Support standard JSON schema object representation for Zod Mini

[logaretm]

Hey there, while trying out the recent standard schema implementation across multiple providers for formwerkjs/formwerk#238 I came across this issue.

When trying to get the input JSON schema for a given Zod mini schema with objects, it throws with the following error:

Error: Uncaught Error: [toJSONSchema]: Non-representable type encountered: object

Here is a small snippet to reproduce:

const zodJson = z.toJSONSchema(z
  .object({
    firstName: z.string(),
    lastName: z.string(),
  }))["~standard"]["jsonSchema"].input({ target: "draft-07" })

is there a plan to support object representations and probably other APIs?

[pullfrog]

  ^{｜ Build this ➔ ｜ Make a plan ➔ ｜ pullfrog.com}

[dosubot]

Hi @logaretm! I'm Dosu and I’m helping the zod team.

I'm a bot trained on Zod's codebase and issues.

The error [toJSONSchema]: Non-representable type encountered: object in Zod Mini happens because the standard JSON Schema API doesn't register the object processor by default—even though the core codebase has the logic to handle objects. This means object schemas can't be converted out-of-the-box in Zod Mini, while the main Zod package does support this conversion and produces valid JSON Schema for objects (docs).

There's no official roadmap or timeline for enabling object support by default in Zod Mini; feature development is community-driven and based on issue resolution and contributions (source).

If you need object support in Zod Mini's JSON Schema output right now, you have a couple of options:

• Use the classic Zod package for schema conversion if possible (docs).
• Manually supply the processor map when invoking the standard schema API in Zod Mini (the core object processor is present, but you need to inject it into the workflow—see json-schema-processors.ts for reference).

There are no public statements or tracking issues indicating a timeline or plan to enable standard JSON Schema object representation by default in Zod Mini (source). If you need help wiring up the processor map or want to discuss a feature request, let me know!

If this answers your question, please close the issue.

To reply, just mention @dosu.

---

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[colinhacks]

cc @pullfrog replicate and make a plan.

[pullfrog]

Plan to Fix JSON Schema Object Representation Issue

Problem Summary

When using z.toJSONSchema(schema)["~standard"]["jsonSchema"].input() with Zod Mini, it throws:

Error: [toJSONSchema]: Non-representable type encountered: object

This affects the standard JSON schema interface used for interoperability across schema libraries.

Root Cause

In packages/zod/src/v4/core/to-json-schema.ts:

• The finalize() function creates ~standard.jsonSchema methods via createStandardJSONSchemaMethod()
• createStandardJSONSchemaMethod() initializes context with empty processors: {}
• Without processors, the schema conversion fails for all types (objects, arrays, etc.)

Implementation Plan

Step 1: Modify createStandardJSONSchemaMethod signature

Change the function to accept processors as a parameter:

export const createStandardJSONSchemaMethod =
  <T extends schemas.$ZodType>(
    schema: T,
    io: "input" | "output",
    processors: Record<string, Processor> = {}  // Add processors parameter
  ) =>
  (params?: StandardJSONSchemaMethodParams): JSONSchema.BaseSchema => {
    const { libraryOptions, target } = params ?? {};
    const ctx = initializeContext({ 
      ...(libraryOptions ?? {}), 
      target, 
      io, 
      processors  // Use passed processors instead of empty object
    });
    process(schema, ctx);
    extractDefs(ctx, schema);
    return finalize(ctx, schema);
  };

Step 2: Update finalize() to pass processors

In the finalize() function, pass ctx.processors when creating standard methods:

jsonSchema: {
  input: createStandardJSONSchemaMethod(schema, "input", ctx.processors),
  output: createStandardJSONSchemaMethod(schema, "output", ctx.processors),
}

Step 3: Update classic schemas (if needed)

Check if classic schemas use createStandardJSONSchemaMethod and update if necessary.

Step 4: Add test coverage

Create a test in packages/zod/src/v4/mini/tests/ to verify:

• Object schemas work with ["~standard"]["jsonSchema"].input()
• Different targets (draft-07, draft-2020-12) work correctly
• Both input and output methods work

Step 5: Verify the fix

Run the reproduction case to confirm it works:

const zodJson = z.toJSONSchema(z.object({
  firstName: z.string(),
  lastName: z.string(),
}))["~standard"]["jsonSchema"].input({ target: "draft-07" })

Files to Modify

1. packages/zod/src/v4/core/to-json-schema.ts - Main fix
2. packages/zod/src/v4/mini/tests/standard-schema.test.ts - Add test coverage

Expected Impact

• ✅ Fixes the reported issue for Zod Mini
• ✅ Enables standard JSON schema support for all types
• ✅ Maintains backward compatibility (processors default to empty object)
• ✅ No breaking changes to public API

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[colinhacks]

Fixed in main, landing soon. Good catch.