PostHog Integration

The PostHog integration receives webhook alerts for metric changes, creating signals in Loop with severity derived from the magnitude of the change.

Endpoint

POST /api/signals/posthog

Authentication

PostHog webhooks use a shared secret sent as a header value. Loop compares the header directly against the configured secret.

Header: X-PostHog-Secret
Format: Raw secret string (no HMAC computation)
Comparison: Timing-safe (crypto.timingSafeEqual)

If the header is missing or the secret does not match, Loop responds with 401.

This is simpler than the HMAC-based verification used by GitHub and Sentry. PostHog sends the secret itself in the header rather than a computed signature.

Severity Mapping

Loop derives severity from the absolute percentage change in the metric:

Change Magnitude	Severity
>= 50%	`critical`
>= 25%	`high`
>= 10%	`medium`
< 10%	`low`

What Gets Created

Each webhook delivery creates:

A signal record with source: "posthog", type metric_change, severity, and full payload.
A linked issue with type signal, status triage, and a title like PostHog: page_load_time 35% (last_7_days).

The issue title includes the metric name, percentage change, and timeframe.

Setup

Generate a webhook secret

Create a random secret string:

openssl rand -hex 32

Save this value for both PostHog and your Loop environment.

Set the environment variable

Add the secret to your Loop API environment:

POSTHOG_WEBHOOK_SECRET=your_generated_secret_here

This variable must be available to the Loop API process at runtime.

Configure the webhook in PostHog

In PostHog, go to Data pipelines > Destinations (or Project Settings > Webhooks depending on your PostHog version).
Add a new webhook destination.

Set the URL to your Loop endpoint:

https://your-loop-api.example.com/api/signals/posthog

Configure the webhook to include the header X-PostHog-Secret with the same secret value you used for POSTHOG_WEBHOOK_SECRET.
Select which actions or alerts should trigger the webhook (e.g., metric threshold alerts).
Save and enable the destination.

Verify the connection

Trigger a test event in PostHog or use a tool like curl to send a test payload:

curl -X POST https://your-loop-api.example.com/api/signals/posthog \
  -H "Content-Type: application/json" \
  -H "X-PostHog-Secret: your_generated_secret_here" \
  -d '{"name": "test_metric", "value": 15, "timeframe": "last_7_days"}'

Check your Loop instance for a new signal with source posthog.

Example Payload

Loop reads the following fields from the PostHog webhook payload:

event.name or name -- the metric name, used in the issue title
value -- the percentage change, used for severity calculation and the issue title
timeframe -- the time period, used in the issue title (defaults to recent)

PostHog

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