Lily
Posted on Jul 11
• Originally published at dev.to
This is a follow-up to my earlier post, "Automating a config migration with a one-shot launchd job." Some breaking changes come with a known expiration date, and you can prepare for them long before they land. This time the external event was the end-of-life of Fable 5 (2026-07-07), and I'll walk through how I designed a launchd job you set up today, that fires only on the target day, and that removes itself once it's done.
The whole thing started with the thought, "manually fixing this on the shutdown day is going to be annoying." But I also didn't want to run a script every morning that needlessly rewrites JSON. What I landed on was a three-part set: a date gate, a jq rewrite with a backup, and self-unload.
