ata-validator

A schema-directed scanner: isValidJSON() answers the verdict from the JSON text without building the document. Parsing is about three quarters of the cost of a request that only needs yes or no, and a rejection now stops at the byte that caused it. The scanner compiles per schema, on the codegen path only, after 64 calls (generating one costs about 20 µs, so a caller that checks one document never pays), and it declines anything outside its supported core: type, properties, required, additionalProperties, items, prefixItems, the length, size and range keywords, pattern, format, const, enum, local $ref (inlined, acyclic, no base-changing keywords below the root), allOf (merged, with the additionalProperties cross-branch rule written out in full), and unevaluated* where it is provably a synonym for additionalProperties/items. Whatever it cannot answer it declines at compile time or bails from at runtime, and the parse path takes over unchanged. tests/test_scanner_differential.js holds the scanner and validate() to the same verdict on the same text: 413,130 comparisons over the official suite, a malformed-JSON corpus and generated corruptions, zero disagreements, and the count must stay at zero.

An AOT module that cannot carry error detail says so. toStandaloneModule with error detail requested builds the error function from the error generator, which declines some schemas, unevaluated* among them; the runtime validator falls back to the interpreted engine there, but a standalone module has nothing to fall back to, so it shipped with an exact verdict and a single ATA9000 stub for every failure, silently. The module still ships, since the verdict is exact and validating the rare failing document with the runtime Validator is a legitimate pattern, but the degradation is loud in every layer: onWarning on the emitter, a NOTE in the module header, a warnings list in the build() report, a printed warning from ata compile, and a refused build under --strict. Found by a gateway team that lost their per-field startup errors to it.