fix(schema-to-json): support serializing Zod 4 z.date() to JSON Schema (#4939)

In Zod 4, toJSONSchema delegates Date schemas to handleUnrepresentable, which threw 'Date cannot be represented in JSON Schema' when unrepresentable was omitted. Configure unrepresentable to return { type: 'string', format: 'date-time' } for date schemas to match Zod 3 output while preserving strict error handling for other unrepresentable types.

Author: kaiizer777

.changeset/fix-zod4-date-json-schema.md

@@ -0,0 +1,5 @@
+---
+"@trigger.dev/schema-to-json": patch
+---
+
+Support serializing Zod 4 `z.date()` schemas to JSON Schema format.

packages/schema-to-json/src/index.ts

@@ -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";
+    },
     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) => {

packages/schema-to-json/tests/index.test.ts

@@ -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", () => {
@@ -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);