interactive.test.ts
@@ -60,7 +60,6 @@ describe('sanity init - studio (interactive)', {timeout: 120_000}, () => {
         'pnpm',
         '--no-mcp',
         '--no-git',
-        '--no-federation',
       ],
       interactive: true,
     })
@@ -91,7 +90,6 @@ describe('sanity init - studio (interactive)', {timeout: 120_000}, () => {
         tmp.path,
         '--no-mcp',
         '--no-git',
-        '--no-federation',
       ],
       interactive: true,
     })
@@ -131,7 +129,6 @@ describe('sanity init - studio (interactive)', {timeout: 120_000}, () => {
         '--typescript',
         '--no-mcp',
         '--no-git',
-        '--no-federation',
       ],
       interactive: true,
     })
@@ -162,7 +159,6 @@ describe('sanity init - studio (interactive)', {timeout: 120_000}, () => {
         '--package-manager',
         'pnpm',
         '--no-git',
-        '--no-federation',
       ],
       interactive: true,
     })
@@ -195,7 +191,6 @@ describe('sanity init - studio (interactive)', {timeout: 120_000}, () => {
         '--package-manager',
         'pnpm',
         '--no-git',
-        '--no-federation',
       ],
       interactive: true,
     })
diff --git a/packages/@sanity/cli/package.json b/packages/@sanity/cli/package.json
index 5846350c3..268ef7254 100644
--- a/packages/@sanity/cli/package.json
+++ b/packages/@sanity/cli/package.json
@@ -80,7 +80,7 @@
     "@sanity/codegen": "catalog:",
     "@sanity/descriptors": "^1.3.0",
     "@sanity/export": "^6.1.0",
-    "@sanity/federation": "0.1.0-alpha.8",
+    "@sanity/federation": "0.1.0-alpha.9",
     "@sanity/generate-help-url": "^4.0.0",
     "@sanity/id-utils": "^1.0.0",
     "@sanity/import": "^6.0.1",
diff --git a/packages/@sanity/cli/src/__tests__/exports.test.ts b/packages/@sanity/cli/src/__tests__/exports.test.ts
index b02f3a377..0879a0a1a 100644
--- a/packages/@sanity/cli/src/__tests__/exports.test.ts
+++ b/packages/@sanity/cli/src/__tests__/exports.test.ts
@@ -144,12 +144,17 @@ async function getSanityPackageTypeExports() {
   return exportedTypes
 }
 
+// Value exports intentionally added in v6 that the v5 CLI didn't have.
+const NEW_EXPORTS = new Set(['unstable_defineApp'])
+
 test('should match exports of the current cli package', async () => {
   const oldCliExports = await getSanityPackageExports()
 
-  expect(Object.keys(newExports).toSorted()).toStrictEqual(
-    Object.keys(oldCliExports.default).toSorted(),
-  )
+  expect(
+    Object.keys(newExports)
+      .filter((name) => !NEW_EXPORTS.has(name))
+      .toSorted(),
+  ).toStrictEqual(Object.keys(oldCliExports.default).toSorted())
 })
 
 test('should include type exports of the old (v5) cli package', async () => {
diff --git a/packages/@sanity/cli/src/actions/build/__tests__/buildStaticFiles.test.ts b/packages/@sanity/cli/src/actions/build/__tests__/buildStaticFiles.test.ts
index b1c3e1a50..cd659c5da 100644
--- a/packages/@sanity/cli/src/actions/build/__tests__/buildStaticFiles.test.ts
+++ b/packages/@sanity/cli/src/actions/build/__tests__/buildStaticFiles.test.ts
@@ -72,7 +72,7 @@ describe('buildStaticFiles', () => {
       await buildStaticFiles({
         basePath: '/',
         cwd,
-        federation: {enabled: true},
+        isWorkbench: true,
         outputDir,
         vite: userVite,
       })
@@ -99,7 +99,7 @@ describe('buildStaticFiles', () => {
       await buildStaticFiles({
         basePath: '/',
         cwd,
-        federation: {enabled: true},
+        isWorkbench: true,
         outputDir,
       })
 
@@ -111,7 +111,7 @@ describe('buildStaticFiles', () => {
       await buildStaticFiles({
         basePath: '/',
         cwd,
-        federation: {enabled: true},
+        isWorkbench: true,
         outputDir,
       })
 
diff --git a/packages/@sanity/cli/src/actions/build/__tests__/getViteConfig.test.ts b/packages/@sanity/cli/src/actions/build/__tests__/getViteConfig.test.ts
index 8eb31a53e..eaea529e0 100644
--- a/packages/@sanity/cli/src/actions/build/__tests__/getViteConfig.test.ts
+++ b/packages/@sanity/cli/src/actions/build/__tests__/getViteConfig.test.ts
@@ -486,7 +486,7 @@ describe('#getViteConfig', () => {
     const options = {
       cwd: mockTestCwd,
       entries: {relativeConfigLocation: '../../sanity.config.ts', relativeEntry: '../../src/App'},
-      federation: {enabled: true},
+      isWorkbench: true,
       mode: 'development' as const,
       reactCompiler: undefined,
     }
@@ -510,7 +510,7 @@ describe('#getViteConfig', () => {
     const options = {
       cwd: mockTestCwd,
       entries: mockEntries,
-      federation: {enabled: false},
+      isWorkbench: false,
       mode: 'development' as const,
       reactCompiler: undefined,
     }
diff --git a/packages/@sanity/cli/src/actions/build/buildApp.ts b/packages/@sanity/cli/src/actions/build/buildApp.ts
index 09ef92495..11d721db1 100644
--- a/packages/@sanity/cli/src/actions/build/buildApp.ts
+++ b/packages/@sanity/cli/src/actions/build/buildApp.ts
@@ -13,6 +13,7 @@ import {
   UserViteConfig,
 } from '@sanity/cli-core'
 import {confirm, logSymbols, spinner, type SpinnerInstance} from '@sanity/cli-core/ux'
+import {isWorkbenchApp} from '@sanity/federation'
 import {parse as semverParse} from 'semver'
 
 import {AppBuildTrace} from '../../telemetry/build.telemetry.js'
@@ -35,7 +36,7 @@ interface InternalBuildOptions {
   calledFromDeploy: boolean | undefined
   determineBasePath: () => string
   entry: string | undefined
-  federation: CliConfig['federation']
+  isWorkbench: boolean
   minify: boolean
   outDir: string | undefined
   output: Output
@@ -63,7 +64,7 @@ export async function buildApp(options: BuildOptions): Promise<void> {
     calledFromDeploy: options.calledFromDeploy,
     determineBasePath: () => determineBasePath(cliConfig, 'app', output),
     entry: cliConfig && 'app' in cliConfig ? cliConfig.app?.entry : undefined,
-    federation: cliConfig.federation,
+    isWorkbench: isWorkbenchApp(cliConfig && 'app' in cliConfig ? cliConfig.app : undefined),
     minify: flags.minify,
     outDir,
     output,
@@ -206,7 +207,7 @@ async function internalBuildApp(options: InternalBuildOptions): Promise<void> {
 
   let importMap: {imports?: Record<string, string>} | undefined
 
-  if (autoUpdatesEnabled && !options.federation?.enabled) {
+  if (autoUpdatesEnabled && !options.isWorkbench) {
     importMap = {
       imports: {
         ...(await buildVendorDependencies({basePath, cwd: workDir, isApp: true, outputDir})),
@@ -224,9 +225,9 @@ async function internalBuildApp(options: InternalBuildOptions): Promise<void> {
       basePath,
       cwd: workDir,
       entry: options.entry,
-      federation: options.federation,
       importMap,
       isApp: true,
+      isWorkbench: options.isWorkbench,
       minify: options.minify,
       outputDir,
       reactCompiler: options.reactCompiler,
diff --git a/packages/@sanity/cli/src/actions/build/buildStaticFiles.ts b/packages/@sanity/cli/src/actions/build/buildStaticFiles.ts
index e6ac88c8d..9c247c491 100644
--- a/packages/@sanity/cli/src/actions/build/buildStaticFiles.ts
+++ b/packages/@sanity/cli/src/actions/build/buildStaticFiles.ts
@@ -19,7 +19,7 @@ export interface ChunkStats {
   name: string
 }
 
-interface StaticBuildOptions extends Pick<CliConfig, 'federation'> {
+interface StaticBuildOptions {
   basePath: string
   cwd: string
   outputDir: string
@@ -29,6 +29,8 @@ interface StaticBuildOptions extends Pick<CliConfig, 'federation'> {
   entry?: string
   importMap?: {imports?: Record<string, string>}
   isApp?: boolean
+  /** Workbench app (opted in via `unstable_defineApp`) — drives the federation build. */
+  isWorkbench?: boolean
   minify?: boolean
   profile?: boolean
   reactCompiler?: ReactCompilerConfig
@@ -51,9 +53,9 @@ export async function buildStaticFiles(
     basePath,
     cwd,
     entry,
-    federation,
     importMap,
     isApp,
+    isWorkbench,
     minify = true,
     outputDir,
     reactCompiler,
@@ -68,7 +70,7 @@ export async function buildStaticFiles(
    * (remote-entry, mf-manifest) — skip client-specific steps like
    * runtime generation, static file copies, and favicons.
    */
-  if (federation?.enabled) {
+  if (isWorkbench) {
     buildDebug('Resolving entries for federation build')
     const entries = await resolveEntries({cwd, entry, isApp})
 
@@ -77,8 +79,8 @@ export async function buildStaticFiles(
       basePath,
       cwd,
       entries,
-      federation,
       isApp,
+      isWorkbench,
       minify,
       mode,
       outputDir,
@@ -123,9 +125,9 @@ export async function buildStaticFiles(
     basePath,
     cwd,
     entries,
-    federation,
     importMap,
     isApp,
+    isWorkbench,
     minify,
     mode,
     outputDir,
diff --git a/packages/@sanity/cli/src/actions/build/buildStudio.ts b/packages/@sanity/cli/src/actions/build/buildStudio.ts
index 66a665dfe..8369dae7e 100644
--- a/packages/@sanity/cli/src/actions/build/buildStudio.ts
+++ b/packages/@sanity/cli/src/actions/build/buildStudio.ts
@@ -13,6 +13,7 @@ import {
   UserViteConfig,
 } from '@sanity/cli-core'
 import {confirm, logSymbols, select, spinner, type SpinnerInstance} from '@sanity/cli-core/ux'
+import {isWorkbenchApp} from '@sanity/federation'
 import {parse as semverParse} from 'semver'
 
 import {StudioBuildTrace} from '../../telemetry/build.telemetry.js'
@@ -37,8 +38,8 @@ interface InternalBuildOptions {
   autoUpdatesEnabled: boolean
   calledFromDeploy: boolean | undefined
   determineBasePath: () => string
-  federation: CliConfig['federation']
   isApp: boolean
+  isWorkbench: boolean
   minify: boolean
   outDir: string | undefined
   output: Output
@@ -78,8 +79,8 @@ export async function buildStudio(options: BuildOptions): Promise<void> {
     autoUpdatesEnabled: options.autoUpdatesEnabled,
     calledFromDeploy,
     determineBasePath: () => determineBasePath(cliConfig, 'studio', output),
-    federation: cliConfig.federation,
     isApp: determineIsApp(cliConfig),
+    isWorkbench: isWorkbenchApp(cliConfig?.app),
     minify: Boolean(flags.minify),
     outDir,
     output,
@@ -276,7 +277,7 @@ async function internalBuildStudio(options: InternalBuildOptions): Promise<void>
 
   let importMap
 
-  if (autoUpdatesEnabled && !options.federation?.enabled) {
+  if (autoUpdatesEnabled && !options.isWorkbench) {
     importMap = {
       imports: {
         ...(await buildVendorDependencies({basePath, cwd: workDir, isApp: false, outputDir})),
@@ -292,8 +293,8 @@ async function internalBuildStudio(options: InternalBuildOptions): Promise<void>
       autoUpdatesCssUrls: autoUpdatesCssUrls.length > 0 ? autoUpdatesCssUrls : undefined,
       basePath,
       cwd: workDir,
-      federation: options.federation,
       importMap,
+      isWorkbench: options.isWorkbench,
       minify,
       outputDir,
       reactCompiler,
diff --git a/packages/@sanity/cli/src/actions/build/getViteConfig.ts b/packages/@sanity/cli/src/actions/build/getViteConfig.ts
index cc505aabf..75c515ac0 100644
--- a/packages/@sanity/cli/src/actions/build/getViteConfig.ts
+++ b/packages/@sanity/cli/src/actions/build/getViteConfig.ts
@@ -34,7 +34,7 @@ import {sanityBuildEntries} from './vite/plugin-sanity-build-entries.js'
 import {sanityFaviconsPlugin} from './vite/plugin-sanity-favicons.js'
 import {sanityRuntimeRewritePlugin} from './vite/plugin-sanity-runtime-rewrite.js'
 
-interface ViteOptions extends Pick<CliConfig, 'federation' | 'schemaExtraction' | 'typegen'> {
+interface ViteOptions extends Pick<CliConfig, 'schemaExtraction' | 'typegen'> {
   /**
    * Root path of the studio/sanity app
    */
@@ -72,6 +72,12 @@ interface ViteOptions extends Pick<CliConfig, 'federation' | 'schemaExtraction'
 
   isApp?: boolean
 
+  /**
+   * Whether this is a workbench app (opted in via `unstable_defineApp`). Drives
+   * the module-federation build — replaces the old `federation.enabled` flag.
+   */
+  isWorkbench?: boolean
+
   /**
    * Whether or not to minify the output (only used in `mode: 'production'`)
    */
@@ -103,9 +109,9 @@ export async function getViteConfig(options: ViteOptions): Promise<InlineConfig>
     basePath: rawBasePath = '/',
     cwd,
     entries,
-    federation,
     importMap,
     isApp,
+    isWorkbench,
     minify,
     mode,
     outputDir,
@@ -197,7 +203,7 @@ export async function getViteConfig(options: ViteOptions): Promise<InlineConfig>
     plugins: [
       // Federation builds only need the federation plugin — skip client-specific
       // plugins (react, favicons, runtime rewrite, build entries, schema, typegen)
-      ...(federation?.enabled
+      ...(isWorkbench
         ? [
             ...sharedPlugins,
             viteFederation({
@@ -251,7 +257,7 @@ export async function getViteConfig(options: ViteOptions): Promise<InlineConfig>
 
   // Federation builds don't produce a client bundle — the federation
   // plugin configures its own environment and build entry point.
-  if (mode === 'production' && !federation?.enabled) {
+  if (mode === 'production' && !isWorkbench) {
     viteConfig.build = {
       ...viteConfig.build,
       assetsDir: 'static',
diff --git a/packages/@sanity/cli/src/actions/dev/__tests__/devAction.test.ts b/packages/@sanity/cli/src/actions/dev/__tests__/devAction.test.ts
index e9fbcec5f..e925990e9 100644
--- a/packages/@sanity/cli/src/actions/dev/__tests__/devAction.test.ts
+++ b/packages/@sanity/cli/src/actions/dev/__tests__/devAction.test.ts
@@ -1,7 +1,7 @@
 import {afterEach, beforeEach, describe, expect, test, vi} from 'vitest'
 
 import {devAction} from '../devAction.js'
-import {createBaseDevOptions, createMockOutput} from './testHelpers.js'
+import {createBaseDevOptions, createMockOutput, workbenchCliConfig} from './testHelpers.js'
 
 const mockStartWorkbenchDevServer = vi.hoisted(() => vi.fn())
 const mockStartAppDevServer = vi.hoisted(() => vi.fn())
@@ -136,7 +136,7 @@ describe('devAction', () => {
     test('starts federation registration when federation is enabled', async () => {
       mockStartStudioDevServer.mockResolvedValue(mockServer({port: 3334}))
 
-      await devAction(createBaseDevOptions({cliConfig: {federation: {enabled: true}}}))
+      await devAction(createBaseDevOptions({cliConfig: workbenchCliConfig()}))
 
       expect(mockStartFederationRegistration).toHaveBeenCalledWith(
         expect.objectContaining({
@@ -157,7 +157,7 @@ describe('devAction', () => {
     test('passes isApp: true for app mode', async () => {
       mockStartAppDevServer.mockResolvedValue(mockServer({port: 3334}))
 
-      await devAction(createBaseDevOptions({cliConfig: {federation: {enabled: true}}, isApp: true}))
+      await devAction(createBaseDevOptions({cliConfig: workbenchCliConfig(), isApp: true}))
 
       expect(mockStartFederationRegistration).toHaveBeenCalledWith(
         expect.objectContaining({isApp: true}),
@@ -168,7 +168,7 @@ describe('devAction', () => {
       const server = mockServer({port: 3334})
       mockStartStudioDevServer.mockResolvedValue(server)
 
-      await devAction(createBaseDevOptions({cliConfig: {federation: {enabled: true}}}))
+      await devAction(createBaseDevOptions({cliConfig: workbenchCliConfig()}))
 
       expect(mockStartFederationRegistration).toHaveBeenCalledWith(
         expect.objectContaining({server: server.server}),
@@ -180,9 +180,7 @@ describe('devAction', () => {
       mockStartFederationRegistration.mockResolvedValue({close: mockFederationClose})
       mockStartStudioDevServer.mockResolvedValue(mockServer({port: 3334}))
 
-      const result = await devAction(
-        createBaseDevOptions({cliConfig: {federation: {enabled: true}}}),
-      )
+      const result = await devAction(createBaseDevOptions({cliConfig: workbenchCliConfig()}))
 
       await result.close()
       expect(mockFederationClose).toHaveBeenCalled()
diff --git a/packages/@sanity/cli/src/actions/dev/__tests__/startFederationRegistration.test.ts b/packages/@sanity/cli/src/actions/dev/__tests__/startFederationRegistration.test.ts
index b174b3fc0..13036ade0 100644
--- a/packages/@sanity/cli/src/actions/dev/__tests__/startFederationRegistration.test.ts
+++ b/packages/@sanity/cli/src/actions/dev/__tests__/startFederationRegistration.test.ts
@@ -1,7 +1,7 @@
 import {afterEach, beforeEach, describe, expect, test, vi} from 'vitest'
 
 import {startFederationRegistration} from '../startFederationRegistration.js'
-import {createMockOutput} from './testHelpers.js'
+import {createMockOutput, workbenchApp, workbenchCliConfig} from './testHelpers.js'
 
 const mockRegisterDevServer = vi.hoisted(() => vi.fn())
 const mockStartDevManifestWatcher = vi.hoisted(() => vi.fn())
@@ -48,7 +48,7 @@ describe('startFederationRegistration', () => {
 
   test('registers studio in registry', async () => {
     await startFederationRegistration({
-      cliConfig: {federation: {enabled: true}},
+      cliConfig: workbenchCliConfig(),
       isApp: false,
       output: createMockOutput(),
       server: mockServer({port: 3334}) as any,
@@ -68,7 +68,7 @@ describe('startFederationRegistration', () => {
     mockGetAppId.mockReturnValue('app-abc')
 
     await startFederationRegistration({
-      cliConfig: {deployment: {appId: 'app-abc'}, federation: {enabled: true}},
+      cliConfig: {app: workbenchApp(), deployment: {appId: 'app-abc'}},
       isApp: false,
       output: createMockOutput(),
       server: mockServer({port: 3334}) as any,
@@ -80,7 +80,7 @@ describe('startFederationRegistration', () => {
 
   test('forwards api.projectId to registerDevServer', async () => {
     await startFederationRegistration({
-      cliConfig: {api: {projectId: 'x1g7jygt'}, federation: {enabled: true}},
+      cliConfig: {api: {projectId: 'x1g7jygt'}, app: workbenchApp()},
       isApp: false,
       output: createMockOutput(),
       server: mockServer({port: 3334}) as any,
@@ -94,7 +94,7 @@ describe('startFederationRegistration', () => {
 
   test('omits projectId when api.projectId is not configured', async () => {
     await startFederationRegistration({
-      cliConfig: {federation: {enabled: true}},
+      cliConfig: workbenchCliConfig(),
       isApp: false,
       output: createMockOutput(),
       server: mockServer({port: 3334}) as any,
@@ -109,7 +109,7 @@ describe('startFederationRegistration', () => {
     const output = createMockOutput()
 
     await startFederationRegistration({
-      cliConfig: {app: {id: 'legacy-app'}, federation: {enabled: true}},
+      cliConfig: {app: workbenchApp({id: 'legacy-app'})},
       isApp: false,
       output,
       server: mockServer({port: 3334}) as any,
@@ -121,7 +121,7 @@ describe('startFederationRegistration', () => {
 
   test('registers without icon/title — they are derived from the inlined manifest', async () => {
     await startFederationRegistration({
-      cliConfig: {federation: {enabled: true}},
+      cliConfig: workbenchCliConfig(),
       isApp: false,
       output: createMockOutput(),
       server: mockServer({port: 3334}) as any,
@@ -135,7 +135,7 @@ describe('startFederationRegistration', () => {
 
   test('registers app under the host applied by the vite dev server', async () => {
     await startFederationRegistration({
-      cliConfig: {federation: {enabled: true}},
+      cliConfig: workbenchCliConfig(),
       isApp: false,
       output: createMockOutput(),
       server: mockServer({host: 'mydev.local', port: 3334}) as any,
@@ -149,7 +149,7 @@ describe('startFederationRegistration', () => {
 
   test('falls back to localhost when the vite server host is not a string', async () => {
     await startFederationRegistration({
-      cliConfig: {federation: {enabled: true}},
+      cliConfig: workbenchCliConfig(),
       isApp: false,
       output: createMockOutput(),
       server: mockServer({host: true, port: 3334}) as any,
@@ -161,7 +161,7 @@ describe('startFederationRegistration', () => {
 
   test('registers app type when isApp is true', async () => {
     await startFederationRegistration({
-      cliConfig: {federation: {enabled: true}},
+      cliConfig: workbenchCliConfig(),
       isApp: true,
       output: createMockOutput(),
       server: mockServer({port: 3334}) as any,
@@ -173,7 +173,7 @@ describe('startFederationRegistration', () => {
 
   test('starts the manifest watcher for studios', async () => {
     await startFederationRegistration({
-      cliConfig: {federation: {enabled: true}},
+      cliConfig: workbenchCliConfig(),
       isApp: false,
       output: createMockOutput(),
       server: mockServer({port: 3334}) as any,
@@ -187,7 +187,7 @@ describe('startFederationRegistration', () => {
 
   test('starts the manifest watcher for core apps', async () => {
     await startFederationRegistration({
-      cliConfig: {federation: {enabled: true}},
+      cliConfig: workbenchCliConfig(),
       isApp: true,
       output: createMockOutput(),
       server: mockServer({port: 3334}) as any,
@@ -204,7 +204,7 @@ describe('startFederationRegistration', () => {
     mockExtractCoreAppManifest.mockResolvedValue(appManifest)
 
     await startFederationRegistration({
-      cliConfig: {federation: {enabled: true}},
+      cliConfig: workbenchCliConfig(),
       isApp: true,
       output: createMockOutput(),
       server: mockServer({port: 3334}) as any,
@@ -220,7 +220,7 @@ describe('startFederationRegistration', () => {
 
   test('wires extractStudioManifest into the studio watcher', async () => {
     await startFederationRegistration({
-      cliConfig: {federation: {enabled: true}},
+      cliConfig: workbenchCliConfig(),
       isApp: false,
       output: createMockOutput(),
       server: mockServer({port: 3334}) as any,
@@ -236,7 +236,7 @@ describe('startFederationRegistration', () => {
     mockRegisterDevServer.mockReturnValue({release: mockCleanup, update: vi.fn()})
 
     const result = await startFederationRegistration({
-      cliConfig: {federation: {enabled: true}},
+      cliConfig: workbenchCliConfig(),
       isApp: false,
       output: createMockOutput(),
       server: mockServer({port: 3334}) as any,
@@ -255,7 +255,7 @@ describe('startFederationRegistration', () => {
 
     await expect(
       startFederationRegistration({
-        cliConfig: {federation: {enabled: true}},
+        cliConfig: workbenchCliConfig(),
         isApp: false,
         output: createMockOutput(),
         server: mockServer({port: 3334}) as any,
@@ -270,7 +270,7 @@ describe('startFederationRegistration', () => {
 
     await expect(
       startFederationRegistration({
-        cliConfig: {federation: {enabled: true}},
+        cliConfig: workbenchCliConfig(),
         isApp: false,
         output: createMockOutput(),
         server: mockServer({port: 3334}) as any,
@@ -288,9 +288,8 @@ describe('startFederationRegistration', () => {
 
     await startFederationRegistration({
       cliConfig: {
-        app: {id: 'legacy-app'},
+        app: workbenchApp({id: 'legacy-app'}),
         deployment: {appId: 'new-app'},
-        federation: {enabled: true},
       },
       isApp: false,
       output,
diff --git a/packages/@sanity/cli/src/actions/dev/__tests__/startWorkbenchDevServer.test.ts b/packages/@sanity/cli/src/actions/dev/__tests__/startWorkbenchDevServer.test.ts
index 5f60fd2d1..71d6d1e28 100644
--- a/packages/@sanity/cli/src/actions/dev/__tests__/startWorkbenchDevServer.test.ts
+++ b/packages/@sanity/cli/src/actions/dev/__tests__/startWorkbenchDevServer.test.ts
@@ -1,7 +1,13 @@
 import {afterEach, beforeEach, describe, expect, test, vi} from 'vitest'
 
 import {startWorkbenchDevServer} from '../startWorkbenchDevServer.js'
-import {createDevOptions, createMockOutput} from './testHelpers.js'
+import {
+  createDevOptions,
+  createMockOutput,
+  studioWorkbenchApp,
+  workbenchApp,
+  workbenchCliConfig,
+} from './testHelpers.js'
 
 const mockResolveLocalPackage = vi.hoisted(() => vi.fn())
 const mockCreateServer = vi.hoisted(() => vi.fn())
@@ -69,9 +75,7 @@ describe('startWorkbenchDevServer', () => {
     })
 
     test('skips workbench when federation is explicitly disabled', async () => {
-      const result = await startWorkbenchDevServer(
-        createDevOptions({cliConfig: {federation: {enabled: false}}}),
-      )
+      const result = await startWorkbenchDevServer(createDevOptions({cliConfig: {}}))
 
       expect(result.workbenchAvailable).toBe(false)
       expect(result.close).toBeTypeOf('function')
@@ -93,7 +97,7 @@ describe('startWorkbenchDevServer', () => {
       mockResolveLocalPackage.mockRejectedValue(new Error('Cannot find package'))
 
       const result = await startWorkbenchDevServer(
-        createDevOptions({cliConfig: {federation: {enabled: true}}}),
+        createDevOptions({cliConfig: workbenchCliConfig()}),
       )
 
       expect(result.workbenchAvailable).toBe(false)
@@ -106,7 +110,7 @@ describe('startWorkbenchDevServer', () => {
 
       const result = await startWorkbenchDevServer(
         createDevOptions({
-          cliConfig: {federation: {enabled: true}},
+          cliConfig: workbenchCliConfig(),
           httpHost: '0.0.0.0',
           httpPort: 4000,
         }),
@@ -119,8 +123,7 @@ describe('startWorkbenchDevServer', () => {
 
   describe('successful startup', () => {
     const federationConfig = {
-      app: {organizationId: 'org-test'},
-      federation: {enabled: true},
+      app: workbenchApp({organizationId: 'org-test'}),
     } as const
 
     test('returns workbenchAvailable: true and close when server starts', async () => {
@@ -179,7 +182,7 @@ describe('startWorkbenchDevServer', () => {
 
       await startWorkbenchDevServer(
         createDevOptions({
-          cliConfig: {app: {organizationId: 'org-123'}, federation: {enabled: true}},
+          cliConfig: {app: workbenchApp({organizationId: 'org-123'})},
         }),
       )
 
@@ -195,7 +198,10 @@ describe('startWorkbenchDevServer', () => {
 
       await startWorkbenchDevServer(
         createDevOptions({
-          cliConfig: {api: {projectId: 'proj-123'}, federation: {enabled: true}},
+          cliConfig: {
+            api: {projectId: 'proj-123'},
+            app: studioWorkbenchApp({organizationId: undefined}),
+          },
         }),
       )
 
@@ -213,8 +219,7 @@ describe('startWorkbenchDevServer', () => {
         createDevOptions({
           cliConfig: {
             api: {projectId: 'proj-123'},
-            app: {organizationId: 'org-explicit'},
-            federation: {enabled: true},
+            app: workbenchApp({organizationId: 'org-explicit'}),
           },
         }),
       )
@@ -230,7 +235,9 @@ describe('startWorkbenchDevServer', () => {
       mockCreateServer.mockResolvedValue(createMockServer())
 
       await expect(
-        startWorkbenchDevServer(createDevOptions({cliConfig: {federation: {enabled: true}}})),
+        startWorkbenchDevServer(
+          createDevOptions({cliConfig: {app: workbenchApp({organizationId: undefined})}}),
+        ),
       ).rejects.toThrow(/Unable to determine organization ID/)
     })
 
@@ -242,7 +249,10 @@ describe('startWorkbenchDevServer', () => {
       await expect(
         startWorkbenchDevServer(
           createDevOptions({
-            cliConfig: {api: {projectId: 'proj-123'}, federation: {enabled: true}},
+            cliConfig: {
+              api: {projectId: 'proj-123'},
+              app: studioWorkbenchApp({organizationId: undefined}),
+            },
           }),
         ),
       ).rejects.toThrow(/Unable to determine organization ID/)
@@ -268,8 +278,7 @@ describe('startWorkbenchDevServer', () => {
 
   describe('remote-preload Link header', () => {
     const federationConfig = {
-      app: {organizationId: 'org-test'},
-      federation: {enabled: true},
+      app: workbenchApp({organizationId: 'org-test'}),
     } as const
 
     function getMiddleware(): (req: {url?: string}, res: ResLike, next: () => void) => void {
@@ -422,8 +431,7 @@ describe('startWorkbenchDevServer', () => {
       await startWorkbenchDevServer(
         createDevOptions({
           cliConfig: {
-            app: {organizationId: 'org-test'},
-            federation: {enabled: true},
+            app: workbenchApp({organizationId: 'org-test'}),
             reactStrictMode: false,
           },
         }),
@@ -442,8 +450,7 @@ describe('startWorkbenchDevServer', () => {
       await startWorkbenchDevServer(
         createDevOptions({
           cliConfig: {
-            app: {organizationId: 'org-test'},
-            federation: {enabled: true},
+            app: workbenchApp({organizationId: 'org-test'}),
             reactStrictMode: true,
           },
         }),
@@ -461,8 +468,7 @@ describe('startWorkbenchDevServer', () => {
       await startWorkbenchDevServer(
         createDevOptions({
           cliConfig: {
-            app: {organizationId: 'org-test'},
-            federation: {enabled: true},
+            app: workbenchApp({organizationId: 'org-test'}),
             reactStrictMode: true,
           },
         }),
@@ -476,8 +482,7 @@ describe('startWorkbenchDevServer', () => {
 
   describe('server startup failure', () => {
     const federationConfig = {
-      app: {organizationId: 'org-test'},
-      federation: {enabled: true},
+      app: workbenchApp({organizationId: 'org-test'}),
     } as const
 
     test('warns and returns without close when listen() throws', async () => {
@@ -510,8 +515,7 @@ describe('startWorkbenchDevServer', () => {
 
   describe('singleton detection', () => {
     const federationConfig = {
-      app: {organizationId: 'org-test'},
-      federation: {enabled: true},
+      app: workbenchApp({organizationId: 'org-test'}),
     } as const
 
     test('skips starting server when lock is held by another process', async () => {
@@ -544,8 +548,7 @@ describe('startWorkbenchDevServer', () => {
 
   describe('registry integration', () => {
     const federationConfig = {
-      app: {organizationId: 'org-test'},
-      federation: {enabled: true},
+      app: workbenchApp({organizationId: 'org-test'}),
     } as const
 
     test('updates lock with actual port after successful startup', async () => {
diff --git a/packages/@sanity/cli/src/actions/dev/__tests__/testHelpers.ts b/packages/@sanity/cli/src/actions/dev/__tests__/testHelpers.ts
index dcdcba694..e454ffa42 100644
--- a/packages/@sanity/cli/src/actions/dev/__tests__/testHelpers.ts
+++ b/packages/@sanity/cli/src/actions/dev/__tests__/testHelpers.ts
@@ -1,4 +1,5 @@
 import {type CliConfig, type Output} from '@sanity/cli-core'
+import {unstable_defineApp} from '@sanity/federation'
 // eslint-disable-next-line import-x/no-extraneous-dependencies
 import {vi} from 'vitest'
 
@@ -7,6 +8,30 @@ import {type DevActionOptions} from '../types.js'
 
 /** Shared test helpers for dev-action test suites. */
 
+/**
+ * A CliConfig whose `app` is a branded `unstable_defineApp(...)` result — the
+ * workbench opt-in. Replaces the old `federation: {enabled: true}` test signal.
+ */
+export function workbenchApp(overrides: Record<string, unknown> = {}): CliConfig['app'] {
+  return unstable_defineApp({
+    name: 'test-app',
+    organizationId: 'org-123',
+    title: 'Test App',
+    ...overrides,
+  }) as unknown as CliConfig['app']
+}
+
+/** Branded workbench app explicitly typed as a studio. */
+export function studioWorkbenchApp(overrides: Record<string, unknown> = {}): CliConfig['app'] {
+  const app = workbenchApp(overrides)
+  ;(app as {applicationType?: string}).applicationType = 'studio'
+  return app
+}
+
+export function workbenchCliConfig(overrides: Partial<CliConfig> = {}): CliConfig {
+  return {app: workbenchApp(), ...overrides} as CliConfig
+}
+
 export function createMockOutput(): Output {
   return {
     error: vi.fn(),
diff --git a/packages/@sanity/cli/src/actions/dev/devAction.ts b/packages/@sanity/cli/src/actions/dev/devAction.ts
index 427f644c1..2d5ac533d 100644
--- a/packages/@sanity/cli/src/actions/dev/devAction.ts
+++ b/packages/@sanity/cli/src/actions/dev/devAction.ts
@@ -1,5 +1,7 @@
 import {styleText} from 'node:util'
 
+import {isWorkbenchApp} from '@sanity/federation'
+
 import {getSharedServerConfig} from '../../util/getSharedServerConfig.js'
 import {startAppDevServer} from './startAppDevServer.js'
 import {startFederationRegistration} from './startFederationRegistration.js'
@@ -58,7 +60,9 @@ export async function devAction(options: DevActionOptions): Promise<{close: () =
     return {close: closeWorkbenchServer}
   }
 
-  const closeFederation = cliConfig?.federation?.enabled
+  // Workbench is opted into solely by calling `unstable_defineApp` — its
+  // branded identity is the only signal.
+  const closeFederation = isWorkbenchApp(cliConfig?.app)
     ? await startFederationRegistration({
         cliConfig,
         isApp: options.isApp,
diff --git a/packages/@sanity/cli/src/actions/dev/getDevServerConfig.ts b/packages/@sanity/cli/src/actions/dev/getDevServerConfig.ts
index e4c0a09e0..3e769d1f7 100644
--- a/packages/@sanity/cli/src/actions/dev/getDevServerConfig.ts
+++ b/packages/@sanity/cli/src/actions/dev/getDevServerConfig.ts
@@ -2,8 +2,10 @@ import path from 'node:path'
 
 import {type CliConfig, getSanityEnvVar, type Output} from '@sanity/cli-core'
 import {spinner} from '@sanity/cli-core/ux'
+import {isWorkbenchApp} from '@sanity/federation'
 
 import {type DevServerOptions} from '../../server/devServer.js'
+import {determineIsApp} from '../../util/determineIsApp.js'
 import {getSharedServerConfig} from '../../util/getSharedServerConfig.js'
 import {resolveReactStrictMode} from '../../util/resolveReactStrictMode.js'
 import {type DevFlags} from './types.js'
@@ -32,7 +34,7 @@ export function getDevServerConfig({
 
   configSpinner.succeed()
 
-  const isApp = cliConfig && 'app' in cliConfig
+  const isApp = cliConfig ? determineIsApp(cliConfig) : false
   const reactStrictMode = resolveReactStrictMode(cliConfig)
 
   const envBasePath = getSanityEnvVar('BASEPATH', isApp ?? false)
@@ -44,7 +46,7 @@ export function getDevServerConfig({
 
   return {
     ...baseConfig,
-    federation: cliConfig?.federation,
+    isWorkbench: isWorkbenchApp(cliConfig?.app),
     reactCompiler: cliConfig && 'reactCompiler' in cliConfig ? cliConfig.reactCompiler : undefined,
     reactStrictMode,
     staticPath: path.join(workDir, 'static'),
diff --git a/packages/@sanity/cli/src/actions/dev/startWorkbenchDevServer.ts b/packages/@sanity/cli/src/actions/dev/startWorkbenchDevServer.ts
index 92047859a..381de12e7 100644
--- a/packages/@sanity/cli/src/actions/dev/startWorkbenchDevServer.ts
+++ b/packages/@sanity/cli/src/actions/dev/startWorkbenchDevServer.ts
@@ -1,4 +1,5 @@
 import {resolveLocalPackage} from '@sanity/cli-core'
+import {isWorkbenchApp} from '@sanity/federation'
 import viteReact from '@vitejs/plugin-react'
 import {createServer, type InlineConfig, type Plugin} from 'vite'
 import {z} from 'zod/mini'
@@ -53,8 +54,9 @@ export async function startWorkbenchDevServer(
 ): Promise<WorkbenchDevServerResult> {
   const {cliConfig, httpHost, httpPort: workbenchPort, output, workDir} = options
 
-  if (!cliConfig?.federation?.enabled) {
-    devDebug('Federation not enabled, skipping workbench dev server')
+  // Workbench is opted into solely by calling `unstable_defineApp`.
+  if (!isWorkbenchApp(cliConfig?.app)) {
+    devDebug('Not a workbench app, skipping workbench dev server')
     return {close: noop, httpHost, workbenchAvailable: false, workbenchPort}
   }
 
diff --git a/packages/@sanity/cli/src/actions/init/__tests__/bootstrapLocalTemplate.test.ts b/packages/@sanity/cli/src/actions/init/__tests__/bootstrapLocalTemplate.test.ts
index 24a1021df..bb1ba9530 100644
--- a/packages/@sanity/cli/src/actions/init/__tests__/bootstrapLocalTemplate.test.ts
+++ b/packages/@sanity/cli/src/actions/init/__tests__/bootstrapLocalTemplate.test.ts
@@ -5,7 +5,6 @@ import path from 'node:path'
 import {type Output} from '@sanity/cli-core'
 import {afterEach, beforeEach, describe, expect, test, vi} from 'vitest'
 
-import {resolveLatestVersions} from '../../../util/resolveLatestVersions.js'
 import {bootstrapLocalTemplate} from '../bootstrapLocalTemplate.js'
 
 vi.mock('../../../util/resolveLatestVersions.js', () => ({
@@ -53,7 +52,6 @@ describe('bootstrapLocalTemplate (app templates)', () => {
       variables: {
         autoUpdates: false,
         dataset: 'production',
-        federation: false,
         organizationId: 'org1',
         projectId: 'abc123',
         projectName: 'my-app',
@@ -77,7 +75,6 @@ describe('bootstrapLocalTemplate (app templates)', () => {
       variables: {
         autoUpdates: false,
         dataset: '',
-        federation: false,
         organizationId: 'org1',
         projectId: '',
         projectName: 'my-app',
@@ -91,83 +88,3 @@ describe('bootstrapLocalTemplate (app templates)', () => {
     expect(appTsx).not.toContain('%dataset%')
   })
 })
-
-describe('bootstrapLocalTemplate (federation)', () => {
-  let tmp: string
-  beforeEach(async () => {
-    tmp = await mkdtemp(path.join(tmpdir(), 'cli-bootstrap-'))
-  })
-  afterEach(async () => {
-    await rm(tmp, {force: true, recursive: true})
-    vi.clearAllMocks()
-  })
-
-  test('overrides the `sanity` dependency with the `workbench` dist-tag when federation is enabled', async () => {
-    await bootstrapLocalTemplate({
-      output: makeOutput(),
-      outputPath: tmp,
-      packageName: 'my-studio',
-      templateName: 'clean',
-      useTypeScript: true,
-      variables: {
-        autoUpdates: false,
-        dataset: 'production',
-        federation: true,
-        organizationId: 'org1',
-        projectId: 'abc123',
-        projectName: 'my-studio',
-      },
-    })
-
-    expect(resolveLatestVersions).toHaveBeenCalledOnce()
-    const resolvedDeps = vi.mocked(resolveLatestVersions).mock.calls[0][0]
-    expect(resolvedDeps.sanity).toBe('workbench')
-
-    const pkgJson = JSON.parse(await readFile(path.join(tmp, 'package.json'), 'utf8'))
-    expect(pkgJson.dependencies.sanity).toBe('1.0.0')
-  })
-
-  test('keeps the `sanity` dependency on the `latest` dist-tag when federation is disabled', async () => {
-    await bootstrapLocalTemplate({
-      output: makeOutput(),
-      outputPath: tmp,
-      packageName: 'my-studio',
-      templateName: 'clean',
-      useTypeScript: true,
-      variables: {
-        autoUpdates: false,
-        dataset: 'production',
-        federation: false,
-        organizationId: 'org1',
-        projectId: 'abc123',
-        projectName: 'my-studio',
-      },
-    })
-
-    expect(resolveLatestVersions).toHaveBeenCalledOnce()
-    const resolvedDeps = vi.mocked(resolveLatestVersions).mock.calls[0][0]
-    expect(resolvedDeps.sanity).toBe('latest')
-  })
-
-  test('overrides the `sanity` devDependency for app templates when federation is enabled', async () => {
-    await bootstrapLocalTemplate({
-      output: makeOutput(),
-      outputPath: tmp,
-      packageName: 'my-app',
-      templateName: 'app-quickstart',
-      useTypeScript: true,
-      variables: {
-        autoUpdates: false,
-        dataset: 'production',
-        federation: true,
-        organizationId: 'org1',
-        projectId: 'abc123',
-        projectName: 'my-app',
-      },
-    })
-
-    expect(resolveLatestVersions).toHaveBeenCalledOnce()
-    const resolvedDeps = vi.mocked(resolveLatestVersions).mock.calls[0][0]
-    expect(resolvedDeps.sanity).toBe('workbench')
-  })
-})
diff --git a/packages/@sanity/cli/src/actions/init/__tests__/bootstrapRemoteTemplate.test.ts b/packages/@sanity/cli/src/actions/init/__tests__/bootstrapRemoteTemplate.test.ts
index 974b0df4d..ec40817bd 100644
--- a/packages/@sanity/cli/src/actions/init/__tests__/bootstrapRemoteTemplate.test.ts
+++ b/packages/@sanity/cli/src/actions/init/__tests__/bootstrapRemoteTemplate.test.ts
@@ -76,7 +76,6 @@ const baseOpts = {
   variables: {
     autoUpdates: false,
     dataset: 'production',
-    federation: true,
     projectId: 'test-project-id',
   },
 }
diff --git a/packages/@sanity/cli/src/actions/init/bootstrapLocalTemplate.ts b/packages/@sanity/cli/src/actions/init/bootstrapLocalTemplate.ts
index 773d39829..79caf3863 100644
--- a/packages/@sanity/cli/src/actions/init/bootstrapLocalTemplate.ts
+++ b/packages/@sanity/cli/src/actions/init/bootstrapLocalTemplate.ts
@@ -89,7 +89,6 @@ export async function bootstrapLocalTemplate(
     ...(isAppTemplate ? sdkAppDependencies.devDependencies : studioDependencies.devDependencies),
     ...template.dependencies,
     ...template.devDependencies,
-    ...(variables.federation && {sanity: 'workbench'}),
   })
   spin.succeed()
 
@@ -142,13 +141,11 @@ export async function bootstrapLocalTemplate(
   const cliConfig = isAppTemplate
     ? createAppCliConfig({
         entry: template.entry!,
-        federation: variables.federation,
         organizationId: variables.organizationId,
       })
     : createCliConfig({
         autoUpdates: variables.autoUpdates,
         dataset: variables.dataset,
-        federation: variables.federation,
         projectId: variables.projectId,
       })
 
diff --git a/packages/@sanity/cli/src/actions/init/bootstrapTemplate.ts b/packages/@sanity/cli/src/actions/init/bootstrapTemplate.ts
index 73d37a347..a356535ea 100644
--- a/packages/@sanity/cli/src/actions/init/bootstrapTemplate.ts
+++ b/packages/@sanity/cli/src/actions/init/bootstrapTemplate.ts
@@ -9,7 +9,6 @@ interface BootstrapTemplateOptions {
   autoUpdates: boolean
   bearerToken: string | undefined
   dataset: string
-  federation: boolean
   organizationId: string | undefined
   output: Output
   outputPath: string
@@ -28,7 +27,6 @@ export async function bootstrapTemplate({
   autoUpdates,
   bearerToken,
   dataset,
-  federation,
   organizationId,
   output,
   outputPath,
@@ -43,7 +41,6 @@ export async function bootstrapTemplate({
   const bootstrapVariables: GenerateConfigOptions['variables'] = {
     autoUpdates,
     dataset,
-    federation,
     organizationId,
     projectId,
     projectName,
diff --git a/packages/@sanity/cli/src/actions/init/createAppCliConfig.ts b/packages/@sanity/cli/src/actions/init/createAppCliConfig.ts
index 185b3b9d8..7c8feebf0 100644
--- a/packages/@sanity/cli/src/actions/init/createAppCliConfig.ts
+++ b/packages/@sanity/cli/src/actions/init/createAppCliConfig.ts
@@ -8,15 +8,11 @@ export default defineCliConfig({
     organizationId: '%organizationId%',
     entry: '%entry%',
   },
-  federation: {
-    enabled: __BOOL__federation__,
-  },
 })
 `
 
 interface GenerateCliConfigOptions {
   entry: string
-  federation: boolean
 
   organizationId?: string
 }
diff --git a/packages/@sanity/cli/src/actions/init/createCliConfig.ts b/packages/@sanity/cli/src/actions/init/createCliConfig.ts
index 167aff579..8ee5bc701 100644
--- a/packages/@sanity/cli/src/actions/init/createCliConfig.ts
+++ b/packages/@sanity/cli/src/actions/init/createCliConfig.ts
@@ -15,16 +15,12 @@ export default defineCliConfig({
      */
     autoUpdates: __BOOL__autoUpdates__,
   },
-  federation: {
-    enabled: __BOOL__federation__,
-  },
 })
 `
 
 interface GenerateCliConfigOptions {
   autoUpdates: boolean
   dataset: string
-  federation: boolean
   projectId: string
 }
 
diff --git a/packages/@sanity/cli/src/actions/init/createStudioConfig.ts b/packages/@sanity/cli/src/actions/init/createStudioConfig.ts
index 242656a9d..67a191466 100644
--- a/packages/@sanity/cli/src/actions/init/createStudioConfig.ts
+++ b/packages/@sanity/cli/src/actions/init/createStudioConfig.ts
@@ -31,7 +31,6 @@ export interface GenerateConfigOptions {
   variables: {
     autoUpdates: boolean
     dataset: string
-    federation: boolean
     organizationId?: string
     projectId: string
     projectName?: string
diff --git a/packages/@sanity/cli/src/actions/init/initAction.ts b/packages/@sanity/cli/src/actions/init/initAction.ts
index f3b3ea176..a1fd41b74 100644
--- a/packages/@sanity/cli/src/actions/init/initAction.ts
+++ b/packages/@sanity/cli/src/actions/init/initAction.ts
@@ -6,7 +6,6 @@ import {type TelemetryTrace} from '@sanity/telemetry'
 import {type Framework, frameworks} from '@vercel/frameworks'
 import deburr from 'lodash-es/deburr.js'
 
-import {promptForFederation} from '../../prompts/init/federation.js'
 import {promptForConfigFiles} from '../../prompts/init/nextjs.js'
 import {getCliUser} from '../../services/user.js'
 import {CLIInitStepCompleted, type InitStepResult} from '../../telemetry/init.telemetry.js'
@@ -251,14 +250,8 @@ export async function initAction(options: InitOptions, context: InitContext): Pr
     return
   }
 
-  let federation = flagOrDefault(options.federation, true)
-  if (shouldPrompt(options.unattended, options.federation)) {
-    federation = await promptForFederation()
-  }
-
   const sharedParams = {
     defaults,
-    federation,
     mcpConfigured,
     options,
     organizationId,
diff --git a/packages/@sanity/cli/src/actions/init/initApp.ts b/packages/@sanity/cli/src/actions/init/initApp.ts
index 188e3cb14..db4f2dd1c 100644
--- a/packages/@sanity/cli/src/actions/init/initApp.ts
+++ b/packages/@sanity/cli/src/actions/init/initApp.ts
@@ -15,7 +15,6 @@ import {type InitOptions} from './types.js'
 export async function initApp({
   datasetName,
   defaults,
-  federation,
   mcpConfigured,
   options,
   organizationId,
@@ -29,7 +28,6 @@ export async function initApp({
 }: {
   datasetName: string
   defaults: {projectName: string}
-  federation: boolean
   mcpConfigured: EditorName[]
   options: InitOptions
   organizationId: string | undefined
@@ -59,7 +57,6 @@ export async function initApp({
     datasetName,
     defaults,
     displayName: '',
-    federation,
     options,
     organizationId,
     output,
diff --git a/packages/@sanity/cli/src/actions/init/initStudio.ts b/packages/@sanity/cli/src/actions/init/initStudio.ts
index ecbcee64d..a10d0c1a3 100644
--- a/packages/@sanity/cli/src/actions/init/initStudio.ts
+++ b/packages/@sanity/cli/src/actions/init/initStudio.ts
@@ -27,7 +27,6 @@ export async function initStudio({
   datasetName,
   defaults,
   displayName,
-  federation,
   isFirstProject,
   mcpConfigured,
   options,
@@ -43,7 +42,6 @@ export async function initStudio({
   datasetName: string
   defaults: {projectName: string}
   displayName: string
-  federation: boolean
   isFirstProject: boolean
   mcpConfigured: EditorName[]
   options: InitOptions
@@ -93,7 +91,6 @@ export async function initStudio({
     datasetName,
     defaults,
     displayName,
-    federation,
     options,
     organizationId,
     output,
diff --git a/packages/@sanity/cli/src/actions/init/scaffoldTemplate.ts b/packages/@sanity/cli/src/actions/init/scaffoldTemplate.ts
index be880735b..343e65fc5 100644
--- a/packages/@sanity/cli/src/actions/init/scaffoldTemplate.ts
+++ b/packages/@sanity/cli/src/actions/init/scaffoldTemplate.ts
@@ -98,7 +98,6 @@ export async function scaffoldAndInstall({
   datasetName,
   defaults,
   displayName,
-  federation,
   options,
   organizationId,
   output,
@@ -114,7 +113,6 @@ export async function scaffoldAndInstall({
   datasetName: string
   defaults: {projectName: string}
   displayName: string
-  federation: boolean
   options: InitOptions
   organizationId: string | undefined
   output: Output
@@ -134,7 +132,6 @@ export async function scaffoldAndInstall({
     autoUpdates,
     bearerToken: templateToken,
     dataset: datasetName,
-    federation,
     organizationId,
     output,
     outputPath,
diff --git a/packages/@sanity/cli/src/actions/init/types.ts b/packages/@sanity/cli/src/actions/init/types.ts
index 72cd0d68c..5a92e8ed9 100644
--- a/packages/@sanity/cli/src/actions/init/types.ts
+++ b/packages/@sanity/cli/src/actions/init/types.ts
@@ -31,7 +31,6 @@ export interface InitOptions {
   coupon?: string
   dataset?: string
   env?: string
-  federation?: boolean
   git?: boolean | string
   importDataset?: boolean
   nextjsAddConfigFiles?: boolean
@@ -70,7 +69,6 @@ interface InitCommandFlags {
   'create-project'?: string
   dataset?: string
   env?: string
-  federation?: boolean
   git?: string
   'import-dataset'?: boolean
   'nextjs-add-config-files'?: boolean
@@ -123,7 +121,6 @@ export function flagsToInitOptions(
     dataset: flags.dataset,
     datasetDefault: flags['dataset-default'],
     env: flags.env,
-    federation: flags.federation,
     fromCreate: flags['from-create'],
     git: flags['no-git'] ? false : flags.git,
     importDataset: flags['import-dataset'],
diff --git a/packages/@sanity/cli/src/commands/__tests__/build.studio.test.ts b/packages/@sanity/cli/src/commands/__tests__/build.studio.test.ts
index a9d601d57..c8093a2dd 100644
--- a/packages/@sanity/cli/src/commands/__tests__/build.studio.test.ts
+++ b/packages/@sanity/cli/src/commands/__tests__/build.studio.test.ts
@@ -85,45 +85,53 @@ describe('#build studio', {timeout: (platform() === 'win32' ? 120 : 60) * 1000},
     expect(files).not.toContain('mf-manifest.json')
   })
 
-  test('should build the "federated-studio" with only federation artifacts', async () => {
-    const cwd = await testFixture('federated-studio')
-    process.chdir(cwd)
-
-    // `@module-federation/vite` short-circuits to an empty plugin array when
-    // it detects vitest/jest in the env, which leaves the federation env without
-    // its plugins and skips emitting `remote-entry.js` / `mf-manifest.json`.
-    // Opt out of that guard for this in-process build.
-    vi.stubEnv('MFE_VITE_NO_TEST_ENV_CHECK', 'true')
-
-    const {error, stderr} = await testCommand(BuildCommand, ['--yes'], {
-      config: {root: cwd},
-    })
-
-    // 1. Build succeeds
-    if (error) throw error
-    expect(stderr).toContain('✔ Build Sanity Studio')
-
-    const distFiles = await readdir(join(cwd, 'dist'))
-
-    // 2. No client artifacts
-    expect(distFiles).not.toContain('index.html')
-    expect(distFiles).not.toContain('static')
-    expect(distFiles).not.toContain('vendor')
-
-    // 3. Stable remote entry (unhashed)
-    expect(distFiles).toContain('remote-entry.js')
-
-    // 4. Federation manifest (valid JSON)
-    expect(distFiles).toContain('mf-manifest.json')
-    const manifest = JSON.parse(await readFile(join(cwd, 'dist', 'mf-manifest.json'), 'utf8'))
-    expect(manifest).toHaveProperty('id')
-    expect(manifest).toHaveProperty('name')
-
-    // 5. Hashed federation chunks
-    expect(distFiles).toContain('assets')
-    const assetFiles = await readdir(join(cwd, 'dist', 'assets'))
-    expect(assetFiles.some((f) => /^remote-entry-.+\.js$/.test(f))).toBe(true)
-  })
+  // Skipped on Windows: forcing `@module-federation/vite`'s plugins to run
+  // in-process (via MFE_VITE_NO_TEST_ENV_CHECK) crashes the vitest worker there —
+  // esbuild's service pipe dies with "Unexpected end of JSON input [plugin onEnd]".
+  // It's a test-harness limitation (real `sanity build` runs as its own process);
+  // the federation-artifact shape is platform-independent, so Linux coverage suffices.
+  test.skipIf(platform() === 'win32')(
+    'should build the "federated-studio" with only federation artifacts',
+    async () => {
+      const cwd = await testFixture('federated-studio')
+      process.chdir(cwd)
+
+      // `@module-federation/vite` short-circuits to an empty plugin array when
+      // it detects vitest/jest in the env, which leaves the federation env without
+      // its plugins and skips emitting `remote-entry.js` / `mf-manifest.json`.
+      // Opt out of that guard for this in-process build.
+      vi.stubEnv('MFE_VITE_NO_TEST_ENV_CHECK', 'true')
+
+      const {error, stderr} = await testCommand(BuildCommand, ['--yes'], {
+        config: {root: cwd},
+      })
+
+      // 1. Build succeeds
+      if (error) throw error
+      expect(stderr).toContain('✔ Build Sanity Studio')
+
+      const distFiles = await readdir(join(cwd, 'dist'))
+
+      // 2. No client artifacts
+      expect(distFiles).not.toContain('index.html')
+      expect(distFiles).not.toContain('static')
+      expect(distFiles).not.toContain('vendor')
+
+      // 3. Stable remote entry (unhashed)
+      expect(distFiles).toContain('remote-entry.js')
+
+      // 4. Federation manifest (valid JSON)
+      expect(distFiles).toContain('mf-manifest.json')
+      const manifest = JSON.parse(await readFile(join(cwd, 'dist', 'mf-manifest.json'), 'utf8'))
+      expect(manifest).toHaveProperty('id')
+      expect(manifest).toHaveProperty('name')
+
+      // 5. Hashed federation chunks
+      expect(distFiles).toContain('assets')
+      const assetFiles = await readdir(join(cwd, 'dist', 'assets'))
+      expect(assetFiles.some((f) => /^remote-entry-.+\.js$/.test(f))).toBe(true)
+    },
+  )
 
   test("should build the 'worst-case-studio' example", async () => {
     const cwd = await testFixture('worst-case-studio')
diff --git a/packages/@sanity/cli/src/commands/__tests__/init/init.authentication.test.ts b/packages/@sanity/cli/src/commands/__tests__/init/init.authentication.test.ts
index 0829ddcbc..f0e6c6803 100644
--- a/packages/@sanity/cli/src/commands/__tests__/init/init.authentication.test.ts
+++ b/packages/@sanity/cli/src/commands/__tests__/init/init.authentication.test.ts
@@ -170,7 +170,6 @@ describe('#init: authentication', () => {
         '--output-path=/test/output',
         '--no-overwrite-files',
         '--template=clean',
-        '--federation',
       ],
       {
         mocks: {
@@ -215,7 +214,6 @@ describe('#init: authentication', () => {
         '--output-path=/test/output',
         '--no-overwrite-files',
         '--template=clean',
-        '--federation',
       ],
       {
         mocks: {
diff --git a/packages/@sanity/cli/src/commands/__tests__/init/init.bootstrap-app.test.ts b/packages/@sanity/cli/src/commands/__tests__/init/init.bootstrap-app.test.ts
index 76ab47c04..3f0a49e3f 100644
--- a/packages/@sanity/cli/src/commands/__tests__/init/init.bootstrap-app.test.ts
+++ b/packages/@sanity/cli/src/commands/__tests__/init/init.bootstrap-app.test.ts
@@ -169,7 +169,6 @@ describe('#init: bootstrap-app-initialization', () => {
         '--dataset=test',
         '--package-manager=npm',
         '--typescript',
-        '--federation',
       ],
       {
         mocks: {
@@ -183,7 +182,6 @@ describe('#init: bootstrap-app-initialization', () => {
       autoUpdates: true,
       bearerToken: undefined,
       dataset: 'test',
-      federation: true,
       organizationId: undefined,
       output: expect.any(Object),
       outputPath: convertToSystemPath('/test/output'),
@@ -258,7 +256,6 @@ describe('#init: bootstrap-app-initialization', () => {
         '--output-path=/test/output',
         '--package-manager=npm',
         '--typescript',
-        '--federation',
       ],
       {
         mocks: {
@@ -272,7 +269,6 @@ describe('#init: bootstrap-app-initialization', () => {
       autoUpdates: true,
       bearerToken: undefined,
       dataset: '',
-      federation: true,
       organizationId: 'org-1',
       output: expect.any(Object),
       outputPath: convertToSystemPath('/test/output'),
@@ -335,7 +331,6 @@ describe('#init: bootstrap-app-initialization', () => {
       autoUpdates: true,
       bearerToken: undefined,
       dataset: '',
-      federation: true,
       organizationId: 'org-1',
       output: expect.any(Object),
       outputPath: convertToSystemPath('/test/output'),
@@ -406,7 +401,6 @@ describe('#init: bootstrap-app-initialization', () => {
       autoUpdates: true,
       bearerToken: undefined,
       dataset: '',
-      federation: true,
       organizationId: 'org-1',
       output: expect.any(Object),
       outputPath: convertToSystemPath('/test/output'),
diff --git a/packages/@sanity/cli/src/commands/__tests__/init/init.create-new-project.test.ts b/packages/@sanity/cli/src/commands/__tests__/init/init.create-new-project.test.ts
index 25c419fdc..7aae59741 100644
--- a/packages/@sanity/cli/src/commands/__tests__/init/init.create-new-project.test.ts
+++ b/packages/@sanity/cli/src/commands/__tests__/init/init.create-new-project.test.ts
@@ -513,7 +513,6 @@ describe('#init: create new project', () => {
         '--no-overwrite-files',
         '--template=moviedb',
         '--no-import-dataset',
-        '--federation',
       ],
       {mocks: {...defaultMocks, isInteractive: true}},
     )
diff --git a/packages/@sanity/cli/src/commands/__tests__/init/init.staging-env.test.ts b/packages/@sanity/cli/src/commands/__tests__/init/init.staging-env.test.ts
index 2d50818f9..0b3c0752a 100644
--- a/packages/@sanity/cli/src/commands/__tests__/init/init.staging-env.test.ts
+++ b/packages/@sanity/cli/src/commands/__tests__/init/init.staging-env.test.ts
@@ -223,7 +223,6 @@ describe('#init: staging env propagation', () => {
         '--dataset=test',
         '--package-manager=npm',
         '--typescript',
-        '--federation',
       ],
       {
         mocks: {
@@ -261,7 +260,6 @@ describe('#init: staging env propagation', () => {
         '--dataset=test',
         '--package-manager=npm',
         '--typescript',
-        '--federation',
       ],
       {
         mocks: {
@@ -291,7 +289,6 @@ describe('#init: staging env propagation', () => {
         '--dataset=test',
         '--package-manager=npm',
         '--typescript',
-        '--federation',
       ],
       {
         mocks: {
diff --git a/packages/@sanity/cli/src/commands/init.ts b/packages/@sanity/cli/src/commands/init.ts
index ebc7213f1..ca539ef9f 100644
--- a/packages/@sanity/cli/src/commands/init.ts
+++ b/packages/@sanity/cli/src/commands/init.ts
@@ -78,11 +78,6 @@ export class InitCommand extends SanityCommand<typeof InitCommand> {
         return input
       },
     }),
-    federation: Flags.boolean({
-      allowNo: true,
-      default: undefined,
-      description: 'Enable federation for this project',
-    }),
     'from-create': Flags.boolean({
       description: 'Internal flag to indicate that the command is run from create-sanity',
       hidden: true,
diff --git a/packages/@sanity/cli/src/exports/index.ts b/packages/@sanity/cli/src/exports/index.ts
index dc374dbf1..adc1be882 100644
--- a/packages/@sanity/cli/src/exports/index.ts
+++ b/packages/@sanity/cli/src/exports/index.ts
@@ -5,3 +5,8 @@ export type {CliApiConfig} from '../types.js'
 export {type CliClientOptions, getCliClient} from '../util/cliClient.js'
 export {loadEnv} from '../util/loadEnv.js'
 export type {CliConfig, UserViteConfig} from '@sanity/cli-core'
+
+// Workbench application extension API. Canonical implementation in
+// `@sanity/federation`; re-exported here so `sanity/cli` can surface it to
+// app authors via `import {unstable_defineApp} from 'sanity/cli'`.
+export {type DefineAppInput, unstable_defineApp} from '@sanity/federation'
diff --git a/packages/@sanity/cli/src/prompts/init/federation.ts b/packages/@sanity/cli/src/prompts/init/federation.ts
deleted file mode 100644
index 6f5f0e644..000000000
--- a/packages/@sanity/cli/src/prompts/init/federation.ts
+++ /dev/null
@@ -1,8 +0,0 @@
-import {confirm} from '@sanity/cli-core/ux'
-
-export function promptForFederation(): Promise<boolean> {
-  return confirm({
-    default: true,
-    message: 'Would you like to enable federation for this project?',
-  })
-}
diff --git a/packages/@sanity/cli/src/server/devServer.ts b/packages/@sanity/cli/src/server/devServer.ts
index c0a0f261f..8e112e705 100644
--- a/packages/@sanity/cli/src/server/devServer.ts
+++ b/packages/@sanity/cli/src/server/devServer.ts
@@ -22,9 +22,9 @@ export interface DevServerOptions {
 
   appTitle?: string
   entry?: string
-  federation?: CliConfig['federation']
   httpHost?: string
   isApp?: boolean
+  isWorkbench?: boolean
   projectName?: string
   schemaExtraction?: CliConfig['schemaExtraction']
   typegen?: CliConfig['typegen']
@@ -44,10 +44,10 @@ export async function startDevServer(options: DevServerOptions): Promise<DevServ
     basePath,
     cwd,
     entry,
-    federation,
     httpHost,
     httpPort,
     isApp,
+    isWorkbench,
     reactCompiler,
     reactStrictMode,
     schemaExtraction,
@@ -85,8 +85,8 @@ export async function startDevServer(options: DevServerOptions): Promise<DevServ
     basePath,
     cwd,
     entries,
-    federation,
     isApp,
+    isWorkbench,
     mode: 'development',
     reactCompiler,
     schemaExtraction,
diff --git a/packages/@sanity/cli/src/util/determineIsApp.ts b/packages/@sanity/cli/src/util/determineIsApp.ts
index 81fb2dafc..db55457ba 100644
--- a/packages/@sanity/cli/src/util/determineIsApp.ts
+++ b/packages/@sanity/cli/src/util/determineIsApp.ts
@@ -1,10 +1,21 @@
 import {type CliConfig} from '@sanity/cli-core'
+import {isWorkbenchApp} from '@sanity/federation'
 
 /**
- * Determine if the current project is an app.
+ * Determine if the current project is an app (as opposed to a studio).
+ *
+ * For workbench apps (`unstable_defineApp`), this is driven by the resolved
+ * `applicationType` — a studio is not an app, everything else is. The
+ * `applicationType` is settled at config-load time (explicit, or inferred from
+ * the presence of a `sanity.config.*`). Legacy configs fall back to the
+ * presence of an `app` field.
  *
  * @returns `true` if the current project is an app, `false` otherwise.
  */
 export function determineIsApp(cliConfig: CliConfig): boolean {
+  const app = cliConfig?.app
+  if (isWorkbenchApp(app)) {
+    return (app as {applicationType?: string}).applicationType !== 'studio'
+  }
   return Boolean(cliConfig && 'app' in cliConfig)
 }
diff --git a/packages/@sanity/cli/src/util/getSharedServerConfig.ts b/packages/@sanity/cli/src/util/getSharedServerConfig.ts
index 6e750df30..68d7a8063 100644
--- a/packages/@sanity/cli/src/util/getSharedServerConfig.ts
+++ b/packages/@sanity/cli/src/util/getSharedServerConfig.ts
@@ -1,5 +1,6 @@
 import {type CliConfig, getSanityEnvVar} from '@sanity/cli-core'
 
+import {determineIsApp} from './determineIsApp.js'
 import {ensureTrailingSlash} from './ensureTrailingSlash.js'
 import {toInt} from './toInt.js'
 
@@ -38,7 +39,7 @@ export function getSharedServerConfig({
   workDir,
 }: GetSharedServerConfigOptions): GetSharedServerConfigResult {
   // Order of preference: CLI flags, environment variables, user build config, default config
-  const isApp = cliConfig && 'app' in cliConfig
+  const isApp = cliConfig ? determineIsApp(cliConfig) : false
 
   const httpHost =
     flags.host ||
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 48adf9c9b..cb0ed0ed5 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -261,6 +261,9 @@ importers:
 
   fixtures/federated-studio:
     dependencies:
+      '@sanity/federation':
+        specifier: 0.1.0-alpha.9
+        version: 0.1.0-alpha.9(typescript@5.9.3)(vite@7.3.3(@types/node@25.0.10)(jiti@2.7.0)(lightningcss@1.32.0)(terser@5.46.0)(tsx@4.21.0)(yaml@2.8.4))
       react:
         specifier: ^19.2.5
         version: 19.2.5
@@ -531,8 +534,8 @@ importers:
         specifier: ^6.1.0
         version: 6.1.0
       '@sanity/federation':
-        specifier: 0.1.0-alpha.8
-        version: 0.1.0-alpha.8(typescript@5.9.3)(vite@7.3.2(@types/node@20.19.41)(jiti@2.7.0)(lightningcss@1.32.0)(terser@5.46.0)(tsx@4.21.0)(yaml@2.8.4))
+        specifier: 0.1.0-alpha.9
+        version: 0.1.0-alpha.9(typescript@5.9.3)(vite@7.3.2(@types/node@20.19.41)(jiti@2.7.0)(lightningcss@1.32.0)(terser@5.46.0)(tsx@4.21.0)(yaml@2.8.4))
       '@sanity/generate-help-url':
         specifier: ^4.0.0
         version: 4.0.0
@@ -895,6 +898,9 @@ importers:
       '@sanity/client':
         specifier: ^7.22.0
         version: 7.22.0
+      '@sanity/federation':
+        specifier: 0.1.0-alpha.9
+        version: 0.1.0-alpha.9(typescript@5.9.3)(vite@7.3.2(@types/node@20.19.41)(jiti@2.7.0)(lightningcss@1.32.0)(terser@5.46.0)(tsx@4.21.0)(yaml@2.8.4))
       babel-plugin-react-compiler:
         specifier: ^1.0.0
         version: 1.0.0
@@ -4859,8 +4865,8 @@ packages:
     engines: {node: '>=20.19 <22 || >=22.12'}
     hasBin: true
 
-  '@sanity/federation@0.1.0-alpha.8':
-    resolution: {integrity: sha512-FMVXDu9XM8+I6XO1jXE3AIfL399CP9aVDotL3KWipPppTuq7iexo0wuD6d7mcYOwrhMukET7Pooy2+Z3WwQ3Iw==}
+  '@sanity/federation@0.1.0-alpha.9':
+    resolution: {integrity: sha512-mSsRVzqSrniPtg50+hhbO2WE8vzX/PGkI123ysS8xrUECV0m/v/9YH3ha159dcuUxG0JzgjAtj1+gVy+TmqANQ==}
     engines: {node: '>=20.19.1 <22 || >=22.12'}
     peerDependencies:
       vite: ^7.0.0 || ^8.0.0
@@ -10277,18 +10283,6 @@ packages:
       utf-8-validate:
         optional: true
 
-  ws@8.19.0:
-    resolution: {integrity: sha512-blAT2mjOEIi0ZzruJfIhb3nps74PRWTCz1IjglWEEpQl5XS/UNama6u2/rjFkDDouqr4L67ry+1aGIALViWjDg==}
-    engines: {node: '>=10.0.0'}
-    peerDependencies:
-      bufferutil: ^4.0.1
-      utf-8-validate: '>=5.0.2'
-    peerDependenciesMeta:
-      bufferutil:
-        optional: true
-      utf-8-validate:
-        optional: true
-
   ws@8.20.1:
     resolution: {integrity: sha512-It4dO0K5v//JtTXuPkfEOaI3uUN87iYPnqo/ZzqCoG3g8uhA66QUMs/SrM0YK7/NAu+r4LMh/9dq2A7k+rHs+w==}
     engines: {node: '>=10.0.0'}
@@ -13320,6 +13314,22 @@ snapshots:
       - utf-8-validate
       - vue-tsc
 
+  '@module-federation/vite@1.16.0(typescript@5.9.3)(vite@7.3.3(@types/node@25.0.10)(jiti@2.7.0)(lightningcss@1.32.0)(terser@5.46.0)(tsx@4.21.0)(yaml@2.8.4))':
+    dependencies:
+      '@module-federation/dts-plugin': 2.5.0(typescript@5.9.3)
+      '@module-federation/runtime': 2.5.0
+      '@module-federation/sdk': 2.5.0
+      es-module-lexer: 2.0.0
+      estree-walker: 3.0.3
+      pathe: 2.0.3
+      vite: 7.3.3(@types/node@25.0.10)(jiti@2.7.0)(lightningcss@1.32.0)(terser@5.46.0)(tsx@4.21.0)(yaml@2.8.4)
+    transitivePeerDependencies:
+      - bufferutil
+      - node-fetch
+      - typescript
+      - utf-8-validate
+      - vue-tsc
+
   '@mswjs/interceptors@0.41.2':
     dependencies:
       '@open-draft/deferred-promise': 2.2.0
@@ -14486,11 +14496,25 @@ snapshots:
       - react-native-b4a
       - supports-color
 
-  '@sanity/federation@0.1.0-alpha.8(typescript@5.9.3)(vite@7.3.2(@types/node@20.19.41)(jiti@2.7.0)(lightningcss@1.32.0)(terser@5.46.0)(tsx@4.21.0)(yaml@2.8.4))':
+  '@sanity/federation@0.1.0-alpha.9(typescript@5.9.3)(vite@7.3.2(@types/node@20.19.41)(jiti@2.7.0)(lightningcss@1.32.0)(terser@5.46.0)(tsx@4.21.0)(yaml@2.8.4))':
     dependencies:
       '@module-federation/runtime': 2.5.0
       '@module-federation/vite': 1.16.0(typescript@5.9.3)(vite@7.3.2(@types/node@20.19.41)(jiti@2.7.0)(lightningcss@1.32.0)(terser@5.46.0)(tsx@4.21.0)(yaml@2.8.4))
       vite: 7.3.2(@types/node@20.19.41)(jiti@2.7.0)(lightningcss@1.32.0)(terser@5.46.0)(tsx@4.21.0)(yaml@2.8.4)
+      zod: 4.3.6
+    transitivePeerDependencies:
+      - bufferutil
+      - node-fetch
+      - typescript
+      - utf-8-validate
+      - vue-tsc
+
+  '@sanity/federation@0.1.0-alpha.9(typescript@5.9.3)(vite@7.3.3(@types/node@25.0.10)(jiti@2.7.0)(lightningcss@1.32.0)(terser@5.46.0)(tsx@4.21.0)(yaml@2.8.4))':
+    dependencies:
+      '@module-federation/runtime': 2.5.0
+      '@module-federation/vite': 1.16.0(typescript@5.9.3)(vite@7.3.3(@types/node@25.0.10)(jiti@2.7.0)(lightningcss@1.32.0)(terser@5.46.0)(tsx@4.21.0)(yaml@2.8.4))
+      vite: 7.3.3(@types/node@25.0.10)(jiti@2.7.0)(lightningcss@1.32.0)(terser@5.46.0)(tsx@4.21.0)(yaml@2.8.4)
+      zod: 4.3.6
     transitivePeerDependencies:
       - bufferutil
       - node-fetch
@@ -18205,7 +18229,7 @@ snapshots:
       webidl-conversions: 8.0.1
       whatwg-mimetype: 4.0.0
       whatwg-url: 15.1.0
-      ws: 8.19.0
+      ws: 8.20.1
       xml-name-validator: 5.0.0
     transitivePeerDependencies:
       - '@noble/hashes'
@@ -20935,8 +20959,6 @@ snapshots:
 
   ws@8.18.0: {}
 
-  ws@8.19.0: {}
-
   ws@8.20.1: {}
 
   wsl-utils@0.3.1:
diff --git a/turbo.json b/turbo.json
index 00473fd74..ee7d61a7f 100644
--- a/turbo.json
+++ b/turbo.json
@@ -15,6 +15,11 @@
       "dependsOn": ["^build"],
       "outputs": [".next/**", "!.next/cache/**", "dist/**", ".sanity/**", "lib/**", "fixtures/**"]
     },
+    "@sanity/cli-test#build": {
+      "dependsOn": ["^build"],
+      "inputs": ["$TURBO_DEFAULT$", "$TURBO_ROOT$/fixtures/**", "$TURBO_ROOT$/pnpm-workspace.yaml"],
+      "outputs": ["dist/**", "fixtures/**"]
+    },
     "build:types": {
       "dependsOn": ["^build", "^build:types", "build"],
       "outputs": ["dist/**/*.d.ts"]