Find your adapter

Start with the schema and behavior you already use. Mimlet keeps the core small; generation and native library integrations are opt-in.

Your input or job	Package	What to expect
A factory or Standard Schema validator	@mimlet/core	Immutable builders, input/output typing, async capabilities, sessions and scenarios; provide the factory.
Modern typebox	@mimlet/typebox	Native creation, checking and codecs; explicit factory escape hatch.
@sinclair/typebox	@mimlet/typebox-legacy	Native legacy TypeBox and Transform semantics.
JSON Schema or Standard JSON Schema conversion	@mimlet/json-schema	Supported draft validation, profiles and bounded generation; inspect unsupported capabilities.
Zod 4 / Zod Mini	@mimlet/zod	Native parsing/codecs, explicit async validation, input generation and factories.
ArkType	@mimlet/arktype	Native morphs/scopes, input checks, input generation and factories.
Valibot	@mimlet/valibot	Input conversion plus native parsing; factories for unsupported refinements.
class-validator DTOs (NestJS)	@mimlet/class-validator	Payloads for e2e tests and the DTO instances ValidationPipe produces; factories provide the values.
Effect 4 (Effect 3 through alpha.3)	@mimlet/effect	Native schemas, codecs, arbitraries and shrinking.
Realistic values	@mimlet/faker	Explicit session-scoped randomness, locale and reference date.
Property tests	@mimlet/fast-check	Native shrinking, scenario recomputation and checked replay.
OpenAPI / AsyncAPI	@mimlet/api	Operation/message fixtures and explicit serialization with offline references.
GraphQL	@mimlet/graphql	Native input fixtures and selection-aware response fixtures.
Protobuf	@mimlet/protobuf	Native values, offline imports and binary codecs.
Avro	@mimlet/avro	Native values, unions, 64-bit integers and binary codecs.
Generated fluent builders	@mimlet/codegen	Deterministic classes, CLI checks, optional self-contained runtime.
A local schema editor	@mimlet/playground	Loopback-only playground with bounded, interruptible workers.
Your own adapter	@mimlet/adapter	Capability inspection and reusable conformance checks.
UI previews, HTTP mocks, test persistence	@mimlet/consumers	Explicit loaders, response resolvers and caller-owned persistence.
Hey API generation	hey-api-builders	The established plugin, now backed by the neutral core.

The dedicated Zod and ArkType adapters are included in 0.1.0-alpha.1. Follow the tested recipes, or retain the core and Standard JSON Schema path when those interfaces already meet your needs. The class-validator adapter was first published as 0.1.0-beta.4; see the NestJS DTO guide.

Validation, conversion and generation are different

Standard Schema describes validation and input/output types. It does not itself provide a generator or make arbitrary callbacks reversible. Conversion to JSON Schema can lose constraints that only the native validator understands.

Use buildValidated() or its async counterpart when decoded, validated output is required. Supply a factory when generation cannot faithfully express a constraint. Inspect the package's capabilities before claiming codec, generation or shrinking support. Pin the tested native-library versions in the compatibility matrix.

Realistic values for tests

Adapters that generate through JSON Schema (@mimlet/json-schema, @mimlet/zod, @mimlet/valibot, @mimlet/arktype, @mimlet/api and the JSON targets of @mimlet/codegen) default to the minimal profile: optional fields are left out and an unconstrained number can be anywhere in its range. profile: 'realistic' fills optional and nullable fields, keeps arrays at one to three items, draws unconstrained numbers from 1 to 100 within the schema's bounds and writes plain strings as readable words:

import { z } from 'zod';
import { fromZod } from '@mimlet/zod';

const Order = z.object({
  reference: z.string(),
  total: z.number().nonnegative(),
  coupon: z.string().nullable().optional(),
  lines: z.array(
    z.object({
      sku: z.string().max(12),
      quantity: z.number().int().positive(),
      note: z.string().optional(),
    })
  ),
});

// The default profile leaves optional fields out and samples the whole safe-integer range.
export const minimal = fromZod(Order).build();
// realistic fills optional and nullable fields with readable words and small numbers.
export const realistic = fromZod(Order, { profile: 'realistic' }).build();

The profile is part of the replay identity, and every value still passes the schema. See realistic values for the exact rules. Fix the values a test depends on with .with().

Keep the meaningful relationships

Faker supplies realistic primitives. Mimlet builders fix the fields that matter; scenarios connect related records. For property tests, shrink independent inputs and recompute the dependent values. See the agent recipes for executable examples of these combinations.