colinhacks
diff --git a/Collapse file
‎…src/v4/classic/tests/json-schema.test.ts‎ ‎…/v4/classic/tests/to-json-schema.test.ts‎packages/zod/src/v4/classic/tests/json-schema.test.ts renamed to packages/zod/src/v4/classic/tests/to-json-schema.test.ts packages/zod/src/v4/classic/tests/json-schema.test.ts renamed to packages/zod/src/v4/classic/tests/to-json-schema.test.ts
Copy file name to clipboardExpand all lines: packages/zod/src/v4/classic/tests/to-json-schema.test.ts
+11Lines changed: 11 additions & 0 deletions b/Collapse file
‎…src/v4/classic/tests/json-schema.test.ts‎ ‎…/v4/classic/tests/to-json-schema.test.ts‎packages/zod/src/v4/classic/tests/json-schema.test.ts renamed to packages/zod/src/v4/classic/tests/to-json-schema.test.ts packages/zod/src/v4/classic/tests/json-schema.test.ts renamed to packages/zod/src/v4/classic/tests/to-json-schema.test.ts
Copy file name to clipboardExpand all lines: packages/zod/src/v4/classic/tests/to-json-schema.test.ts
+11Lines changed: 11 additions & 0 deletions
diff --git a/Collapse file
‎packages/zod/src/v4/core/to-json-schema.ts‎
Copy file name to clipboardExpand all lines: packages/zod/src/v4/core/to-json-schema.ts
+1-1Lines changed: 1 addition & 1 deletion b/Collapse file
‎packages/zod/src/v4/core/to-json-schema.ts‎
Copy file name to clipboardExpand all lines: packages/zod/src/v4/core/to-json-schema.ts
+1-1Lines changed: 1 addition & 1 deletion
@@ -1943,3 +1943,14 @@ test("examples on pipe", () => {
 //   `);
 
 // });
+
+test("use output type for preprocess", () => {
+  const a = z.preprocess((val) => String(val), z.string());
+
+  expect(z.toJSONSchema(a, { io: "input" })).toMatchInlineSnapshot(`
+    {
+      "$schema": "https://json-schema.org/draft/2020-12/schema",
+      "type": "string",
+    }
+  `);
+});
@@ -499,7 +499,7 @@ export class JSONSchemaGenerator {
           break;
         }
         case "pipe": {
-          const innerType = this.io === "input" ? def.in : def.out;
+          const innerType = this.io === "input" ? (def.in._zod.def.type === "transform" ? def.out : def.in) : def.out;
           this.process(innerType, params);
           result.ref = innerType;
           break;