Sentry

Error tracking and performance monitoring for both frontend and backend. Captures unhandled exceptions, performance traces, and session replays to aid debugging in production.

Architecture

Component	Path	Purpose
Backend setup	backend/src/lib/sentry.ts	SDK init, sensitive data scrubbing
Backend capture	backend/src/middleware/errorHandler.ts	Exception capture in middleware
Frontend setup	frontend/src/main.tsx	SDK init, session replay

Configuration

Secret	Purpose
SENTRY_DSN_BACKEND	Backend error reporting endpoint
Frontend DSN	Configured in main.tsx (public, not secret)

Backend DSN stored as GitHub Environment Secret, synced to Fly.io. See Deployment Pipeline.

Backend Integration

The error handler middleware (backend/src/middleware/errorHandler.ts) is the last middleware in the Backend Middleware pipeline. It:

1. Catches all unhandled exceptions from routes and services
2. Scrubs sensitive data (tokens, passwords, cookies, authorization headers)
3. Attaches request context (URL, method, user ID)
4. Reports to Sentry
5. Returns a structured JSON error response to the client

See Error Handling Pattern for the error response format.

Sensitive Data Scrubbing

Before sending events to Sentry, the following are stripped:

Data Type	Fields Scrubbed
Auth	authorization, cookie, set-cookie headers
Credentials	password, token, secret, apiKey body fields
PII	Configurable via beforeSend hook

This prevents credentials and PII from appearing in the Sentry dashboard.

Frontend Integration

Frontend Sentry integration in frontend/src/main.tsx includes:

Feature	Purpose
Error boundary	Catches React render errors
Session replay	Records user sessions for debugging
Performance tracing	Measures page load and navigation timing
Breadcrumbs	Logs user actions leading to errors

Environment Awareness

Sentry events are tagged with:

• environment: development, staging, or production (maps to APP_ENV)
• release: Git commit SHA for source map matching

Only staging and production environments send events to Sentry. Development errors are logged locally.

Related

• Error Handling Pattern — Structured error responses
• Backend Middleware — Error handler middleware position
• External Integrations — All third-party integrations
• Frontend Architecture — Frontend Sentry setup
• CI-CD Workflows — Source map upload on deploy
• Security Scanning — Complementary security monitoring