Libretto vs MDV

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.

MDV (Markdown Data Views) is a markdown superset that extends standard .md files with embedded live data, interactive charts, and presentation-ready slides. The goal is a single document format that serves simultaneously as developer documentation, a live dashboard, and a shareable slide deck — without requiring a separate tool for each use case. MDV files can embed SQL queries, API calls, and data transforms directly in markdown, with results rendering as tables, charts, or visualizations on the fly. The syntax extends frontmatter conventions that markdown users already know, keeping the learning curve minimal. Output can be previewed in a local server, exported as HTML, or converted to a slide deck — the same source file serves all three outputs. MDV surfaced on Hacker News with 44 points and active discussion around the concept of "living documents" — reports and runbooks that stay current because their data sources are live queries rather than screenshots. For developer-heavy teams who live in their editors and resist adopting heavyweight BI tools, MDV offers a markdown-native alternative that slots into existing documentation workflows.