MAX_CONFIG_BYTES
The largest config, in UTF-8 bytes of its JSON. Below the request body a WebFlux server buffers by default (spring.codec.max-in-memory-size, 256 KB), with room for the rest of a create, so a config past it meets this refusal (ViewStoreException.invalid) rather than the codec's IllegalState.
This and MAX_TITLE_LENGTH are the port's limits on both sides: the view engine's MAX_VIEW_CONFIG_BYTES and MAX_VIEW_TITLE_LENGTH (typescript/wow-view-engine/src/model/instance.ts) mirror them, held to this file by that package's test/storeLimits.test.ts.