When Four Hours Suffices

Last week I wrote about flipping the Staff→Voice→Measure hierarchy to Staff→Measure→Voice. The structural reasons were sound, but I'd estimated a week for the implementation. Forty files to touch, thousands of tests to update, the whole spine of the system. With a 1:1 ratio of code to tests, that's rather a lot of surface area to cover. This usually means a lot of pain.

The actual time: four hours.

Claude Code's systematic approach made the difference. Seven discrete steps, continuous test validation, zero functionality regression. Tests failed as expected during refactoring, but the effort to fix them was absolutely minimal. This wasn't vibe coding; I controlled the process carefully, directing each step. Yet even with that careful oversight, the work required was remarkably little. Claude 4.5, being new and even more capable, may well have been key here.

The result was better than expected as well: 30–99% less allocation through transducer-based lazy sequences, 211 fewer lines of code, clearer logic throughout. What surprises me isn't that AI-assisted development helped; it's the magnitude. A tenth of the expected time isn't incremental improvement. That's a different category of capability entirely.

Now on to some small bits and bobs before the real work on the client starts: windows, drawing, printing, etc.

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