Cursor makes you ship 10x faster. That means bugs reach production 10x faster too. DeepTracer is the safety net that catches what slipped through — investigates it automatically, explains it in plain English, and sends you the fix.
session.user.email. The customer is created on every checkout request and the ID is returned for use in payment intent creation.
session.user.email is null for all Google sign-ins — Stripe throws on line 7.
if (!session?.user?.email) before the Stripe call. Return a 400 prompting email verification.
AI-assisted code has patterns. It assumes everything is defined. It writes the happy path. It forgets your production environment isn't your laptop. DeepTracer knows these patterns — and watches for all of them.
Cursor writes code that assumes every field is populated. In production, OAuth users, new signups, and incomplete profiles break that assumption instantly.
session.user is null for all Google OAuth signups until email verification. Correlates to commit d8f3a1c — same line Cursor wrote 2h ago. Fix: guard with if (!session?.user?.email).
Cursor writes clean, readable async code. It rarely adds error handling unless you ask. External APIs — Stripe, Resend, OpenAI — fail in ways the happy path never hits.
Resend rate limit hits during traffic spikes over 40 req/min. No try/catch means the entire signup route throws. Wrap in try/catch and add a catch that still creates the user — send welcome email async via queue.
Cursor generates code referencing environment variables it found in your .env.local. It has no idea what's set in Vercel production — or Railway, Render, or Fly.io.
OPENAI_API_KEY returns undefined in your Vercel environment. The key exists in .env.local but was never added to Vercel → Settings → Environment Variables. Fix takes 30 seconds.
You asked Cursor to add an AI feature. It did — cleanly. But it hooked the API call to onChange instead of onSubmit. Your OpenAI bill is now running at $40/hour.
streamAI() fires on every keystroke — no debounce, no submit gate. At current rate: $36,000/month. Move to onSubmit + add 400ms debounce. Caught 6.2 hours before your next AWS billing alert.
Cursor writes the code. DeepTracer watches production. When something breaks, the investigation surfaces right back inside Cursor via MCP — so you can fix it without switching context.
You prompt. Cursor writes. Ship the feature fast — that's the whole point.
Push to main. Vercel deploys. DeepTracer starts watching immediately — no config needed.
Error fires in production. DeepTracer investigates automatically — root cause, evidence, fix — in under 2 seconds.
Query the investigation via DeepTracer MCP. Ask Cursor to apply the fix. Done — without switching tabs.
Add the SDK to start monitoring. Then add DeepTracer as a Cursor MCP tool — and investigations appear right inside your editor when you need them.
One file. Five lines. Works with Next.js, Node.js, Express — any JavaScript app. Add it once, never think about it again.
src/instrumentation.tsDEEPTRACER_KEY to your .env.local and Vercel env varsAdd DeepTracer as an MCP server in Cursor's settings. Then query any investigation without leaving your editor — ask Cursor to fix the bug with the investigation as context.
DEEPTRACER_KEYget_investigation to query any error.That $290 spike in the Patterns section above — one day of Guardian Mode catches it before checkout. $19/month.
Agent wakes when you ask it to
Agent never sleeps · catches issues first
onChange pattern from above — $290 in 7 hours, projected $36K/month. Guardian Mode catches the spike within minutes and sends a Slack alert. One prevented incident = 18+ months of Pro paid for.
~/.cursor/mcp.json, it appears as a tool in Cursor Composer. You can type get_investigation checkout TypeError and Cursor will query your live production data and return the root cause, evidence, and suggested fix — right in the chat. No browser tab, no copy-pasting. The investigation data comes from your actual app, not a simulation.
instrumentation.ts hook runs once at server start, not per-request.
src/app/checkout/route.ts:7) but never the actual code content. The MCP server reads only your own project's data — nothing crosses project boundaries.
Add five lines. Connect the MCP server. Your agent is watching before your next deploy lands.
Free forever · no credit card · works with any Next.js or Node.js app