feat: prefer real user ID in analytics tracking

When a user is authenticated, cache their real user ID in personal
settings and use it as the distinct ID for PostHog events instead of
the anonymous UUID. This improves analytics accuracy by linking events
to actual user accounts.

Author: theFong

pkg/analytics/posthog.go

@@ -100,7 +100,8 @@ func SetAnalyticsPreference(enabled bool) error {
 	return nil
 }
 
-// GetOrCreateAnalyticsID returns a stable anonymous UUID for tracking, creating one if needed.
+// GetOrCreateAnalyticsID returns the user's distinct ID for tracking.
+// It prefers the real user ID if available, falling back to a stable anonymous UUID.
 func GetOrCreateAnalyticsID() string {
 	fs := files.AppFs
 	home, err := getHomeDir()
@@ -111,6 +112,9 @@ func GetOrCreateAnalyticsID() string {
 	if err != nil {
 		return ""
 	}
+	if settings.UserID != "" {
+		return settings.UserID
+	}
 	if settings.AnalyticsID != "" {
 		return settings.AnalyticsID
 	}
@@ -119,6 +123,28 @@ func GetOrCreateAnalyticsID() string {
 	return settings.AnalyticsID
 }
 
+// SetUserID persists the real user ID into personal settings so that
+// future analytics events use it as the distinct ID.
+func SetUserID(userID string) {
+	if userID == "" {
+		return
+	}
+	fs := files.AppFs
+	home, err := getHomeDir()
+	if err != nil {
+		return
+	}
+	settings, err := files.ReadPersonalSettings(fs, home)
+	if err != nil {
+		return
+	}
+	if settings.UserID == userID {
+		return
+	}
+	settings.UserID = userID
+	_ = files.WritePersonalSettings(fs, home, settings)
+}
+
 // CaptureAnalyticsOptIn sends an event recording the user's analytics consent choice.
 // This is sent regardless of the user's choice so we can measure opt-in rates.
 func CaptureAnalyticsOptIn(optedIn bool) {

pkg/cmd/cmd.go

@@ -169,6 +169,7 @@ func NewBrevCommand() *cobra.Command { //nolint:funlen,gocognit,gocyclo // defin
 			user, err := noLoginCmdStore.GetCurrentUser()
 			if err == nil && user != nil {
 				userID = user.ID
+				analytics.SetUserID(userID)
 			}
 			if userID == "" {
 				userID = analytics.GetOrCreateAnalyticsID()

pkg/files/files.go

@@ -19,6 +19,7 @@ type PersonalSettings struct {
 	DefaultEditor    string `json:"default_editor"`
 	AnalyticsEnabled *bool  `json:"analytics_enabled,omitempty"` // nil = never asked, true = opted in, false = opted out
 	AnalyticsID      string `json:"analytics_id,omitempty"`      // stable anonymous ID for analytics
+	UserID           string `json:"user_id,omitempty"`           // real user ID from the API, cached locally
 }
 
 const (