Mintplex-Labs/anything-llm · error

Fallback provider and model are required.

Error message

Fallback provider and model are required.

What it means

Validation error propagated from ModelRouter.create: the request did not include both a fallback provider and fallback model, which are mandatory so the router always has a route to use when no rule matches.

Source

Thrown at server/endpoints/modelRouter.js:64

        console.error(e);
        response.sendStatus(500);
      }
    }
  );

  app.post(
    "/model-routers/new",
    [validatedRequest, flexUserRoleValid([ROLES.admin])],
    async (request, response) => {
      try {
        const user = await userFromSession(request, response);
        const data = reqBody(request);
        const { router, error } = await ModelRouter.create(
          data,
          user?.id || null
        );

        if (error) return response.status(400).json({ router, error });
        await Telemetry.sendTelemetry("model_router_created");
        return response.status(200).json({ router });
      } catch (e) {
        console.error(e);
        response.sendStatus(500);
      }
    }
  );

  app.put(
    "/model-routers/:id",
    [validatedRequest, flexUserRoleValid([ROLES.admin])],
    async (request, response) => {
      try {
        const { id } = request.params;
        const data = reqBody(request);
        const { router, error } = await ModelRouter.update(Number(id), data);
        if (error) return response.status(400).json({ router, error });

View on GitHub (pinned to 3aec848f28)

Solutions

1. Specify both a fallback provider and a fallback model when creating the router.
2. Verify the provider name is one of the supported providers.

When it happens

Trigger: Thrown at server/endpoints/modelRouter.js:64 when the library encounters an invalid state.

Common situations: Router creation payload missing the fallback provider or model.

AI-assisted analysis of Mintplex-Labs/anything-llm@3aec848f28 (2026-08-18). Data as JSON: /api/errors/f4bdbcbb385502c3. Report an issue: GitHub.