Describe the bug

I run into this issue by using the awesome vite-plugin-kit-routes. The issue describes the same problem but I guess Sveltekit should complain about conflicting routes to solve the issue.

I have the following route structure:

routes
└── (group)
    └── base
        ├── +page.svelte
        └── (optional-group)
            └── [[optionalParam]]
                └── +page.svelte

This generates the following routes

• (group)/base
• (group)/base/(optional-group)/[[optionalParam]]

(Un)Fortunately, the paths are actually resolving the correct page.svelte

• /base -> (group)/base
• /base/myparam -> (group)/base/(optional-group)/[[optionalParam]]

If I remove one of the groups, (group) or (optional-group), I got the following error message:

The "/base" and "/base/(optional-group)/[[optionalParam]]" routes conflict with each other

I guess the error should also appear when using the groups?

To use this route structure correctly

• change [[optionalParam]] to [requiredParam]
• remove the conflicting page (group)base/+page.ts

Reproduction

https://stackblitz.com/edit/sveltejs-kit-page-groupted-duplicate?file=README.md

Logs

System Info

System:
    OS: macOS 15.4
    CPU: (10) arm64 Apple M1 Max
    Memory: 511.97 MB / 32.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 22.12.0 - ~/.nvm/versions/node/v22.12.0/bin/node
    Yarn: 3.6.3 - ~/.nvm/versions/node/v22.12.0/bin/yarn
    npm: 10.9.0 - ~/.nvm/versions/node/v22.12.0/bin/npm
  Browsers:
    Chrome: 135.0.7049.85
    Safari: 18.4
  npmPackages:
    @sveltejs/kit: 2.20.4 => 2.20.4 
    @sveltejs/vite-plugin-svelte: 5.0.3 => 5.0.3 
    svelte: 5.25.7 => 5.25.7 
    vite: 6.2.5 => 6.2.5

Severity

annoyance

Additional Information

No response