# GitHub Actions "reserveCache failed: Cache size exceeds limit"

> Fix actions/cache reserveCache failing because the cache entry is too large or the repo cache quota is exhausted.

Source: https://latchkey.dev/learn/github-actions/github-actions-cache-reservecache-size-failed  
Updated: 2026-06-26

Before uploading, the cache client reserves space. The reservation fails if the entry exceeds the per-cache size limit or the repository has hit its total cache quota (caches are evicted by least-recently-used).

## Diagnose it: was the cache hit, and was it the right one?

Cache bugs split into three shapes and they need different fixes: the cache never saved, it saved but the key never matches on restore, or it restored a stale entry through a `restore-keys` prefix and is now poisoning the build. The step output tells you which one you have.

```.github/workflows/ci.yml
- uses: actions/cache@v4
  id: cache
  with:
    path: ~/.npm
    key: ${{ runner.os }}-npm-${{ hashFiles('**/package-lock.json') }}
    restore-keys: |
      ${{ runner.os }}-npm-

- name: What happened
  run: |
    echo "exact hit: ${{ steps.cache.outputs.cache-hit }}"
    echo "key used:  ${{ steps.cache.outputs.cache-matched-key }}"
```

> `cache-hit` is only `true` on an exact key match. A `restore-keys` prefix match reports `cache-hit: false` while still restoring files, which is exactly how a stale cache gets mistaken for no cache at all.

## Cache limits that produce confusing failures

- Repository cache is capped at 10 GB. Past that, GitHub evicts least-recently-used entries, so a large cache can silently stop persisting.
- Caches are scoped by branch. A cache written on a feature branch is not visible to another feature branch, only to its base and its own descendants.
- An entry not read for 7 days is evicted, so a rarely-run workflow effectively never has a warm cache.
- Restoring a cache built for a different tool version is worse than a cold start, because you get a corrupted tree instead of a clean install. Always include the tool version in the key.

## FAQ

### What causes GitHub Actions "reserveCache failed: cache size exceeds limit"?

There are 2 common causes: entry over the per-cache size limit and repo cache quota exhausted. A single cache entry exceeds the 10 GB per-cache cap.

### How do I fix GitHub Actions "reserveCache failed: cache size exceeds limit"?

Shrink what you cache. Cache only the package manager store, not entire build trees.

### What does GitHub Actions "reserveCache failed: cache size exceeds limit" actually mean?

The cache save step warns that reserveCache failed with a size or quota message; the cache is not saved.

### How do I stop GitHub Actions "reserveCache failed: cache size exceeds limit" happening again?

Keep cache entries well under the per-cache limit. The prevention section lists 2 changes that keep it from recurring.

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Latchkey runs CI/CD that repairs its own failures. Agent entry points: https://latchkey.dev/agent.txt, https://latchkey.dev/openapi.json, https://latchkey.dev/llms.txt