Rakuten engineers let Claude Code rework code on its own for 7 hours
In plain words
Rakuten used Claude Code to run a seven-hour autonomous refactoring of the open-source vLLM codebase and to speed up feature delivery.
What happened: New features now ship in 5 days instead of 24.
Source: claude.com ↗
How to do it yourself
Our suggested steps. The company didn't publish theirs.
- 1
Pick a well-defined coding job (refactor, upgrade a library, add tests).
- 2
Make sure the repo has tests and a CLAUDE.md describing conventions.
- 3
Run Claude Code with the prompt below on a new branch.
- 4
Let it run, then review the diff and test results.
- 5
Merge in small PRs.
The instructions to give the AI
Paste this into Claude Code (the free plan is fine), swap the [brackets] for your details, and test it on a few real examples.
This is one part of the setup. It won't connect to your phone, inbox or other apps on its own; the steps above cover that.
Agent instructions (prompt)
On a new branch, [describe refactor/upgrade]. First read CLAUDE.md and the test suite. Plan the change in steps, then implement step by step, running tests after each. Don't change public APIs unless required; list any you change. Finish with a summary of changes and remaining risks.
[Highlighted] = replace with your own details before you run it.
What you should get back: A step-by-step plan, the code change on a new branch, and a passing test run.
Written by Quickly and Good, inspired by this case.
More detail: tools, prices and what you'll need
The company used: Claude Code
You could use: Claude Code
- Claude Code
AI coding agent that builds and edits software from plain-English instructions.
See pricing · Official site ↗
Prices from each tool's own pricing page, checked Oct 2026.
What you'll need
- ☐A developer environment and the coding agent (e.g. Claude Code)
- ☐API access to the systems it must touch
- ☐Clear written instructions and project rules
- ☐Version control and a way to undo changes
- ☐Testing and code review by someone who can read the code
Can I do this myself?
Only if you can code or are learning to. Otherwise hire a builder.
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