@mmstack/telemetry-posthog

Experimental. The API may still change and this package is not yet battle-tested in production. Pin a version and expect some churn.

PostHog adapter for @mmstack/telemetry-core. An EventSink over your own posthog-js instance, plus a reactive session-replay URL handle.

Install

npm install @mmstack/telemetry-posthog

No PostHog SDK is bundled or required as a peer. You bring your own inited client (so replay, autocapture, and flags stay configured your way) and the adapter uses a minimal structural slice of it.

Usage

import posthog from 'posthog-js';
import { provideTelemetry } from '@mmstack/telemetry-core';
import { posthogSink } from '@mmstack/telemetry-posthog';

posthog.init('<key>', { api_host: 'https://eu.posthog.com' });

provideTelemetry({
  sinks: [posthogSink({ posthog })],
});

telemetry.event(name, attrs) forwards to posthog.capture(name, attrs). Events emitted inside a span carry trace_id / span_id automatically, so a PostHog event links back to the trace your OTLP backend received.

Session replay handle

If the client exposes get_session_replay_url, the adapter publishes it in the TelemetryHandles registry as a signal, keyed by sink name: posthog.replay_url for the default (the POSTHOG_REPLAY_URL constant), <name>.replay_url when you pass a custom name, so two PostHog sinks never shadow each other. It starts undefined and fills in once recording begins, so other sinks or your own code can attach the replay link to spans and errors:

const replayUrl = inject(TelemetryHandles).get<string>(POSTHOG_REPLAY_URL);

Pass null for the client and the factory returns null, dropping the sink so the facade stays a noop.