At a glance
Event Tracking Broken (core event stopped firing) is a Nerve Centre alert tracked from PostHog event data. It fires when a designated core event, for examplepurchase,add_to_cart, orcheckout_started, records zero occurrences for more than an hour. A single core event going silent is a precise, high-confidence sign that instrumentation broke on a specific flow, even when overall event volume still looks healthy. This is the most surgical of the tracking alarms.
| What it counts | Alert events raised when a core event’s count stays at zero for more than one hour. |
| Sample type | Backend API data from PostHog event counts, evaluated against the alert rule on each refresh. |
| Why it matters | One broken event can hide a whole revenue flow while the rest of your dashboard looks normal. This alert isolates the exact event that stopped. |
| Reading the value | A non-zero count means a core event went silent. Open the alert to see which event and when it last fired. |
| Currency | count |
| Time window | RT |
| Alert trigger | core event count = 0 for >1h |
| Sentiment key | ph_alert_tracking_broken |
| Roles | owner, marketing |
Calculation
Calculated automatically from your PostHog data. See the At a glance summary above for what the metric tracks and the worked example below for a typical reading.Worked example
A representative reading of Event Tracking Broken (core event stopped firing) for a typical merchant on PostHog. Supposepurchase normally fires 40 to 80 times an hour. After a checkout refactor on 18 Apr 26, the event handler is renamed and purchase records zero for two consecutive hours while pageview and add_to_cart keep flowing. The alert fires. Because only one event went dark, you can go straight to the checkout instrumentation rather than auditing the whole site. Cross-reference Core Events Firing to confirm which events are still healthy. For deeper investigation, use Vortex Mind to trace upstream causes; for natural-language exploration, ask Ask Viq.
Sibling cards merchants should reference together
| Card | Why merchants reach for it |
|---|---|
ph_core_events_firing | Event Health sibling: the live count of core events still firing. |
ph_alert_event_volume_drop | Nerve Centre sibling: broad event volume collapse. |
ph_top_events | Event Health sibling: your highest-volume events. |
ph_event_volume | Executive sibling: total event volume. |
ph_health_score | Executive sibling: overall tracking health score. |
Reconciling against the vendor’s own dashboard
Where to look in PostHog’s own dashboard: In PostHog, open the Activity or live events view and filter to the named core event. If it has not appeared for over an hour, the gap matches the alert. A trend insight on that single event, viewed hourly, makes the silence visible against its normal cadence. Why the Vortex IQ value may legitimately differ:| Reason | Direction | What to do |
|---|---|---|
| Event naming. A rename ships the same action under a new event name; the old name reads zero. | Variable | Check for a renamed event firing in parallel. |
| Low-traffic hour. A genuinely quiet event may hit zero overnight without being broken. | Variable | Confirm the event normally fires hourly. |
| Ingestion lag. Brief ingestion delays can show a temporary zero that recovers. | Marginal | Re-check after the next refresh. |