Your loader's schema is defined using a function. This is no

Error message

Your loader's schema is defined using a function. This is no longer supported and the schema will be ignored. Please update your loader to use the `createSchema()` utility instead, or report this to the loader author. In a future major version, this will cause the loader to break entirely.

What it means

The zod validation of your content config detected a loader object whose `schema` is a plain function. The Content Layer API expects schemas as a zod schema object or created via createSchema(); the function form is transformed to undefined and ignored with this deprecation warning, and a future major version will break such loaders entirely.

Source

Thrown at packages/astro/src/content/utils.ts:88

				z.object({
					type: z.literal(CONTENT_LAYER_TYPE),
					schema: z.any().optional(),
					loader: z.union([
						z.function(),
						z.object({
							name: z.string(),
							load: z.function({
								input: [z.custom<LoaderContext>()],
								output: z.custom<{
									schema?: any;
									types?: string;
								} | void>(),
							}),
							schema: z
								.any()
								.transform((v) => {
									if (typeof v === 'function') {
										logger.warn(
											'content',
											`Your loader's schema is defined using a function. This is no longer supported and the schema will be ignored. Please update your loader to use the \`createSchema()\` utility instead, or report this to the loader author. In a future major version, this will cause the loader to break entirely.`,
										);
										return undefined;
									}
									return v;
								})
								.superRefine((v, ctx) => {
									if (v !== undefined && !('_zod' in v)) {
										ctx.addIssue({
											code: z.ZodIssueCode.custom,
											message: 'Invalid Zod schema',
										});
										return z.NEVER;
									}
								})
								.optional(),
							createSchema: z

View on GitHub (pinned to e294953aa8)

Solutions

Import createSchema from 'astro:content' and wrap the schema: schema: createSchema(({ image }) => z.object({...}))
If the loader is third-party, upgrade it or report the warning to its author
Alternatively return a plain zod schema object rather than a function

Example fix

// before: custom-loader.ts
export function myLoader(): Loader {
  return {
    name: 'my-loader',
    load: async ({ store, logger }) => { /* ... */ },
    schema: () => z.object({ title: z.string() }),
  };
}

// after
import { createSchema } from 'astro:content';
export function myLoader(): Loader {
  return {
    name: 'my-loader',
    load: async ({ store, logger }) => { /* ... */ },
    schema: createSchema(() => z.object({ title: z.string() })),
  };
}

Defensive patterns

Strategy: type-guard

Validate before calling

// Warn at loader-construction time if a legacy function schema slips in
function assertModernSchema(loader: { schema?: unknown }) {
  if (typeof loader.schema === 'function') {
    throw new Error('Loader schema must use createSchema(), not a function');
  }
}

Type guard

interface ModernLoader { schema?: object; createSchema?: () => Promise<{ schema: object }> }
function usesLegacyFunctionSchema(loader: { schema?: unknown }): loader is { schema: () => unknown } {
  return typeof loader.schema === 'function';
}

Prevention

Always author loader schemas with createSchema() from 'astro:content'
When adopting a third-party loader, check its changelog for createSchema support
Watch deprecation warnings after major upgrades — they become hard errors in the next major

When it happens

Trigger: Writing a custom loader with schema: () => z.object({...}) instead of schema: createSchema((ctx) => z.object({...})); using a third-party loader written against the pre-createSchema API.

Common situations: Copy-pasting older examples or blog posts; community loaders (CMS adapters, etc.) not yet updated; upgrading a project across the Astro 4 to 5 boundary where the loader API changed.

Understand the failure class

Background: "is deprecated and will be removed" — deprecation warnings for old API names, keywords, and options, and how to migrate before the removal release — this error's family across 29 libraries.

Related errors

AI-assisted analysis of withastro/astro@e294953aa8 (2026-09-09). Data as JSON: /api/errors/cb7f7978384fb0b5. Report an issue: GitHub.