unstable_concat return type is not been propagate to the input

export function getAllServicesPlugin() {
  const t = initTRPC.context<typeof createTRPCContext>().create();

  return {
    pluginProc: t.procedure
      .input(serviceWithDateRangeSchema)
      .use(async (opts) => {
        const { input, ctx } = opts;

        if (input.selectedServices.selectedCategory === "specific") {
          return opts.next({
            input: {
              dateRange: input.dateRange,
              services: input.selectedServices.services,
            },
          });
        }
        const categorizedRepositories = await getCategorizedRepositories(
          ctx.connection,
        );

        return opts.next({
          input: {
            dateRange: input.dateRange,
            services:
              input.selectedServices.selectedCategory === "all-engineering"
                ? Object.values(categorizedRepositories).flat()
                : (categorizedRepositories[
                    input.selectedServices.selectedCategory
                  ] ?? []),
          },
        });
      }),
  };
}

const metricsRouter = createTRPCRouter({
  getBranchBuildDuration: publicProcedure
    .input(serviceWithDateRangeSchema)
    .output(
      z.object({
        overTime: z.array(branchBuildDuration),
        aggregativeMetric: aggregativeMetricSchema,
      }),
    )
    .unstable_concat(allServicePlugin.pluginProc)
    .query(
      async ({
        ctx: { connection },
        input: {
          dateRange: { from, to },
          services,
        },
      }) => {
        ...
      },
    )});