I am Sebastian Tekieli - a software developer and technical leader with over 20 years of experience building internet products for the largest brands in Poland and beyond.
Currently, I work as an AI Platform Architect at WebWave, where I design the technical architecture of a SaaS platform built around AI, with multi-agent systems as a core component. My role spans technology decisions, integration patterns, proof-of-concept prototyping, and defining quality standards for code, data, and AI outputs.
Through WebsiteInit, I offer fractional CTO services, Ruby on Rails development, AI agent architecture, and mobile systems consulting to founders and growing teams who need senior engineering without the full-time overhead.
Alongside my work at WebWave, I am building Legatus.team, an AI agent platform for delegating real work across everyday tools, and Gymiti, a vertical SaaS product for studio room reservations and freelance-trainer payouts.
I work closely with development teams, Product Owners, and business stakeholders in agile, iterative environments focused on fast delivery of value.
My career started at DreamLab Onet.pl and Interia.pl, where I built portals and admin panels used by millions of Polish internet users. Later, I spent seven years as CTO at DataFeedWatch, growing the IT team from 3 to 26 people and building e-commerce integrations for global brands like Adidas and Reebok.
I also founded two startups - GoTranslate.pl and Cominer.io - which taught me the discipline of shipping fast, measuring everything, and surviving on real user feedback.
At Visuality, I combined technical project management with hands-on delivery for PeopleForce and Vibemetrics, building Hotwire Native mobile applications and Rails product features while creating an architecture knowledge base designed for AI-assisted engineering.
Today, I combine that operational experience with modern AI tooling to help companies build systems that are both ambitious and reliable.
June 2026 - Present
An AI agent platform designed for delegating real work. Legatus agents operate inside the tools people already use: drafting and sending email, scheduling meetings, updating documents, and completing workflows across more than 20 applications including Gmail, Google Calendar, Slack, Notion, GitHub, and HubSpot. When an API is unavailable, the agent can use a real browser to complete the task.
January 2026 - Present
A SaaS platform for studios that rent rooms to freelance trainers, covering reservations and automated monthly payouts. It serves fitness, yoga, pilates, CrossFit, physiotherapy, and dance studios whose room-rental model is not addressed by standard gym-management systems.
First production customer: MoveCenter.pl.
Building an AI agent platform that completes real work across 20+ applications through native integrations and browser automation.
Building a multi-tenant SaaS platform for studio room reservations, trainer payouts, billing, and international growth.
Architecting an AI-powered SaaS platform with multi-agent systems as a core component. Defining integration patterns, quality standards, and technical roadmap.
Led full-cycle recruitment for Ruby on Rails and React developers while supporting modern web products built with Rails, Stimulus, Hotwire, Tailwind CSS, Alpine.js, and Kamal. Contributed hands-on to Ruby, Hotwire, Hotwire Native, Swift, Kotlin, React Native, Expo, Dart, and Flutter delivery with a focus on quality, scalability, and maintainability.
Worked directly with the CEO to ship end-to-end Rails and Hotwire features, optimize PostgreSQL and Redis usage, and create the product's first AI-agent technical documentation and architecture knowledge base.
Worked directly with the product CEO to build and ship iOS and Android apps on the existing web platform using Hotwire Native, Turbo, Strada, Swift, and Kotlin, including SSO, bridge components, push notifications, geolocation, and Firebase integrations.
Leading security audits, recruitment, mentoring, and technical strategy for a digital insurance multiagency.
Leading Ruby/Rails team, Open Banking integration, PSD2, and roadmap prioritization.
Grew the IT team from 3 to 26 people. Built e-commerce integrations, plugins, and testing culture for clients like Adidas and Reebok.
Built a public email search engine indexing up to 20,000 emails per day.
Created a marketplace application for fast, professional translation ordering.
Built and maintained portal sites, admin panels, and documentation for major Polish web services.
Prepared development environments, advised on technology choices, and built RMFOn.pl backend.
Maintained theme services for ITI Group / Onet.pl. Worked on new Onet.pl homepage and multiple vertical portals.
I am available for fractional CTO engagements, architecture reviews, and project-based development. Let's talk about your next phase.
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