posthog-common-errors

name	posthog-common-errors
description	Diagnose and fix common PostHog errors: events not appearing, flags returning undefined, 401/429 errors, SDK initialization failures, and identity issues. Trigger: "posthog error", "fix posthog", "posthog not working", "debug posthog", "posthog events missing", "posthog broken".
allowed-tools	Read, Grep, Bash(curl:*)
version	1.12.0
license	MIT
author	Jeremy Longshore <[e-mail]>
tags	["saas","posthog","debugging"]
compatibility	Designed for Claude Code

PostHog Common Errors

Overview

Diagnosis and solutions for the most common PostHog integration errors. Covers event capture failures, authentication issues, feature flag problems, identity fragmentation, and SDK initialization errors.

Prerequisites

• PostHog SDK installed (posthog-js or posthog-node)
• Access to browser console or server logs
• PostHog project API key (phc_...) available

Instructions

Error 1: Events Not Appearing in Dashboard

Symptoms: posthog.capture() calls execute without error but events never show in PostHog Activity tab.

Diagnoses and fixes:

// Problem A: Not flushing in serverless/scripts
// posthog-node queues events — they're lost if process exits before flush
const posthog = new PostHog('phc_...');
posthog.capture({ distinctId: 'user-1', event: 'test' });
// FIX: Always flush before exit
await posthog.shutdown(); // or await posthog.flush()

// Problem B: Wrong API host
posthog.init('phc_...', {
  api_host: 'https://app.posthog.com', // WRONG — this is the UI
});
// FIX: Use the ingest endpoint
posthog.init('phc_...', {
  api_host: 'https://us.i.posthog.com', // CORRECT for US Cloud
  // api_host: 'https://eu.i.posthog.com', // For EU Cloud
});

// Problem C: Ad blocker blocking posthog-js requests
// FIX: Set up a reverse proxy (see posthog-sdk-patterns)