Opus rebuilt a closed grid control from scratch: 500 files and thousands of tests

Opus 5.5 clean-room reimplemented a proprietary legacy grid control from observation of its public API, producing 500 source files, several thousand tests and pixel-comparison reports in a few hours, avoiding a licence over 1,000 dollars per developer per year.

$1,000a year

How it works

Opus studies the public API of the legacy control
Reimplements it from observation
Produces 500 source files and several thousand tests
Pixel-comparison reports check the match

Why it’s worth knowing

Clean-room means it never saw the original code, only how the control behaves.

Where it’s from

Summarized from a public post on news.ycombinator.com. See the original ↗

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