DEV Community: Vojta Holeš

Just published: the 3am production incident that made me build BreakShield CI. If you've ever debugged a breaking change at 3am — this one's for you 🛡️

Vojta Holeš — Tue, 02 Jun 2026 18:56:34 +0000

Vojta Holeš

Jun 2

The 3am Production Incident That Made Me Build BreakShield CI

#typescript #github #webdev #devops

Comments

2 min read

The 3am Production Incident That Made Me Build BreakShield CI

Vojta Holeš — Tue, 02 Jun 2026 18:55:34 +0000

It was 3am when my phone started ringing.

Our API was down. Half the app was broken. Users were angry. The on-call engineer was panicking.

After two hours of debugging we found it. Someone had removed the email field from UserResponse. Three other services were using it. Nobody caught it in code review. Nobody even knew those services existed.

We fixed it. Deployed at 5am. Wrote the post-mortem. Added it to the "lessons learned" doc that nobody reads.

Three months later it happened again.

The problem nobody talks about

Every team I've worked with has the same issue.

You have a TypeScript interface. It's used in 6 places across 4 different files. You remove one field. You open a PR. Your teammates review it. Nobody catches it because nobody knows about those 6 places.

The tests pass. The build passes. You merge.

And then production breaks.

The scary part? This isn't a skill issue. Senior engineers with 10 years of experience make this mistake. It's a tooling problem. Code review wasn't designed to catch this.

What I built

I spent a weekend building BreakShield CI — a GitHub App that does one thing:

Catches breaking API changes before you merge.

When you open a pull request, it automatically:

Parses your TypeScript interfaces and OpenAPI specs with a full AST
Finds every place in your codebase that uses the changed API
Shows you exactly which file and which line will break
Posts a report directly in your PR
Blocks merge if the risk is HIGH or CRITICAL

No config. No CLI. No YAML. Install once, works on every PR forever.

What it looks like in practice

You remove email from UserResponse. BreakShield CI posts this in your PR:

🔴 HIGH RISK — 1 breaking change

UserResponse.email — removed field File: src/types/user.ts Confidence: 94% — AST-verified

2 consumers affected:

src/components/UserCard.tsx:23 return ${user.name} <${user.email}>

src/pages/profile.tsx:41 const { email, name } = user

Your teammate sees this. They don't need to know the codebase. They don't need to grep for usages. The information is right there.

Why AST and not regex

Most tools use regex to find breaking changes. Regex lies.

If your interface has a field called emailAddress and you search for email, regex will find it. AST won't — because AST actually understands your code.

BreakShield CI uses ts-morph to parse a full TypeScript AST. It knows the difference between a property access, a destructuring, and a type annotation. Every finding is verified at the compiler level.

If there's no evidence — there's no warning. No noise, no false positives.

The 3am call I didn't get

Last week a teammate removed a field from a shared interface. BreakShield CI caught it. The PR comment listed 4 consumer files. We updated them before merging.

I didn't get a 3am call.

That's the whole point.

Try it

BreakShield CI is free during beta. It takes 30 seconds to install.

👉 breakshield-ci.vercel.app

If you've ever had a 3am production incident caused by a breaking change — you know exactly why I built this.

Just launched BreakShield CI — a free GitHub App that catches breaking API changes in PRs using AST analysis. Would love feedback from the TypeScript community!

Vojta Holeš — Tue, 02 Jun 2026 15:57:39 +0000

Vojta Holeš

Jun 2

I Built a GitHub App That Catches Breaking API Changes Before They Ship

#showdev #api #github #typescript

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2 min read

I Built a GitHub App That Catches Breaking API Changes Before They Ship

Vojta Holeš — Tue, 02 Jun 2026 15:55:11 +0000

Last week I spent 10 hours debugging a production issue. Someone had removed a field from a TypeScript interface. Three other files were using it. Nobody caught it in code review because nobody knew those files existed.

That's when I decided to build BreakShield CI.

What it does

BreakShield CI is a GitHub App that automatically analyzes every pull request for breaking API changes. It runs in the background — no config, no CLI, no YAML.

When it finds something, it posts a comment directly in your PR:

Which interface or endpoint changed
What exactly changed (removed field, type change, optional → required)
Which files and lines in your codebase actually use the changed API
A risk level: SAFE / LOW / MEDIUM / HIGH / CRITICAL

HIGH and CRITICAL risk PRs get a failing Check Run that blocks merge.

How it works technically

The interesting part is the analysis engine.

Most tools use regex to find breaking changes. BreakShield CI uses a full TypeScript AST via ts-morph. This means it actually understands your code — not just searches for strings.

For every changed .ts file in a PR it:

Parses both the before and after version into an in-memory AST
Extracts all exported interfaces, type aliases, and functions
Diffs them to find breaking changes
Searches the codebase for files that use the changed API
AST-verifies each match — direct access, destructuring, type annotations
Scores each finding by confidence (0–100)

For OpenAPI specs it uses @apidevtools/swagger-parser to dereference all $ref pointers and diffs paths, parameters, request bodies, and response schemas.

What it detects

Breaking (blocks merge on HIGH/CRITICAL):

Removed field from interface
Changed field type
Optional → required
Removed endpoint
Removed function parameter
Added required field to request body

Safe (informational only):

Added optional field
New endpoint added

The confidence scoring

Every finding needs evidence. No evidence = no warning.

Evidence is scored by usage type:

obj.field direct access → 90%
const { field } = obj destructuring → 80%
: UserResponse type annotation → 80%
GitHub Search hit without AST verification → 35%

Low confidence noise is filtered automatically.

Try it

BreakShield CI is free during beta. Install it in 30 seconds:

👉 breakshield-ci.vercel.app

Would love feedback from anyone working with TypeScript APIs or microservices.
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