npm "cb() never called!" / Unexpected EOF - Fix Corrupted npm State in CI

These npm internal errors - "cb() never called!", "Unexpected end of JSON input", or unexpected EOF - generally mean npm hit corrupted cache data or a truncated download rather than a real dependency problem.

What this error means

An install aborts with an internal npm error like "cb() never called!" or "Unexpected end of JSON input". It is not a dependency conflict; it points at a damaged cache entry or a partially written file, and a clean cache often resolves it.

npm output

npm error cb() never called!
npm error This is an error with npm itself. Please report this error at:
npm error <https://github.com/npm/cli/issues>
# or:
npm error Unexpected end of JSON input while parsing ...

Common causes

Corrupted npm cache (_cacache)

A truncated or damaged entry in ~/.npm/_cacache - often from a killed install or a flaky restore of a cached cache - makes npm read invalid data.

Truncated download or interrupted install

A network drop mid-fetch, or a prior OOM/cancellation, can leave partial files that npm chokes on next run.

How to fix it

Verify or clean the cache and reinstall

Repair the cache, then do a clean install.

Terminal

npm cache verify
# if that does not clear it:
npm cache clean --force
rm -rf node_modules
npm ci

Retry past transient corruption

Re-run the job after cleaning - a one-off truncation usually does not recur.
Bust the CI cache key if the error repeats from a restored cache.
Update npm if you are on an old version with known cache bugs.

How to prevent it

Run npm cache verify periodically or bust caches on failure.
Avoid killing installs mid-run; let them finish or clean up after.
Keep npm reasonably current.