diff --git a/bp/auth/routes.py b/bp/auth/routes.py
index ee40a33..ce04927 100644
--- a/bp/auth/routes.py
+++ b/bp/auth/routes.py
@@ -67,12 +67,18 @@ def register(url_prefix="/auth"):
         if redirect_uri != expected_redirect:
             return "Invalid redirect_uri", 400
 
+        # Account's own device id — always available via factory hook
+        account_did = g.device_id
+
         # Not logged in
         if not g.get("user"):
             if prompt == "none":
-                # Silent check — no interactive login, return error
+                # Silent check — pass account_did so client can watch for future logins
                 sep = "&" if "?" in redirect_uri else "?"
-                return redirect(f"{redirect_uri}{sep}error=login_required&state={state}")
+                return redirect(
+                    f"{redirect_uri}{sep}error=login_required"
+                    f"&state={state}&account_did={account_did}"
+                )
             authorize_path = request.full_path
             store_login_redirect_target()
             return redirect(url_for("auth.login_form", next=authorize_path))
@@ -110,7 +116,10 @@ def register(url_prefix="/auth"):
                 s.add(oauth_code)
 
         sep = "&" if "?" in redirect_uri else "?"
-        return redirect(f"{redirect_uri}{sep}code={code}&state={state}")
+        return redirect(
+            f"{redirect_uri}{sep}code={code}&state={state}"
+            f"&account_did={account_did}"
+        )
 
     # --- Grant verification (internal endpoint) ------------------------------
 
@@ -276,6 +285,20 @@ def register(url_prefix="/auth"):
         # Fresh account session ID for grant tracking
         qsession[ACCOUNT_SESSION_KEY] = secrets.token_urlsafe(32)
 
+        # Signal login for this device so client apps can detect it
+        try:
+            from shared.browser.app.redis_cacher import get_redis
+            import time as _time
+            _redis = get_redis()
+            if _redis:
+                await _redis.set(
+                    f"did_auth:{g.device_id}",
+                    str(_time.time()).encode(),
+                    ex=30 * 24 * 3600,
+                )
+        except Exception:
+            current_app.logger.exception("[auth] failed to set did_auth in Redis")
+
         redirect_url = pop_login_redirect_target()
         return redirect(redirect_url, 303)
 
@@ -296,6 +319,15 @@ def register(url_prefix="/auth"):
             except SQLAlchemyError:
                 current_app.logger.exception("[auth] failed to revoke grants")
 
+        # Clear login signal for this device
+        try:
+            from shared.browser.app.redis_cacher import get_redis
+            _redis = get_redis()
+            if _redis:
+                await _redis.delete(f"did_auth:{g.device_id}")
+        except Exception:
+            pass
+
         qsession.pop(SESSION_USER_KEY, None)
         qsession.pop(ACCOUNT_SESSION_KEY, None)
         from shared.infrastructure.urls import blog_url
@@ -318,6 +350,15 @@ def register(url_prefix="/auth"):
             except SQLAlchemyError:
                 current_app.logger.exception("[auth] failed to revoke grants")
 
+        # Clear login signal for this device
+        try:
+            from shared.browser.app.redis_cacher import get_redis
+            _redis = get_redis()
+            if _redis:
+                await _redis.delete(f"did_auth:{g.device_id}")
+        except Exception:
+            pass
+
         qsession.pop(SESSION_USER_KEY, None)
         qsession.pop(ACCOUNT_SESSION_KEY, None)
         from shared.infrastructure.urls import blog_url