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Integration Tanstack Start

PostHogOfficialCreated by PostHog

  • Skill
  • Tool integration
  • Software development
  • MIT
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From the author

PostHog integration for TanStack Start full-stack applications
— the description by PostHog

AutoGineer summary

Written by AutoGineer from the skill’s own files, not by the author

This skill provides a comprehensive workflow for implementing PostHog in TanStack Start projects. It covers both client-side and server-side tracking, ensuring consistent data collection across the full stack. The integration emphasizes best practices such as using environment variables for configuration, implementing singleton patterns for server-side clients, and maintaining session correlation between frontend and backend requests.

What it does

  • Provides a step-by-step workflow for PostHog integration
  • Configures client-side tracking via PostHogProvider
  • Sets up server-side event capture using posthog-node
  • Demonstrates user identification patterns for authentication flows
  • Includes guidance on error tracking and feature flag usage
  • Ensures session correlation between client and server requests

When to use it

  • When adding product analytics to a new or existing TanStack Start application
  • When you need to track server-side business logic alongside client interactions
  • When implementing feature flags or session replay in a full-stack environment
  • When you need to ensure consistent user identification across API boundaries

Advantages

  • Follows established patterns for TanStack Start architecture
  • Maintains data integrity by linking client and server sessions
  • Promotes secure handling of API keys via environment variables
  • Provides clear separation between client-side and server-side tracking logic

Usage examples

“How do I initialize PostHog in my TanStack Start root route?”
The skill guides you to wrap your application in the PostHogProvider within __root.tsx, configuring it with your project token and host settings.
“How should I track events on the server in my API routes?”
The skill instructs you to use a singleton PostHog client from posthog-node and pass the session ID from the frontend via the X-PostHog-Session-Id header.

Install

  1. Download the skill as a ZIP:

    https://autogineer.com/agent-skills/posthog/integration-tanstack-start/download

  2. Unzip it into the cross-client skills folder of your project:

    mkdir -p .agents/skills && unzip integration-tanstack-start.zip -d .agents/skills

Documentation by PostHog

PostHog integration for TanStack Start

This skill helps you add PostHog analytics to TanStack Start applications.

Workflow

Follow these steps in order to complete the integration:

  1. basic-integration-1.0-begin.md - PostHog Setup - Begin ← Start here

  2. basic-integration-1.1-edit.md - PostHog Setup - Edit

  3. basic-integration-1.2-revise.md - PostHog Setup - Revise

  4. basic-integration-1.3-conclude.md - PostHog Setup - Conclusion

Reference files

  • references/EXAMPLE.md - TanStack Start example project code

  • references/tanstack-start.md - Tanstack start - docs

  • references/identify-users.md - Identify users - docs

  • references/basic-integration-1.0-begin.md - PostHog setup - begin

  • references/basic-integration-1.1-edit.md - PostHog setup - edit

  • references/basic-integration-1.2-revise.md - PostHog setup - revise

  • references/basic-integration-1.3-conclude.md - PostHog setup - conclusion

The example project shows the target implementation pattern. Consult the documentation for API details.

Key principles

  • Environment variables: Always use environment variables for PostHog keys. Never hardcode them.

  • Minimal changes: Add PostHog code alongside existing integrations. Don't replace or restructure existing code.

  • Match the example: Your implementation should follow the example project's patterns as closely as possible.

Framework guidelines

  • For feature flags, use useFeatureFlagEnabled() or useFeatureFlagPayload() hooks - they handle loading states and external sync automatically

  • Add analytics capture in event handlers where user actions occur, NOT in useEffect reacting to state changes

  • Do NOT use useEffect for data transformation - calculate derived values during render instead

  • Do NOT use useEffect to respond to user events - put that logic in the event handler itself

  • Do NOT use useEffect to chain state updates - calculate all related updates together in the event handler

  • Do NOT use useEffect to notify parent components - call the parent callback alongside setState in the event handler

  • To reset component state when a prop changes, pass the prop as the component's key instead of using useEffect

  • useEffect is ONLY for synchronizing with external systems (non-React widgets, browser APIs, network subscriptions)

  • Use PostHogProvider in the root route (__root.tsx) for client-side tracking

  • Use posthog-node for server-side event capture in API routes (src/routes/api/) - do NOT use posthog-js on the server

  • Create a singleton PostHog server client to avoid re-initialization on every request

  • Use TanStack Router's built-in navigation events for pageview tracking instead of useEffect

  • Use PostHogProvider in the root component defined in either the file-based convention (__root.tsx) or code-based convention (wherever createRootRoute() is called) so all child routes have access to the PostHog client

Identifying users

Identify users during login and signup events. Refer to the example code and documentation for the correct identify pattern for this framework. If both frontend and backend code exist, pass the client-side session and distinct ID using X-POSTHOG-DISTINCT-ID and X-POSTHOG-SESSION-ID headers to maintain correlation.

Error tracking

Add PostHog error tracking to relevant files, particularly around critical user flows and API boundaries.

Files

references/tanstack-start.md

TanStack Start - Docs

This tutorial shows how to integrate PostHog with a TanStack Start app for both client-side and server-side analytics.

Installation

Install the required packages:

Terminal

PostHog AI

npm install @posthog/react posthog-node

  • @posthog/react - React package for our JS Web SDK for client-side usage

  • posthog-node - PostHog Node.js SDK for server-side event capture

Identifying users

Identifying users is required. Call posthog.identify('your-user-id') after login to link events to a known user. This is what connects frontend event captures, session replays, LLM traces, and error tracking to the same person — and lets backend events link back too.

See our guide on identifying users for how to set this up.

Initialize PostHog on the client

Wrap your app with PostHogProvider in your root route with your project token, host, and other options.

src/routes/__root.tsx

PostHog AI

// src/routes/__root.tsx
import { HeadContent, Scripts, createRootRoute } from '@tanstack/react-router'
import { PostHogProvider } from '@posthog/react'
export const Route = createRootRoute({
  head: () => ({
    meta: [
      { charSet: 'utf-8' },
      { name: 'viewport', content: 'width=device-width, initial-scale=1' },
    ],
  }),
  shellComponent: RootDocument,
})
function RootDocument({ children }: { children: React.ReactNode }) {
  return (
    <html lang="en">
      <head>
        <HeadContent />
      </head>
      <body>
        <PostHogProvider
          apiKey="<ph_project_token>"
          options={{
            api_host: 'https://us.i.posthog.com',
            defaults: '2026-01-30',
            capture_exceptions: true
          }}
        >
          {children}
        </PostHogProvider>
        <Scripts />
      </body>
    </html>
  )
}

Once the provider is in place, PostHog automatically captures pageviews, sessions, and web vitals.

Capture events on the client

Use the usePostHog hook from @posthog/react in any component to capture custom events:

src/routes/checkout.tsx

PostHog AI

import { usePostHog } from '@posthog/react'
function CheckoutButton({ orderId, total }: { orderId: string; total: number }) {
  const posthog = usePostHog()
  const handleClick = () => {
    posthog.capture('checkout_started', {
      order_id: orderId,
      total: total,
    })
  }
  return <button onClick={handleClick}>Checkout</button>
}
Identify users

Call posthog.identify() when a user logs in to link their events to a user ID:

TSX

PostHog AI

import { usePostHog } from '@posthog/react'
function LoginForm() {
  const posthog = usePostHog()
  const handleLogin = async (userId: string, email: string) => {
    // ... your login logic
    posthog.identify(userId, {
      email: email,
    })
    posthog.capture('user_logged_in')
  }
}

Call posthog.reset() on logout to clear the identified user.

Initialize PostHog on the server

Create a server-side PostHog client using posthog-node. Use a singleton pattern so you reuse the same client across requests:

src/utils/posthog-server.ts

PostHog AI

// src/utils/posthog-server.ts
import { PostHog } from 'posthog-node'
let posthogClient: PostHog | null = null
export function getPostHogClient() {
  if (!posthogClient) {
    posthogClient = new PostHog(
      '<ph_project_token>',
      {
        host: 'https://us.i.posthog.com',
        flushAt: 1,
        flushInterval: 0,
      },
    )
  }
  return posthogClient
}

Capture events on the server

Use the server client in TanStack Start API routes to capture events server-side. Server-side capture is useful for tracking events that shouldn't be spoofable from the client, like purchases or authentication:

src/routes/api/checkout.ts

PostHog AI

// src/routes/api/checkout.ts
import { createFileRoute } from '@tanstack/react-router'
import { json } from '@tanstack/react-start'
import { getPostHogClient } from '../../utils/posthog-server'
export const Route = createFileRoute('/api/checkout')({
  server: {
    handlers: {
      POST: async ({ request }) => {
        const body = await request.json()
        const posthog = getPostHogClient()
        posthog.capture({
          distinctId: body.userId,
          event: 'item_purchased',
          properties: {
            item_id: body.itemId,
            price: body.price,
            source: 'api',
          },
        })
        return json({ success: true })
      },
    },
  },
})

The server-side capture call requires a distinctId (the user identifier), an event name, and optional properties.

Next steps

Installing the JS Web SDK and Node SDK means all of their functionality is available in your TanStack Start project. To learn more about this, have a look at our JS Web SDK docs and Node SDK docs.

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Requirements and compatibility

Works with: Claude Code, Claude apps, OpenAI Codex, GitHub Copilot, Cursor, Gemini CLI, Kiro, OpenCode, Goose, Amp, Roo Code, JetBrains Junie, Factory Droid, Devin (ex-Windsurf), Mistral Vibe, OpenHands, Letta

“Works with” means the tool reads the open Agent Skills format; a skill written for one tool may use features others lack.

Needs: Needs Node.js

Security

No issues found by our static scan· No issues found

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Attribution and licence

Created by
PostHog
Publisher
PostHog (Official)
Source
PostHog/skills · skills/posthog/integration/skills/tanstack-start · commit a5d30e7
Licence
MIT License (redistribution allowed)
  • LICENSE (added by AutoGineer from LICENSE)
  • ATTRIBUTION.md (written by AutoGineer)
Synced
Also distributed in
PostHog/skills

AutoGineer is not affiliated with or endorsed by PostHog or PostHog.

Download ZIP

The ZIP holds the skill’s files, its licence files and an ATTRIBUTION.md. Download integration-tanstack-start.zip