diff --git a/packages/rstack/src/fmt/config.ts b/packages/rstack/src/fmt/config.ts
index 949116a..86ba749 100644
--- a/packages/rstack/src/fmt/config.ts
+++ b/packages/rstack/src/fmt/config.ts
@@ -1,5 +1,6 @@
-import { dirname, relative } from 'node:path';
+import { dirname } from 'node:path';
 import micromatch from 'micromatch';
+import { createRelativePathResolver } from './relativePath.ts';
 import type {
   FmtConfig,
   FmtConfigDefinition,
@@ -14,6 +15,7 @@ type ResolveFmtConfigOptions = {
 };
 
 type PathMatcher = (filePath: string) => boolean;
+type FmtOptionsResolver = (filePath: string) => ResolvedFmtOptions;
 
 const neverMatches: PathMatcher = () => false;
 
@@ -87,26 +89,30 @@ const normalizeFmtConfig = (config: FmtConfig | undefined, rootPath: string): Re
   };
 };
 
-/** Applies matching overrides to the shared formatter options. */
-const resolveFmtOptions = (filePath: string, config: ResolvedFmtConfig): ResolvedFmtOptions => {
+/** Creates a reusable resolver for applying per-file formatter overrides. */
+const createFmtOptionsResolver = (config: ResolvedFmtConfig): FmtOptionsResolver => {
   if (config.overrides.length === 0) {
-    return config.baseOptions;
+    return () => config.baseOptions;
   }
 
-  let options = config.baseOptions;
-  const relativeFilePath = relative(config.rootPath, filePath);
+  const resolveRelativePath = createRelativePathResolver(config.rootPath);
 
-  for (const override of config.overrides) {
-    if (!override.options || !override.matches(relativeFilePath)) {
-      continue;
-    }
-    if (options === config.baseOptions) {
-      options = { ...options };
+  return (filePath) => {
+    let options = config.baseOptions;
+    const relativeFilePath = resolveRelativePath(filePath);
+
+    for (const override of config.overrides) {
+      if (!override.options || !override.matches(relativeFilePath)) {
+        continue;
+      }
+      if (options === config.baseOptions) {
+        options = { ...options };
+      }
+      Object.assign(options, override.options);
     }
-    Object.assign(options, override.options);
-  }
 
-  return options;
+    return options;
+  };
 };
 
 /** Resolves a formatter config definition and its project root. */
@@ -121,4 +127,5 @@ const resolveFmtConfig = async ({
   return normalizeFmtConfig(config, rootPath);
 };
 
-export { normalizeFmtConfig, resolveFmtConfig, resolveFmtOptions };
+export { createFmtOptionsResolver, normalizeFmtConfig, resolveFmtConfig };
+export type { FmtOptionsResolver };
diff --git a/packages/rstack/src/fmt/discovery.ts b/packages/rstack/src/fmt/discovery.ts
index 532859b..bacd755 100644
--- a/packages/rstack/src/fmt/discovery.ts
+++ b/packages/rstack/src/fmt/discovery.ts
@@ -1,11 +1,14 @@
-import { resolveFmtOptions } from './config.ts';
+import { createFmtOptionsResolver, type FmtOptionsResolver } from './config.ts';
 import { discoverFmtPaths } from './discoverPaths.ts';
 import { createIgnoreMatcher } from './ignore.ts';
-import type { DiscoverFmtFilesOptions, FmtFileRequest, ResolvedFmtConfig } from './types.ts';
+import type { DiscoverFmtFilesOptions, FmtFileRequest } from './types.ts';
 
-const createFileRequest = (filePath: string, config: ResolvedFmtConfig): FmtFileRequest => ({
+const createFileRequest = (
+  filePath: string,
+  resolveOptions: FmtOptionsResolver,
+): FmtFileRequest => ({
   path: filePath,
-  options: resolveFmtOptions(filePath, config),
+  options: resolveOptions(filePath),
 });
 
 /** Discovers worker-ready files without automatically reading Prettier config or ignore files. */
@@ -28,7 +31,8 @@ const discoverFmtFiles = async ({
   }
 
   const filePaths = candidates.filter((filePath) => !isIgnored(filePath));
-  const files = filePaths.map((filePath) => createFileRequest(filePath, config));
+  const resolveOptions = createFmtOptionsResolver(config);
+  const files = filePaths.map((filePath) => createFileRequest(filePath, resolveOptions));
   if (!files.some((file) => file.options.plugins?.length)) {
     return files;
   }
diff --git a/packages/rstack/src/fmt/stdin.ts b/packages/rstack/src/fmt/stdin.ts
index ec69200..f6b6a5f 100644
--- a/packages/rstack/src/fmt/stdin.ts
+++ b/packages/rstack/src/fmt/stdin.ts
@@ -1,4 +1,5 @@
 import { resolve } from 'node:path';
+import { createFmtOptionsResolver } from './config.ts';
 import { createFileRequest } from './discovery.ts';
 import { formatFmtSource } from './format.ts';
 import { createIgnoreMatcher } from './ignore.ts';
@@ -78,7 +79,7 @@ const runFmtStdin = async ({
     return;
   }
 
-  let file = createFileRequest(absolutePath, config);
+  let file = createFileRequest(absolutePath, createFmtOptionsResolver(config));
   if (file.options.plugins?.length) {
     const { createFmtPluginResolver } = await import(
       /* rspackChunkName: 'fmtPlugins' */
diff --git a/packages/rstack/tests/fmt/config.test.ts b/packages/rstack/tests/fmt/config.test.ts
index 605b8c5..e4d083b 100644
--- a/packages/rstack/tests/fmt/config.test.ts
+++ b/packages/rstack/tests/fmt/config.test.ts
@@ -1,6 +1,6 @@
 import path from 'node:path';
 import { expect, test } from 'rstack/test';
-import { normalizeFmtConfig, resolveFmtOptions } from '../../src/fmt/config.ts';
+import { createFmtOptionsResolver, normalizeFmtConfig } from '../../src/fmt/config.ts';
 
 const rootPath = path.join(import.meta.dirname, 'project');
 
@@ -12,8 +12,9 @@ test('reuses base options when no override matches', () => {
     },
     rootPath,
   );
+  const resolveOptions = createFmtOptionsResolver(config);
 
-  expect(resolveFmtOptions(path.join(rootPath, 'index.js'), config)).toBe(config.baseOptions);
+  expect(resolveOptions(path.join(rootPath, 'index.js'))).toBe(config.baseOptions);
 });
 
 test('applies basename and path overrides in declaration order', () => {
@@ -38,12 +39,25 @@ test('applies basename and path overrides in declaration order', () => {
     },
     rootPath,
   );
+  const resolveOptions = createFmtOptionsResolver(config);
 
-  const options = resolveFmtOptions(path.join(rootPath, 'src/index.ts'), config);
-  const testOptions = resolveFmtOptions(path.join(rootPath, 'src/index.test.ts'), config);
+  const options = resolveOptions(path.join(rootPath, 'src/index.ts'));
+  const testOptions = resolveOptions(path.join(rootPath, 'src/index.test.ts'));
 
   expect(options).not.toBe(config.baseOptions);
   expect(options).toEqual({ semi: true, singleQuote: true, tabWidth: 4 });
   expect(testOptions).toEqual({ singleQuote: true });
   expect(config.baseOptions).toEqual({ singleQuote: false });
 });
+
+test('applies overrides outside the config root', () => {
+  const config = normalizeFmtConfig(
+    {
+      overrides: [{ files: '../shared/*.ts', options: { semi: false } }],
+    },
+    rootPath,
+  );
+  const resolveOptions = createFmtOptionsResolver(config);
+
+  expect(resolveOptions(path.join(rootPath, '../shared/index.ts'))).toEqual({ semi: false });
+});