Transformation engine

In 2.1.x, kgateway uses the classic transformation engine. Classic transformation is a C++ filter that is statically linked into a custom Envoy build, and templates are powered by version 3.4 of the Inja template engine.

For the template syntax and the list of supported functions, see Templating language.

Strict validation compatibility

Strict validation runs an Envoy preflight against the generated xDS snapshot to block configuration that would be rejected at the data plane. In 2.1.x, strict validation works with classic transformation. For configuration steps, see Strict validation.