fix(studio): honor Vite BASE_URL as TanStack Router basepath

[Copilot]

When Studio is mounted under /_studio/ (CLI --ui, which sets VITE_BASE=/_studio/), TanStack Router matched the full pathname against root-defined routes and interpreted _studio as the $package param. All sub-routes 404'd (notFoundError on route "/$package"), e.g. /_studio/packages and /_studio/:package/objects/:name.

Changes

• apps/studio/src/router.ts — derive basepath from import.meta.env.BASE_URL and pass it to createRouter. Normalizes to '/' for root deployments and strips the trailing slash for sub-path deployments ('/_studio/' → '/_studio'). Works transparently for CLI dev mode, Vercel, and standalone — no caller-side config required.
• apps/studio/CHANGELOG.md — changelog entry.

// apps/studio/src/router.ts
function resolveBasepath(): string {
  const base = (import.meta.env.BASE_URL ?? '/').trim();
  if (!base || base === '/' || base === './') return '/';
  return base.endsWith('/') ? base.slice(0, -1) : base;
}

export const router = createRouter({
  routeTree,
  basepath: resolveBasepath(),
});

Verification

Reproduced and validated via Playwright against vite dev with VITE_BASE=/_studio/:

URL	Before	After
/_studio/packages	"Not Found" (matched /$package="_studio"/packages)	Package Manager
/_studio/api-console	"Not Found"	API Console
/_studio/	renders, but sub-routes broken	renders, sub-routes resolve

The notFoundError console warning is gone.

[vercel]

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Project	Deployment	Actions	Updated (UTC)
objectstack-demo	Ready	Preview, Comment	Apr 17, 2026 2:11am
spec	Ready	Preview, Comment	Apr 17, 2026 2:11am

[Copilot]

Pull request overview

Updates Studio’s TanStack Router configuration so routing works correctly when the app is mounted under a sub-path (notably /_studio/ in CLI --ui mode), by aligning the router basepath with Vite’s runtime import.meta.env.BASE_URL.

Changes:

• Derive and normalize TanStack Router basepath from import.meta.env.BASE_URL to prevent sub-path prefixes being treated as route params.
• Add a Studio changelog entry describing the routing fix for sub-path deployments.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
apps/studio/src/router.ts	Introduces resolveBasepath() and passes normalized basepath into createRouter() to support /_studio/ mounting.
apps/studio/CHANGELOG.md	Adds an “Unreleased” patch note documenting the sub-path routing fix.

[Copilot]

apps/studio/CHANGELOG.md now contains multiple ## Unreleased sections (there are at least three). Adding another one at the top makes it harder to track changes and can break tooling or release processes that assume a single Unreleased section. Consider consolidating all Unreleased entries into a single top section, and convert the older Unreleased blocks into versioned releases (or remove them if they were historical artifacts).