GitHub Actions "Node.js 12 actions are not supported"

Unlike the node16 warning phase, the node12 runtime was fully removed. An action declaring runs.using: node12 now fails the run outright because the runtime no longer exists on the runner.

What this error means

A run fails because an action requires the removed node12 runtime.

Error: Node.js 12 actions are not supported. Please use a Node.js 20 action instead.
The action 'some/old-action@v1' requires node12 which is no longer available.

Common causes

Very old action version

A long-unmaintained or outdated pin still targets node12, which runners no longer provide.

How to fix it

Upgrade or replace the action

1. Bump the action to a maintained version on node20.
2. If no node20 release exists, replace the action with a maintained equivalent or inline the logic in a run step.

How to prevent it

• Audit pinned action versions periodically and drop abandoned ones.
• Prefer actively maintained actions.

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