diff --git a/packages/cli/src/__tests__/resolve-vite-config.spec.ts b/packages/cli/src/__tests__/resolve-vite-config.spec.ts
new file mode 100644
index 0000000000..a1205f1d05
--- /dev/null
+++ b/packages/cli/src/__tests__/resolve-vite-config.spec.ts
@@ -0,0 +1,120 @@
+import fs from 'node:fs';
+import { mkdtempSync } from 'node:fs';
+import { tmpdir } from 'node:os';
+import path from 'node:path';
+
+import { afterEach, beforeEach, describe, expect, it } from 'vitest';
+
+import { findViteConfigUp } from '../resolve-vite-config';
+
+describe('findViteConfigUp', () => {
+  let tempDir: string;
+
+  beforeEach(() => {
+    // Resolve symlinks (macOS /var -> /private/var) to match path.resolve behavior
+    tempDir = fs.realpathSync(mkdtempSync(path.join(tmpdir(), 'vite-config-test-')));
+  });
+
+  afterEach(() => {
+    fs.rmSync(tempDir, { recursive: true, force: true });
+  });
+
+  it('should find config in the start directory', () => {
+    fs.writeFileSync(path.join(tempDir, 'vite.config.ts'), '');
+    const result = findViteConfigUp(tempDir, tempDir);
+    expect(result).toBe(path.join(tempDir, 'vite.config.ts'));
+  });
+
+  it('should find config in a parent directory', () => {
+    const subDir = path.join(tempDir, 'packages', 'my-lib');
+    fs.mkdirSync(subDir, { recursive: true });
+    fs.writeFileSync(path.join(tempDir, 'vite.config.ts'), '');
+
+    const result = findViteConfigUp(subDir, tempDir);
+    expect(result).toBe(path.join(tempDir, 'vite.config.ts'));
+  });
+
+  it('should find config in an intermediate directory', () => {
+    const subDir = path.join(tempDir, 'packages', 'my-lib', 'src');
+    fs.mkdirSync(subDir, { recursive: true });
+    fs.writeFileSync(path.join(tempDir, 'packages', 'vite.config.ts'), '');
+
+    const result = findViteConfigUp(subDir, tempDir);
+    expect(result).toBe(path.join(tempDir, 'packages', 'vite.config.ts'));
+  });
+
+  it('should return undefined when no config exists', () => {
+    const subDir = path.join(tempDir, 'packages', 'my-lib');
+    fs.mkdirSync(subDir, { recursive: true });
+
+    const result = findViteConfigUp(subDir, tempDir);
+    expect(result).toBeUndefined();
+  });
+
+  it('should not traverse beyond stopDir', () => {
+    const parentConfig = path.join(tempDir, 'vite.config.ts');
+    fs.writeFileSync(parentConfig, '');
+    const stopDir = path.join(tempDir, 'packages');
+    const subDir = path.join(stopDir, 'my-lib');
+    fs.mkdirSync(subDir, { recursive: true });
+
+    const result = findViteConfigUp(subDir, stopDir);
+    // Should not find the config in tempDir because stopDir is packages/
+    expect(result).toBeUndefined();
+  });
+
+  it('should prefer the closest config file', () => {
+    const subDir = path.join(tempDir, 'packages', 'my-lib');
+    fs.mkdirSync(subDir, { recursive: true });
+    fs.writeFileSync(path.join(tempDir, 'vite.config.ts'), '');
+    fs.writeFileSync(path.join(tempDir, 'packages', 'vite.config.ts'), '');
+
+    const result = findViteConfigUp(subDir, tempDir);
+    expect(result).toBe(path.join(tempDir, 'packages', 'vite.config.ts'));
+  });
+
+  it('should find .js config files', () => {
+    const subDir = path.join(tempDir, 'packages', 'my-lib');
+    fs.mkdirSync(subDir, { recursive: true });
+    fs.writeFileSync(path.join(tempDir, 'vite.config.js'), '');
+
+    const result = findViteConfigUp(subDir, tempDir);
+    expect(result).toBe(path.join(tempDir, 'vite.config.js'));
+  });
+
+  it('should find .mts config files', () => {
+    const subDir = path.join(tempDir, 'packages', 'my-lib');
+    fs.mkdirSync(subDir, { recursive: true });
+    fs.writeFileSync(path.join(tempDir, 'vite.config.mts'), '');
+
+    const result = findViteConfigUp(subDir, tempDir);
+    expect(result).toBe(path.join(tempDir, 'vite.config.mts'));
+  });
+
+  it('should find .cjs config files', () => {
+    const subDir = path.join(tempDir, 'packages', 'my-lib');
+    fs.mkdirSync(subDir, { recursive: true });
+    fs.writeFileSync(path.join(tempDir, 'vite.config.cjs'), '');
+
+    const result = findViteConfigUp(subDir, tempDir);
+    expect(result).toBe(path.join(tempDir, 'vite.config.cjs'));
+  });
+
+  it('should find .cts config files', () => {
+    const subDir = path.join(tempDir, 'packages', 'my-lib');
+    fs.mkdirSync(subDir, { recursive: true });
+    fs.writeFileSync(path.join(tempDir, 'vite.config.cts'), '');
+
+    const result = findViteConfigUp(subDir, tempDir);
+    expect(result).toBe(path.join(tempDir, 'vite.config.cts'));
+  });
+
+  it('should find .mjs config files', () => {
+    const subDir = path.join(tempDir, 'packages', 'my-lib');
+    fs.mkdirSync(subDir, { recursive: true });
+    fs.writeFileSync(path.join(tempDir, 'vite.config.mjs'), '');
+
+    const result = findViteConfigUp(subDir, tempDir);
+    expect(result).toBe(path.join(tempDir, 'vite.config.mjs'));
+  });
+});
diff --git a/packages/cli/src/pack-bin.ts b/packages/cli/src/pack-bin.ts
index 5acb4898e5..80c9dc6ae3 100644
--- a/packages/cli/src/pack-bin.ts
+++ b/packages/cli/src/pack-bin.ts
@@ -128,7 +128,9 @@ cli
     }
 
     async function runBuild() {
-      const viteConfig = await resolveViteConfig(process.cwd());
+      const viteConfig = await resolveViteConfig(process.cwd(), {
+        traverseUp: flags.config !== false,
+      });
 
       const configFiles: string[] = [];
       if (viteConfig.configFile) {
diff --git a/packages/cli/src/resolve-vite-config.ts b/packages/cli/src/resolve-vite-config.ts
index 8cbb1acb67..085a77529e 100644
--- a/packages/cli/src/resolve-vite-config.ts
+++ b/packages/cli/src/resolve-vite-config.ts
@@ -1,8 +1,96 @@
+import fs from 'node:fs';
+import path from 'node:path';
+
+const VITE_CONFIG_FILES = [
+  'vite.config.ts',
+  'vite.config.js',
+  'vite.config.mjs',
+  'vite.config.mts',
+  'vite.config.cjs',
+  'vite.config.cts',
+];
+
+/**
+ * Find a vite config file by walking up from `startDir` to `stopDir`.
+ * Returns the absolute path of the first config file found, or undefined.
+ */
+export function findViteConfigUp(startDir: string, stopDir: string): string | undefined {
+  let dir = path.resolve(startDir);
+  const stop = path.resolve(stopDir);
+
+  while (true) {
+    for (const filename of VITE_CONFIG_FILES) {
+      const filePath = path.join(dir, filename);
+      if (fs.existsSync(filePath)) {
+        return filePath;
+      }
+    }
+    const parent = path.dirname(dir);
+    if (parent === dir || !parent.startsWith(stop)) {
+      break;
+    }
+    dir = parent;
+  }
+  return undefined;
+}
+
+function hasViteConfig(dir: string): boolean {
+  return VITE_CONFIG_FILES.some((f) => fs.existsSync(path.join(dir, f)));
+}
+
+/**
+ * Find the workspace root by walking up from `startDir` looking for
+ * monorepo indicators (pnpm-workspace.yaml, workspaces in package.json, lerna.json).
+ */
+function findWorkspaceRoot(startDir: string): string | undefined {
+  let dir = path.resolve(startDir);
+  while (true) {
+    if (fs.existsSync(path.join(dir, 'pnpm-workspace.yaml'))) {
+      return dir;
+    }
+    const pkgPath = path.join(dir, 'package.json');
+    if (fs.existsSync(pkgPath)) {
+      try {
+        const pkg = JSON.parse(fs.readFileSync(pkgPath, 'utf-8'));
+        if (pkg.workspaces) {
+          return dir;
+        }
+      } catch {
+        // Skip malformed package.json and continue searching parent directories
+      }
+    }
+    if (fs.existsSync(path.join(dir, 'lerna.json'))) {
+      return dir;
+    }
+    const parent = path.dirname(dir);
+    if (parent === dir) {
+      break;
+    }
+    dir = parent;
+  }
+  return undefined;
+}
+
+export interface ResolveViteConfigOptions {
+  traverseUp?: boolean;
+}
+
 /**
  * Resolve vite.config.ts and return the config object.
  */
-export async function resolveViteConfig(cwd: string) {
+export async function resolveViteConfig(cwd: string, options?: ResolveViteConfigOptions) {
   const { resolveConfig } = await import('./index.js');
+
+  if (options?.traverseUp && !hasViteConfig(cwd)) {
+    const workspaceRoot = findWorkspaceRoot(cwd);
+    if (workspaceRoot) {
+      const configFile = findViteConfigUp(path.dirname(cwd), workspaceRoot);
+      if (configFile) {
+        return resolveConfig({ root: cwd, configFile }, 'build');
+      }
+    }
+  }
+
   return resolveConfig({ root: cwd }, 'build');
 }