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Arnab Chatterjee
Arnab Chatterjee

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How I Cut CI Time in Half Without Touching the Codebase

There was a time when every pull request in our repo felt like a test of patience. Push a small change, grab a coffee, and then… wait. Thirty, sometimes forty five minutes for the pipeline to turn green. And the kicker? Most of that time was wasted on tests that almost never surfaced real bugs.

At first, I blamed hardware. Maybe we needed faster runners, more powerful machines, or a bigger CI budget. But the truth was harder to swallow: the problem wasn’t performance, it was focus.

The trap we all fall into

If you’ve worked with CI long enough, you’ve seen it. The default playbook: run everything, every time. It feels safe. It looks rigorous. But in practice it:

  • Slows feedback until it’s meaningless.

  • Clutters results with flaky failures you stop trusting.

  • Turns CI into a tax on developer momentum.

The irony is, all that extra testing doesn’t actually make you safer. It just makes you slower.

The mindset shift that saved me

The breakthrough came when I stopped equating confidence with “maximum coverage per commit.” Confidence isn’t about throwing every test at every push. It’s about getting the right signals at the right time. That’s when I started looking at smarter ways of testing, not just brute force. This is where new approaches like AI for QA Testing started to make sense

That meant catching likely failures quickly, then proving nothing else regressed on a schedule. Not “more tests,” but smarter scheduling of the ones we already had.

The playbook: what I actually changed

Once I stopped obsessing over “more coverage” and started asking for “better signal,” the fixes almost wrote themselves. None of them touched application code. All of them reshaped how our pipeline thought about tests.

1. Prioritize by risk

Not every test deserves equal airtime. A broken login or checkout can sink you faster than a typo in the footer, so those flows became always-on.

The rest I ranked by three questions:

  • Did the change land close to this code?
  • Has this test actually caught failures before?
  • If it breaks, will users or the business feel it?

That simple exercise turned my giant test suite into a layered one: critical flows up front, everything else running when it truly mattered.

2. Parallelize like you mean it

We already “ran in parallel,” but not really. Some jobs still dragged on forever while others finished in seconds.

So we fixed it on two levels: Across machines, the matrix builds fanned out tests across different runners. Within machines, each runner spawned multiple workers, with shards balanced by historical duration, not just raw test count.

The result? No more “long tail” shard holding the whole build hostage.

3. A fast lane and a deep lane

fast lane and a deep lane

The big unlock was splitting the pipeline into two tracks:

  • Fast lane (every push): unit tests, core integration checks, and 2–3 critical E2E journeys. They told me in minutes if my PR was doomed.

  • Deep lane (nightly/periodic): the full regression, stretched across browsers and devices. That’s where the rare edge cases surfaced, without blocking daytime merges.

This separation gave me speed and safety, without the constant trade-off.

4. Cut the noise

Finally, we killed off distractions:

  • Superseded builds were auto-canceled. No point finishing a job for code that’s already outdated.

  • Documentation-only commits skipped the heavy pipeline entirely.

  • Chronic flaky tests were quarantined. They still ran in the nightly, but they no longer held the team hostage.

CI went from a bottleneck to a trustworthy partner, much faster, quieter, and still safe.

When I Introduced AI Browser Testing with Bug0

After fixing the basics, my CI was leaner, but not perfect. Some bugs only popped up in specific browsers. Flaky tests still caused too much noise. And building + maintaining end-to-end flows by hand was draining time I didn’t have.

What I was missing wasn’t raw speed anymore, it was breadth and resilience. I needed coverage across browsers and devices, tests that wouldn’t collapse after every UI tweak, and a way to trust failures without spending all day babysitting them.

That’s when I decided to try Bug0, , an AI browser testing platform. I wasn’t looking for a magic button; I wanted something that could handle the orchestration and grunt work around tests so my team could stay focused on features.

Here’s what changed once Bug0 entered the picture:

1. Smarter coverage without extra hand-tuning

Automated Testing by AI QA Engineer

Before Bug0, keeping end-to-end tests relevant felt like a full-time chore. Writing them was slow, and every UI tweak risked breaking half the suite.

With Bug0, I didn’t have to manually script everything. Its AI agents explored our staging environment, automatically mapping out key user journeys like login, checkout, onboarding, all the flows that actually matter. From there, it generated Playwright tests that were self-healing, so small UI changes didn’t knock them over.

Smart Test Planning by AI QA

The best part: Bug0’s flows adapted, and QA reviewers kept them sharp. Bug0 isn’t just AI for QA testing it combines automated flow discovery with human QA review. That hybrid approach meant coverage I could trust without burning cycles on brittle scripts.

2. Browser flows I didn’t have to hand-craft

Smart Testing by AI QA

On staging, Bug0’s agents explored the app like a user would, clicking, navigating, filling forms, and proposed realistic end-to-end journeys. I could review and adopt them. Better still, these flows were self-healing: small UI changes didn’t break them instantly. That cut down hours of maintenance.

3. Results where I already work

Bug0 result in github CI

Instead of another dashboard to check, Bug0 surfaced results directly in my CI checks and pull requests. Failures showed up with context, so I didn’t waste time hunting through logs.

4. Automatic noise control

Flaky tests stopped blocking merges. Bug0 flagged and quarantined them automatically. They still ran in the nightly deep lane, but my day-to-day workflow finally felt reliable again.

What Bug0 does not do

  • It doesn’t rewrite your application code.
  • It doesn’t replace a full regression run.
  • It doesn’t “auto-magically” write unit tests.

Bug0 fits in as an AI QA Engineer for your pipeline — handling prioritization, orchestration, and end-to-end coverage without touching your codebase.

The impact for us

New Pipeline with AI QA

Within weeks, we saw faster time-to-first-failure because risky tests ran early. Cleaner pipelines with far fewer flaky distractions. Browser flows that caught real issues (including edge cases we’d never have scripted manually).

Bug0 didn’t replace our testing pipeline, but amplified it. We still kept nightly full sweeps and regular reviews, but the day-to-day bottlenecks melted away.

Why AI Beats Traditional Scripted QA for CI

Scripted QA has always struggled to keep up with modern CI pipelines. Every time the UI shifts, a dozen tests break. Every new feature means hours spent writing brittle scripts that don’t survive the next sprint. And when you’re running those scripts in CI, that maintenance overhead quickly becomes a blocker.

This is where AI for QA testing shines. Instead of relying on static scripts, AI agents adapt as the product evolves. They can explore staging environments, generate self-healing browser flows, and surface failures directly in pull requests. In practice, that means fewer false positives, less time wasted on flaky tests, and faster signal when it matters.

Think of it as the difference between micromanaging every step versus having an AI browser testing assistant that understands user flows and keeps them resilient in CI. The result is broader coverage, less maintenance, and pipelines that move at the same speed as your team.

Guardrails: keeping speed honest

The temptation, once things speed up, is to declare victory and move on. But CI isn’t just about being fast, it’s about being fast and trustworthy. So I set a few guardrails.

Nightly full sweeps still run, because nothing replaces broad coverage. Every decision, whether a test ran, skipped, or quarantined needs explainability, so I can trace back “why this test first.” Flaky tests get no free pass: they’re fixed quickly or quarantined until they are. And I kept an eye on the right metrics like time-to-first-failure, p95 pipeline duration, the percentage of tests run per PR, and escaped defects.

Those checks made sure the improvements weren’t a shortcut. They were a foundation.

Results after a few weeks

The difference was obvious within two or three weeks. Instead of waiting twelve minutes to see if a PR was doomed, failures surfaced in less than five. Our p95 CI duration dropped by about half, and for once, “green” actually meant reliable, not just “rerun until it passes.”

Most importantly, quality didn’t slip with no increase in escaped defects. The nightly deep lane even caught a couple of regressions that would have been invisible otherwise, without blocking daytime merges.

Faster, cleaner, and still safe. That’s what the combination of smarter scheduling and Bug0 gave us.

Closing

In the end, CI speed isn’t about brute force or endless coverage. It’s about focus. You don’t need every test on every push, what you need is the right ones at the right time. With disciplined sweeps to keep you honest. For me, splitting fast and deep lanes and layering an AI QA approach with Bug0, turned CI from a traffic jam into a steady flow. The result? More signal during the day, fewer surprises at night, and a team that spends time shipping features instead of waiting on green ticks.

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