diff --git a/src/auth/github.ts b/src/auth/github.ts
index 7e6528b..c14d47e 100644
--- a/src/auth/github.ts
+++ b/src/auth/github.ts
@@ -7,6 +7,20 @@ const DEVICE_CODE_URL = 'https://github.com/login/device/code';
 const TOKEN_URL = 'https://github.com/login/oauth/access_token';
 const POLLING_SAFETY_MARGIN_MS = 3000;
 
+function abortableSleep(ms: number, signal?: AbortSignal): Promise<void> {
+  return new Promise((resolve, reject) => {
+    if (signal?.aborted) {
+      reject(new Error('Cancelled'));
+      return;
+    }
+    const timer = setTimeout(resolve, ms);
+    signal?.addEventListener('abort', () => {
+      clearTimeout(timer);
+      reject(new Error('Cancelled'));
+    }, { once: true });
+  });
+}
+
 const AUTH_DIR = resolve(homedir(), '.config/flynn');
 const AUTH_FILE = resolve(AUTH_DIR, 'auth.json');
 
@@ -49,11 +63,11 @@ export async function requestDeviceCode(): Promise<DeviceCodeResponse> {
  * Poll GitHub for an access token after the user has entered the device code.
  * Blocks until the user authorizes or the code expires.
  */
-export async function pollForToken(deviceCode: string, interval: number): Promise<string> {
+export async function pollForToken(deviceCode: string, interval: number, signal?: AbortSignal): Promise<string> {
   let currentInterval = interval;
 
   while (true) {
-    await new Promise(r => setTimeout(r, currentInterval * 1000 + POLLING_SAFETY_MARGIN_MS));
+    await abortableSleep(currentInterval * 1000 + POLLING_SAFETY_MARGIN_MS, signal);
 
     const response = await fetch(TOKEN_URL, {
       method: 'POST',
@@ -153,12 +167,13 @@ export function getGitHubToken(): string | null {
  */
 export async function loginGitHub(
   onPrompt: (userCode: string, verificationUri: string) => void,
+  signal?: AbortSignal,
 ): Promise<string> {
   const deviceCode = await requestDeviceCode();
 
   onPrompt(deviceCode.user_code, deviceCode.verification_uri);
 
-  const token = await pollForToken(deviceCode.device_code, deviceCode.interval);
+  const token = await pollForToken(deviceCode.device_code, deviceCode.interval, signal);
   storeToken(token);
   return token;
 }
diff --git a/src/auth/openai.ts b/src/auth/openai.ts
index f403d2c..9e480ef 100644
--- a/src/auth/openai.ts
+++ b/src/auth/openai.ts
@@ -12,6 +12,20 @@ const TOKEN_URL = `${ISSUER}/oauth/token`;
 const POLLING_SAFETY_MARGIN_MS = 3000;
 const REFRESH_SAFETY_MARGIN_MS = 30_000;
 
+function abortableSleep(ms: number, signal?: AbortSignal): Promise<void> {
+  return new Promise((resolve, reject) => {
+    if (signal?.aborted) {
+      reject(new Error('Cancelled'));
+      return;
+    }
+    const timer = setTimeout(resolve, ms);
+    signal?.addEventListener('abort', () => {
+      clearTimeout(timer);
+      reject(new Error('Cancelled'));
+    }, { once: true });
+  });
+}
+
 const AUTH_DIR = resolve(homedir(), '.config/flynn');
 const AUTH_FILE = resolve(AUTH_DIR, 'auth.json');
 
@@ -256,9 +270,9 @@ async function requestDeviceAuth(): Promise<DeviceAuthResponse> {
   return response.json() as Promise<DeviceAuthResponse>;
 }
 
-async function pollDeviceToken(deviceAuthId: string, userCode: string, intervalMs: number): Promise<DeviceTokenResponse> {
+async function pollDeviceToken(deviceAuthId: string, userCode: string, intervalMs: number, signal?: AbortSignal): Promise<DeviceTokenResponse> {
   while (true) {
-    await new Promise(r => setTimeout(r, intervalMs + POLLING_SAFETY_MARGIN_MS));
+    await abortableSleep(intervalMs + POLLING_SAFETY_MARGIN_MS, signal);
 
     const response = await fetch(DEVICE_TOKEN_URL, {
       method: 'POST',
@@ -365,13 +379,14 @@ export async function ensureValidOpenAIAuth(): Promise<OpenAIOAuthInfo> {
  */
 export async function loginOpenAI(
   onPrompt: (userCode: string, verificationUri: string) => void,
+  signal?: AbortSignal,
 ): Promise<OpenAIOAuthInfo> {
   const device = await requestDeviceAuth();
   const intervalMs = Math.max(parseInt(device.interval) || 5, 1) * 1000;
 
   onPrompt(device.user_code, DEVICE_URL);
 
-  const deviceToken = await pollDeviceToken(device.device_auth_id, device.user_code, intervalMs);
+  const deviceToken = await pollDeviceToken(device.device_auth_id, device.user_code, intervalMs, signal);
   const tokens = await exchangeAuthorizationCode(deviceToken.authorization_code, deviceToken.code_verifier);
 
   const expiresAt = Date.now() + (tokens.expires_in ?? 3600) * 1000;
diff --git a/src/frontends/tui/minimal.ts b/src/frontends/tui/minimal.ts
index b131a8b..79d985c 100644
--- a/src/frontends/tui/minimal.ts
+++ b/src/frontends/tui/minimal.ts
@@ -1142,19 +1142,29 @@ export class MinimalTui {
     if (target === 'github') {
       console.log(`${colors.gray}Starting GitHub OAuth device flow...${colors.reset}`);
 
+      const controller = new AbortController();
+      const onSigint = () => controller.abort();
+      this.rl?.once('SIGINT', onSigint);
+
       try {
         await loginGitHub((userCode, verificationUri) => {
           console.log('');
           console.log(`${colors.gray}Please visit:${colors.reset} ${verificationUri}`);
           console.log(`${colors.gray}and enter code:${colors.reset} ${userCode}`);
           console.log('');
-          console.log(`${colors.gray}Waiting for authorization...${colors.reset}`);
-        });
+          console.log(`${colors.gray}Waiting for authorization... (Ctrl+C to cancel)${colors.reset}`);
+        }, controller.signal);
 
         console.log(`${colors.gray}GitHub authentication successful! Token stored.${colors.reset}\n`);
       } catch (error) {
-        const message = error instanceof Error ? error.message : String(error);
-        console.log(`${colors.gray}GitHub login failed:${colors.reset} ${message}\n`);
+        if (controller.signal.aborted) {
+          console.log(`${colors.gray}GitHub login cancelled.${colors.reset}\n`);
+        } else {
+          const message = error instanceof Error ? error.message : String(error);
+          console.log(`${colors.gray}GitHub login failed:${colors.reset} ${message}\n`);
+        }
+      } finally {
+        this.rl?.removeListener('SIGINT', onSigint);
       }
 
       return;
@@ -1222,6 +1232,10 @@ export class MinimalTui {
 
       console.log(`${colors.gray}Starting OpenAI OAuth device flow...${colors.reset}`);
 
+      const controller = new AbortController();
+      const onSigint = () => controller.abort();
+      this.rl?.once('SIGINT', onSigint);
+
       let credentialStored = false;
       try {
         await loginOpenAI((userCode, verificationUri) => {
@@ -1229,14 +1243,20 @@ export class MinimalTui {
           console.log(`${colors.gray}Please visit:${colors.reset} ${verificationUri}`);
           console.log(`${colors.gray}and enter code:${colors.reset} ${userCode}`);
           console.log('');
-          console.log(`${colors.gray}Waiting for authorization...${colors.reset}`);
-        });
+          console.log(`${colors.gray}Waiting for authorization... (Ctrl+C to cancel)${colors.reset}`);
+        }, controller.signal);
 
         console.log(`${colors.gray}OpenAI authentication successful! Token stored.${colors.reset}\n`);
         credentialStored = true;
       } catch (error) {
-        const message = error instanceof Error ? error.message : String(error);
-        console.log(`${colors.gray}OpenAI login failed:${colors.reset} ${message}\n`);
+        if (controller.signal.aborted) {
+          console.log(`${colors.gray}OpenAI login cancelled.${colors.reset}\n`);
+        } else {
+          const message = error instanceof Error ? error.message : String(error);
+          console.log(`${colors.gray}OpenAI login failed:${colors.reset} ${message}\n`);
+        }
+      } finally {
+        this.rl?.removeListener('SIGINT', onSigint);
       }
 
       // Offer to set auth_mode if config is available