GitHub Actions: Early August 2026 Updates [GA]

### Value Prop

These GitHub Actions updates give you sharper visibility and tighter control over your CI/CD workflows. A new REST API lets your team check runner version deprecation timelines before they become a problem, while a new `vulnerability-alerts` read permission for `GITHUB_TOKEN` enables least-privilege access to Dependabot alerts. Four new `job` context properties also make it easier for reusable workflows to know their own source identity at runtime — so your shared workflows can reference exactly where they came from.

### Expected Outcome

Teams that rely on GitHub Actions can proactively plan runner upgrades instead of reacting to deprecation notices, reducing disruption to their pipelines. Finer-grained token permissions help organizations enforce security best practices without sacrificing access to the data their workflows need. Reusable workflow authors gain the runtime context they need to build more self-aware, maintainable automation.

No repository files, tests, or implementation entry points are named. Start by reading the issue's descriptions of the runner deprecation API, the vulnerability-alerts GITHUB_TOKEN permission, and the four job context properties; the issue does not define a code change or a concrete completion test.

索引モデルが issue の本文から書いたものです。