diff --git a/packages/rstack/src/config.ts b/packages/rstack/src/config.ts
index cf03b0b9..9f1ec1e4 100644
--- a/packages/rstack/src/config.ts
+++ b/packages/rstack/src/config.ts
@@ -22,6 +22,8 @@ type RslintConfigFactory = (
   lint: typeof import('@rslint/core'),
 ) => RslintConfig | Promise<RslintConfig>;
 
+type RslintConfigInput = RslintConfig | RslintConfigFactory;
+
 export type Configs = {
   app?: RsbuildConfigDefinition;
   lib?: RslibConfigDefinition;
@@ -32,6 +34,29 @@ export type Configs = {
   staged?: StagedConfig;
 };
 
+/** Shared configuration input; lint factories receive the tool exports. */
+export type RstackConfig = Omit<Configs, 'lint'> & {
+  extends?: readonly RstackConfig[];
+  lint?: RslintConfigInput;
+};
+
+const normalizeLintConfig = (
+  config: RslintConfigInput,
+): RslintConfigDefinition =>
+  typeof config === 'function'
+    ? async () => config(await import('@rslint/core'))
+    : config;
+
+/** Normalize one shared configuration without resolving factories or inheritance. */
+export const normalizeRstackConfig = ({
+  extends: _extends,
+  lint,
+  ...configs
+}: RstackConfig): Configs =>
+  lint === undefined
+    ? configs
+    : { ...configs, lint: normalizeLintConfig(lint) };
+
 export type LoadedRstackConfig = {
   configs: Configs;
   filePath: string | null;
@@ -142,7 +167,7 @@ type Define = {
    *
    * @see {@link https://rstack.rs/config | Configuration guide}
    */
-  lint: (config: RslintConfig | RslintConfigFactory) => void;
+  lint: (config: RslintConfigInput) => void;
   /**
    * Defines the Prettier config for formatting.
    *
@@ -190,13 +215,7 @@ export const define: Define = {
   },
   doc: (config) => setConfig('doc', config),
   test: (config) => setConfig('test', config),
-  lint: (config) =>
-    setConfig(
-      'lint',
-      typeof config === 'function'
-        ? async () => config(await import('@rslint/core'))
-        : config,
-    ),
+  lint: (config) => setConfig('lint', normalizeLintConfig(config)),
   fmt: (config) => setConfig('fmt', config),
   staged: (config) => setConfig('staged', config),
 };
diff --git a/packages/rstack/tests/config/normalize.test.ts b/packages/rstack/tests/config/normalize.test.ts
new file mode 100644
index 00000000..50ab40c6
--- /dev/null
+++ b/packages/rstack/tests/config/normalize.test.ts
@@ -0,0 +1,46 @@
+import { expect, rs, test } from 'rstack/test';
+import { normalizeRstackConfig, type RstackConfig } from '../../src/config.ts';
+import { resolveConfigLayers } from '../../src/configLayers.ts';
+
+test('preserves tool definitions without resolving factories or inheritance', () => {
+  const app = rs.fn(() => ({}));
+  const staged = rs.fn(() => ['rs lint']);
+  const shared: RstackConfig = {
+    extends: [{ fmt: { singleQuote: true } }],
+    app,
+    staged,
+  };
+
+  expect(normalizeRstackConfig(shared)).toEqual({ app, staged });
+  expect(shared.extends).toEqual([{ fmt: { singleQuote: true } }]);
+  expect(app).not.toHaveBeenCalled();
+  expect(staged).not.toHaveBeenCalled();
+});
+
+test('resolves sync and async lint factories lazily with tool exports', async () => {
+  const syncLint = rs.fn((lint: typeof import('@rslint/core')) => [
+    lint.js.configs.recommended,
+  ]);
+  const asyncLint = rs.fn((lint: typeof import('@rslint/core')) =>
+    Promise.resolve([lint.ts.configs.recommended]),
+  );
+  const shared: RstackConfig[] = [
+    { lint: [] },
+    { lint: syncLint },
+    { lint: asyncLint },
+  ];
+  const configs = shared.map(normalizeRstackConfig);
+
+  expect(syncLint).not.toHaveBeenCalled();
+  expect(asyncLint).not.toHaveBeenCalled();
+  expect(shared[1].lint).toBe(syncLint);
+
+  const resolved = await resolveConfigLayers(configs, 'lint');
+  const { js, ts } = await import('@rslint/core');
+
+  expect(resolved).toEqual([
+    [],
+    [js.configs.recommended],
+    [ts.configs.recommended],
+  ]);
+});
diff --git a/packages/rstack/tests/types/shared-config/index.ts b/packages/rstack/tests/types/shared-config/index.ts
new file mode 100644
index 00000000..fa9e5535
--- /dev/null
+++ b/packages/rstack/tests/types/shared-config/index.ts
@@ -0,0 +1,51 @@
+import type { RstackConfig } from '../../../src/config.ts';
+
+export const baseConfig: RstackConfig = {
+  app: { source: { entry: { index: './src/index.ts' } } },
+  lib: { lib: [{ format: 'esm' }] },
+  doc: { title: 'Docs' },
+  test: { retry: 2 },
+  lint: [],
+  fmt: { singleQuote: true },
+  staged: { '*.ts': 'rs lint' },
+};
+
+export const syncConfig: RstackConfig = {
+  extends: [baseConfig] as const,
+  app: ({ command }) => ({
+    source: { define: { COMMAND: JSON.stringify(command) } },
+  }),
+  lib: ({ env }) => ({
+    lib: [{ format: 'esm' }],
+    mode: env === 'production' ? 'production' : 'development',
+  }),
+  test: () => ({ retry: 1 }),
+  lint: ({ js, ts }) => [js.configs.recommended, ts.configs.recommended],
+  fmt: () => ({ singleQuote: true }),
+  staged: (files) => (files.length ? ['rs lint'] : []),
+};
+
+export const asyncConfig: RstackConfig = {
+  app: ({ env }) =>
+    Promise.resolve({
+      source: { define: { ENV: JSON.stringify(env) } },
+    }),
+  lib: () => Promise.resolve({ lib: [{ format: 'esm' }] }),
+  doc: () => Promise.resolve({ title: 'Docs' }),
+  test: () => Promise.resolve({ retry: 2 }),
+  lint: ({ js }) => Promise.resolve([js.configs.recommended]),
+  fmt: () => Promise.resolve({ singleQuote: true }),
+  staged: (files) => Promise.resolve(files.length ? ['rs fmt'] : []),
+};
+
+export function sharedConfig(options: { retry?: number } = {}): RstackConfig {
+  return {
+    extends: [syncConfig, asyncConfig],
+    test: { retry: options.retry ?? 2 },
+  };
+}
+
+export const invalidConfig: RstackConfig = {
+  // @ts-expect-error Lint factories receive tool exports, not build parameters.
+  lint: (_params: { env: string }) => [],
+};
diff --git a/packages/rstack/tests/types/shared-config/tsconfig.json b/packages/rstack/tests/types/shared-config/tsconfig.json
new file mode 100644
index 00000000..430aa357
--- /dev/null
+++ b/packages/rstack/tests/types/shared-config/tsconfig.json
@@ -0,0 +1,9 @@
+{
+  "extends": "../tsconfig.json",
+  "compilerOptions": {
+    "module": "NodeNext",
+    "moduleResolution": "NodeNext",
+    "allowImportingTsExtensions": true
+  },
+  "include": ["index.ts"]
+}