Solo dev builds browser parametric CAD tool Extrudo in a month with Claude: 322 commits, 82 ADRs
slartibartfastda · reddit · 2026-10-14
A developer built Extrudo, a browser-based parametric CAD tool for 3D printing (constraint sketches, extrude, fillet, named dimensions, live slider rebuilds), almost entirely with Claude — free, accountless, offline-capable, GPL-3.0 on GitHub.
Build stats
- 1 month, first commit Sept 25, 322 commits on main; mostly Opus 5.5, planning with Fable, chores via opencode with cheaper models
- Stack: OpenCascade compiled to WebAssembly in a Web Worker behind 9k lines of C++, planegcs constraint solver, three.js viewport, React UI; CI runs 528 test files (Vitest + Playwright) per push
Multi-agent workflow
- One Claude Code session acts as coordinator: picks tasks from the roadmap, records decisions as ADRs (82 so far), writes worker briefs with file lists, signatures, test cases and acceptance checks
- Headless workers on a second PC, each job in its own git worktree/branch; coordinator reviews every diff and merges only when CI is green
Lessons
- Invest early in a well-designed roadmap
- Don't fan out too wide: 8-16 parallel agents burned too much of the plan; cap at 2-3 jobs
- Keep CLAUDE.md short as a map; details live in an ADR digest agents read per-area
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