A product built end to end,from the crawler to the invoice.
SaaS · billing · PDF reports · 2026
SightStack audits a website with a real browser, Lighthouse and Claude, and delivers a designed PDF report scored across six dimensions. I built all of it: the product, the billing, the tax handling and the operations.
The product and the need
Small companies want to know what is wrong with their site and what to fix first, without hiring an agency to find out. A free preview scores the site from Lighthouse alone; the paid report adds the analysis and the fixes.
Decisions that held
Three apps, one repository
A Next.js front end, a NestJS API and a queue worker in one Nx monorepo, sharing types and a 29-model database schema.
AI output that cannot break a report
Every model answer is validated against a schema twice, and a rejected answer is retried with the exact fields that failed.
An AI outage is a state, not an error
When the model provider is down, jobs wait on a backoff of up to about six hours, customer emails pause, and the admin can retry everything in one click.
Tax done properly
EU VAT with VAT-ID checks, rate-change detection and the one-stop-shop threshold, and fiscal invoices issued automatically, with a retry queue.
How it grew
329 commits since March 2026, all mine, with around 2,500 unit test cases and 261 end-to-end tests in the repository.
The product
Working model
Scoped, built and run by me. Live at sightstack.app.