Libretto vs Skills (mattpocock)

Libretto is an open-source browser automation toolkit built by Saffron Health to solve a critical problem with AI-driven web agents: non-determinism. Standard agent-controlled browsers using Playwright or Puppeteer routinely fail 20-30% of the time on production workflows because they rely on LLM judgment for timing and element selection. Libretto replaces that with a record-replay system that captures precise interaction timing and DOM fingerprints, achieving a reported 95% success rate on identical workflows. The library works by recording a "golden path" of a browser session — capturing not just actions but the exact CSS selectors, visual context, and timing windows during which those actions are valid. On replay, it verifies each step against expected page state before proceeding, and falls back to an LLM-assisted recovery mode when pages drift (e.g., after a UI update). Saffron Health built it to maintain integrations with EHR portals that change frequently and where failure has compliance consequences. Saffron open-sourced Libretto after using it internally for 18 months across 40+ healthcare software integrations. The HN thread highlighted the appeal for fintech, legal, and healthcare automation where reliability, not just capability, is the product. The toolkit targets TypeScript/Node.js environments and integrates cleanly with existing Playwright infrastructure.

Skills is a curated library of AI agent prompts and workflows for real software engineering, created by TypeScript educator Matt Pocock. The project trended to 28,000 GitHub stars with its blunt tagline: "Agent skills for real engineers — not vibe coding." It's a deliberate pushback against chaos-first AI coding in favor of structured, methodical engineering. The library organizes into four categories: Planning & Design (to-prd for converting conversations into PRDs, grill-me for stress-testing plans), Development (tdd for test-driven AI assistance, triage-issue for bug investigation), Tooling & Setup (pre-commit hooks, git safety guards), and Writing & Knowledge (documentation utilities, Obsidian integration). Each skill installs with a single npx command — npx skills@latest add mattpocock/skills/tdd — and plugs into Claude agent setups. With 28,000 stars and 2,200 forks after trending on GitHub on April 27, 2026, Skills has clearly struck a nerve. It's as much a cultural statement as a product: AI coding tools should be used deliberately, with tests, with planning, and with guardrails. The TDD and triage-issue skills address real gaps in how current AI coding agents handle existing codebases rather than greenfield projects.