Start: Dev server takes 5-12s to boot on fresh/cold start (SPA mode, Vite 8)

Which project does this relate to?

Start

Describe the bug

The first bun run dev command, or running it after a period of inactivity, takes 5–12 seconds to boot the dev server. Subsequent runs are fast, but any cold start (e.g. after rm -rf node_modules && bun install) consistently shows this delay.

I'm unsure whether this is a Vite 8 issue or a general TanStack Start problem. However, this occurs with a very simple fresh project.

I'm using a MacBook M3 Pro, so I don't believe this is a device-related issue.

Note: I am using SPA mode.

Your Example Website or App

https://github.com/abed-daloopa/tanstack-start-dev-server-slow-start

Steps to Reproduce the Bug or Issue

1. Clone the repo: git clone https://github.com/abed-daloopa/tanstack-start-dev-server-slow-start
2. cd tanstack-start-dev-server-slow-start
3. rm -rf node_modules
4. bun install
5. bun run dev
6. Observe the startup time

Expected behavior

The dev server should start more quickly

Screenshots or Videos

Platform

• Start Version: 1.167.16
• Router Version: 1.168.10
• Router Plugin Version: 1.167.12
• OS: macOS (Apple M3 Pro)
• Bundler: Vite 8.0.3
• Runtime: Bun

Additional context

• This happens consistently on cold starts (after clearing node_modules or after a period of inactivity).
• Warm/subsequent starts are noticeably faster.
• The project is minimal, essentially a fresh TanStack Start setup with SPA mode enabled.
• Could potentially be related to Vite 8 or the router plugin initialization.

Start with the linked reproduction repository and run the listed rm -rf node_modules, bun install, and bun run dev steps. Compare cold and warm startup times while investigating whether Vite 8 or router plugin initialization accounts for the delay. Done means identifying the responsible initialization path and demonstrating a faster cold start with regression coverage if applicable.