The browser pixel under-counts signups badly: ~96% of paid traffic is mobile
in-app browsers where iOS ITP / ad-blockers drop client events, and the OAuth
path never fired it reliably. Meta recorded ~0 registrations for a 7.5K-spend
campaign while PostHog saw 98 facebook signups — so Meta could neither optimize
toward nor attribute signups, which is the main driver of the low signup rate.
This adds a server-side CAPI CompleteRegistration:
- MetaCapiService + @Global module. Fail-open: no-ops unless META_CAPI_PIXEL_ID
+ META_CAPI_ACCESS_TOKEN are set; never throws (signup must not break).
SHA-256 hashed email + fbp/fbc/IP/UA.
- Fired from the better-auth user.create.after hook for ALL signups (reliable,
covers Google OAuth which the browser pixel missed entirely).
- A session-gated POST /analytics/meta/complete-registration endpoint adds
fbp/fbc/IP/UA (ad-click attribution) for the email path.
- The browser pixel now passes a shared event_id (signup_<userId>); the
premature Google client-pixel fire (fired on click, before completion) is
removed.
- All sources dedupe via event_id=signup_<userId>.
Activate by setting META_CAPI_PIXEL_ID + META_CAPI_ACCESS_TOKEN (Events Manager)
in the api env; META_CAPI_TEST_EVENT_CODE routes to Test Events for verification.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
