Sebastian Webb

Solutions Software Engineer, London
+44 7886 309 293
Technical Profile
I invent and develop software used by thousands of developers. For a decade I hand-coded visual IDE and performance solutions. Now, I use multi-device parallel AI agents for rapid output I test carefully.
Agentic AI
CLI tools
Claude/Codex
Cursor/Xterm.js
Orchestration
Context Design
Collaboration
Core Stack
TypeScript
Node/React
HTML/JSX
CSS/Tailwind
PHP (OOP)
My/PG SQL
Infrastructure
AWS / CDK
Postgres / RLS
Docker
Google Cloud
GitHub Actions
Playwright

Experience

Themeover: Founder & Lead Developer 2012 – Present

Built and evolved Microthemer, a visual CSS editor for WordPress with over 2 million downloads. Partnered with a product designer on UI/UX decisions. Built a reputation for a reliable product and exceptional customer service: 100% 5-star reviews across wordpress.org, Product Hunt, and AppSumo (verified purchases). Appeared on industry-leading podcasts and ran social media campaigns grossing $50k+ ROI.

Mappd: Multi-Tenant SaaS for a Design Agency 2026

Hired as the sole engineer to build a customer-journey-mapping platform from Figma designs, delivered in just over a month across frontend, API, database, auth and cloud. Built a React 19 SPA on a Hono and Drizzle API with end-to-end type safety and no code generation, multi-tenant isolation via Postgres row-level security and a three-tier role model, WorkOS authentication, and the full AWS estate provisioned as CDK across staging and production.

KanSpec: Parallel AI Agent Orchestration 2026

To get more done as a solo engineer, I built KanSpec, a project-management and AI-orchestration tool. Requirements, tasks and decisions live as YAML in the repo, keeping each agent's context in version control. Agents run in parallel Git worktrees through embedded terminals so I can preview their work side by side, while an integration branch keeps their output off the shared branch.

Integrated AI into Production Software 2025

Built a generative AI design engine on Vertex AI for live DOM manipulation, with a custom XPath analysis system that lets LLMs inspect a page like a developer. Achieved sub-second latency with a geo-optimised flash model, and secured the model's output using static analysis to whitelist domains and block unsafe functions and properties.

Capable of Complex Solutions for Unsolved Problems

How can Sass work with a live editor if it takes many seconds to compile? I invented a selective Sass compilation engine achieving 50ms compile times on projects with 3,000+ selectors. It uses an AST parser to create a dependency map that only compiles what changed. How can ::before elements be clickable if browsers do not support that? By building a projection engine using CSSOM coordinate measurement.