Compatibility contract

This describes the published 0.1.0-alpha.2 train and its tested source contracts. A supported interface, a native parser, an automatic generator and a shrinker are different capabilities. Native package versions below are explicit conformance targets or exhaustively tested bounded ranges. Fixture manifests, lockfiles and tests/vendor-versions.json are the executable source of truth.

Input or integration	Tested target	Generation and types	Validation, codecs and limits
Typed factories	Core API	Inferred values/arguments, sync or async; caller owns generation.	Optional Standard Schema validation; no schema dependency.
Standard Schema	v1 interface	Any conforming validator plus an input factory.	Native input/output distinction; sync/async execution and options. Standards acceptance alone is not auto-generation.
Standard JSON Schema	v1 interface	Input conversion plus generation; input/output types retained.	Must also supply Standard Schema to validate native output; opaque refinements can reject generated input.
TypeBox	typebox 1.3.34	Native minimal/default creation, complete anyOf-branch selection, custom factories.	Strict checking, root/field Codec handling, named contexts; no lossy JSON conversion.
Legacy TypeBox	@sinclair/typebox 0.34.48–0.34.52	Separate native minimal/default creation and anyOf selection.	Native Transform, references, recursion, Date and format cases. Native version semantics are not rewritten.
Zod	4.4.3–4.6.5	Dedicated Zod/Mini builders, input JSON generation and typed factories.	Native parsing/codecs; explicit async path avoids the Standard entry probe.
Valibot	1.5.0; converter 1.8.0	Native adapter converts synchronous schema input.	Original parsing/transformations. Async/native-only schemas use a factory with Standard Schema.
ArkType	2.2.5	Dedicated builders, input JSON generation and native typed factories.	Native morphs/scopes and input checks retained; no private AST dependency.
Effect	3.22.2	Native decoded arbitrary re-encoded as input; sync/async factory escape hatches.	Native input/output arbitraries, codecs and fast-check 3 shrinking. Effect 4 is not represented as compatible.
JSON Schema	Draft-07, 2019-09, 2020-12	json-schema-faker 0.6.3; explicit versioned alternative providers.	Separate Ajv 8.20.0 validators and ajv-formats 3.0.1; checked output, offline references and bounded attempts.
Faker	10.5.0	Explicit factories, locale fallback and stable named session streams.	Native schemas can validate results; fixed reference dates and versioned replay.
fast-check	4.10.2	Native arbitraries, fixture mappings, parameter/scenario shrinking.	Sync/async properties, assertions and replay; arbitrary derivation from every schema is not claimed.
OpenAPI	3.0, 3.1, 3.2	Request/response envelope builders and component projection.	Directional policy, media/status selection and explicit serializers; not a full document validator or HTTP client.
AsyncAPI	2.0–2.6, 3.0–3.1	Headers/payload message envelopes.	Native dialect selection; message identity and offline references. No broker connection.
GraphQL	graphql 17.0.2	Native inputs and selection-aware output fixtures.	Original schema rules, custom scalars and bounded recursion; not live resolver execution.
Protobuf	protobufjs 8.8.0	Native message fixtures and lossless integer representation.	Explicit offline imports, oneofs, binary codecs and input limits.
Avro	avsc 5.7.9	Native fixtures, recursive records and explicit union branches.	BigInt-backed signed 64-bit values, defaults and binary codecs; unknown logical semantics need explicit support.
Hey API	openapi-ts 0.99.0	Generated named builders using the shared core.	Real Swagger 2/OpenAPI 3.0/3.1 generation, compilation and installed ESM consumer tests; breaking v3 migration.

See each package guide for its exact constructors and unsupported features. Unsupported automatic generation has a factory/provider escape hatch; an exhausted sampling budget is not proof of unsatisfiability.

Execution and TypeScript

All packages are ESM. Native synchronous CommonJS exports and Node10 resolution are not advertised; package diagnostics intentionally use the ESM-only profile. The full workspace is verified with Node 22.18.0 on Linux, macOS and Windows, and additionally Node 24 on Linux, using TypeScript 6.0.3. Runtime versions are pinned where reproducibility requires them and recorded by the corresponding CI jobs.

The dependency-free core and portable consumer/adapter/Faker declarations are additionally tested with TypeScript 5.8.3. Do not extrapolate that result to modern TypeBox or vendor declarations requiring newer compiler features. Some native vendor/consumer declarations require Web/DOM types; the core does not.

The packed core runs as native ESM in Chromium, Firefox and WebKit, and in Bun 1.4.2 and Deno 2.9.7. Deno's acceptance contract receives no filesystem, network, environment or subprocess permissions. This is a core portability claim, not a claim that Node filesystem/worker/codegen packages run in browsers or Deno. The playground browser UI is exercised on all three browser engines against its local Node server. Playwright engine versions come from the locked test fixture.

Semantic boundaries

Input patches precede transformations and native validation. Validators may apply their own transformations; the builder does not silently repair explicit overrides. The pinned Zod Standard Schema entry can probe an async refinement synchronously before running it asynchronously. For effectful refinements that must execute once, the published @mimlet/zod package provides fromZodAsync and fromZodFactoryAsync, which use native async parsing directly. Other Standard Schema integrations can provide an explicit safeParseAsync-based Standard Schema wrapper. Calling one standards entry is not a promise about a vendor's internal callback count.

TypeBox minimal creation is not random sampling; use a factory, Faker integration or a suitable provider for realistic data. Root union output can differ from its selected input branch because the original codec is retained. Native schemas and callbacks are trusted application code and are not serialized into replay files.

Generic JSON generation explicitly rejects unsupported dynamic/recursive references, anchors and unknown assertions rather than dropping them. Custom vocabularies require paired versioned extension support. Patterns and opaque callbacks can still require separately restricted execution. See security.

A seed reproduces a supported configuration and provider version, not arbitrary future dependency releases. Named-stream isolation applies where a provider uses those scopes, not to every field of a third-party generator. Fixture capture is available when the actual value must survive dependency changes.

Version ranges in alpha.2

Alpha.1 used exact peer pins. Alpha.2 widens Zod to >=4.4.3 <=4.6.5 and legacy TypeBox to >=0.34.48 <=0.34.52. tests/vendor-versions.json pins every currently published version in those intervals by tarball integrity. pnpm test:vendors reuses the full native conformance, negative-type and coverage suites for each version in isolated installations, including a production dependency audit. Future versions require a new reviewed matrix entry.

Modern TypeBox remains exactly 1.3.34. Probing 1.3.30–1.3.33 found that a property named a/b~c is reported as /a/b~c rather than the unambiguous JSON Pointer /a~1b~0c. The existing path-preservation regression fails on those versions; the adapter does not guess a repair. ArkType remains pinned to 2.2.5.

Zod's provider metadata now records the loaded vendor version, so a range upgrade cannot silently reuse a replay identity that describes a different Zod release.