GitHub Actions "missing download info for actions/cache" (v3 sunset)

GitHub retired the legacy cache service backing actions/cache v3 and the older toolkit. Pinned v3 (and setup-* actions bundling the old cache client) stop resolving cache entries and fail with missing download info.

What this error means

Cache restore/save steps using actions/cache v3 fail with a missing download info or cache-service-unavailable error.

github-actions

Failed to restore: Cache service responded with 400
Error: missing download info for actions/cache@v3
The cache service backing this version has been sunset. Upgrade to actions/cache@v4.

Common causes

Pinned to actions/cache v3

The v3 cache backend was retired; the old client can no longer reserve or download cache entries.

setup-* action bundling old cache logic

An outdated setup-node/python/etc with cache: enabled may use the retired client internally.

How to fix it

Upgrade actions/cache to v4

Change actions/cache@v3 to actions/cache@v4 in all workflows.
Upgrade any setup-* actions that enable caching to current major versions.
Re-run and confirm cache hits resolve.

.github/workflows/ci.yml

- uses: actions/cache@v4
  with:
    path: ~/.npm
    key: npm-${{ hashFiles('**/package-lock.json') }}

How to prevent it

Keep cache and setup-* actions on maintained majors.
Watch deprecation notices for cache backend changes.