DentSignal engineering case study · Deployment

The code changed. The live page did not.

A repository check said the new version existed, but visitors could still receive an older page. The missing step was checking the actual deployment and custom domain.

Area: Vercel, GitHub Actions, custom-domain checks
Evidence: Historical PR-reported validation
Boundary: Cited revisions, not current uptime

Plain English

Three things to know.

What broke
The source repository and the public website disagreed, so a green source check gave false confidence.
What changed
The checks followed one chain: source revision, exact deployment, then the custom domain visitors use.
Why it matters
A repair is not finished when the file is correct. It is finished when the intended version reaches the real surface.

Simplified repair

Check the destination, not only the source.

Broken · simplified example

assert source_has("new page")
# Stops here.
# The live domain may still be old.

The test proves what is in the repository, not what a visitor receives.

Fixed · simplified example

assert source_has("new page")
assert deployment_matches(revision)
assert custom_domain_has("new page")
assert custom_domain_lacks("old page")

The same release contract now reaches the deployed URL and the public domain.

Illustration only — not copied from private source.

How it was checked

Historical PR-reported validation

The cited revision history reports source-contract checks, exact-project deployment verification, deployment-URL checks, and cache-busted custom-domain checks with stale-copy rejection.