← All topics

Vendor case studies: 17 sourced coding agent stories

Stories published by the company selling the tool, or a company it owns. Read the caveats on these closely. Of the 17 stories, 17 were published by a tool vendor. 11 involve an existing codebase and 3 started from scratch. Every number links to where it was published.

• Vendor-published Language port brownfield

  GitHub ports the Copilot agent runtime from TypeScript to 800K+ lines of Rust, mostly by one engineer

  GitHub (Microsoft) · 2026-09-16

  • 832,378 lines Production Rust written
  • ~430,000 lines TypeScript passed through the port (author estimate)
  • ~14.5 weeks Porting window

  GitHub Copilot

• Vendor-published Test migration brownfield

  Asana finishes a five-year Enzyme → React Testing Library migration in two weeks with Codex

  Asana · 2026-08-19

  • ~2 weeks Calendar time
  • ~1.5 weeks Engineering effort
  • Up to 4 Parallel agents

  OpenAI Codex

• Vendor-published Language port brownfield

  Bun's 535,000-line Zig codebase is ported to Rust in 11 days by up to 64 parallel Claude Code agents

  Bun (Oven / Anthropic) · 2026-07-08

  • 535,496 lines of Zig (excluding comments), 1,448 .zig files Source size
  • 11 days (May 3 to merged May 14, 2026) Time
  • 6,778 Commits

  Claude Code

• Vendor-published Research / benchmark brownfield

  Legacy-Bench: frontier agents pass only 16.9–42.5% of COBOL, Java 7 and Fortran tasks

  Factory · 2026-04-01

  • 16.9%–42.5% Pass rate range (12 model–agent combos)
  • >70% Same models on Terminal-Bench 2 / SWE-bench Verified
  • 42.5% Best overall (GPT-5.3-Codex)

  Factory Droid, OpenAI Codex, Gemini CLI

• 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

• Vendor-published Refactor / maintenance brownfield

  Cisco uses Codex across 15+ repos to cut build times ~20% and speed up C/C++ defect fixing

  Cisco · 2026-01

  • 1,500+ per month Engineering hours saved
  • ~20% reduction Build time
  • 10–15× increase Defect resolution throughput

  OpenAI Codex

• Vendor-published Migration brownfield

  Nubank uses fine-tuned Devin to split a 6M-line ETL monolith, claiming 8–12x engineering-hour efficiency

  Nubank · 2024-12

  • 6M+ lines, ~100,000 data-class implementations Codebase
  • 18 months, 1,000+ engineers Original estimate
  • 8–12x Engineering-hour efficiency

  Devin

• Vendor-published Upgrade / modernisation brownfield

  Amazon upgrades tens of thousands of production apps to Java 17 with Amazon Q Developer

  Amazon · 2024-08-01

  • Tens of thousands (Java 8/11 → 17) Applications upgraded
  • 4,500+ years Development work saved (estimate)
  • $260M from performance improvements Annual cost savings (estimate)

  Amazon Q Developer

• Vendor-published Company rollout

  Stripe rolls Claude Code out to 1,370 engineers with a zero-configuration binary

  Stripe

  • 1,370 Engineers with Claude Code enabled
  • 2–3 months Time to produce signed enterprise binary
  • 6 Coding assistants enabled at Stripe

  Claude Code

• Vendor-published Language port brownfield

  Stripe migrates 10,000 lines of Scala to Java in four days

  Stripe

  • 10,000 Lines migrated
  • 4 days Actual duration
  • 10 engineering weeks Manual estimate

  Claude

• Vendor-published Upgrade / modernisation brownfield

  Altisource modernizes 350,000 lines of legacy Java with Amazon Q Developer

  Altisource

  • 350,000+ lines Legacy Java modernized
  • +25% (one modernization team, 'up to') Developer productivity
  • ~160 → 200 Story points (3-month avg per engineer)

  Amazon Q Developer

• Vendor-published Company rollout

  DTCC reports 40% higher developer throughput in an Amazon Q Developer proof of concept

  DTCC

  • +40% average Developer throughput (POC)
  • −30% average Code defects (POC)
  • +5% Security scores across repos

  Amazon Q Developer

• Vendor-published Company rollout

  Palo Alto Networks onboards 2,000 developers to a Sourcegraph Cody + Claude coding assistant in 3 months

  Palo Alto Networks

  • 2,000 in 3 months Developers onboarded
  • 150 developers Pilot group
  • Up to +40%, average 20–25% Coding productivity

  Sourcegraph Cody

• Vendor-published Language port brownfield

  Wiz ports a 50,000-line Python PDF library to Go in about 20 hours with Claude Code

  Wiz

  • ~50,000 lines of Python (pypdf) Source size
  • 18,413 lines of Go Output size
  • ~20 hours (10 active development, 10 testing) Time

  Claude Code

• Vendor-published Migration brownfield

  Block uses Claude Fable to orchestrate code migrations of thousands of pull requests, with two humans approving every deploy

  Block

  • "hundreds or thousands of individual pull requests across multiple repos and millions of lines of code" Migration size
  • "we might merge a thousand pull requests orchestrated by Fable" PRs per migration
  • "up to dozens of smaller, more cost-effective models like Opus or Sonnet" Worker models

  Buzz (Block)