Manifest V3 "background.scripts is not supported" in CI

In Manifest V3 the background.scripts and background.page keys are not valid: V3 uses a single background.service_worker. The linter or store flags the old key when the manifest is otherwise V3.

What this error means

web-ext lint or the store reports that background.scripts (or background.persistent) requires manifest version 2 or lower, while the manifest declares version 3.

web-ext

MANIFEST_FIELD_UNSUPPORTED
"/background/scripts" is not supported in manifest version 3.
"background.scripts" requires manifest version of 2 or lower.

Common causes

A V2 background block under a V3 manifest

The manifest was bumped to version 3 but still carries background.scripts or background.persistent from V2.

A build tool injected the legacy field

A bundler config or template still emits the V2 background shape into the output manifest.

How to fix it

Use a service worker background

Replace scripts/page with a single service_worker entry.
Remove persistent, which has no meaning in V3.
Adapt background code to the non-persistent service worker lifecycle.

manifest.json

"background": {
  "service_worker": "background.js"
}

Fix the manifest template in the build

Update the source or bundler config so the emitted manifest uses the V3 background shape.

How to prevent it

Lint the built manifest against V3 in CI.
Remove all V2 background keys when migrating.
Keep the manifest template in sync with the declared version.