diff --git a/src/plugin/pkce-flow.test.ts b/src/plugin/pkce-flow.test.ts
index 5672838..341d57e 100644
--- a/src/plugin/pkce-flow.test.ts
+++ b/src/plugin/pkce-flow.test.ts
@@ -64,7 +64,7 @@ describe('handleCallbackRequest - Issue #4', () => {
 
     const mockResponse = {
       end: vi.fn(),
-      writeHead: vi.fn(),
+      writeHead: vi.fn() as unknown as http.ServerResponse['writeHead'],
     } as unknown as http.ServerResponse;
 
     const mockServer = {
@@ -103,7 +103,7 @@ describe('handleCallbackRequest - Issue #4', () => {
 
     const mockResponse = {
       end: vi.fn(),
-      writeHead: vi.fn(),
+      writeHead: vi.fn() as unknown as http.ServerResponse['writeHead'],
     } as unknown as http.ServerResponse;
 
     const mockServer = {
@@ -132,6 +132,37 @@ describe('handleCallbackRequest - Issue #4', () => {
     if ((resolvedResult as { type: string }).type !== 'failed') throw new Error('expected failed');
     expect((resolvedResult as { error?: string }).error).toBe('Authentication failed: invalid_scope');
   });
+
+  it('sets Cache-Control: no-store on error callback response', async () => {
+    const handleCallbackRequest = await loadHandleCallbackRequest();
+
+    const mockResponse = {
+      end: vi.fn(),
+      writeHead: vi.fn() as unknown as http.ServerResponse['writeHead'],
+    } as unknown as http.ServerResponse;
+
+    const mockServer = {
+      close: vi.fn(),
+    } as unknown as http.Server;
+
+    const parsedUrl = url.parse('/callback?error=access_denied', true);
+
+    await handleCallbackRequest(
+      mockResponse,
+      mockServer,
+      parsedUrl,
+      'valid-state',
+      'verifier',
+      'http://localhost:8787/callback',
+      () => {},
+    );
+
+    expect(mockResponse.writeHead).toHaveBeenCalledTimes(1);
+    const [, headers] = (mockResponse.writeHead as unknown as ReturnType<typeof vi.fn>).mock.calls[0];
+    expect(headers['Cache-Control']).toBe('no-store, no-cache, must-revalidate, proxy-revalidate');
+    expect(headers['Pragma']).toBe('no-cache');
+    expect(headers['Expires']).toBe('0');
+  });
 });
 
 
diff --git a/src/plugin/pkce-flow.ts b/src/plugin/pkce-flow.ts
index 31ce4ce..dd415ad 100644
--- a/src/plugin/pkce-flow.ts
+++ b/src/plugin/pkce-flow.ts
@@ -297,6 +297,19 @@ export function generateCodeVerifier(): string {
   return Buffer.from(bytes).toString('base64url');
 }
 
+/**
+ * Sends an HTML response with cache-control headers appropriate for OAuth callbacks
+ */
+function writeHtmlResponse(response: http.ServerResponse, html: string): void {
+  response.writeHead(200, {
+    'Cache-Control': 'no-store, no-cache, must-revalidate, proxy-revalidate',
+    'Content-Type': 'text/html',
+    'Expires': '0',
+    'Pragma': 'no-cache',
+  });
+  response.end(html);
+}
+
 /**
  * Handles the OAuth callback request
  */
@@ -317,8 +330,7 @@ export async function handleCallbackRequest(
   if (error) {
     const displayMessage = errorDescription ? `${error}: ${errorDescription}` : error;
 
-    response.writeHead(200, { 'Content-Type': 'text/html' });
-    response.end(buildHtmlResponse(false, displayMessage));
+    writeHtmlResponse(response, buildHtmlResponse(false, displayMessage));
     server.close();
     resolve({
       error: `Authentication failed: ${displayMessage}`,
@@ -328,8 +340,7 @@ export async function handleCallbackRequest(
   }
 
   if (receivedState !== state) {
-    response.writeHead(200, { 'Content-Type': 'text/html' });
-    response.end(buildHtmlResponse(false, 'Invalid state parameter'));
+    writeHtmlResponse(response, buildHtmlResponse(false, 'Invalid state parameter'));
     server.close();
     resolve({
       error: 'Invalid state parameter. Please try again.',
@@ -339,8 +350,7 @@ export async function handleCallbackRequest(
   }
 
   if (!code) {
-    response.writeHead(200, { 'Content-Type': 'text/html' });
-    response.end(buildHtmlResponse(false, 'No authorization code received'));
+    writeHtmlResponse(response, buildHtmlResponse(false, 'No authorization code received'));
     server.close();
     resolve({
       error: 'No authorization code received.',
@@ -350,9 +360,8 @@ export async function handleCallbackRequest(
   }
 
   // Exchange code for tokens
-  response.writeHead(200, { 'Content-Type': 'text/html' });
-  response.end(buildHtmlResponse(true, 'You can close this window and return to OpenCode.'));
-  server.close();
+    writeHtmlResponse(response, buildHtmlResponse(true, 'You can close this window and return to OpenCode.'));
+    server.close();
 
   const result = await exchangeCodeForTokens(code, codeVerifier, redirectUri);
   resolve(result);