diff --git a/backend/internal/api/api_test.go b/backend/internal/api/api_test.go
index 9edfb48..a6db7f3 100644
--- a/backend/internal/api/api_test.go
+++ b/backend/internal/api/api_test.go
@@ -765,6 +765,56 @@ func TestProfile_RejectsInvalidHRZones(t *testing.T) {
 	}
 }
 
+func TestSessionMe_ReportsGarminConnectedAfterSuccessfulAuth(t *testing.T) {
+	s, _, _ := newTestServer(t)
+	router := s.Router()
+
+	rec := doJSON(t, router, http.MethodGet, "/api/session/me", nil)
+	var before sessionMeResponse
+	unmarshalBody(t, rec, &before)
+	if before.GarminConnected {
+		t.Fatal("expected a fresh account to report garmin_connected=false")
+	}
+
+	rec = doJSON(t, router, http.MethodPost, "/api/auth/login", nil) // mock.Client defaults to AuthSuccess
+	if rec.Code != http.StatusOK {
+		t.Fatalf("auth/login status = %d, body = %s", rec.Code, rec.Body.String())
+	}
+
+	rec = doJSON(t, router, http.MethodGet, "/api/session/me", nil)
+	var after sessionMeResponse
+	unmarshalBody(t, rec, &after)
+	if !after.GarminConnected {
+		t.Fatal("expected garmin_connected=true after a successful auth")
+	}
+}
+
+func TestSessionMe_GarminConnectedStaysFalseOnMFARequiredOrFailed(t *testing.T) {
+	s, _, userID := newTestServer(t)
+	client, err := s.garminFor(context.Background(), userID)
+	if err != nil {
+		t.Fatalf("garminFor: %v", err)
+	}
+	mockClient, ok := client.(*mock.Client)
+	if !ok {
+		t.Fatalf("expected *mock.Client, got %T", client)
+	}
+	mockClient.AuthResults = []garmin.AuthResult{{Status: garmin.AuthMFARequired, Message: "MFA required"}}
+
+	router := s.Router()
+	rec := doJSON(t, router, http.MethodPost, "/api/auth/login", nil)
+	if rec.Code != http.StatusOK {
+		t.Fatalf("auth/login status = %d, body = %s", rec.Code, rec.Body.String())
+	}
+
+	rec = doJSON(t, router, http.MethodGet, "/api/session/me", nil)
+	var me sessionMeResponse
+	unmarshalBody(t, rec, &me)
+	if me.GarminConnected {
+		t.Fatal("expected garmin_connected=false after mfa_required")
+	}
+}
+
 func TestDeleteProfile_DeletesUserAndTerminatesGarminClient(t *testing.T) {
 	s, db, userID := newTestServer(t)
 	router := s.Router()
diff --git a/backend/internal/api/auth.go b/backend/internal/api/auth.go
index 295e2ff..dea11d7 100644
--- a/backend/internal/api/auth.go
+++ b/backend/internal/api/auth.go
@@ -1,7 +1,9 @@
 package api
 
 import (
+	"context"
 	"encoding/json"
+	"log"
 	"net/http"
 
 	"geniusrun/backend/internal/garmin"
@@ -25,11 +27,22 @@ func authStatusString(s garmin.AuthStatus) string {
 	}
 }
 
-func (s *Server) recordAuthResult(userID int64, res garmin.AuthResult) {
+// recordAuthResult updates the in-memory auth status/message for userID,
+// and -- on a successful authentication -- persists that this account has
+// connected to Garmin at least once (store.MarkGarminConnected), which is
+// what the login gate actually checks (the in-memory auth status resets on
+// every backend restart; this doesn't).
+func (s *Server) recordAuthResult(ctx context.Context, userID int64, res garmin.AuthResult) {
 	s.mu.Lock()
 	s.userAuthStatus[userID] = res.Status
 	s.userAuthMessage[userID] = res.Message
 	s.mu.Unlock()
+
+	if res.Status == garmin.AuthSuccess {
+		if err := s.DB.MarkGarminConnected(ctx, userID); err != nil {
+			log.Printf("api: mark garmin connected for user %d: %v", userID, err)
+		}
+	}
 }
 
 func (s *Server) handleAuthLogin(w http.ResponseWriter, r *http.Request) {
@@ -44,7 +57,7 @@ func (s *Server) handleAuthLogin(w http.ResponseWriter, r *http.Request) {
 		writeError(w, http.StatusBadGateway, err.Error())
 		return
 	}
-	s.recordAuthResult(userID, res)
+	s.recordAuthResult(r.Context(), userID, res)
 	writeJSON(w, http.StatusOK, authResponse{Status: authStatusString(res.Status), Message: res.Message})
 }
 
@@ -72,7 +85,7 @@ func (s *Server) handleAuthMFA(w http.ResponseWriter, r *http.Request) {
 		writeError(w, http.StatusBadGateway, err.Error())
 		return
 	}
-	s.recordAuthResult(userID, res)
+	s.recordAuthResult(r.Context(), userID, res)
 	writeJSON(w, http.StatusOK, authResponse{Status: authStatusString(res.Status), Message: res.Message})
 }
 
diff --git a/backend/internal/api/isolation_test.go b/backend/internal/api/isolation_test.go
index f25e4e6..0572354 100644
--- a/backend/internal/api/isolation_test.go
+++ b/backend/internal/api/isolation_test.go
@@ -181,3 +181,25 @@ func TestIsolation_DeleteProfileOnlyDeletesOwnAccount(t *testing.T) {
 		t.Fatalf("userA profile status after userB deleted themselves = %d, body = %s", rec.Code, rec.Body.String())
 	}
 }
+
+// TestIsolation_GarminConnectedNeverLeaksAcrossUsers confirms one user's
+// successful Garmin auth never flips garmin_connected for another user.
+func TestIsolation_GarminConnectedNeverLeaksAcrossUsers(t *testing.T) {
+	s, db, _ := newTestServer(t) // provisions "test-user" (userA)
+	if _, err := db.ProvisionUser(newCtx(), "user-b", "B"); err != nil {
+		t.Fatalf("ProvisionUser(b): %v", err)
+	}
+
+	router := s.Router()
+	rec := doJSON(t, router, http.MethodPost, "/api/auth/login", nil) // as userA
+	if rec.Code != http.StatusOK {
+		t.Fatalf("auth/login status = %d, body = %s", rec.Code, rec.Body.String())
+	}
+
+	rec = doJSONAs(t, router, "user-b", http.MethodGet, "/api/session/me", nil)
+	var meB sessionMeResponse
+	unmarshalBody(t, rec, &meB)
+	if meB.GarminConnected {
+		t.Fatal("userA's successful Garmin auth leaked into userB's garmin_connected flag")
+	}
+}
diff --git a/backend/internal/api/session.go b/backend/internal/api/session.go
index 3376e36..d35c666 100644
--- a/backend/internal/api/session.go
+++ b/backend/internal/api/session.go
@@ -32,10 +32,11 @@ type SessionConfig struct {
 }
 
 type sessionMeResponse struct {
-	Name        string `json:"name"`
-	Email       string `json:"email"`
-	HasProfile  bool   `json:"has_profile"`
-	DisplayName string `json:"display_name,omitempty"`
+	Name            string `json:"name"`
+	Email           string `json:"email"`
+	HasProfile      bool   `json:"has_profile"`
+	DisplayName     string `json:"display_name,omitempty"`
+	GarminConnected bool   `json:"garmin_connected"`
 }
 
 func (s *Server) handleSessionLogin(w http.ResponseWriter, r *http.Request) {
@@ -113,6 +114,12 @@ func (s *Server) handleSessionMe(w http.ResponseWriter, r *http.Request) {
 	if u, found := userFromContext(r.Context()); found {
 		resp.HasProfile = true
 		resp.DisplayName = u.DisplayName
+		profile, err := s.DB.GetProfile(r.Context(), u.ID)
+		if err != nil {
+			writeError(w, http.StatusInternalServerError, err.Error())
+			return
+		}
+		resp.GarminConnected = profile.GarminConnectedAt != nil
 	}
 	writeJSON(w, http.StatusOK, resp)
 }