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fix(schema-to-json): support serializing Zod 4 z.date() to JSON Schema #4962

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fix(schema-to-json): support serializing Zod 4 z.date() to JSON Schema #4962

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5 changes: 5 additions & 0 deletions .changeset/fix-zod4-date-json-schema.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
"@trigger.dev/schema-to-json": patch
---

Support serializing Zod 4 `z.date()` schemas to JSON Schema format.
12 changes: 12 additions & 0 deletions packages/schema-to-json/src/index.ts
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Expand Up @@ -156,12 +156,24 @@ function convertZod4Schema(schema: any, options?: ConversionOptions): JSONSchema
target: "draft-7",
io: "output",
reused: useReferences ? "ref" : "inline",
unrepresentable: ({ zodSchema }) => {
const def = (zodSchema as any)._zod?.def;
if (def?.type === "date") {
return { type: "string", format: "date-time" };
}
return "throw";
},
Comment on lines +159 to +165

@devin-ai-integration devin-ai-integration Bot Sep 20, 2026

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🟡 Older Zod versions weaken schemas

With Zod 4.0–4.4, the unrepresentable function disables throwing for non-date types. Those releases only compare the option with "throw", so unsupported schemas become {} and accept rejected values.

Learn more

The package accepts Zod ^4.0.0, but function-valued unrepresentable handlers were added only in later Zod 4 releases. Earlier releases treat every value except the literal "throw" as permissive behavior. The callback therefore never runs there, although the existing override still converts dates. Other unrepresentable nodes lose their previous errors and emit unconstrained schemas.

Example: With Zod 4.1, converting z.symbol() previously throws. After this change it emits {}, which permits strings and numbers even though z.symbol() rejects them.

Recommended fix: Either raise both Zod dependency ranges to the first version supporting UnrepresentableHandler, or preserve compatibility by detecting that capability and explicitly throwing from override for every non-date unrepresentable node on older releases. Add a test installed against the minimum supported Zod 4 version.

Devin Review

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override: ({ zodSchema, jsonSchema }) => {
const def = zodSchema._zod.def;
if (def.type === "undefined") {
throw new Error("Undefined cannot be represented in JSON Schema");
}

if (def.type === "date") {
jsonSchema.type = "string";
jsonSchema.format = "date-time";
}

if (def.type === "object" && jsonSchema.required) {
// Early Zod 4 permalinks do not propagate optional output through unions.
const required = jsonSchema.required.filter((key) => {
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41 changes: 41 additions & 0 deletions packages/schema-to-json/tests/index.test.ts
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Expand Up @@ -110,6 +110,45 @@ describe("schemaToJsonSchema", () => {
"Undefined cannot be represented in JSON Schema"
);
});

it("converts date schemas to string with date-time format", () => {
const schema = z.date();
const result = schemaToJsonSchema(schema);

expect(result).toBeDefined();
expect(result?.jsonSchema).toMatchObject({
type: "string",
format: "date-time",
});
});

it("converts object with date schemas and wrappers", () => {
const schema = z.object({
createdAt: z.date(),
updatedAt: z.date().optional(),
deletedAt: z.date().nullable(),
history: z.array(z.date()),
});

const result = schemaToJsonSchema(schema);

expect(result).toBeDefined();
expect(result?.jsonSchema).toMatchObject({
type: "object",
properties: {
createdAt: { type: "string", format: "date-time" },
updatedAt: { type: "string", format: "date-time" },
deletedAt: {
anyOf: [{ type: "string", format: "date-time" }, { type: "null" }],
},
history: {
type: "array",
items: { type: "string", format: "date-time" },
},
},
required: ["createdAt", "deletedAt", "history"],
});
});
});

it("preserves explicitly required metadata on current optional schemas", () => {
Expand Down Expand Up @@ -290,6 +329,8 @@ describe("schemaToJsonSchema", () => {
describe("canConvertSchema", () => {
it("should return true for supported schemas", () => {
expect(canConvertSchema(z3.string())).toBe(true);
expect(canConvertSchema(z3.date())).toBe(true);
expect(canConvertSchema(z4.date())).toBe(true);
expect(canConvertSchema(y.string())).toBe(true);
expect(canConvertSchema(type("string"))).toBe(true);
expect(canConvertSchema(Schema.String)).toBe(true);
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