apps/web/src/lib/__tests__/posthog.test.ts

@@ -0,0 +1,37 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+
+// Mock the underlying posthog-js SDK (not @/lib/posthog) so we exercise the
+// real capturePageView implementation.
+const captureMock = vi.fn();
+vi.mock("posthog-js", () => ({
+  default: {
+    init: vi.fn(),
+    capture: captureMock,
+    identify: vi.fn(),
+    reset: vi.fn(),
+    people: { set: vi.fn() },
+  },
+}));
+
+import { capturePageView } from "../posthog";
+
+describe("capturePageView", () => {
+  beforeEach(() => {
+    captureMock.mockClear();
+  });
+
+  it("includes the query string so UTM params are not dropped (attribution regression)", async () => {
+    window.history.pushState({}, "", "/?utm_source=facebook&utm_campaign=traffic_lpv_v1");
+
+    capturePageView("/");
+
+    await vi.waitFor(() => expect(captureMock).toHaveBeenCalledTimes(1));
+    const [event, props] = captureMock.mock.calls[0];
+    expect(event).toBe("$pageview");
+    // The whole point: $current_url must carry the UTMs, not just origin+path.
+    expect(props.$current_url).toContain("utm_source=facebook");
+    expect(props.$current_url).toContain("utm_campaign=traffic_lpv_v1");
+    expect(props.$current_url).toBe(window.location.href);
+    expect(props.$pathname).toBe("/");
+  });
+});

apps/web/src/lib/posthog.ts

@@ -25,7 +25,11 @@ export function initPostHog(): void {
     ph.init(key, {
       api_host: "https://t.sase.tr",
       defaults: "2026-01-30",
-      person_profiles: "identified_only",
+      // "always" (not "identified_only") so anonymous ad visitors get a person
+      // profile that captures first-touch UTM/referrer ($initial_utm_*). Required
+      // for ad→signup attribution. Volume is ~34k events/mo (PostHog free tier is
+      // 1M/mo), so the cost impact is negligible at current scale.
+      person_profiles: "always",
       capture_pageview: false,
       capture_pageleave: false,
       autocapture: false,
@@ -61,7 +65,14 @@ export function capture(event: string, properties?: Record<string, unknown>): vo
 }
 
 export function capturePageView(path: string): void {
-  load().then((ph) => ph.capture("$pageview", { $current_url: window.location.origin + path }));
+  // Pass the full URL (incl. query string) so PostHog can parse UTM params and
+  // persist first-touch attribution ($initial_utm_*, $utm_*). Previously this
+  // sent only `origin + path`, silently dropping every ad UTM — so all paid
+  // traffic was mis-bucketed as "direct". The index route keeps unknown search
+  // params, so window.location.href still holds the UTMs at mount.
+  load().then((ph) =>
+    ph.capture("$pageview", { $current_url: window.location.href, $pathname: path }),
+  );
 }
 
 export function setPeopleProperties(properties: Record<string, unknown>): void {