Wire PostHog analytics into AI Notebook template

[CarmenDou]

Summary

Adds PostHog analytics across the AI Notebook template, instrumented via the official PostHog Next.js wizard. Tracks 11 custom events spanning auth, chat, document upload, workspace creation, and AI-feature usage, plus identifies signed-in users for cohort analysis. Already deployed to https://aipdfchat.insforge.site and emitting events to PostHog.

What lands in this PR

New files:

• instrumentation-client.ts — client-side PostHog init via Next 13.4+ instrumentation hook, with /ingest reverse-proxy hosts
• lib/posthog-server.ts — server-side singleton for API-route event captures

Config:

• next.config.js — /ingest/* rewrites so client requests avoid ad blockers
• package.json — adds posthog-js and posthog-node
• .env.example — documents the two new optional env vars (NEXT_PUBLIC_POSTHOG_PROJECT_TOKEN, NEXT_PUBLIC_POSTHOG_HOST); template still works with them blank

Instrumented events (11):

Event	File	Notable properties
user_signed_up	components/sign-up-form.tsx	also calls posthog.identify
user_signed_in	components/sign-in-form.tsx	also calls posthog.identify
document_uploaded	app/api/documents/upload/route.ts	file_size_bytes, chunk_count, ingest_status
chat_message_sent	app/api/chat/route.ts	is_new_chat, workspace_id
workspace_created	app/api/workspaces/route.ts	workspace_id, workspace_name
flashcards_generated	components/flashcards-modal.tsx	card_count
flashcard_graded	app/api/flashcards/[id]/grade/route.ts	grade, next_interval_days
audio_overview_generated	app/api/workspaces/[id]/audio/route.ts	document_count, script_turn_count
mindmap_generated	app/api/workspaces/[id]/mindmap/route.ts	document_count
chat_share_link_created	components/share-chat-button.tsx	chat_id
chat_share_link_revoked	components/share-chat-button.tsx	chat_id

Opt-in design

The template stays functional with no PostHog token configured. With the env vars blank, all posthog.* calls become inert no-ops at runtime. Fork-and-go users do not need a PostHog account to ship.

Test plan

• npm run build passes
• With NEXT_PUBLIC_POSTHOG_PROJECT_TOKEN set, sign-up triggers user_signed_up in PostHog Live Events
• Uploading a PDF triggers document_uploaded with non-zero chunk_count
• Generating a mindmap triggers mindmap_generated
• Generating audio triggers audio_overview_generated
• Without the env var, the app still runs and no requests hit /ingest/*

🤖 Generated with Claude Code

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Summary by cubic

Adds PostHog analytics to the AI Notebook template with client/server setup, reverse‑proxied /ingest endpoints that honor NEXT_PUBLIC_POSTHOG_HOST, and 11 events across auth, chat, uploads, workspaces, and learning tools. Identifies signed‑in users and gracefully swallows analytics failures; fully optional when env vars are unset.

• New Features

  • Client init via Next.js instrumentation and a server capture helper; /ingest/* is reverse‑proxied and the assets host is derived from NEXT_PUBLIC_POSTHOG_HOST (US/EU/self‑host) to avoid ad blockers.
  • Captures 11 events with useful properties (auth sign‑in/up with identify and captureException, chat messages, document uploads, workspace creation, flashcards generated/graded, audio overview, mindmap, share link create/revoke); API routes call posthog.shutdown() and swallow failures so requests don't error.
  • Added dependencies: posthog-js, posthog-node.

• Migration

  • To enable, set NEXT_PUBLIC_POSTHOG_PROJECT_TOKEN and optionally NEXT_PUBLIC_POSTHOG_HOST (example: https://us.i.posthog.com).

^{Written for commit 6b91b19. Summary will update on new commits.}

[cubic-dev-ai]

4 issues found across 16 files

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[Fermionic-Lyu]

LGTM, Approved.