People who worked with me, in public. A former manager, now a CTO: “[a true bias for action](https://www.linkedin.com/in/przemyslaw-zalewski-ciunkos/details/recommendations/)” and “[always accompanied by a pull request ready to go](https://www.linkedin.com/in/przemyslaw-zalewski-ciunkos/details/recommendations/)”. An engineer from a team I led: “[someone you can always count on](https://www.linkedin.com/in/przemyslaw-zalewski-ciunkos/details/recommendations/)”. Business register, tax ID and D-U-N-S are on the [trust page](/trust).

You 🤝 Przemysław? Senior full-stack engineer for hire

Q: Why the Batman thing?

Because every “senior full-stack engineer” page looks the same. This one you will remember. The page itself is the work sample: static HTML, no framework, a CSP without inline scripts, axe in CI. View source.

I don’t know who you are. I don’t know what you need. But I have a very particular set of skills, acquired over a very long career. Fifteen years of it.

TypeScript, React, Node.js, Cloudflare, Postgres, PostHog. AI coding agents under rules I write and tests I enforce. Available now on a B2B contract, Wrocław or remote.

Book a free 30‑min call Email me instead

Your team in trouble? Light the signal. Three question marks in the sky, one phone number at the bottom.

15+ years shipping softwarenine of them in TypeScript, React and Node.js
iOS, Android, macOS, Windowsapps I build and ship end to end, store review included
~2/3 of merged PRs built with agentsin 2026, under my rules, nearly all through my review
CASA Tier 2 and WCAG 2.2 AAas automated gates on every pull request

Riddle me this

Interrogation room

Five questions. The Riddler asks, you answer. You get a case file matched to you, not a brochure.

Demo loading…

The numbers don’t lie. The Riddler does.

15+years shipping software

2017first React app in production

~2/3of merged PRs in 2026 built with AI coding agents, nearly all through my review or merge

800+pull requests reviewed on one product, 2018 to 2026

Riddle me this

Think twice, click once

Ten riddles. Some old, some new, a few you will want to send to a friend. The Riddler counts on your first answer.

Demo loading…

Case files

Closed cases. Names only where I am allowed to use them. Open any folder.

Patriot Mail: an AI email client through CASA Tier 2 and onto the App Store

The problem: A greenfield AI‑native email client for web, iOS and macOS, built at Sanddev, needed Google’s CASA Tier 2 security assessment before it could read Gmail, and it had to work for older people.
What I did: I was the principal engineer at Sanddev. I wrote the delivery plan, shaped the product vision and treated prompt injection through untrusted email as a design constraint before any model touched a mailbox. CASA and OWASP ASVS controls became a Playwright suite that runs on every pull request. WCAG 2.2 AA sits behind an automated axe gate.
Result: I led CASA Tier 2 to a pass in January 2026, with third-party pentest findings fixed, and led the yearly reassessment, validated in October 2026; the questionnaire turned into a check on every PR. Live on the App Store on iOS and macOS since April 2026. Text scaling to 200% and a calm‑email mode shipped for older users. At that reassessment five items came back for missing evidence; I fixed the code first, then resubmitted updated evidence, and all five were accepted on 27 October.

CASA Tier 2 iOS + macOS WCAG 2.2 AA Open ↗

See also: SaaS & MVP · Mobile & desktop apps

Offer: From an AI‑built MVP to a product people pay for

An AI coding agent as a team member, under enforced rules

The problem: Coding agents write code faster than a team can review it. A team of four wanted the speed without a slop swamp on main.
What I did: I authored the rule set shared by Claude Code and Codex: mechanical checks over written rules, lint and test gates for security, API surface and CSP, agents working on main with hooks, every PR reviewed by a human, AI‑assisted content disclosed as such.
Result: In 2026 about two thirds of merged pull requests across two products were built with coding agents, and nearly all went through my review or merge. I merged 260+ PRs of my own and reviewed 300+ of other engineers’. My commits across those two products went from under 1,000 in 2025 to 7,500+ by October 2026.

~2/3 PRs with agents 300+ reviews 7,500+ commits in 2026

Offer: AI engineer for your team (Node.js, LLM agents)

Sandtime.io, built at Sanddev: founding engineer, eight platforms, one codebase

The problem: A time-tracking SaaS had to live where people work: desktop tray, browser, phone and app stores.
What I did: I authored the original product vision and architecture in 2018 and made the first commit. React Native wrappers for iOS and Android, Electron for macOS, Windows and Linux, a Chrome extension, multi-tenant routing, SSO, Dockerized services, Paddle and Mac App Store subscriptions, CI/CD.
Result: Eight platforms shipped and run in production. The only engineer active in every year of the product, 8,000+ commits and close to half of all merges to trunk. In 2026 alone: 270+ tagged releases in ten months, about 99% of support answered by me, and a vulnerability disclosure program with a public Hall of Fame.

8 platforms 8,000+ commits since 2018 Open ↗

See also: Mobile & desktop apps · SaaS & MVP

Offer: Your company tool, sold to other companies (SaaS)

Suppression-list platform: MVP to product, 300+ GB in production

The problem: A UK email publisher needed suppression lists built to grow to terabyte scale with constant-time sign‑up and zero-downtime deploys.
What I did: I led a small team from MVP to the full platform. Postgres partitioning by tenant and list, parallel request pipelines, blue/green deploys. One‑click unsubscribe shipped four months before Google and Yahoo announced the requirement.
Result: 300+ GB and millions of events in production, zero-downtime deploys, an opt‑out path that kept working through a deliberate backend outage, and a compliance feature that landed before the deadline existed. In August 2026 I found orphaned table partitions left behind by deleted accounts and sales demos, stopped them piling up and recovered about 140 GB.

300+ GB outage-tested opt‑out blue/green

My own chat app: 30,000 concurrent users on sharded .NET servers

The problem: An ad-supported anonymous chat grew faster than one server could carry, and nobody else was going to run it.
What I did: Horizontally scaled, sharded C# and .NET servers, my own chat network, a moderation panel, automated NSFW detection, support answered by me.
Result: 30,000 concurrent users, 1.5 million+ downloads and 37,000+ ratings across 21 national stores (4.5 average in the US). It paid my bills for five years and ended when Windows Phone did.

30,000 concurrent 1.5M+ downloads 5 years

Sources: Promegle, US store 2015: 17,378 ratings

See also: C# & .NET (legacy) · SaaS & MVP

Korona Krulów: a satirical React game for 100,000+ players

The problem: Spring 2020, lockdown, a joke that deserved a game before the joke got old.
What I did: React, 400+ actions, a leaderboard, open source on GitHub, built in my evenings.
Result: 100,000+ players and ~700 upvotes on Wykop at launch.

100,000+ players 2 weeks open source Open ↗

Sources: Wykop: 698 upvotes · Antyradio · Wieści24 · Code on GitHub

Why so serious? Because the pipeline is red.

Five habits, one deck of cards. Pick one up.

Agents under rules

Claude Code and Codex work on main with hooks, lint and test gates. The model suggests, the criteria decide. Every PR gets a human review and AI‑assisted content is disclosed.

Zero bug policy

A bug is fixed or consciously closed, never parked. Alerts and error tracking in every project, so I learn about problems before the client does.

Review as a craft

800+ pull requests reviewed on one product since 2018. I review for the product and its reasons. The code comes second.

Measured, not assumed

PostHog in every project from day one. A tracking plan per feature, and dashboards leadership reads instead of asking me for numbers.

No product manager? Fine.

Where there is no PM I set priorities directly with the people using the software and answer support myself.

Pick a card. In your head.

Six cards. Pick one, remember it, don’t click it. The Joker will make it disappear.

Press

Written up elsewhere

Real links, from Windows Phone apps in 2012 to a game in 2020. Online I go by Ciunkos. Some outlets are gone, so those links open an archived copy.

Antyweb AwardMar 25, 2013“The jury picked the best apps in the AppAward contest”AppAward 2013: Pogaduszki won the Other category on Windows Phone, out of 300 apps entered across iOS, Android and Windows Phone.Read (in Polish) Microsoft PolskaSep 2, 2012“The best Polish apps for Windows Phone”Microsoft Poland’s hand‑picked list of the best Polish Windows Phone apps featured my Kwejk app (archived copy from September 2012).Read the archived copy (in Polish) wp7.com.plApr 7, 2012“More about the Gadu app”A chat with me about Gadu: “for that period Gadu was the most downloaded app on the Polish Marketplace.”Read (in Polish) AntyradioMay 4, 2020“Fight the epidemic as the government and win the Korona Krulów. A satirical game with TVP news bars”“The work of one programmer, who built it literally at night.” Antyradio’s review of the game.Read the archived copy (in Polish) Gazeta PlusMay 2, 2020“The game »Korona Krulów«. Lead the PiS government and make decisions in a time of plague…”News piece on the game, the day after launch.Read the archived copy (in Polish) Wieści24May 2, 2020“…A game about the coronavirus in Poland has appeared online: Korona Krulów”News coverage of the game the day after launch.Read (in Polish)

More mentions (9)

WykopMay 1, 2020“Feel like the Chairman and run the country in Korona Krulów: the game is out”Korona Krulów launch day: 698 upvotes and 152 comments.Read (in Polish) OnMSFTJan 11, 2013“Windows Store app highlight: Windows Phone Store, grab the latest Windows Phone apps via Windows 8”My Windows 8 app for browsing the Windows Phone Store, featured as a highlight.Read windows‑phone.plJan 11, 2013“The »Windows Phone Store« app for Windows 8”“Built by Ciunkos, known for apps like Pogaduszki and Memgenerator.”Read the archived copy (in Polish) appsblog.plSep 26, 2012“Memgenerator: make a funny picture on your phone”Review of Memgenerator, my Windows Phone meme maker.Read (in Polish) KomórkomaniaMay 12, 2012“Pogaduszki: a Gadu‑Gadu client for Windows Phone”Review of Pogaduszki, my Gadu‑Gadu messenger: 4.5 stars from 68 ratings at the time.Read (in Polish) Telix.plMay 11, 2012“Pogaduszki: a new GG client for Windows Phone”Launch of Pogaduszki for Windows Phone 7.5: free, no ads, push through my own server.Read (in Polish) wp7.com.plMay 5, 2012“Unofficial GG client »Pogaduszki« now available”Pogaduszki ready “after many hours of work and testing”, no splash screen so it starts faster.Read (in Polish) windows‑phone.plMay 2, 2012“Pogaduszki, a new GG client!”After my first Gadu‑Gadu app was pulled over a copyright claim, I rebuilt it as Pogaduszki without the infringing parts.Read the archived copy (in Polish) GaduNewsApr 30, 2012“GG Network pulls an unofficial messenger from Windows Phone”Gadu, the first native Gadu‑Gadu client on Windows Phone 7, comes down after a trademark claim. Quotes my statement.Read the archived copy (in Polish)

Ask the agent

It answers for me, from this site only. Tap a question below or type your own.

Demo loading…

Two-Face decides

Can’t decide whether to book a call? Let the coin decide. Fair warning: it is rigged in your favor.

One click. The coin does the rest.

Book a free 30‑min call Email me instead

Before you book

Riddle me this: what is fast, careful and never says “you’re absolutely right”?

Me, on all three. Fast, because coding agents do much of the typing. Careful, because lint and test gates fail the build and a human reviews every pull request. And if your plan is wrong, I say so on the free call, before it eats a sprint.

Our core language is named after a snake, an island or a coffee.

Then I am not your lead and I say so now. TypeScript, React, Node.js and Cloudflare are what I sell, C# and .NET for ten years before that. Python scripts and services when the work needs it, yes.

When can you start?

Now, on a B2B contract. Solo, or leading a team of up to four. Need something sooner? A one‑week code audit or a pull request review can start now.

Remote?

Wrocław or remote. Nine years with US, UK and EU teams, across a nine‑hour time difference when needed.

Will you work with our coding agents?

Yes, under rules I write. Lint and test gates fail the build when the agent breaks them, a human reviews every pull request, AI‑assisted content is disclosed. Proof: the agent case file.

You are one person. What if you disappear?

The work stays with you. Code, CI and docs live in your repository and accounts from day one, every project keeps a runbook and architecture notes, and notice is one month on both sides with a written handover. If I am ill, you hear it the same day. How I work.

Who owns the code, and who gets to see it?

You own it. It lives in your repository from the first commit, and the contract transfers the copyright to you in writing. Client names are missing from this page for a reason: NDAs hold, and yours would too. Security is on record: Patriot Mail passed CASA Tier 2 in January and again in October 2026, both assessments led by me.

Who vouches for you?

People who worked with me, in public. A former manager, now a CTO: “a true bias for action” and “always accompanied by a pull request ready to go”. An engineer from a team I led: “someone you can always count on”. Business register, tax ID and D‑U‑N‑S are on the trust page.

What if it does not work out?

You find out in week one, not in month three. A sprint gives you something to touch in week one. Want a smaller first step? Start with the one‑week code audit or a review of one pull request, then decide. Liability cover depends on the engagement and is agreed in writing.

Why the Batman thing?

Because every “senior full‑stack engineer” page looks the same. This one you will remember. The page itself is the work sample: static HTML, no framework, a CSP without inline scripts, axe in CI. View source.

One foot in the door

Not ready for a project? Start with one week or one pull request.

Two ways to see how I work before you commit to a sprint. Fixed scope, and the plan in writing within 24 hours of the call.

One-week code audit

I read the repo, CI, tests, deploys and the parts the team avoids, by hand. You get a written report with risks ranked by cost, what to fix first, a plan with milestones and a go or no‑go you can defend. The report is yours whether or not we continue.

Code review of one pull request or one module

Send me the diff that worries you. Within a few days you get line‑level comments, the three things I would change first and whether I would merge it. I have reviewed 800+ pull requests on one product since 2018.

Book a call to pick one Free 30‑minute call first. If neither fits, I say so on the call.

You