[mattjohnsonpint]

Follow-up to #16163, targeting its branch. (Thus, no changeset required, since it's in the base PR.)

The filesystem-cache adapter fixes loading transformed modules into workerd, but subsequent runs can still fail when cached tests import cloudflare:test.

The plugin generates a random virtual module ID each session. Cached imports retain the previous ID, which the next session no longer recognizes, causing the virtual module to fall through to filesystem loading.

Derive stable IDs from the resolved project root and name, preserving project isolation and main dependencies for watch-mode reruns. Remap legacy UUID-based IDs so Vitest can invalidate stale cached importers without requiring users to clear their caches.

Regression coverage:

• Import cloudflare:test and read bindings with both module registries.
• Verify each project imports its own main and uses its own SELF entrypoint across cached runs.
• Populate a legacy UUID-based cache, then migrate without changing the configuration source or clearing cached files.
• Verify changing Wrangler’s main between cached runs imports the new entrypoint without modifying Vitest config or clearing the cache.
• Explicitly enable filesystem caching in both coverage fixtures.

Merge order

1. Merge this PR into edmundhung/fix-vitest-fs-module-cache (PR [vitest-plugin] Fix filesystem module caching #16163).
2. Merge [vitest-plugin] Fix V8 coverage teardown with Vitest 5.0.4 #16248 into main. It fixes the separate V8 coverage teardown incompatibility introduced by Vitest 5.0.4.
3. Rebase edmundhung/fix-vitest-fs-module-cache onto the updated main. Resolve the coverage-fixture conflicts in favor of fsModuleCache: true, retaining the V8 teardown fix and expanded regression tests from [vitest-plugin] Fix V8 coverage teardown with Vitest 5.0.4 #16248.
4. Rerun the cache and coverage tests with Vitest 5.0.4, then merge [vitest-plugin] Fix filesystem module caching #16163 into main.

The explicit fsModuleCache: true settings here intentionally conflict with #16248’s temporary false overrides so those overrides are removed when the fixes are combined.

Validation

• Cache regressions passed with Vitest 5.0.4.
• Legacy-cache migration passed with Vitest 5.0.3.
• Watch and module-registry compatibility checks passed with Vitest 4.1.0.
• Both cache-enabled coverage tests passed with Vitest 5.0.3.
• With Vitest 5.0.4, Istanbul coverage passed; V8 coverage remains blocked by [vitest-plugin] Fix V8 coverage teardown with Vitest 5.0.4 #16248.
• Build, typechecking, type-aware lint, and formatting passed.

---

• Tests
  • Tests included/updated
  • Automated tests not possible - manual testing has been completed as follows:
  • Additional testing not necessary because:
• Public documentation
  • Cloudflare docs PR(s):
  • Documentation not necessary because: this restores cached test behavior without changing the public API.

---

[changeset-bot]

⚠️ No Changeset found

Latest commit: b90d5b5

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[workers-devprod]

Codeowners approval required for this PR:

• @cloudflare/wrangler

Show detailed file reviewers

• packages/vitest-plugin/src/pool/plugin.ts: [@cloudflare/wrangler]
• packages/vitest-plugin/test/coverage.test.ts: [@cloudflare/wrangler]
• packages/vitest-plugin/test/fs-module-cache.test.ts: [@cloudflare/wrangler]

[ask-bonk]

LGTM

github run

[pkg-pr-new]

@cloudflare/autoconfig

npm i https://pkg.pr.new/@cloudflare/autoconfig@16249

@cloudflare/build-output-utils

npm i https://pkg.pr.new/@cloudflare/build-output-utils@16249

@cloudflare/codemods

npm i https://pkg.pr.new/@cloudflare/codemods@16249

@cloudflare/config

npm i https://pkg.pr.new/@cloudflare/config@16249

@cloudflare/containers-shared

npm i https://pkg.pr.new/@cloudflare/containers-shared@16249

create-cloudflare

npm i https://pkg.pr.new/create-cloudflare@16249

@cloudflare/deploy-helpers

npm i https://pkg.pr.new/@cloudflare/deploy-helpers@16249

@cloudflare/kv-asset-handler

npm i https://pkg.pr.new/@cloudflare/kv-asset-handler@16249

miniflare

npm i https://pkg.pr.new/miniflare@16249

@cloudflare/pages-functions

npm i https://pkg.pr.new/@cloudflare/pages-functions@16249

@cloudflare/pages-shared

npm i https://pkg.pr.new/@cloudflare/pages-shared@16249

@cloudflare/runtime-types

npm i https://pkg.pr.new/@cloudflare/runtime-types@16249

@cloudflare/unenv-preset

npm i https://pkg.pr.new/@cloudflare/unenv-preset@16249

@cloudflare/vite-plugin

npm i https://pkg.pr.new/@cloudflare/vite-plugin@16249

@cloudflare/vitest-plugin

npm i https://pkg.pr.new/@cloudflare/vitest-plugin@16249

@cloudflare/workers-auth

npm i https://pkg.pr.new/@cloudflare/workers-auth@16249

@cloudflare/workers-editor-shared

npm i https://pkg.pr.new/@cloudflare/workers-editor-shared@16249

@cloudflare/workers-utils

npm i https://pkg.pr.new/@cloudflare/workers-utils@16249

wrangler

npm i https://pkg.pr.new/wrangler@16249

commit: b90d5b5