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Greenfield projects: 14 sourced coding agent stories

Agents building new code from an empty repository. Of the 14 stories, 3 were published by a tool vendor and 11 by the people who did the work. 0 involve an existing codebase and 14 started from scratch. Every number links to where it was published.

• Practitioner (own blog/paper) New product greenfield

  Three people build Loft with coding agents over three months, then ship its open format 53 hours after the first commit

  Loft · 2026-10-16

  • 3 people Team
  • ~3 months (July 10 – Oct 16) V1 duration
  • Nearly 2,000 (merges excluded) V1 commits

  Claude Code, OpenAI Codex

• Practitioner (own blog/paper) New product greenfield

  Foxbox Digital ships a production marketing site with two engineers in 14 days using Claude Code

  Foxbox Digital (agency) · 2026-10-14

  • 2 weeks Calendar time
  • 2 engineers Team
  • ~9,200 Lines of code

  Claude Code

• Practitioner (own blog/paper) New product greenfield

  Sparq builds a 22-agent internal platform with Claude Code: 34,000 lines across 453 commits

  Sparq · 2026-10-14

  • ~34,000 Python Lines of code
  • 453 / 159 Commits / PRs
  • 4 Repositories

  Claude Code

• Practitioner (own blog/paper) New product greenfield

  Token Clicker: a 33,716-line browser idle game shipped 19 hours after its specs with Claude Code

  Julien Renaux (independent developer) · 2026-09-28

  • 19 hours 39 minutes wall-clock (night included) Specs to launch
  • 33,716 lines TypeScript in src/
  • 1,758 unit, 34 pacing, 28 end-to-end Tests

  Claude Code

• Practitioner (own blog/paper) New product greenfield

  Solo developer builds a cross-platform tower defense game in about 30 days with Claude Code, for ~$2,755 in tokens

  Julien Renaux (independent developer) · 2026-09-10

  • ~30 days, ~12 working sessions Duration
  • 9,436 Tool calls
  • 17.7M Output tokens

  Claude Code

• Practitioner (own blog/paper) Refactor / maintenance greenfield

  An agent-written 150,000-line Rust app shows refactoring one 17,155-line file cut input tokens per change by 83%

  Giles Edwards-Alexander (writing on martinfowler.com) · 2026-07-30

  • ~150,000 lines (~120k Rust) App size
  • 17,155 lines Largest file before
  • 3,695 lines Largest file after

  Claude Code, Cursor

• Vendor-published New product greenfield

  OpenAI team ships an internal product with zero hand-written code: ~1M lines and ~1,500 merged PRs in five months with Codex

  OpenAI · 2026-02-11

  • ~5 months Duration
  • On the order of 1 million lines (incl. infra, tooling, docs) Codebase size
  • ~1,500 PRs merged

  OpenAI Codex

• Vendor-published New product greenfield

  16 parallel Claude agents build a 100,000-line Rust C compiler that builds Linux, for ~$20,000

  Anthropic (Nicholas Carlini) · 2026-02-05

  • Just under $20,000 API cost
  • ~2 weeks, nearly 2,000 Claude Code sessions Duration
  • 100,000-line compiler Output

  Claude Code

• Vendor-published New product greenfield

  Cursor's agent swarm writes a 1M+ line browser in about a week, and critics find it barely compiles

  Cursor (Wilson Lin) · 2026-01-14

  • Close to a week Duration
  • 1M+ lines across ~1,000 files Output
  • Hundreds of concurrent workers Agents

  Cursor

• Practitioner (own blog/paper) Language port greenfield

  Simon Willison ports an HTML5 parser from Python to JavaScript with Codex CLI in about 4.5 hours

  Simon Willison (independent developer) · 2025-12-15

  • ~4–4.5 hours Idea to finished library
  • 8 Prompts
  • 9,000 lines of JavaScript, 43 commits Output

  OpenAI Codex

• Practitioner (own blog/paper) New product greenfield

  Emil Stenström builds JustHTML, a pure-Python HTML5 parser passing all 9,200+ html5lib tests, with Copilot agent mode

  Emil Stenström (independent developer) · 2025-12-14

  • A couple of months of off-hours Time
  • ~3,000 lines (plus ~11,000 lines of tests) Implementation code
  • All 9,200+ html5lib-tests passing

  GitHub Copilot

• Practitioner (own blog/paper) New product greenfield

  Solo developer ships a 20,000-line native macOS app, writing fewer than 1,000 lines by hand

  Indragie Karunaratne (independent developer) · 2025-07-01

  • ~20,000 lines Codebase size
  • <1,000 lines (author's estimate) Written by hand
  • 2,000 lines of Python, written by Claude in a few hours of iteration Release automation script

  Claude Code

• Practitioner (own blog/paper) New product greenfield

  Cloudflare's Kenton Varda prompts an OAuth 2.1 provider library out of Claude Code in about five days

  Cloudflare · 2025-06-03

  • ~5 days of heavy work (with other duties), plus minor commits over the month Time with AI
  • ~5,000 lines incl. comments, tests and docs Library size
  • 2–5x longer ("a few weeks, maybe months") Author's by-hand estimate

  Claude Code

• Practitioner (own blog/paper) New product greenfield

  Pieter Levels builds a browser flight sim with Cursor in ~3 hours; it hits $1M ARR in 17 days

  Pieter Levels (indie maker) · 2025-03-11

  • ~3 hours (author's estimate) Time to first playable version
  • $87,000 MRR (~$1M ARR) Revenue after 17 days
  • 320,000 Players after 17 days

  Cursor