Fix Zod v4 oneOf unions in strict schemas#1896
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| // Handle unions (OpenAI strict mode supports anyOf, but not oneOf) | ||
| const oneOf = jsonSchema.oneOf; | ||
| if (Array.isArray(oneOf)) { | ||
| jsonSchema.anyOf = Array.isArray(jsonSchema.anyOf) ? [...jsonSchema.anyOf, ...oneOf] : oneOf; |
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When a schema contains both anyOf and oneOf, this change concatenates the oneOf variants into anyOf, which weakens validation semantics from “must satisfy both keywords” to a single OR over all variants. In JSON Schema, anyOf and oneOf are independent constraints, so merging them can make previously invalid data pass validation. This can silently broaden accepted outputs for mixed-composition schemas rather than only translating unsupported oneOf usage.
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Addressed in 2957e7f. The oneOf rewrite now preserves mixed-composition semantics instead of flattening into an existing anyOf: standalone oneOf becomes an allOf of anyOf plus a not(any overlap) exclusivity guard, and when a schema already has anyOf we keep that as a separate allOf term rather than merging the variants. Added regression coverage for mixed anyOf/oneOf schemas, and yarn jest tests/helpers/zod.test.ts --runInBand plus yarn jest tests/lib/transform.test.ts tests/helpers/zod.test.ts --runInBand pass.
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Closes #1709
Zod v4 can emit
oneOffor discriminated unions, but strict OpenAI schemas supportanyOfinstead. This convertsoneOfunions before the existing strict-schema recursion runs, so nested discriminated unions are still processed normally.Verification:
yarn jest tests/helpers/zod.test.ts --runInBandyarn jest tests/lib/transform.test.ts tests/helpers/zod.test.ts --runInBandgit diff --check