vercel/ai · error · InvalidArgumentError

Invalid argument for parameter schemaName: Schema name is no

Error message

Invalid argument for parameter schemaName: Schema name is not supported for enum output.

What it means

generateObject/streamObject in 'enum' output mode takes `enum` values instead of a named JSON schema, so passing a `schemaName` is invalid. validateObjectGenerationInput proactively rejects the combination with InvalidArgumentError before any model call. This prevents users from assuming a schema name is transmitted when it would be ignored or rejected.

Source

Thrown at packages/ai/src/generate-object/validate-object-generation-input.ts:119

  if (output === 'enum') {
    if (schema != null) {
      throw new InvalidArgumentError({
        parameter: 'schema',
        value: schema,
        message: 'Schema is not supported for enum output.',
      });
    }

    if (schemaDescription != null) {
      throw new InvalidArgumentError({
        parameter: 'schemaDescription',
        value: schemaDescription,
        message: 'Schema description is not supported for enum output.',
      });
    }

    if (schemaName != null) {
      throw new InvalidArgumentError({
        parameter: 'schemaName',
        value: schemaName,
        message: 'Schema name is not supported for enum output.',
      });
    }

    if (enumValues == null) {
      throw new InvalidArgumentError({
        parameter: 'enumValues',
        value: enumValues,
        message: 'Enum values are required for enum output.',
      });
    }

    for (const value of enumValues) {
      if (typeof value !== 'string') {
        throw new InvalidArgumentError({
          parameter: 'enumValues',

View on GitHub (pinned to 69428b1f8b)

Solutions

1. Remove the schemaName property from the generateObject/streamObject call when using output: 'enum'
2. Keep schemaName only for output: 'object' or 'array' calls where a JSON schema is provided
3. Conditionally build the options object so schema-dependent fields are only set for schema-based modes

Example fix

// before
const { object } = await generateObject({
  model, output: 'enum', enum: ['A','B'], schemaName: 'Choice'
});
// after
const { object } = await generateObject({
  model, output: 'enum', enum: ['A','B']
});

if (output === 'enum' && 'schemaName' in args && args.schemaName != null) {
  throw new Error('schemaName is not allowed with output: enum');
}

function isEnumArgs(args: { output?: string; schemaName?: string }): boolean {
  return args.output !== 'enum' || args.schemaName == null;
}

try {
  await generateObject(args);
} catch (e) {
  if (InvalidArgumentError.isInstance(e) && e.parameter === 'schemaName') {
    delete args.schemaName;
    return generateObject(args);
  }
  throw e;
}

When it happens

Trigger: Calling generateObject({ output: 'enum', enum: [...], schemaName: 'MyEnum' }) or the same with streamObject. Any non-null schemaName combined with output:'enum' triggers it.

Common situations: Refactoring code from a 'object'/'array' output mode (where schemaName is valid) to 'enum' mode and leaving schemaName in place; copy-pasted options objects shared between calls; older code predating the enum output mode.

Related errors

• Invalid argument for parameter enumValues: Enum values are r
• Invalid argument for parameter enumValues: Enum values must
• Invalid argument for parameter output: Invalid output type.
• Invalid argument for parameter schema: Schema is not support
• Invalid argument for parameter schemaDescription: Schema des

AI-assisted analysis of vercel/ai@69428b1f8b (2026-08-30). Data as JSON: /api/errors/2b146f8deeffffcf. Report an issue: GitHub.