experimental.bundledDev: hotUpdate runs without environment injection (this.environment undefined), leaving stale output until restart #23314

Describe the bug

Under experimental.bundledDev, a plugin's hotUpdate hook is invoked with this.environment undefined. Reading this.environment is the documented way to scope hotUpdate behavior (https://vite.dev/changes/hotupdate-hook), so plugins following the docs throw a TypeError on every file edit.

Mechanism, as far as we can tell from the source (checked on main and v8.1.5):

• ROLLUP_HOOKS (packages/vite/src/node/constants.ts) includes watchChange but not hotUpdate.
• injectEnvironmentToHooks (packages/vite/src/node/build.ts) wraps resolveId/load/transform explicitly and every other hook only if (ROLLUP_HOOKS.includes(hook)) — so no environment-bound wrapper exists for hotUpdate, and under bundled dev the hook executes with the engine's bare plugin context.

The consequence is worse than a crash: the throw is captured as a build error, the dev server keeps running, and it serves stale output on every subsequent edit until restart. (#23024 improved terminal printing for failed HMR updates, but the hook-contract violation and the stale serving remain.) For anyone running Vite behind a wrapper — hosted dev servers, CI preview environments — this presents as "HMR silently stopped working."

Real-world occurrence: @tanstack/start-plugin-core reads this.environment.name on the first line of its hotUpdate hook (plugin.ts) — deterministic breakage on @tanstack/start-plugin-core 1.171.17–1.171.34, tracked in TanStack/router#8062 (guard PR TanStack/router#8061). These versions are pulled transitively by current @tanstack/react-start releases, so the blast radius is every TanStack Start app trying bundled dev.

Related issues, which we believe are distinct facets of the same underlying gap:

• experimental.bundledDev: plugin hotUpdate is called without server, timestamp or read #23125 — the hotUpdate options object missing server/timestamp/read (this issue is about the this context instead).
• experimental.bundledDev: virtual modules fail with UNRESOLVED_ENTRY when their lazy entry is compiled #23124 (closed, Phase 2 milestone).
• feat(bundled-dev): support hotUpdate and handleHotUpdate hook #22956 — the open PR adding a hotUpdate adapter for bundled dev, which presumably becomes the real fix. This issue is about the behavior of current releases until it lands.

Suggested behavior until #22956 lands (in order of preference)

1. Bind the environment for hotUpdate when plugins are handed to the full-bundle dev engine, even while the Phase 2 semantics (Bundled dev mode design doc and Road Map #22746) are still being designed.
2. Or skip hotUpdate hooks entirely under bundled dev, with a one-time warning naming the plugin — an explicitly unsupported hook should not run with a context that violates its documented contract.
3. At minimum, make the failure loud and attributed, rather than degrading to stale serving.

Reproduction

https://github.com/TIMTOMTOP/tanstack-hotupdate-repro

Steps to reproduce

1. npm install && npm run dev (repro pins vite@8.2.1, @tanstack/react-start@1.168.44 → @tanstack/start-plugin-core@1.171.34)
2. Set experimental: { bundledDev: true } (already set in the repro config)
3. Edit any source file
4. hotUpdate throws TypeError: Cannot read properties of undefined (reading 'name'); the error is captured as a build error and the dev server serves stale output for all subsequent edits until restart

System Info

vite: 8.2.1 (also verified the ROLLUP_HOOKS omission on v8.1.5 and main)
@tanstack/react-start: 1.168.44 (→ @tanstack/start-plugin-core 1.171.34)
See reproduction repository for the full manifest.

Used Package Manager

npm

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate. (Closest are experimental.bundledDev: plugin hotUpdate is called without server, timestamp or read #23125 / experimental.bundledDev: virtual modules fail with UNRESOLVED_ENTRY when their lazy entry is compiled #23124 — different facets, cross-linked above.)
• Make sure this is a Vite issue and not a framework-specific issue.
• Check that this is a concrete bug.
• The provided reproduction is a minimal reproducible example of the bug.