[Andreas-Garcia]

Summary

Projects adopting portable agent instructions can run a reusable, read-only drift check on pull requests without access to the private agent configuration.

Changes

• Add an agent drift workflow pinned to the public agent-config v1.1.0 commit.
• Exercise compliant and divergent instructions and scoped rules in CI.
• Document the caller contract and add repository guidance for contributors and release handling.

The check covers the structural contract supported by the pinned engine; it does not certify the accuracy of instructions or actual agent loading.

Test plan

• actionlint .github/workflows/agent-drift.yml .github/workflows/test-actions.yml
• shellcheck .github/tests/agent-drift.sh
• Run the fixture against the installed public v1.1.0 checker: compliant project passes and modified Claude instructions fail.
• Independent review found no actionable defects; the scoped-rule coverage gap it identified is now covered. A real caller workflow run remains outstanding.