Invalid Zod output for basic object

[benbrandt]

Description

When having a basic object type, the produced Zod validator is missing a keyParam

It is generating

z.record(z.unknown())

When it should be

z.record(z.string(), z.unknown())

Reproducible example or configuration

For some reason I can't get this to work in stackblitz, but this is roughly the minimal requirement:

export default defineConfig({
  input: {
    openapi: '3.1.0',
    info: {
      title: 'Eample',
      version: '1.0.0',
    },
    components: {
      schemas: {
        example: {
          properties: {
            _meta: {
              additionalProperties: {},
              description: 'hi',
              type: ['object', 'null'],
            },
          },
          type: 'object',
        },
      },
    },
  },
  output: {
    path: './src/schema',
  },
  plugins: ['@hey-api/transformers', '@hey-api/typescript', 'zod'],
});

OpenAPI specification (optional)

No response

System information (optional)

No response

[dosubot]

Hi @benbrandt! I'm Dosu and I’m helping the openapi-ts team.

The Zod plugin generates z.record(z.unknown()) when it can't determine the key type from your OpenAPI schema. This is likely because the schema for _meta uses additionalProperties: {} without specifying a type, and the generator defaults to unknown when type inference fails. The documentation and migration guide confirm that undetermined types now default to unknown instead of any, but they don't mention a way to explicitly set the key type for records or control this behavior via configuration options see docs.

To work around this, try making your OpenAPI schema more explicit. For example, set additionalProperties: { type: "string" } or another specific type if possible. This should help the generator infer the correct key/value types and produce z.record(z.string(), z.unknown()) or the appropriate variant.

If you need the output to always use z.string() as the key, you may need to post-process the generated schema or adjust your schema definitions to be less ambiguous, since the plugin doesn't currently expose a direct configuration for this.

To reply, just mention @dosu.

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[benbrandt]

Ok will handle by changing this to additionalProperties: true

[benbrandt]

Ok that didn't solve it, I still have to apply post-processing

[mrlubos]

@benbrandt Zod 4?

[benbrandt]

Yes sorry, using zod 4. Maybe I thought that was the default? do I need to set it for the plugin to use zod 4?

[benbrandt]

Speaking of, I would expect the generated import to be zod/v4 not just zod so I overwrite that as well: https://github.com/agentclientprotocol/typescript-sdk/blob/d65d868bfdd63d809d65b85b0387d0b7dd9d1d46/scripts/generate.js#L47

[mrlubos]

Speaking of, I would expect the generated import to be zod/v4 not just zod so I overwrite that as well: https://github.com/agentclientprotocol/typescript-sdk/blob/d65d868bfdd63d809d65b85b0387d0b7dd9d1d46/scripts/generate.js#L47

Why? All Zod examples use 'zod' by default https://zod.dev/

That being said, I do plan to eventually expose a way to override this but it would be tied to Deno

[mrlubos]

Yes sorry, using zod 4. Maybe I thought that was the default? do I need to set it for the plugin to use zod 4?

Nope, it's the default. Unless you have v3 installed and it detects that as default, then you'd need to explicitly state you want v4

[benbrandt]

It's to allow for us as a library to support either 3.25 or 4+: colinhacks/zod#4371