z.file() and OpenAPI code generators - format: "binary" vs contentMediaType?

[superxiao]

Context

Using @orpc/openapi with OpenAPIHandler and OpenAPIReferencePlugin to generate OpenAPI specs from
contracts.

When using z.file() in a contract:

  import { oc } from "@orpc/contract";
  import { z } from "zod/v4";

  const contract = oc
    .input(z.object({ file: z.file() }))
    .output(z.object({ downloadFile: z.file() }))
    .route({ method: "POST", path: "/upload" });

The generated OpenAPI spec shows:

  {
    "type": "string",
    "contentMediaType": "*/*"
  }

We're using https://orval.dev/ to generate TypeScript client code from the spec. With the above output,
orval generates string for the file field. However, when we manually add format: "binary" via the
registry, orval correctly generates Blob.

Current Workaround

  import { JSON_SCHEMA_INPUT_REGISTRY } from "@orpc/zod/zod4";

  const fileSchema = z.file();
  JSON_SCHEMA_INPUT_REGISTRY.add(fileSchema, {
    type: "string",
    format: "binary",
  });

(And JSON_SCHEMA_OUTPUT_REGISTRY for output schemas)

Question

I'm not 100% sure where the issue lies - it could be:

1. oRPC side: Should z.file() automatically include format: "binary" alongside contentMediaType for
   wider compatibility with code generators?
2. orval side: Should orval recognize contentMediaType: "*/*" (or any contentMediaType) as indicating
   binary content?
3. Or is the manual registry the intended approach to bridge this issue?

Just wanted to understand the recommended pattern here. The workaround works fine, but wondering if
there's a cleaner way or if this is something missing on either side.

Environment

• @orpc/openapi
• @orpc/zod with ZodToJsonSchemaConverter
• zod/v4

[unnoq]

You do not need format: binary in openapi 3.1 https://swagger.io/specification/

[superxiao]

Thanks for the clarification! I tested and confirmed oRPC is doing the right thing.

Using z.file().mime("image/png") correctly generates:

{
"type": "string",
"contentMediaType": "image/png"
}

The issue is on the orval side - it only recognizes format: "binary" and ignores contentMediaType, even
for binary MIME types like image/png or application/octet-stream. I'll create an issue there.