I build software that takes the user’s side.
In browsers, that meant ad blockers, shopping tools, and other browser extensions used by over twenty million people worldwide. With AI agents, it means integrations and harnesses that keep the human in charge.
I’m Zack Babtkis. I was a Senior Staff engineer at PayPal and a founding engineer at ZeroClick, and I now consult independently.
Who you're hiring
Zack Babtkis
You work with me directly: I take the intro call, write the code, and deliver the work.
I’ve also designed, built, and shipped two independent products: TrueRate, a Chrome extension that exposed hidden hotel fees on the major booking sites, and Unhabit, an iOS Safari extension that blocks distracting websites. Together they reached tens of thousands of installs.
LinkedIn · GitHub · the longer story · references on request
Services
Agentic AI
MCP server development
Your customers are asking for a Claude or ChatGPT integration. I built agent-facing APIs at ZeroClick. I’ll build your MCP server and submit it to the Claude and ChatGPT directories.
MCP readiness audit · $2,000AI enablement for teams
Your team has the AI tools and little shipped to show for it. At ZeroClick I engineered the harness of conventions, tooling, and review gates that let agents ship production code. I’ll build that system for your team.
Agent-readiness audit · $3,000Prototype to production
You vibe-coded something that works in a demo. I make it survive real users: tests, auth, data, deployment.
Production readiness audit · $2,500Web extensions
Safari & iOS porting
Your Chrome extension doesn’t exist on Safari or iPhone. I built Honey’s first iOS extension and owned Pie’s. I’ll port yours from Chrome and get it through App Store review.
Port assessment · $2,500New extension from scratch
Chrome, Safari, or Firefox. I shipped extension features to twenty million users at Honey and Pie, and built TrueRate alone.
Scoped per projectExtension for your existing app
Your app, extended into Safari. I shipped Unhabit’s iOS Safari extension end to end and built Pie’s app shells.
Scoped per projectApps
Web apps
I’ve built web apps since 2012: seismic dashboards at UC Santa Barbara, the DSP dashboard that won a 2015 UX Award at Gimbal, financing tools at ProducePay, and pie.yt at ZeroClick.
Scoped per projectiOS & Mac apps
Swift shells, Xcode Cloud, and App Store review. I shipped Pie’s iOS and Mac app shells and two products of my own.
Scoped per projectFree tool
Safari WebExtension Manifest Checker
Before you scope a Safari or iOS port, find out what will break. Paste your extension’s manifest.json and get a report on which manifest keys, permissions, background scripts, and APIs Safari supports on macOS and iPhone, which it ignores, and which block conversion. It runs entirely in your browser and uploads nothing. If the report raises questions, the port assessment answers them.
Check your manifestWhere I've shipped
Independent work
TrueRate
Chrome extension that revealed hidden hotel fees (resort, wifi, parking) on Expedia, Hotels.com, Travelocity, and Orbitz, with a scraping API and an iOS app behind itChrome + iOS + API · 2019–2020
Unhabit
iOS Safari extension that blocks distracting sites with cooldowns and scheduling, all on-deviceiOS App Store · 2023At companies
PayPal Honey
Designed and built its first iOS browser extension · $4B exit to PayPalSenior Staff · 2019–2024
Pie Adblock
Owned the Safari and iOS extensions, led the Creator NetworkFounding engineer · 2024–2026
pie.yt
Built and shipped end to end. AI agents I directed wrote the entire codebase.Live · try it
ZeroClick
Built the agent-facing APIs and MCP servers for its agent-commerce infrastructure2024–2026
Gimbal (Infillion)
Built the DSP dashboard that won a 2015 UX Award and the dashboard merchants used to manage in-store beacons. Worked on mapping human networks (friends, family, shared audiences) from beacon and geofence signals in a graph database.Location intelligence · 4 years
ProducePay
Helped build the trading platform, including the messaging system growers and distributors use to negotiate trades. Led architecture for the Pre-Season financing platform.Produce marketplace · 2018–2019Earlier: the NEES@UCSB real-time seismic data portal at UC Santa Barbara’s Earth Research Institute.
Working on something like this?
Tell me what you're building and what's in your way. I read every message myself. If I'm not the right person for the job, I'll tell you, and I'll suggest someone who is.