Browser mode hangs at "0 passed" when a test file path contains a "+"

[Pduhard]

Describe the bug

When the absolute path of a test file contains a +, browser mode hangs forever at Test Files 0 passed with no error. The browser launches and the orchestrator loads, but no test ever runs until the process is killed.

Root cause: createTestIframe in packages/browser/src/client/orchestrator.ts interpolates the test-file path (iframeId) into the tester iframe URL query without encoding:

    const src = `/?sessionId=${getBrowserState().sessionId}&iframeId=${iframeId}`

The tester reads it back with new URL(location.href).searchParams.get('iframeId'). A + in a URL query component is decoded as a space, so the tester's iframeId (…/a b.test.ts) no longer matches the one the orchestrator sends in its prepare/execute events (…/a+b.test.ts). The tester ignores every event, the orchestrator's prepare promise never resolves, and the run hangs.

This hits any project whose path contains a + — e.g. a git worktree named feat+whatever-…. Confirmed on main and v4.1.8.

Reproduction

https://github.com/Pduhard/vitest-browser-hang-plus-path

    pnpm install
    pnpm exec playwright install chromium
    pnpm test

The repo contains a single test file named a+b.test.ts, so its absolute path always contains a + wherever it is cloned.

• Expected: the test in a+b.test.ts runs and passes.
• Actual: the run hangs forever at Test Files 0 passed / Tests 0 passed.
• Control: renaming the file to ab.test.ts (no +) makes it pass in ~1s.

System Info

System:
    OS: macOS 26.3
    CPU: (10) arm64 Apple M5
    Memory: 24.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 22.22.1
    npm: 10.9.4
    pnpm: 10.28.0
  Browsers:
    Chrome: 148.0.7778.215
    Safari: 26.3
  npmPackages:
    @vitest/browser-playwright: 4.1.8 => 4.1.8
    playwright: 1.60.0 => 1.60.0
    vitest: 4.1.8 => 4.1.8

Used Package Manager

pnpm

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[lmammino]

Any plan to get this released?