AI Coding Tip 037 - Stop Patching Blind
Old code, new AI, same unwritten test suite.
TL;DR: Patch code that never had a test written for it, and every quick fix becomes tomorrow's outage.
Common Mistake ❌
You assume a decades old, stable feature must have some kind of safety net, because it has been shipping without complaints for almost twenty years.
Automated testing wasn't standard practice when much of that code was written.
Nobody ever wrote a test for it, not because a team decided to skip that step.
The step simply didn't exist yet as an expectation.
In September 2026, Microsoft shipped a security update for Excel, documented on its own KB5002914 support page, and paste operations started failing silently across Excel 2016, Office 2019, Office 2021 LTSC, Office 2024 LTSC, and Microsoft 365 Apps.
AutoFill broke too, presumably out of solidarity 🙂.
Microsoft's follow-up fix, KB5002665, later confirmed the trigger in its own...
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