--- name: schema-first-development-d73e3399041a description: > Focused schema-first guidance for this repo's effect/Schema and @beep/schema patterns. Use when adding or refactoring schemas, replacing exported interface/type data models, fixing schema-first lint violations, modeling literal domains or tagged unions, applying schema defaults or transformations, decoding external input, or reviewing schema code for repo-law compliance. --- # Schema-First Development Use this skill for schema-heavy work in this repository. Treat schema-first rules as enforced repository law, not style preference. The primary sources are: - `standards/effect-first-development.md` - `packages/tooling/tool/cli/src/commands/Lint/SchemaFirst.ts` - `standards/schema-first.inventory.jsonc` Keep `Schema` as the source of truth for pure data models. ## Workflow 1. Classify the task. - New schema or domain model - Refactor from exported `interface` / type literal - Boundary decode, transform, or defaulting work - Literal domain or tagged union modeling - Review or lint-fix 2. Load only the reference file you need. - Repository laws: `references/repo-laws.md` - Local shared schema primitives: `references/local-primitives.md` - Pattern selection and anti-patterns: `references/pattern-catalog.md` - Real repository examples: `references/examples.md` 3. Check local Effect v4 source for nontrivial Schema API choices. `.repos/effect` points to `$HOME/YeeBois/references/effect/effect`, the Effect child of the reference workspace; Effect `main` is v4. - Start with `.repos/effect/packages/effect/SCHEMA.md`. - Confirm behavior in `.repos/effect/packages/effect/src/Schema.ts` or the specialized module (`SchemaAST`, `SchemaGetter`, `SchemaIssue`, `SchemaRepresentation`, `SchemaTransformation`) when using advanced APIs. - Prefer exact upstream or repo-local helpers over memory and ad-hoc plumbing. 4. Apply the laws in this order. - Model pure data with `Schema` first. - Model plain object data as a branded `S.Opaque` over an annotated `S.Struct` (`S.TaggedStruct` for `_tag` data). Keep `S.Class` / `S.TaggedClass` / `S.Error` / `S.TaggedError` for errors, persisted entities, schemas with instance members, and `.extend` chains. Every schema class and Opaque declaration carries `{ readonly brand: unique symbol }`. - Check upstream `effect/Schema` first, then reuse `@beep/schema` and existing local schemas before inventing new checks. Where upstream covers a `foundation/modeling` concept's intent, its covered facets retire in the same PR that migrates their consumers, with no alias; the whole concept retires unless the lines reading its uncovered members outnumber the lines using its covered facets (ADAPT, per the facet census in `standards/architecture/DECISIONS.md` "Upstream-First Foundation/Modeling"). - Move normalization, defaults, nullable handling, and JSON parsing into the schema. - Annotate reusable non-class schemas with `.pipe($I.annoteSchema(...))` (`LiteralKit` included); classes take `$I.annote(...)` as their trailing argument. - Derive guards, equivalence, arbitraries, codecs, tagged-union helpers, and literal helpers from the schema instead of writing parallel helpers. - Prefer Effect schema codecs; map schema errors with `Effect.mapError(...)` when the error leaves the local helper/module boundary. 5. Verify before finishing. - No exported pure-data `interface` or type literal remains. - No schema value ends with `Schema`. - Non-class schemas export same-name runtime type aliases. - Tagged unions use the repo-preferred construction. - Finite variants are modeled as discriminated unions instead of optional payload bags. - JSON boundaries use schema codecs, not native JSON helpers. ## Fast Rules - Prefer `import * as S from "effect/Schema"` and canonical Effect aliases. - Create file-local identity composers with `@beep/identity/packages`. - Plain data is `class X extends S.Opaque()(S.Struct({...}).pipe($I.annoteSchema("X", {...}))) {}`. Construct with `X.make(...)`; there is no `new X(...)` and no `.extend`. Annotate the Struct inside the pipe, because `X.annotate(...)` drops the statics. See `references/repo-laws.md` section 2. - Use named intermediate schemas for reused concepts. - Prefer `LiteralKit` for named literal domains: its keyed API (`.Enum`, `.is`, `$match`, `.toTaggedUnion(...)`) plus the `S.Literals` members it inherits (`.literals`, `.pick(...)`, `.mapMembers(...)`). Use `S.Literals` for anonymous inline unions never referenced by name. - Prefer `MappedLiteralKit` when a protocol/code mapping needs both encoded and decoded literal helper surfaces. - Do not add `as const` to inline array literals passed directly to `LiteralKit(...)`; its const type parameters preserve the literal tuple. - Model finite variants, lifecycle states, status/result cases, and case-specific payloads as discriminated unions, not one optional/nullish payload bag. - Decode external optional/nullish case bags into internal tagged models when compatibility requires the wire shape. - Use `S.toTaggedUnion("")` for discriminators such as `kind`, `status`, `type`, `subtype`, `profile`, or `family`. - Use `S.TaggedUnion(...)` only for canonical `_tag` object unions. - Fix a tag with `S.TaggedStruct` / `S.TaggedClass` / `S.TaggedError`, and any other required single-literal field with `S.tag(v)`, never `S.Literal(v)`; `bun run beep laws schema-tag-idioms --check` enforces it. - Prefer schema-derived tagged-union helpers (`.cases`, `.guards`, `.isAnyOf`, `.match`) when constructing, guarding, or branching on a schema tagged union. - Use `S.OptionFromNullOr`, `S.OptionFromNullishOr` and `S.OptionFromOptionalKey` for absence at the boundary. Optional fields use exact keys (EF-40): `S.optionalKey`, `S.withDecodingDefaultKey`, `S.OptionFromOptionalKey`, never their `undefined`-admitting siblings. - Use `S.OptionFrom*` when the wire/schema field is optional or nullish. If runtime `Option` values are already being shaped into an object, prefer `O.getSomesStruct({...})` (`@beep/utils`) for heterogeneous struct spreads with known keys — runtime-identical to `R.getSomes` but type-preserving per key; reserve `R.getSomes({...})` for homogeneous dynamic-key dictionaries. Use `O.all({...})` for all-or-nothing fixed-shape composition. (Amended 2026-07-05 — see `standards/architecture/DECISIONS.md`.) - Use `S.withConstructorDefault(...)`, `S.withDecodingDefaultKey(...)`, and `S.decodeTo(...)` with `SchemaTransformation` for normalization and fallback behavior. - Prefer built-in schema constructors and checks before `S.makeFilter(...)`. - Treat broad exported/domain/boundary primitives such as `S.String`, `S.Number`, and unbounded arrays as prompts to ask whether the schema should be more precise. - If you need a custom reusable check, include `identifier`, `title`, and `description`. - Use `S.is(schema)` for guards, `S.toEquivalence(schema)` for comparisons, and `Arbitrary.schema(schema)` (`effect/Arbitrary`) for schema-modeled property tests. - Use `S.fromJsonString(S.Unknown)` or `S.fromJsonString(schema)` for JSON string boundaries. - Use `S.decodeUnknownEffect` / `S.decodeEffect` and `S.encodeUnknownEffect` / `S.encodeEffect` by default. Reach for `S.decodeUnknownResult`, `S.decodeResult`, or `S.decodeUnknownOption` only for deliberate non-throwing synchronous helpers; do not teach or add `S.decodeSync`, `S.decodeUnknownSync`, `S.encodeSync`, or `S.encodeUnknownSync`. If a legacy synchronous wrapper must still throw, convert Result failures with `Result.getOrThrowWith(...)` so raw schema issues do not escape the boundary. ## Escalation - Use `effect-first-development` when the task is broader than schema work, including service/layer wiring and typed error flow outside schema modeling. --- Source attribution: kriegcloud Original project: https://github.com/kriegcloud/beep-effect/blob/8f19a8ad84a531ee4073d8521c51d37776aa2d2d/.claude/skills/schema-first-development/SKILL.md License: Apache-2.0 License information: https://www.apache.org/licenses/LICENSE-2.0 Original upstream instructions; downloaded from Mega AI Hub. ## Upstream license notice Apache License Version 2.0, January 2004 http://www.apache.org/licenses/ TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 1. Definitions. "License" shall mean the terms and conditions for use, reproduction, and distribution as defined by Sections 1 through 9 of this document. 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See the License for the specific language governing permissions and limitations under the License. # Mega AI Hub resource metadata Creator / publisher: kriegcloud Original project: https://github.com/kriegcloud/beep-effect/blob/8f19a8ad84a531ee4073d8521c51d37776aa2d2d/.claude/skills/schema-first-development/SKILL.md Attribution basis: Source repository record Fields of work: Development & Engineering Roles: Backend Developer, Data Engineer, ML / AI Engineer Specialties: API, Backend Tools: Effect, Beep/Schema Country applicability: Country not specified Classification basis: Source catalog labels Instruction SHA-256: 3cb2cd6647b6cb5c67c4c63a6d0f639599f554e26886582d4107ec5482eaf7cb