Field notes
Patterns from the design partner work – what shipped, what didn't, and what changed when prototypes started running on the real codebase.
- Field note
AI coding tools versus AI prototyping tools: where each one fits
AI coding tools (Cursor, Claude Code, Windsurf) refactor existing codebases for engineers. AI prototyping tools split into greenfield (Lovable, v0, Bolt) and brownfield (Else, Alloy, Builder.io). The PM is in the third bucket – the one that ships a PR.
2026-05-18Paul Johns - Field note
Why Lovable rebuilds your design system every time
Every time a PM opens Lovable against an existing product, they rebuild the design system inside the tool. Kyle Grant at HP calls it the recreation tax.
2026-05-12Paul Johns - Field note
The setup is the gate
The setup is the gate between PMs who can build and PMs who cannot. It is npm, environment variables, the dev server. Tools that run in the browser solve it.
2026-05-07Paul Johns - Field note
Tools that can't imitate your actual product
Lovable, v0, and Bolt look nothing like your actual product. The structural reason — and what it means for a PM working on an existing codebase.
2026-05-06Paul Johns - Field note
Cursor for product managers
Cursor is built for someone who already lives in a terminal. Most PMs do not. What an executive ask for Cursor access actually buys a product team.
2026-05-05Paul Johns - Field note
The existing codebase advantage
Every AI prototyping tool assumes you're starting from zero. Else is built for the opposite — the product that already ships, the codebase that already runs.
2026-05-01Paul Johns - Field note
The prototype is the product. Until engineering rebuilds it.
PMs argue whether the prototype replaces the PRD. Wrong fight. The real gap: between the prototype that got validated and the product engineering ships.
2026-05-01Paul Johns - Field note
AI prototyping for product managers
AI prototyping for product managers: pick the hypothesis, match the product, protect the polish. The three-move playbook PMs use to ship prototypes that merge.
2026-04-27Paul Johns - Field note
When design says start over
When vibe-coded prototypes fail design review: why lookalike components trigger rebuilds, and how to choose tools that avoid the cycle.
2026-04-21Paul Johns - Field note
Super competent. Super skilled. But I didn't see anything.
Your PMs are shipping fast. Engineering is shipping nothing. The vibe-coding paradox and why tool architecture matters.
2026-04-14Paul Johns - Field note
Vibe coding for product managers
Why PM-built prototypes disappear in the engineering handoff: the structural reasons, what the handoff actually breaks, and how to fix it with the right tool.
2026-04-07Paul Johns