Built a split-pane resume editor: text on one side, live preview on the other, both driven by a single document model, so what you see while editing is exactly what gets exported as PDF Implemented drag-and-drop reordering and undo/redo history (Zustand + zundo), plus a client-side pagination engine to handle page breaks in a multi-page resume Added design controls for fonts, color themes, spacing, margins, alignment, and templates, backed by a single source of truth store, so saved sections populate new documents without re-entry Hosted PDF generation on a standalone Puppeteer service instead of running headless Chrome inside serverless functions, avoiding cold-start and memory limits on Vercel Added a profile system so experience, education, and skills, and other sections are entered once and reused across multiple resumes without retyping Integrated OpenAI and Claude behind a shared layer for bullet and section rewriting and job-description-driven resume generation, with per-user daily credit limits