---
title: "Development posts — Marcin Jasion"
description: "All Development posts by Marcin Jasion. 4 posts."
canonical: https://mjasion.pl/posts/development/
---

# Development

4 posts in this category.

- 2026-05-25 — [Two Agents, One MCP Server: Using a Second Claude as a Harness for the First](https://mjasion.pl/posts/development/two-agents-one-mcp-harness/) — How to test AI-generated code: a differential-testing pattern over MCP. One agent built my Polish tax calculator and exposed it over MCP. A second Claude Code agent, with no shared context, audited the math against raw broker data and found real bugs. This is what harness engineering looks like in practice.
- 2026-02-25 — [Why I'm Choosing Cloudflare and TanStack for My Side Projects](https://mjasion.pl/posts/development/why-i-chose-cloudflare-and-tanstack/) — After building with Vercel and Supabase, I switched to Cloudflare and TanStack. Here's why - and what I gained.
- 2022-04-09 — [Deploy your first blockchain contract to Ethereum](https://mjasion.pl/posts/development/first-blockchain-contract/) — Step by step guide to deploy first contract on Ethereum blockchain
- 2020-04-17 — [How to label GitLab notification in Gmail by headers?](https://mjasion.pl/posts/development/label-gitlab-notifications/) — You can label emails by headers in Gmail. To do this you have to create a script that periodically scans for new emails in your inbox. To demonstrate it I will use Gitlab notifications and we will add labels to messages basing on their headers