- Buildkite Agent v4 becomes the default stable release on 1 September 2026, with automatic upgrades for non‑pinned installations.
- Breaking changes include secret upload failures unless opted‑in, reversed hook order, default propagation of agent config vars, removal of OpenTracing (replaced by OpenTelemetry), removal of legacy Docker integration, and several renamed...
- Consult the upgrade guide, test the v4 beta, and update hooks, plugins, configuration, or observability setups before the switch.