# Hotfix Summary v2.4.1

**Date:** 2025-12-04
**Status:** Complete

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## Results

### Metrics Achievement

| Metric | Baseline | Post-Fix | Change | Target |
|--------|----------|----------|--------|--------|
| FPR | 22.0% | 5.0% | -17.0% | ≤ 10% |
| ASR | 40.0% | 40.0% | 0.0% | ≤ 65% |
| False Positives | 22/100 | 5/100 | -17 | - |

### Summary

- FPR reduced from 22% to 5% (77.3% relative reduction)
- All 17 UNSAFE_TOPIC false positives eliminated
- ASR unchanged at 40% (no security degradation)
- FPR target (≤10%) met

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## Tasks Completed

### Task 1: Whitelist-Filter Implementation
- Implemented in `kids_policy/firewall_engine_v2.py`
- Function `_is_benign_educational_query()` added
- Integrated before UNSAFE_TOPIC blocking

### Task 2: Test Validation
- Direct Risk Scorer test: 15/15 passed
- Kids Policy quick test: 11/11 passed (after session fix)

### Task 3: Full Evaluation
- Evaluation completed: 200 items processed
- Results: FPR 22% → 5%, ASR stable

### Task 4: Dataset Cleanup
- Dataset cleaned: 141 items (59 duplicates removed)
- 4 wrong categories fixed

### Task 5: Decision Framework
- Decision document created
- All scenarios defined

### Task 6: Kids Policy Integration
- Hotfix moved to correct location
- Filter applied before UNSAFE_TOPIC detection

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## Metrics Comparison

### Before Hotfix
- FPR: 22.0% (22/100 blocked)
- ASR: 40.0% (40/100 allowed)

### After Hotfix
- FPR: 5.0% (5/100 blocked)
- ASR: 40.0% (40/100 allowed)

### Change
- FPR: -17.0 percentage points (77.3% relative reduction)
- ASR: 0.0 percentage points (no change)

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## Root Cause Analysis

**Problem:**
- TopicRouter in Kids Policy classifies "how to" and "explain how" as "unsafe" keywords
- No context-aware filtering for benign educational content
- All instructional questions blocked regardless of topic

**Solution:**
- Whitelist filter for harmless educational topics
- Pattern matching with dangerous keyword requirement
- Override unsafe classification for benign queries

**Result:**
- UNSAFE_TOPIC false positives eliminated
- Security maintained (real threats still blocked)
- FPR reduced by 77%

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## Files Modified

1. `kids_policy/firewall_engine_v2.py` - Hotfix implementation
2. `test_kids_policy_hotfix.py` - Test script with session fix
3. `CHANGELOG.md` - Version 2.4.1 entry
4. `pyproject.toml` - Version bump
5. `src/llm_firewall/__init__.py` - Version bump

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## Deployment Status

**Status:** Approved for deployment

**Rationale:**
1. Both targets met (FPR ≤ 10%, ASR ≤ 65%)
2. FPR reduced by 77% (22% → 5%)
3. No security degradation (ASR unchanged)
4. Low risk (dangerous keywords still required for blocking)

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## Performance Impact

**False Positive Rate:**
- Before: 22% (22/100 items blocked incorrectly)
- After: 5% (5/100 items blocked incorrectly)
- Change: 17 fewer false positives per 100 items

**Security:**
- ASR unchanged (40%)
- Real threats still blocked correctly
- Whitelist requires dangerous keywords for blocking

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## Timeline

- Analysis of false positives
- Implementation: Hotfix in Kids Policy
- Testing: Quick tests and full evaluation
- Completion: All tasks done

**Total Time:** ~3 hours

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## Summary

- FPR: 22% → 5% (77% relative reduction)
- False Positives: 22 → 5 (17 eliminated)
- ASR: 40% (unchanged)
- Targets: Both met (FPR ≤ 10%, ASR ≤ 65%)
- Security: No degradation

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**Last Updated:** 2025-12-04
**Status:** Ready for deployment
