# NLP-3.5 Hardening — Final Report

**Date:** 2026-06-18  
**Sprint Status:** ✅ COMPLETE

---

## Summary

All 9 tasks completed. The NLP pipeline is now production-hardened.

| Task | Description | Status |
|------|-------------|--------|
| 1 | Performance breakdown | ✅ Measured per-stage |
| 2 | Timing instrumentation | ✅ `timing_ms` in response |
| 3 | Smart text processing | ✅ AraSpell skipped for >300 chars |
| 4 | Priority system | ✅ grammar(3) > punctuation(2) > spelling(1) > autocomplete(0) |
| 5 | Global overlap resolver | ✅ Span collision detection (exact + partial) |
| 6 | AutoComplete hooks | ✅ Priority=0 registered |
| 7 | Stress test | ✅ All sizes pass (50-2000 chars) |
| 8 | API validation | ✅ 5/5 schemas compatible |
| 9 | UI safety guarantee | ✅ 4/4 overlap tests clean |

---

## Performance Before vs After

| Text Size | Before Hardening | After Hardening | Improvement |
|-----------|-----------------|-----------------|-------------|
| 50 chars | ~8s | 8.7s | Same (full pipeline) |
| 100 chars | ~19s | 12.9s | 32% faster |
| 250 chars | ~90s (estimated) | 37.0s | 59% faster |
| 500 chars | **>180s TIMEOUT** | **28.2s** | ✅ Fixed |
| 1000 chars | **Would timeout** | **28.1s** | ✅ Fixed |
| 2000 chars | **Would timeout** | **33.8s** | ✅ Fixed |

### Root Cause: AraSpell Bottleneck

```
250 chars → AraSpell takes 26,000ms (72% of total)
500+ chars → AraSpell SKIPPED → Grammar + Punctuation only (~28s)
```

The smart text processing strategy eliminates the timeout:
- **0-300 chars**: Full pipeline (Spelling + Grammar + Punctuation)
- **300+ chars**: Grammar + Punctuation only (AraSpell skipped)

---

## Overlap Resolution — Before vs After

| Test Sentence | Before | After |
|---------------|--------|-------|
| المهندسون يعملوا...الأجتماع | ❌ grammar+punctuation overlap | ✅ CLEAN |
| اناا ذهبت الي المدرسه | ✅ clean | ✅ CLEAN |
| هو ذهبوا الي المكتبه | ✅ clean | ✅ CLEAN |
| الطقص جميل اليوم | ✅ clean | ✅ CLEAN |

### Priority System

```
grammar      = 3 (highest)
punctuation  = 2
spelling     = 1
autocomplete = 0 (lowest, reserved for NLP-4)
```

**Rules enforced:**
- Higher priority ALWAYS wins
- One span = one highlight (no stacking)
- Partial overlaps: higher priority kept, lower dropped
- All type combinations handled (grammar>spelling, grammar>punctuation, punctuation>spelling)

---

## Timing Instrumentation

Response now includes per-stage timing:
```json
{
  "timing_ms": {
    "spelling_ms": 4767,
    "grammar_ms": 2294,
    "punctuation_ms": 867,
    "total_ms": 7929
  }
}
```

This is additive (does NOT break existing `status`, `suggestions`, `corrected` fields).

---

## API Backward Compatibility ✅

| Endpoint | Schema | Compatible |
|----------|--------|------------|
| /api/analyze | +timing_ms (additive) | ✅ |
| /api/spelling | unchanged | ✅ |
| /api/grammar | unchanged | ✅ |
| /api/punctuation | unchanged | ✅ |
| /api/summarize | unchanged | ✅ |

---

## Pipeline Status After Hardening

```
NLP-1 AraSpell       ✅ Production Ready
NLP-2 Grammar        ✅ Production Ready
NLP-3 Punctuation    ✅ Production Ready
NLP-3.5 Hardening    ✅ COMPLETE
NLP-4 AutoComplete   ⬜ READY TO START
```

---

## Files Modified

| File | Changes |
|------|---------|
| `src/app.py` | Smart text processing, timing instrumentation, global overlap resolver |

## Files Created

| File | Content |
|------|---------|
| `docs/audit/hardening-final-report.md` | This report |
| `docs/audit/analyze-stress-test.md` | Stress test results |
| `docs/audit/nlp-performance-breakdown.md` | Per-stage latency data |
| `docs/audit/suggestion-priority-audit.md` | Priority system documentation |
| `docs/audit/overlap-resolution-report.md` | Overlap resolver documentation |
| `docs/audit/text-processing-strategy.md` | Adaptive processing strategy |