Function executeRouter

packages/start-server-core/src/createStartHandler.ts:542–592

(
        serverContext: TODO,
        matchedRoutes?: ReadonlyArray<AnyRoute>,
      )

      // Router execution function
      const executeRouter = async (
        serverContext: TODO,
        matchedRoutes?: ReadonlyArray<AnyRoute>,
      ): Promise<Response> => {
        const acceptHeader = request.headers.get('Accept') || '*/*'
        const acceptParts = acceptHeader.split(',')
        const supportedMimeTypes = ['*/*', 'text/html']

        const isSupported = supportedMimeTypes.some((mimeType) =>
          acceptParts.some((part) => part.trim().startsWith(mimeType)),
        )

        if (!isSupported) {
          return Response.json(
            { error: 'Only HTML requests are supported here' },
            { status: 500 },
          )
        }

        const manifest = await resolveManifest(
          matchedRoutes,
          await getTransformFn({ warmup: false, request }),
          cache,
        )
        const routerInstance = await getRouter()

        attachRouterServerSsrUtils({
          router: routerInstance,
          manifest,
        })

        routerInstance.update({ additionalContext: { serverContext } })
        await routerInstance.load()

        if (routerInstance.state.redirect) {
          return routerInstance.state.redirect
        }

        await routerInstance.serverSsr!.dehydrate()

        const responseHeaders = getStartResponseHeaders({
          router: routerInstance,
        })
        cbWillCleanup = true

        return cb({
          request,
          router: routerInstance,
          responseHeaders,
        })
      }

      // Main request handler
      const requestHandlerMiddleware = async ({ context }: TODO) => {