4. Scope: supported tiers and current boundaries🔗

Triptych's expressiveness is layered. The grammar tier remains small enough for generated reconciliation proofs, constraints can narrow its language, and value escapes can return arbitrary types. This chapter describes the supported surface and the boundary of the current compiler.

Supported now. Triptych generates readable specifications, executable parsers, and reconciliation proofs for acyclic, non-recursive grammars built from literals, finite alternatives, optional items, sign, built-in digit, hexadecimal, and bit runs, and separated repetition. Values and constraints may use the analyzable DSLs or user-supplied escape functions. Declared external parsers and printers receive explicit proof contracts.

Not currently supported. The generated grammar surface does not directly support the user-defined character classes or unseparated repetition needed by general Base64, field boundaries that depend on earlier values such as Graph6, or recursive formats such as JSON, s-expressions, and Cedar policies. These formats currently require a hand-written parser and a separately proved specification. The next chapter describes the planned extensions.