migration
- Spring Boot 4 Keeps a Tracer With Tracing Off
In Spring Boot 4, management.tracing.enabled=false binds to nothing. The replacement switches off export, not the Tracer bean.
- The Build Was Green the Whole Time
The migration compiled and its tests passed. Then the software ran, and five failures turned up that no build step had reported.
- Upgrade Errors That Named the Wrong Layer
Five Maven repos, three framework families, one JDK 25. Most errors pointed at a layer the fix didn't live in. The first failure printed nothing.
- Five Things Spring Boot 4.1 Doesn't Tell You Until It's Too Late
Spring Boot 3.5 lost OSS support on June 30, 2026. Boot 4 modularized autoconfiguration, and its silent failures cost an afternoon.