No docs, two languages, a SCADA platform: Claude Code got 80-90% right
An undocumented legacy codebase mixing two languages, a SCADA platform and proprietary hardware logic. With little help, Claude Code worked out most of it, with only a couple of misunderstandings.
Done withClaude CodeSpotted· by HN user TYPE_FASTER· Oct 15, 2026
Result Ready for the refactor the team had planned
“It was mostly right, probably 80-90%, had a couple mis-understandings.”
Spotted: found in the wild. Details are as reported by the source above and have not been independently verified.
What they did
Integrated Claude Code with IntelliJ and pointed it at a legacy codebase that combines two programming languages, one of the smaller SCADA platforms, and hardware logic in a vendor tool’s proprietary format. There was no documentation and they gave it little help.
How it went
It was mostly right, probably 80-90%, with a couple of misunderstandings: it just figured it out. They expect it to be very helpful for the refactoring the team was already planning. Separately, Claude built them a near-MVP Chrome extension one morning before they hit the Pro plan limit.
Try it yourself with Claude Code
Read this legacy codebase: [paths]. There's no documentation. Write a map of how it fits together: the languages and platforms involved, the main components, how data and signals flow between them, and anything you're unsure about. Mark each claim as confirmed from the code or inferred. Then propose a refactoring plan toward [goal] in small, safe steps.
A starting prompt written by Agents in the Wild. Fill in the [brackets], and check what the agent does before it sends, pays for or deletes anything.
Markdown files should just open, so they asked Claude Code for a viewer. It opens instantly: faster, they say, than any other macOS app, and faster than Bitwarden's Chrome extension shows its fill menu.
Migrating a password reset flow, Claude Code and Opus produced code on par with a mid level developer. It needed close supervision throughout, and cost roughly 2 months of Pro subscription for about half a day's work.
A URL shortener side project ran on AWS. Claude Code wrote the GitHub Actions workflows for the move and fixed each failure as it came up. The writer reports zero downtime.
A 7-app monorepo needed an 8 GB memory setting and 25 seconds to typecheck. Claude Code made the changes for the move to oxlint, oxfmt and tsgo, and the team validated each step.
Turning plan files into Claude Code workflows took 5-6 hours each. A script that converts them deterministically, and flags what can move out of the LLM, cut that to 20-30 minutes at about 20% of the tokens.
An inherited app on Azure, an error, and a hunt that could easily take 1-2 days by hand. With CLI access to Azure and the repo, Claude Code ran the config and network checks and found the root cause in about 45 minutes.