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opencode/packages/opencode/specs/effect/schema.md
2026-04-13 10:04:32 -04:00

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# Schema migration
Practical reference for migrating data types in `packages/opencode` from Zod-first definitions to Effect Schema with Zod compatibility shims.
## Goal
Use Effect Schema as the source of truth for domain models, IDs, inputs, outputs, and typed errors.
Keep Zod available at existing HTTP, tool, and compatibility boundaries by exposing a `.zod` field derived from the Effect schema.
## Preferred shapes
### Data objects
Use `Schema.Class` for structured data.
```ts
export class Info extends Schema.Class<Info>("Foo.Info")({
id: FooID,
name: Schema.String,
enabled: Schema.Boolean,
}) {
static readonly zod = zod(Info)
}
```
If the class cannot reference itself cleanly during initialization, use the existing two-step pattern:
```ts
const _Info = Schema.Struct({
id: FooID,
name: Schema.String,
})
export const Info = Object.assign(_Info, {
zod: zod(_Info),
})
```
### Errors
Use `Schema.TaggedErrorClass` for domain errors.
```ts
export class NotFoundError extends Schema.TaggedErrorClass<NotFoundError>()("FooNotFoundError", {
id: FooID,
}) {}
```
### IDs and branded leaf types
Keep branded/schema-backed IDs as Effect schemas and expose `static readonly zod` for compatibility when callers still expect Zod.
## Compatibility rule
During migration, route validators, tool parameters, and any existing Zod-based boundary should consume the derived `.zod` schema instead of maintaining a second hand-written Zod schema.
The default should be:
- Effect Schema owns the type
- `.zod` exists only as a compatibility surface
- new domain models should not start Zod-first unless there is a concrete boundary-specific need
## When Zod can stay
It is fine to keep a Zod-native schema temporarily when:
- the type is only used at an HTTP or tool boundary
- the validator depends on Zod-only transforms or behavior not yet covered by `zod()`
- the migration would force unrelated churn across a large call graph
When this happens, prefer leaving a short note or TODO rather than silently creating a parallel schema source of truth.
## Ordering
Migrate in this order:
1. Shared leaf models and `schema.ts` files
2. Exported `Info`, `Input`, `Output`, and DTO types
3. Tagged domain errors
4. Service-local internal models
5. Route and tool boundary validators that can switch to `.zod`
This keeps shared types canonical first and makes boundary updates mostly mechanical.
## Checklist
- [ ] Shared `schema.ts` leaf models are Effect Schema-first
- [ ] Exported `Info` / `Input` / `Output` types use `Schema.Class` where appropriate
- [ ] Domain errors use `Schema.TaggedErrorClass`
- [ ] Migrated types expose `.zod` for back compatibility
- [ ] Route and tool validators consume derived `.zod` instead of duplicate Zod definitions
- [ ] New domain models default to Effect Schema first
## Notes
- Use `@/util/effect-zod` for all Schema -> Zod conversion.
- Prefer one canonical schema definition. Avoid maintaining parallel Zod and Effect definitions for the same domain type.
- Keep the migration incremental. Converting the domain model first is more valuable than converting every boundary in the same change.