diff --git a/packages/rstack/src/fmt/cli.ts b/packages/rstack/src/fmt/cli.ts
index 47e3735..cbbd7d3 100644
--- a/packages/rstack/src/fmt/cli.ts
+++ b/packages/rstack/src/fmt/cli.ts
@@ -147,11 +147,19 @@ const formatFileCount = (count: number, isError = false): string => {
   return `${isError ? color.red(formattedCount) : formattedCount} ${count === 1 ? 'file' : 'files'}`;
 };
 
+const reportNoSupportedFiles = (patterns: string[]): void => {
+  const targets = (patterns.length ? patterns : ['.'])
+    .map((pattern) => color.cyan(JSON.stringify(pattern)))
+    .join(', ');
+  logger.error(`No supported files matched ${targets}, or all matching files were ignored.`);
+  process.exitCode = 2;
+};
+
 const logFmtResult = (
   result: FmtRunResult,
   mode: FmtMode,
   cwd: string,
-  matchedFileCount: number,
+  processedFileCount: number,
   durationSeconds: number,
 ): void => {
   let writtenCount = 0;
@@ -177,12 +185,12 @@ const logFmtResult = (
       return;
     }
 
-    const matchedFiles = formatFileCount(matchedFileCount);
+    const processedFiles = formatFileCount(processedFileCount);
     const time = prettyTime(durationSeconds);
     const message =
       writtenCount > 0
-        ? `Formatted ${formatCount(writtenCount)} of ${matchedFiles} in ${time}.`
-        : `Checked ${matchedFiles} in ${time}. No changes needed.`;
+        ? `Formatted ${formatCount(writtenCount)} of ${processedFiles} in ${time}.`
+        : `Checked ${processedFiles} in ${time}. No changes needed.`;
     logger[result.exitCode === 0 ? 'success' : 'info'](message);
     return;
   }
@@ -193,15 +201,15 @@ const logFmtResult = (
 
   if (differentCount > 0) {
     const differentFiles = formatFileCount(differentCount, true);
-    const matchedFiles = formatFileCount(matchedFileCount);
+    const processedFiles = formatFileCount(processedFileCount);
     const checkOption = color.cyan('--check');
     logger.error(
       `Formatting issues found in ${differentFiles}. Run without ${checkOption} to fix.`,
     );
-    logger.info(`Checked ${matchedFiles} in ${prettyTime(durationSeconds)}.`);
+    logger.info(`Checked ${processedFiles} in ${prettyTime(durationSeconds)}.`);
   } else if (result.exitCode === 0) {
     logger.success(
-      `Checked ${formatFileCount(matchedFileCount)} in ${prettyTime(durationSeconds)}. No issues found.`,
+      `Checked ${formatFileCount(processedFileCount)} in ${prettyTime(durationSeconds)}. No issues found.`,
     );
   }
 };
@@ -263,11 +271,7 @@ const runFmtCLI = async (args: string[]): Promise<void> => {
       if (noErrorOnUnmatchedPattern) {
         return;
       }
-      const targets = (patterns.length ? patterns : ['.'])
-        .map((pattern) => color.cyan(JSON.stringify(pattern)))
-        .join(', ');
-      logger.error(`No supported files matched ${targets}, or all matching files were ignored.`);
-      process.exitCode = 2;
+      reportNoSupportedFiles(patterns);
       return;
     }
 
@@ -281,8 +285,13 @@ const runFmtCLI = async (args: string[]): Promise<void> => {
       maxWorkers,
     });
 
+    if (result.processedFileCount === 0) {
+      reportNoSupportedFiles(patterns);
+      return;
+    }
+
     const durationSeconds = (performance.now() - startTime) / 1000;
-    logFmtResult(result, mode, cwd, files.length, durationSeconds);
+    logFmtResult(result, mode, cwd, result.processedFileCount, durationSeconds);
     process.exitCode = result.exitCode;
   } catch (error) {
     logger.error(error);
diff --git a/packages/rstack/src/fmt/runner.ts b/packages/rstack/src/fmt/runner.ts
index ec3192b..aa0cc5c 100644
--- a/packages/rstack/src/fmt/runner.ts
+++ b/packages/rstack/src/fmt/runner.ts
@@ -9,17 +9,23 @@ import type { FmtWorkerPool } from './workerPool.ts';
 
 /** Formats one file and reports whether its contents differ. */
 type FormatFile = FmtWorkerPool['formatFile'];
+type FmtFileOutcome = FmtFileResult | 'unchanged' | 'unsupported';
+
+interface FmtWorkerPoolResult {
+  files: FmtFileResult[];
+  processedFileCount: number;
+}
 
 /** Converts a formatter outcome into the shared per-file result. */
 const runFmtFile = async (
   file: FmtFileRequest,
   shouldWrite: boolean,
   formatFile: FormatFile,
-): Promise<FmtFileResult | undefined> => {
+): Promise<FmtFileOutcome> => {
   try {
     const result = await formatFile(file, shouldWrite);
-    if (result !== 'changed') {
-      return;
+    if (result === 'unchanged' || result === 'unsupported') {
+      return result;
     }
 
     return {
@@ -40,7 +46,7 @@ const runFmtFilesInWorkerPool = async (
   files: FmtFileRequest[],
   shouldWrite: boolean,
   maxWorkers?: number,
-): Promise<FmtFileResult[]> => {
+): Promise<FmtWorkerPoolResult> => {
   const { createFmtWorkerPool } = await import('./workerPool.ts');
   const workerPool = await createFmtWorkerPool(files.length, maxWorkers);
 
@@ -48,7 +54,21 @@ const runFmtFilesInWorkerPool = async (
     const results = await Promise.all(
       files.map((file) => runFmtFile(file, shouldWrite, workerPool.formatFile)),
     );
-    return results.filter((result): result is FmtFileResult => result !== undefined);
+    const processedFiles: FmtFileResult[] = [];
+    let processedFileCount = 0;
+
+    for (const result of results) {
+      if (result === 'unsupported') {
+        continue;
+      }
+
+      processedFileCount++;
+      if (result !== 'unchanged') {
+        processedFiles.push(result);
+      }
+    }
+
+    return { files: processedFiles, processedFileCount };
   } finally {
     await workerPool.terminate();
   }
@@ -77,12 +97,15 @@ const runFmtFiles = async ({
   maxWorkers,
 }: RunFmtFilesOptions): Promise<FmtRunResult> => {
   const shouldWrite = mode === 'write';
-  const results =
-    files.length === 0 ? [] : await runFmtFilesInWorkerPool(files, shouldWrite, maxWorkers);
+  const result =
+    files.length === 0
+      ? { files: [], processedFileCount: 0 }
+      : await runFmtFilesInWorkerPool(files, shouldWrite, maxWorkers);
 
   return {
-    files: results,
-    exitCode: getFmtExitCode(results),
+    ...result,
+    exitCode:
+      files.length > 0 && result.processedFileCount === 0 ? 2 : getFmtExitCode(result.files),
   };
 };
 
diff --git a/packages/rstack/src/fmt/types.ts b/packages/rstack/src/fmt/types.ts
index 111ddb4..db9b2d6 100644
--- a/packages/rstack/src/fmt/types.ts
+++ b/packages/rstack/src/fmt/types.ts
@@ -96,6 +96,8 @@ type FmtFileResult = SuccessfulFmtFileResult | FailedFmtFileResult;
 
 interface FmtRunResult {
   files: FmtFileResult[];
+  /** Number of processed files, excluding files with no supported parser. */
+  processedFileCount: number;
   /** Recommended CLI exit code. */
   exitCode: FmtExitCode;
 }
diff --git a/packages/rstack/tests/cli/fmt/index.test.ts b/packages/rstack/tests/cli/fmt/index.test.ts
index 07391ce..36ee926 100644
--- a/packages/rstack/tests/cli/fmt/index.test.ts
+++ b/packages/rstack/tests/cli/fmt/index.test.ts
@@ -610,3 +610,41 @@ test.each(['--no-error-on-unmatched-pattern', '--noErrorOnUnmatchedPattern'])(
     }
   },
 );
+
+test('counts only supported files', () => {
+  writeProjectFile('index.ts', 'const value = 1;\n');
+  writeProjectFile('notes.unknown', 'plain text');
+
+  const result = runFmt(['--check', 'index.ts', 'notes.unknown']);
+
+  expect(result.status).toBe(0);
+  expect(normalizeDuration(result.stdout)).toBe(
+    'start   Checking formatting...\nsuccess Checked 1 file in <duration>. No issues found.\n',
+  );
+  expect(result.stderr).toBe('');
+});
+
+test('returns exit code 2 when all matched files are unsupported', () => {
+  writeProjectFile('notes.unknown', 'plain text');
+
+  for (const modeArgs of [[], ['--check'], ['--list-different']]) {
+    const result = runFmt([...modeArgs, 'notes.unknown']);
+
+    expect(result.status).toBe(2);
+    expect(result.stdout).not.toContain('success');
+    expect(result.stderr).toContain(
+      'No supported files matched "notes.unknown", or all matching files were ignored.',
+    );
+    expect(result.stderr).not.toContain('\n    at ');
+  }
+});
+
+test('does not treat unsupported files as unmatched patterns', () => {
+  writeProjectFile('notes.unknown', 'plain text');
+
+  const result = runFmt(['--no-error-on-unmatched-pattern', 'notes.unknown']);
+
+  expect(result.status).toBe(2);
+  expect(result.stdout).toBe('');
+  expect(result.stderr).toContain('No supported files matched "notes.unknown"');
+});
diff --git a/packages/rstack/tests/fmt/runner.test.ts b/packages/rstack/tests/fmt/runner.test.ts
index 385ac5e..7a31d38 100644
--- a/packages/rstack/tests/fmt/runner.test.ts
+++ b/packages/rstack/tests/fmt/runner.test.ts
@@ -31,6 +31,7 @@ test('does not rewrite unchanged files', async () => {
     expect(result).toMatchObject({
       exitCode: 0,
       files: [],
+      processedFileCount: 1,
     });
     expect(statSync(filePath).mtimeMs).toBe(mtimeMs);
   });
@@ -46,6 +47,7 @@ test('writes changed files', async () => {
     expect(result).toMatchObject({
       exitCode: 0,
       files: [{ path: filePath, status: 'written' }],
+      processedFileCount: 1,
     });
     expect(readFileSync(filePath, 'utf8')).toBe('const value = 1;\n');
   });
@@ -75,6 +77,7 @@ for (const mode of ['check', 'list-different'] as const) {
       expect(result).toMatchObject({
         exitCode: 1,
         files: [{ path: filePath, status: 'different' }],
+        processedFileCount: 1,
       });
       expect(readFileSync(filePath, 'utf8')).toBe(source);
     });
@@ -96,6 +99,7 @@ test('continues after a file fails and gives errors exit-code precedence', async
         { path: invalidPath, status: 'error' },
         { path: validPath, status: 'different' },
       ],
+      processedFileCount: 2,
     });
     expect(readFileSync(validPath, 'utf8')).toBe('const value=1');
   });
@@ -113,7 +117,7 @@ test('omits unsupported files from the result', async () => {
       },
     ]);
 
-    expect(result).toMatchObject({ exitCode: 0, files: [] });
+    expect(result).toMatchObject({ exitCode: 2, files: [], processedFileCount: 0 });
     expect(readFileSync(filePath, 'utf8')).toBe('plain text');
   });
 });
diff --git a/packages/rstack/tests/fmt/runnerWorkerPreflight.test.ts b/packages/rstack/tests/fmt/runnerWorkerPreflight.test.ts
index 1b3871b..127beae 100644
--- a/packages/rstack/tests/fmt/runnerWorkerPreflight.test.ts
+++ b/packages/rstack/tests/fmt/runnerWorkerPreflight.test.ts
@@ -47,6 +47,7 @@ test('does not start the worker pool when there are no files', async () => {
   await expect(runFmtFiles({ files: [], mode: 'write' })).resolves.toMatchObject({
     files: [],
     exitCode: 0,
+    processedFileCount: 0,
   });
   expect(mocks.createFmtWorkerPoolCalls).toEqual([]);
 });
diff --git a/packages/rstack/tests/fmt/runnerWriteFailure.test.ts b/packages/rstack/tests/fmt/runnerWriteFailure.test.ts
index db92d9a..a7ea7b4 100644
--- a/packages/rstack/tests/fmt/runnerWriteFailure.test.ts
+++ b/packages/rstack/tests/fmt/runnerWriteFailure.test.ts
@@ -40,6 +40,7 @@ test('returns an error when a file write fails', async () => {
         error: { message: 'file write failed' },
       },
     ],
+    processedFileCount: 1,
   });
   expect(mocks.terminateCalls).toBe(1);
 });