Jackson 3 exceptions are unchecked, so existing `catch (IOException e)` blocks silently stop handling JSON parse errors after the Spring Boot 4 upgrade.
Jackson 3 also moves packages from `com.fasterxml.jackson` to `tools.jackson`, which the compiler does flag.
Spring Boot 3.5 lost open-source support at the end of June 2026, so this migration is now a security schedule, not a preference.