diff --git a/services/auth-guest/README.md b/services/auth-guest/README.md
index 209465ad45..3fb962be55 100644
--- a/services/auth-guest/README.md
+++ b/services/auth-guest/README.md
@@ -34,7 +34,7 @@ links feature and start the service.
   PIN; redeeming a token or verifying a PIN sets a session cookie. `renew` and
   `verify/pin` are rate-limited.
 - Stores only hashes of the token secret, of the PIN and of the nonce, and
-  deletes the stored record when the share is removed or expires. 
+  deletes the stored record when the share is removed or expires.
 
 ## Guest links flow
 
@@ -209,9 +209,11 @@ sequenceDiagram
    publishes `GuestTokenRenewed` without a PIN; no nonce cookie is set. Each
    path is limited per share by its own quota (cooldown plus daily cap), and an
    exceeded limit fails with `429`. Without a valid session nothing happens
-   while the newest link is neither used nor expired. Both paths require an
-   existing record; otherwise the request fails with `tokenNotFound`. If
-   publishing fails, the previous record is restored.
+   while the newest link is neither used nor expired. The response body's
+   `withPin` reports whether the mail carries a PIN, which tells the
+   session-authorized path apart from the silent renewal. Both paths require an
+   existing record; otherwise the request fails with `tokenNotFound`.
+   If publishing fails, the previous record is restored.
 4. **Verify PIN** — the guest posts the PIN, the `permissionId` and the nonce
    cookie to
    `POST /graph/v1beta1/extensions/org.libregraph/guestLinks/verify/pin`.
@@ -245,10 +247,12 @@ Rate-limited responses (`429`) also carry a `retryAfter` field (seconds) and a
 - **Authorization:** the session cookie, when it carries a valid, unexpired
   session token for the given share; without it the renewal is silent (no PIN,
   no nonce cookie)
-- **Success:** `200`, no session cookie. With a valid session a new link and
-  PIN are sent by mail and the nonce cookie is set. Without one a new link is
-  sent by mail, unless the newest link can still be redeemed, in which case
-  nothing happens; the response is the same either way.
+- **Success:** `200`, no session cookie, `{ "withPin": <bool> }`. `withPin` is
+  `true` only when a valid session authorized the renewal and a new link and PIN
+  were sent by mail (the nonce cookie is set as well). In every other successful
+  case — silent rotation without a PIN, or nothing sent because the newest link
+  can still be redeemed — it is `false`, which keeps those cases
+  indistinguishable to callers without a session.
 - **Errors:** `400 invalidRequest`, `404 tokenNotFound`, `404 shareNotFound`,
   `409 conflict`, `410 shareExpired`, `429 tooManyRequests` (with
   `Retry-After`), `503 serviceUnavailable`, `500 internalError`
diff --git a/services/auth-guest/pkg/server/http/renew.go b/services/auth-guest/pkg/server/http/renew.go
index 73ad6dc911..a1047abb27 100644
--- a/services/auth-guest/pkg/server/http/renew.go
+++ b/services/auth-guest/pkg/server/http/renew.go
@@ -18,8 +18,16 @@ type RenewRequest struct {
 	PermissionID string `json:"permissionId"`
 }
 
+// RenewResponse is the response body of the renew endpoint. WithPin reports
+// whether the renewal email contains a PIN, which is true exactly when the
+// request was authorized by a valid session.
+type RenewResponse struct {
+	WithPin bool `json:"withPin"`
+}
+
 // RenewHandler generates a new guest link token and PIN for the share
-// identified by the permission id, authorized by the session cookie.
+// identified by the permission id, authorized by the session cookie. The
+// response body reports whether the renewal email contains a PIN.
 func RenewHandler(log log.Logger, s authguest.AuthGuest, cfg *config.Config) func(w http.ResponseWriter, r *http.Request) {
 	return func(w http.ResponseWriter, r *http.Request) {
 		var req RenewRequest
@@ -51,6 +59,9 @@ func RenewHandler(log log.Logger, s authguest.AuthGuest, cfg *config.Config) fun
 			setNonceCookie(w, cfg, req.PermissionID, nonce)
 		}
 
+		// A non-empty nonce means the PIN path ran, so the mail carries a PIN.
+		w.Header().Set("Content-Type", "application/json")
 		w.WriteHeader(http.StatusOK)
+		_ = json.NewEncoder(w).Encode(RenewResponse{WithPin: nonce != ""})
 	}
 }
diff --git a/services/auth-guest/pkg/server/http/renew_test.go b/services/auth-guest/pkg/server/http/renew_test.go
index ef37ae560c..06d3e6c5ed 100644
--- a/services/auth-guest/pkg/server/http/renew_test.go
+++ b/services/auth-guest/pkg/server/http/renew_test.go
@@ -61,8 +61,13 @@ func TestRenewHandlerWithSessionCookie(t *testing.T) {
 	newRenewHandler(t, svcMock)(rr, req)
 
 	assert.Equal(t, http.StatusOK, rr.Code)
+	assert.Equal(t, "application/json", rr.Header().Get("Content-Type"))
 	svcMock.AssertCalled(t, "Renew", mock.Anything, "share-1", "session-token")
 
+	var resp RenewResponse
+	require.NoError(t, json.NewDecoder(rr.Body).Decode(&resp))
+	assert.True(t, resp.WithPin)
+
 	wantName := nonceCookieName(testNonceCookieName, "share-1")
 	var cookie *http.Cookie
 	for _, c := range rr.Result().Cookies() {
@@ -81,7 +86,7 @@ func TestRenewHandlerWithSessionCookie(t *testing.T) {
 
 func TestRenewHandlerWithoutSessionCookie(t *testing.T) {
 	svcMock := mocks.NewAuthGuest(t)
-	svcMock.On("Renew", mock.Anything, "share-1", "").Return("nonce-value", nil)
+	svcMock.On("Renew", mock.Anything, "share-1", "").Return("", nil)
 
 	body, err := json.Marshal(RenewRequest{PermissionID: "share-1"})
 	require.NoError(t, err)
@@ -91,6 +96,10 @@ func TestRenewHandlerWithoutSessionCookie(t *testing.T) {
 
 	assert.Equal(t, http.StatusOK, rr.Code)
 	svcMock.AssertCalled(t, "Renew", mock.Anything, "share-1", "")
+
+	var resp RenewResponse
+	require.NoError(t, json.NewDecoder(rr.Body).Decode(&resp))
+	assert.False(t, resp.WithPin)
 }
 
 func TestRenewHandlerSkipsNonceCookieWhenEmpty(t *testing.T) {
@@ -113,6 +122,10 @@ func TestRenewHandlerSkipsNonceCookieWhenEmpty(t *testing.T) {
 
 	assert.Equal(t, http.StatusOK, rr.Code)
 	assert.Empty(t, rr.Result().Cookies())
+
+	var resp RenewResponse
+	require.NoError(t, json.NewDecoder(rr.Body).Decode(&resp))
+	assert.False(t, resp.WithPin)
 }
 
 func TestRenewHandlerNonceCookiePerShare(t *testing.T) {