Properties with default values but not in `required` array are generated as required in TypeScript

[betovelandia]

openapi-typescript version

7.8.0

Node.js version

22.7.0

OS + version

MacOS 26.0.1

Description

When generating TypeScript types from our OpenAPI 3.1 spec, we noticed that properties with a default value but not listed in the schema’s required array are generated as required in the resulting TypeScript types. According to the OpenAPI spec these should be optional.

Reproduction

OpenAPI Schema Example:

{
  "SomethingCreate": {
    "type": "object",
    "properties": {
      "user": { "$ref": "#/components/schemas/UReference" },
      "role": { "$ref": "#/components/schemas/RReference" },
      "reserved": {
        "type": "boolean",
        "default": false
      },
      "send_invite": {
        "type": "boolean",
        "default": false
      }
    },
    "required": ["user", "role"]
  }
}

Generated TypeScript Output:

SomethingCreate: {
  user: components["schemas"]["UReference"];
  role: components["schemas"]["RReference"];
  reserved: boolean;
  send_invite: boolean;
};

Expected result

reserved and send_invite should be optional in the generated TypeScript, since they are not in the required array.

Actual Behavior:
Both are generated as required properties.

Is this a bug or expected behavior? If it’s a bug, could you clarify if there’s a workaround or if a fix is planned?

Thank you!

Required

• My OpenAPI schema is valid and passes the Redocly validator (npx @redocly/cli@latest lint)

Extra

• I’m willing to open a PR (see CONTRIBUTING.md)

[bkis]

FYI: https://openapi-ts.dev/migration-guide#defaultnonnullable-true-by-default

I guess the reason for this decision is that in the majority of cases people are dealing with read models (as in the R in CRUD) and a property with a default value is actually guaranteed to have a value, so in those cases it's nice to have it required in the types.

This creates some semantic friction IMO... but you can also just turn this feature off if you want.