maxDepth

How deeply subschema application may nest.

The reference graph a catalog describes is cyclic: a function's arguments are dynamic values, a dynamic value may be a function call, and a function call resolves through anyFunction back to the catalog's own functions. The cycle guard stops a traversal that revisits the same subschema at the same place in the instance; this stops one that descends forever through an instance that keeps nesting. It is a stack-depth bound, and Kotlin/Native aborts the process on overflow rather than raising something catchable.

This counts subschema applications, not levels of nesting in the payload, and the two are an order of magnitude apart. Reaching an argument one call deeper costs roughly eight frames — the $ref to FunctionCall, its oneOf, anyFunction, that oneOf, the function, its allOf, its properties, then the argument itself.

So the number is derived rather than chosen: a renderer will evaluate an expression dev.ynagai.a2ui.core.function.DEFAULT_CALL_DEPTH calls deep, and refusing to validate what the evaluator will happily run is the wrong way round. Thirty-two calls at eight frames each is this. The specification's own suite needs 64 of them (checkable_components #8), so the default leaves a factor of four — measured by a test, not assumed.