Tiered merge gate: remove owner from routine PR review

[sergstack]

Goal

Remove the owner from routine pre-merge review while keeping hard safety boundaries. Owner decision 2026-07-07: implement directly, shadow mode skipped.

Design

Principle: the PR author (any agent) never decides mergeability; a deterministic GitHub-side gate does. The owner reviews only changes that can alter system behavior.

Tiers

• Tier 0/1 — auto-merge: docs changes outside protected paths. The merge gate workflow auto-approves and enables auto-merge; merge happens when required checks pass. Post-merge weekly digest review via weekly_ai_os_review replaces pre-merge review.
• Tier 2 — owner review, always: AGENTS.md, CLAUDE.md, GOAL_MODE.md, MASTER_STATUS.md, CURRENT_STATUS.md, SYNC_CONTRACT.md, scripts/, tests/, .github/, any PROJECT_INSTRUCTIONS.md. Enforced server-side via CODEOWNERS + required code-owner review, so even a tampered workflow cannot bypass it.

Mechanics

1. Branch ruleset on main: PRs only (no direct pushes — prevents a repeat of the [Audit] Local main has 6 unpushed direct commits bypassing PR flow and CI #134 local-main drift), 1 required approval, code-owner review required, required check docs-safety, no force-push/deletion. Bypass: repository admin (owner can always merge manually).
2. .github/CODEOWNERS listing Tier 2 paths -> @sergstack.
3. .github/workflows/auto-merge.yml: classifies the PR diff against the protected-path list; if clean -> approves + gh pr merge --auto; if protected -> leaves it to owner review. Approvals are dismissed on new pushes and re-evaluated.
4. Repo settings: allow auto-merge; allow Actions to approve PRs.
5. Gate hardening: new scripts/check_index_coverage.py (Knowledge dirs vs index files — the drift class from [Audit] [LLM] status file and README omit 8 existing Knowledge files; stale review metadata #135/[Audit] AI_OS_PROJECT_FILES_INDEX.md missing 8 existing [AI OS] Knowledge files #136 becomes machine-checked) wired into docs-safety, sync_aios.py, AGENTS.md validation list, and pytest.

Residual risks (accepted)

• Content quality of auto-merged docs is caught post-merge (weekly digest), not pre-merge; docs-only repo keeps reverts cheap.
• Prompt-injection-shaped content in Tier 0/1 docs merges without human eyes; behavior kernels (PROJECT_INSTRUCTIONS, AGENTS) stay human-gated, which bounds the blast radius.
• Bundle/source content sync remains policy-only ([Audit] Bundle/source content consistency is not validated; AIOS_04 embedded copy already drifted #137 follow-up) until an automated check exists.

Sequencing

The implementation PR is stacked after the current audit queue: merge order #139 -> #140 -> #141 -> #142 -> #143 -> this. The ruleset activates immediately; the owner merges the existing stack via admin bypass.

Acceptance

• A docs-only PR outside protected paths merges with zero owner actions after checks pass.
• A PR touching any protected path cannot merge without owner review, even if the workflow file itself is modified in that PR.
• Direct pushes to main are rejected.

[sergstack]

Owner-only activation steps

The file side is implemented in PR #145. The three repo-settings changes below were intentionally blocked for the agent (removing two-party review must be a human action). Run from any terminal with gh authed as sergstack:

1. Allow auto-merge on the repo:

gh api -X PATCH repos/sergstack/AI-OS -F allow_auto_merge=true

2. Allow Actions to approve PRs:

gh api -X PUT repos/sergstack/AI-OS/actions/permissions/workflow -f default_workflow_permissions=read -F can_approve_pull_request_reviews=true

3. Create the protective ruleset on main (PR-only, 1 approval, code-owner review, required docs-safety, admin bypass for you):

cat > /tmp/ruleset.json <<'EOF'
{
  "name": "main-merge-gate",
  "target": "branch",
  "enforcement": "active",
  "conditions": {"ref_name": {"include": ["~DEFAULT_BRANCH"], "exclude": []}},
  "bypass_actors": [{"actor_id": 5, "actor_type": "RepositoryRole", "bypass_mode": "always"}],
  "rules": [
    {"type": "deletion"},
    {"type": "non_fast_forward"},
    {"type": "pull_request", "parameters": {
      "required_approving_review_count": 1,
      "require_code_owner_review": true,
      "dismiss_stale_reviews_on_push": true,
      "require_last_push_approval": false,
      "required_review_thread_resolution": false
    }},
    {"type": "required_status_checks", "parameters": {
      "strict_required_status_checks_policy": false,
      "required_status_checks": [{"context": "docs-safety"}]
    }}
  ]
}
EOF
gh api -X POST repos/sergstack/AI-OS/rulesets --input /tmp/ruleset.json

Notes:

• After step 3, merging the existing audit stack (docs: index missing AI OS Knowledge files (#136) #139->docs: add per-bundle scope table to [AI OS] Knowledge_Bundles README #143) may show "bypass rules and merge" — that's you using the admin bypass; expected.
• Steps can run before or after merging governance: tiered merge gate — auto-merge Tier 0/1, owner review only for protected paths #145; the gate workflow only starts acting once governance: tiered merge gate — auto-merge Tier 0/1, owner review only for protected paths #145 is on main.
• Rollback: delete the ruleset (gh api -X DELETE repos/sergstack/AI-OS/rulesets/<id>), set can_approve_pull_request_reviews=false, revert governance: tiered merge gate — auto-merge Tier 0/1, owner review only for protected paths #145.