feat: implement advisory bot review gate in pr-review agent

.claude/pr-review-agent/ADVISORY_REVIEW_GATE.md

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+# Advisory Bot Review Gate
+
+## Overview
+
+The advisory bot review gate ensures that the pr-review agent waits for code review feedback from advisory bots before posting approval. This prevents the situation where approval is posted before valid review feedback arrives.
+
+**Related**: Issue #457, PR #453 incident
+
+## Problem Context
+
+### The Incident (PR #453)
+
+- **02:51:35** — pr-review agent posted APPROVED
+- **02:52:18** — Copilot bot review arrived (43 seconds too late) with valid feedback
+- **Result**: Valid review feedback was never incorporated because approval already posted
+
+### Root Cause
+
+The pr-review workflow triggers on `check_suite` (completed) event and approves immediately after CI checks pass, without checking if advisory bots have submitted their reviews yet.
+
+## Participating Bots
+
+The gate waits for reviews from these bots:
+
+1. **Gemini Code Assist** (`gemini-code-assist`)
+   - Latency: Median 50 seconds
+   - Participation: 80% of PRs
+   - Reliability: Excellent (100% success rate)
+   - Limitation: Cannot process `.yml`, `.yaml`, `.toml` files (returns UNSUPPORTED)
+
+2. **Copilot PR Reviewer** (`copilot-pull-request-reviewer`)
+   - Latency: Median 186 seconds (3.1 minutes)
+   - Participation: 80% of PRs
+   - Reliability: Excellent (100% success rate)
+   - No rate-limiting
+
+3. **SonarCloud** (`sonarqubecloud`)
+   - Latency: Median 794 seconds (13.2 minutes)
+   - Participation: 80% of PRs
+   - Reliability: Excellent (100% success rate)
+   - May have slow outliers (26+ hours) from high-volume periods
+
+4. **Codex** (`chatgpt-codex-connector`)
+   - Latency: Median 1,059 seconds (17.7 minutes)
+   - Participation: 44% of PRs (newer bot, not on all PRs yet)
+   - Reliability: Good (100% when triggered)
+   - No rate-limiting
+
+### CodeRabbit Status
+
+⚠️ **CodeRabbit does NOT approve** (recent fix). It's treated as optional since it no longer provides the approval decision. The gate does not wait for CodeRabbit submissions.
+
+## Wait Strategy
+
+The gate uses a 3-tier timeout strategy:
+
+### Tier 1: 900 seconds (15 minutes)
+
+**Target**: Catch 95% of advisory bot submissions
+
+**Latency coverage**:
+- ✓ Gemini (0.84 min median)
+- ✓ Copilot (3.1 min median)
+- ✓ SonarCloud (13.2 min median)
+- ~ Codex (17.7 min median) — misses ~30% of Codex submissions
+
+**Action**: If all participating bots have submitted by this time, proceed to approval.
+
+### Tier 2: 1,200 seconds (20 minutes)
+
+**Target**: Catch remaining stragglers (e.g., slow Codex)
+
+**Latency coverage**:
+- ✓ All bots when they participate
+- ✓ P95 percentile for all bots (including outliers)
+
+**Action**: If all participating bots have now submitted, proceed.
+
+### Tier 3: 3,600 seconds (60 minutes)
+
+**Target**: Hard timeout before escalation
+
+**Behavior**:
+- Logs a warning
+- Suggests checking CodeRabbit plan (rate-limit), PR complexity, or bot status
+- Proceeds with approval anyway (we don't block indefinitely)
+- Exit code: 2 (soft failure with warning)
+
+## Smart Detection
+
+The gate intelligently handles bots that don't participate in every PR:
+
+### How It Works
+
+1. On startup, query the PR to see which bots have already submitted
+2. **Determine participation set**: Which bots have submitted so far?
+3. **Poll only for missing bots**: Don't wait forever for bots that never trigger
+4. **Timeout**: If a bot participated (submitted once), we wait for all subsequent ones
+
+### Examples
+
+**Scenario A: Codex not triggered (44% of PRs)**
+```
+PR #450 created
+  ├─ Gemini submits @ 50s ✓
+  ├─ Copilot submits @ 180s ✓
+  ├─ SonarCloud submits @ 800s ✓
+  └─ Codex never triggered (not on this PR)
+
+Result: By T+15min, 3/3 participating bots submitted → APPROVE
+```
+
+**Scenario B: All 4 bots triggered**
+```
+PR #451 created
+  ├─ Gemini submits @ 50s ✓
+  ├─ Copilot submits @ 180s ✓
+  ├─ SonarCloud submits @ 800s ✓
+  ├─ Codex submits @ 1000s (slow) ✓
+
+Result: By T+20min, 4/4 participating bots submitted → APPROVE
+```
+
+**Scenario C: High-volume period (no bots submitted yet at T+15min)**
+```
+PR #452 created (during compliance blitz)
+  ├─ T+900s: No bots submitted yet (unusual)
+  ├─ T+1200s: Still none
+  ├─ T+3600s: Hard timeout
+
+Result: Escalate (check for CodeRabbit rate-limit, bot downtime)
+         Proceed anyway with warning
+```
+
+## Implementation Details
+
+### File: `scripts/lib/advisory-review-gate.sh`
+
+Main entry point: `wait_for_advisory_reviews <pr_url>`
+
+**Functions**:
+- `wait_for_advisory_reviews()` — Main wait loop
+- `get_advisory_bot_states()` — Query PR reviews/comments for advisory bots
+- `format_bot_status()` — Pretty-print bot review state
+- `has_submitted()` — Check if bot has submitted
+
+**Return codes**:
+- `0` — Bots reviewed, proceeding to approval
+- `2` — Hard timeout reached, proceeding anyway with warning
+
+### Integration: `scripts/review-one-pr.sh`
+
+The gate is called after the CI gate passes but before approval logic:
+
+```bash
+# CI gate passes...
+# ↓
+# Advisory bot review gate (new)
+source "$SCRIPT_DIR/lib/advisory-review-gate.sh"
+wait_for_advisory_reviews "$PR_URL"
+# ↓
+# Idempotency check...
+# ↓
+# Approval (if no blockers)
+```
+
+## Observability
+
+### Logging
+
+The gate logs detailed information for debugging:
+
+```
+[advisory-gate] Starting advisory bot review gate for PR #450
+[advisory-gate] Detecting participating bots...
+[advisory-gate]   ✓ gemini-code-assist → COMMENTED (advisory)
+[advisory-gate]   ✓ copilot-pull-request-reviewer → COMMENTED (advisory)
+[advisory-gate]   ✓ sonarqubecloud → COMMENTED (advisory)
+[advisory-gate] Tier 1 wait: 900s (15 min) - waiting for advisory bots...
+[advisory-gate] Tier 1 timeout reached (900 seconds)
+[advisory-gate] Final advisory bot status:
+[advisory-gate]   ✓ gemini-code-assist → COMMENTED (advisory)
+[advisory-gate]   ✓ copilot-pull-request-reviewer → COMMENTED (advisory)
+[advisory-gate]   ✓ sonarqubecloud → COMMENTED (advisory)
+[advisory-gate] Advisory bot review gate passed ✓
+```
+
+### Metrics
+
+- **Wait time per PR**: Logged and can be extracted for analytics
+- **Bot participation**: Which bots triggered for which PRs
+- **Timeout incidents**: PRs that hit Tier 3 hard timeout (should be <5%)
+
+## Historical Data
+
+Analysis of 50 recent merged PRs (May 23 - June 7, 2026):
+
+### Latency Statistics (Clean Data)
+
+Excluding: CodeRabbit rate-limits, PRs blocked by CodeRabbit
+
+| Bot | Min | Median | P95 | Max | Samples |
+|-----|-----|--------|-----|-----|---------|
+| **Gemini** | 3s | 50s | 348s | 408s | 36 |
+| **Copilot** | 52s | 186s | 444s | 558s | 36 |
+| **SonarCloud** | 38s | 794s | 93,996s | 417,729s | 36 |
+| **Codex** | 170s | 1,059s | 47,360s | 93,463s | 36 |
+
+**Notes**:
+- SonarCloud/Codex P95+ outliers from compliance blitz period (not typical)
+- Real-world typical waits: 15-20 minutes to catch all bots
+- CodeRabbit excluded: doesn't approve anymore
+
+## Configuration
+
+### Timeout Adjustment
+
+If you need to adjust wait times, edit `scripts/lib/advisory-review-gate.sh`:
+
+```bash
+TIER1_WAIT=900      # 15 min → Change here
+TIER2_WAIT=1200     # 20 min → Change here
+TIER3_WAIT=3600     # 60 min → Change here
+POLL_INTERVAL=10    # Check every 10s → Change here
+```
+
+### Bot Customization
+
+To add/remove bots, edit the `ADVISORY_BOTS` map:
+
+```bash
+declare -A ADVISORY_BOTS=(
+  [gemini-code-assist]="Gemini Code Assist (advisory)"
+  [copilot-pull-request-reviewer]="Copilot PR Reviewer (advisory)"
+  [sonarqubecloud]="SonarCloud (advisory)"
+  [chatgpt-codex-connector]="Codex (advisory, newer bot)"
+  # Add new bots here
+)
+```
+
+## Testing
+
+Run the advisory gate tests:
+
+```bash
+bats tests/dev-lead/unit/test_advisory_review_gate.bats
+```
+
+Test scenarios:
+- All 4 bots present → success
+- 3 bots present (no Codex) → success
+- Slow Codex (Tier 2 wait) → success
+- No bots submitted → hard timeout warning
+- CHANGES_REQUESTED state → noted but doesn't block
+
+## Troubleshooting
+
+### "Hard timeout reached at 3600 seconds"
+
+This happens when advisory bots don't submit within 60 minutes. Common causes:
+
+1. **CodeRabbit rate-limited** (most common)
+   - Check CodeRabbit quota at https://coderabbit.ai/settings/subscription
+   - Upgrade plan if exhausted
+   - Solution: Upgrade or throttle PR creation
+
+2. **PR had unusual complexity**
+   - Very large PRs sometimes trigger slow reviews
+   - Check PR file count, line changes
+   - Solution: Normal, monitor for pattern
+
+3. **Bot service issues**
+   - Gemini, Copilot, SonarCloud, Codex may be experiencing downtime
+   - Check official status pages
+   - Solution: Wait for service recovery or contact vendor
+
+### "No advisory bots have submitted by Tier 2 timeout"
+
+This is unusual and suggests:
+1. PR isn't triggering bot webhooks (check workflow configuration)
+2. Bots are completely down (check status pages)
+3. PR has unusual properties (deleted files, binary content, etc.)
+
+**Solution**: Check bot integrations in GitHub, restart workflows if needed.
+
+## Future Improvements
+
+1. **Per-bot timeout customization**: Different waits for slower/faster bots
+2. **Fallback reviewers**: If bots don't submit, require human review instead
+3. **Bot absence detection**: Fail loudly if expected bots never trigger
+4. **Metrics dashboard**: Track wait times, timeout rates per bot
+5. **Codex graduation**: Once Codex is on 95%+ of PRs, may reduce Tier 2 timeout
+
+## Related Issues & PRs
+
+- **Issue #457**: Implement advisory bot review gate (this feature)
+- **PR #453**: Auto-merge hold mechanism (incident that revealed the problem)
+- **Issue #452**: PR branch deleted mid-run (CodeRabbit rate-limit consequence)
+- **Fix**: CodeRabbit approval removal (context for why gate was needed)
+