remix-run/react-router · error

The `prerender`/`prerender.paths` config must be a boolean,

Error message

The `prerender`/`prerender.paths` config must be a boolean, an array of string paths, or a function returning a boolean or array of string paths.

What it means

The `prerender` config field must be a boolean, a function returning boolean/string[], an array of string paths, or an object whose `paths` field is one of those shapes. This validation runs whenever `prerender` is truthy, and anything else — a string like `"all"`, a number, an object without a valid `paths` key — returns this error before the build proceeds.

Source

Thrown at packages/react-router-dev/config/config.ts:559

    ...userAndPresetConfigs,
  };

  if (!ssr && serverBundles) {
    serverBundles = undefined;
  }

  if (prerender) {
    let isValidPrerenderPathsConfig = (p: unknown) =>
      typeof p === "boolean" || typeof p === "function" || Array.isArray(p);

    let isValidPrerenderConfig =
      isValidPrerenderPathsConfig(prerender) ||
      (typeof prerender === "object" &&
        "paths" in prerender &&
        isValidPrerenderPathsConfig(prerender.paths));

    if (!isValidPrerenderConfig) {
      return err(
        "The `prerender`/`prerender.paths` config must be a boolean, an array " +
          "of string paths, or a function returning a boolean or array of string paths.",
      );
    }

    if (typeof prerender === "object" && "unstable_concurrency" in prerender) {
      return err(
        "The `prerender.unstable_concurrency` config field has been stabilized as `prerender.concurrency`",
      );
    }

    let isValidConcurrencyConfig =
      typeof prerender != "object" ||
      !("concurrency" in prerender) ||
      (typeof prerender.concurrency === "number" &&
        Number.isInteger(prerender.concurrency) &&
        prerender.concurrency > 0);

View on GitHub (pinned to 6beaca3952)

Solutions

1. Use the boolean form for full prerendering: `prerender: true`.
2. List specific paths: `prerender: ["/", "/about"]`.
3. Use a function for dynamic sets: `prerender: ({ getStaticPaths }) => getStaticPaths()`.
4. If using the object form, put one of those same shapes under `paths`: `prerender: { paths: ["/"] }`.

Example fix

// before
export default { prerender: "all" };

// after
export default { prerender: true };
// or
export default { prerender: { paths: ["/", "/about"] } };

type PrerenderShape = boolean | (() => boolean | string[]) | string[] | { paths: boolean | (() => boolean | string[]) | string[] };
function isValidPrerender(p: unknown): p is PrerenderShape {
  const ok = (v: unknown) => typeof v === "boolean" || typeof v === "function" || Array.isArray(v);
  return ok(p) || (typeof p === "object" && p !== null && "paths" in p && ok((p as any).paths));
}
if (!isValidPrerender(config.prerender)) throw new Error("invalid prerender config");

function isValidPrerender(p: unknown): p is boolean | Function | string[] | { paths: boolean | Function | string[] } {
  const ok = (v: unknown) => typeof v === "boolean" || typeof v === "function" || Array.isArray(v);
  return ok(p) || (typeof p === "object" && p !== null && "paths" in p && ok((p as any).paths));
}

When it happens

Trigger: Setting `prerender: "all"` (invalid; the boolean form is `prerender: true`), `prerender: 1`, `prerender: { paths: "/about" }` (string instead of array), or any other shape that fails `isValidPrerenderPathsConfig` in either the top-level or `paths` position.

Common situations: Copy-pasting config from blog posts that use a string shorthand from another framework (Next.js `dynamicParams`-style strings); migrating from an older version and guessing the API; typos like `paths:` given a single string instead of an array.

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

• The "serverBundles" function must only return strings contai
• The `prerender.concurrency` config must be a positive intege
• Route config in "${routeConfigFile}" is invalid.
• React Router Vite plugin not found in Vite config
• Custom Vite manifest paths are not supported

AI-assisted analysis of remix-run/react-router@6beaca3952 (2026-08-18). Data as JSON: /api/errors/854df947b1dbb1e2. Report an issue: GitHub.