diff --git a/src/lib/asana-client.ts b/src/lib/asana-client.ts
index 6b86b5f..12bd938 100644
--- a/src/lib/asana-client.ts
+++ b/src/lib/asana-client.ts
@@ -428,7 +428,10 @@ export async function refreshTokenIfNeeded(): Promise<boolean> {
     saveConfig({
       ...config,
       accessToken: tokenResponse.access_token,
-      refreshToken: tokenResponse.refresh_token,
+      // Asana does not rotate refresh tokens: the refresh_token grant response
+      // omits the field. Keep the stored one or auto-refresh breaks after the
+      // first renewal.
+      refreshToken: tokenResponse.refresh_token ?? config.refreshToken,
       expiresAt: Date.now() + (tokenResponse.expires_in * 1000),
     })
 
diff --git a/src/lib/oauth.ts b/src/lib/oauth.ts
index d0b14fc..00bee77 100644
--- a/src/lib/oauth.ts
+++ b/src/lib/oauth.ts
@@ -62,7 +62,11 @@ export function buildAuthorizeUrl(params: {
 
 export interface OAuthTokenResponse {
   access_token: string
-  refresh_token: string
+  /**
+   * Present on the authorization_code grant. Asana does not rotate refresh
+   * tokens, so the refresh_token grant response omits this field.
+   */
+  refresh_token?: string
   expires_in: number
   token_type: string
 }
diff --git a/test/lib/asana-client.test.ts b/test/lib/asana-client.test.ts
index c1413c7..d942016 100644
--- a/test/lib/asana-client.test.ts
+++ b/test/lib/asana-client.test.ts
@@ -268,6 +268,49 @@ describe('asana-client module', () => {
       global.fetch = originalFetch
     })
 
+    test('keeps stored refresh token when refresh response omits refresh_token', async () => {
+      // Asana's refresh_token grant response does not rotate the refresh token,
+      // so the response has no refresh_token field. Persisting `undefined`
+      // would drop it from config.json and permanently break auto-refresh
+      // after the first renewal (login silently "expires" ~1h later).
+      const mockResponse = {
+        access_token: 'new-access-token',
+        expires_in: 3600,
+        token_type: 'bearer',
+      }
+
+      const originalFetch = global.fetch
+      try {
+        global.fetch = mock(() => {
+          return Promise.resolve({
+            ok: true,
+            json: () => Promise.resolve(mockResponse),
+          })
+        }) as any
+
+        const config: AsanaConfig = {
+          accessToken: 'old-access-token',
+          authType: 'oauth',
+          refreshToken: 'old-refresh-token',
+          expiresAt: Date.now() - 1000, // Expired
+        }
+
+        mkdirSync(TEST_CONFIG_DIR, { recursive: true })
+        writeFileSync(TEST_CONFIG_FILE, JSON.stringify(config))
+
+        const result = await refreshTokenIfNeeded()
+
+        expect(result).toBe(true)
+
+        const updatedConfig = JSON.parse(readFileSync(TEST_CONFIG_FILE, 'utf-8'))
+        expect(updatedConfig.accessToken).toBe('new-access-token')
+        expect(updatedConfig.refreshToken).toBe('old-refresh-token')
+      }
+      finally {
+        global.fetch = originalFetch
+      }
+    })
+
     test('refreshes token when it will expire soon', async () => {
       const mockResponse = {
         access_token: 'new-access-token',