/instrument-repo

Add production observability to a repository. Detects stack, installs SDKs, writes config, opens PR.

Shared Config

SENTRY_ORG=misty-step
SENTRY_TEAM=misty-step
POSTHOG_PROJECT_ID=293836
POSTHOG_HOST=https://us.i.posthog.com

All repos share ONE PostHog project (segmented by events). Each repo gets its OWN Sentry project.

Detection

Before instrumenting, detect what we're working with:

# Language detection
[ -f package.json ] && echo "typescript"
[ -f go.mod ] && echo "go"
[ -f pyproject.toml ] || [ -f setup.py ] && echo "python"
[ -f Package.swift ] && echo "swift"
[ -f Cargo.toml ] && echo "rust"

# Framework detection (TypeScript)
grep -q '"next"' package.json 2>/dev/null && echo "nextjs"
grep -q '"hono"' package.json 2>/dev/null && echo "hono"
grep -q '"express"' package.json 2>/dev/null && echo "express"
grep -q '"react-native"' package.json 2>/dev/null && echo "react-native"

# LLM usage detection (for Helicone)
grep -rq '@ai-sdk\|openai\|anthropic\|@google/genai' package.json src/ lib/ app/ 2>/dev/null && echo "has-llm"
grep -rq 'openai\|anthropic\|langchain' *.go cmd/ internal/ 2>/dev/null && echo "has-llm"
grep -rq 'openai\|anthropic\|langchain' *.py src/ 2>/dev/null && echo "has-llm"

# Existing instrumentation
grep -q '@sentry' package.json 2>/dev/null && echo "has-sentry"
grep -q 'posthog' package.json 2>/dev/null && echo "has-posthog"
grep -rq 'helicone' src/ lib/ app/ 2>/dev/null && echo "has-helicone"

Per-repo Workflow

1. cd ~/Development/$REPO
2. Detect language, framework, LLM usage, existing instrumentation
3. git fetch origin && git checkout -b infra/observability origin/main (or master)
4. Create Sentry project if needed → mcp__sentry__create_project
5. Install packages (language-specific)
6. Write/update config files from templates
7. Update .env.example
8. Typecheck/build to verify
9. git add <specific files> && git commit
10. git push -u origin infra/observability
11. gh pr create with structured body

What to Add (Decision Matrix)

Condition	Sentry	PostHog	Helicone
Any app/service	YES	—	—
User-facing web app	YES	YES	—
Has LLM SDK imports	YES	maybe	YES
CLI tool	YES	NO	maybe
GitHub Action / lib	NO	NO	NO

Sentry Sampling Rates

Cost-conscious defaults (5k errors/mo free tier):

tracesSampleRate: 0.1          # 10% of transactions
replaysSessionSampleRate: 0    # Don't record sessions by default
replaysOnErrorSampleRate: 1.0  # Always replay on error

Templates

Next.js → templates/nextjs/

Files to create:

• sentry.client.config.ts — Client-side Sentry init
• sentry.server.config.ts — Server-side Sentry init
• sentry.edge.config.ts — Edge runtime Sentry init (same as server)
• instrumentation.ts — Next.js instrumentation hook
• lib/sentry.ts — Shared Sentry config factory with PII scrubbing
• components/posthog-provider.tsx — PostHog React provider
• components/posthog-pageview.tsx — Route-aware pageview tracking
• lib/posthog.ts — PostHog client init + helpers

Install: pnpm add @sentry/nextjs posthog-js posthog-node

Next.js config: wrap with withSentryConfig() in next.config.ts

PostHog /ingest rewrite in next.config.ts:

async rewrites() {
  return [
    { source: "/ingest/static/:path*", destination: "https://us-assets.i.posthog.com/static/:path*" },
    { source: "/ingest/:path*", destination: "https://us.i.posthog.com/:path*" },
    { source: "/ingest/decide", destination: "https://us.i.posthog.com/decide" },
  ];
},

Node.js (Express/Hono) → templates/node/

Files to create:

• lib/sentry.ts — Sentry init for Node

Install: pnpm add @sentry/node

Express: Sentry.setupExpressErrorHandler(app) after all routes Hono: Import and init at app entry, use onError hook

Go → templates/go/

Files to create:

• internal/observability/sentry.go — Sentry init + flush helper

Install: go get github.com/getsentry/sentry-go

Python → templates/python/

Files to create:

• observability.py — Sentry init

Install: pip install sentry-sdk or add to pyproject.toml

Swift → templates/swift/

Files to create:

• SentrySetup.swift — Sentry init via SPM

SPM dependency: https://github.com/getsentry/sentry-cocoa PostHog SPM: https://github.com/PostHog/posthog-ios

Rust → templates/rust/

Files to create:

• src/sentry_init.rs — Sentry guard init

Install: Add sentry = "0.35" to Cargo.toml

React Native → templates/react-native/

Install: pnpm add @sentry/react-native posthog-react-native

Helicone → templates/helicone/

Files to create:

• lib/ai-provider.ts — Helicone-proxied AI SDK provider

Pattern: Change baseURL on AI SDK provider to Helicone gateway, add auth + property headers.

Commit Message

feat: add observability (Sentry [+ PostHog] [+ Helicone])

- Sentry: error tracking with PII-safe defaults
[- PostHog: product analytics with privacy masking]
[- Helicone: LLM cost tracking via gateway proxy]
- Updated .env.example with required variables

PR Body

## Summary
Add production observability to {repo}.

## Changes
- Sentry error tracking (DSN: `{dsn}`)
  - PII scrubbing (emails, IPs, sensitive headers)
  - Environment-aware (production/preview/development)
  - Traces sample rate: 10%
[- PostHog product analytics
  - Pageview tracking via `/ingest` proxy rewrite
  - Privacy: `respect_dnt: true`, manual pageview capture]
[- Helicone LLM cost tracking
  - Proxied through gateway for cost/latency monitoring
  - Tagged with product name and environment]
- Updated `.env.example` with all required variables

## Required Env Vars
| Variable | Where | Value |
|----------|-------|-------|
| `NEXT_PUBLIC_SENTRY_DSN` | Vercel | `{dsn}` |
| `SENTRY_AUTH_TOKEN` | Vercel + GH Actions | org-level token |
[| `NEXT_PUBLIC_POSTHOG_KEY` | Vercel | project API key |]
[| `HELICONE_API_KEY` | Vercel (server) | Helicone API key |]

## Test Plan
- [ ] `pnpm build` passes
- [ ] Deploy to preview → check Sentry for test error
- [ ] Set env vars on Vercel production
[- [ ] Verify PostHog Live Events after deploy]
[- [ ] Verify Helicone dashboard shows tagged requests]

Env Var Reference

Variable	Scope	Notes
NEXT_PUBLIC_SENTRY_DSN	Per-project	Unique per Sentry project
SENTRY_DSN	Per-project (server-only)	Same DSN, no NEXT_PUBLIC prefix
SENTRY_AUTH_TOKEN	Shared	For source map uploads
SENTRY_ORG	misty-step	Hardcode in config
SENTRY_PROJECT	Per-project	Matches Sentry project slug
NEXT_PUBLIC_POSTHOG_KEY	Shared	PostHog project API key
NEXT_PUBLIC_POSTHOG_HOST	/ingest	Via rewrite proxy
HELICONE_API_KEY	Shared (server-only)	Never expose client-side

Audit Mode

When --audit flag or repo already has instrumentation:

1. Check Sentry config against best practices (PII scrubbing, sampling rates, env detection)
2. Check PostHog config (respect_dnt, manual pageview, proxy rewrite)
3. Check Helicone config (product tag, environment tag, user-id)
4. Report findings, fix issues, open PR with fixes

Anti-Patterns

• tracesSampleRate: 1 — exhausts free tier instantly
• Missing PII scrubbing — privacy violation
• sendDefaultPii: true — leaks emails/IPs
• PostHog without /ingest rewrite — blocked by ad blockers
• Helicone API key in client-side code — key exposure
• Hardcoded DSN in code instead of env var — can't change per environment
• Missing respect_dnt: true on PostHog — privacy violation