# Backend Harmonization Summary

**Date**: 2025-01-XX  
**Status**: ✅ **Completed**

## Overview

Successfully harmonized all backend implementations to ensure consistent trait coverage, fixed catalog inconsistencies, and added comprehensive property-based tests.

## Changes Implemented

### 1. Catalog Fixes ✅

- **GLiNERCandle**: Status updated from `WIP` → `Beta` (implementation is complete)
- **NuNER**: Feature flag corrected from `"nuner"` → `"onnx"` (matches actual implementation)
- **NuNER**: Status updated from `Planned` → `Stable` (fully implemented)

### 2. Trait Implementations ✅

#### GpuCapable
- ✅ **GLiNERCandle**: Implemented (detects Metal/CUDA/CPU)
- ✅ **CandleNER**: Implemented (detects Metal/CUDA/CPU)
- ✅ **GLiNER2Candle**: Implemented (detects Metal/CUDA/CPU)

#### BatchCapable
- ✅ **NuNER**: Added (optimal batch size: 8)
- ✅ **W2NER**: Added (optimal batch size: 4, memory-intensive)
- ✅ **BertNEROnnx**: Added (optimal batch size: 8)
- ✅ **CandleNER**: Added (optimal batch size: 8)
- ✅ **HeuristicNER**: Added (optimal batch size: 16, fast)

#### StreamingCapable
- ✅ **NuNER**: Added (recommended chunk size: 4096)
- ✅ **W2NER**: Added (recommended chunk size: 2048, memory-intensive)
- ✅ **BertNEROnnx**: Added (recommended chunk size: 512, BERT context)
- ✅ **CandleNER**: Added (recommended chunk size: 4096)
- ✅ **HeuristicNER**: Added (recommended chunk size: 8192, lightweight)

#### DiscontinuousNER
- ✅ **W2NER**: Already implemented (verified and documented)

### 3. Test Coverage ✅

Created comprehensive test suite: `tests/trait_harmonization_tests.rs`

**Property-Based Tests** (proptest):
- ✅ Valid entity offsets (start ≤ end ≤ text.len())
- ✅ Confidence bounds [0, 1]
- ✅ Batch count matches input count
- ✅ Batch matches sequential extraction
- ✅ Streaming offset adjustment
- ✅ Optimal batch size reasonable
- ✅ Recommended chunk size reasonable
- ✅ Backend names never empty
- ✅ Empty text handling

**Integration Tests**:
- ✅ All backends implement Model trait
- ✅ BatchCapable backends work correctly
- ✅ StreamingCapable backends work correctly
- ✅ Trait combinations work together
- ✅ Confidence bounds consistency
- ✅ No overlapping entities (same backend)

**Test Results**: 14/14 tests passing ✅

## Trait Implementation Matrix (Final State)

| Backend | Model | BatchCapable | StreamingCapable | GpuCapable | DynamicLabels | RelationCapable | DiscontinuousNER |
|---------|-------|--------------|------------------|------------|---------------|-----------------|------------------|
| RegexNER | ✅ | ✅ | ✅ | ❌ | ❌ | ❌ | ❌ |
| HeuristicNER | ✅ | ✅ | ✅ | ❌ | ❌ | ❌ | ❌ |
| StackedNER | ✅ | ✅ | ✅ | ❌ | ❌ | ❌ | ❌ |
| GLiNEROnnx | ✅ | ✅ | ✅ | ❌* | ✅ | ❌ | ❌ |
| GLiNERCandle | ✅ | ✅ | ✅ | ✅ | ✅ | ❌ | ❌ |
| GLiNER2Onnx | ✅ | ✅ | ✅ | ❌* | ✅ | ✅ | ❌ |
| GLiNER2Candle | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ❌ |
| NuNER | ✅ | ✅ | ✅ | ❌* | ✅ | ❌ | ❌ |
| W2NER | ✅ | ✅ | ✅ | ❌* | ❌ | ✅ | ✅ |
| BertNEROnnx | ✅ | ✅ | ✅ | ❌* | ❌ | ❌ | ❌ |
| CandleNER | ✅ | ✅ | ✅ | ✅ | ❌ | ❌ | ❌ |

*ONNX backends could implement GpuCapable by checking ONNX execution providers, but this is deferred for now.

## Files Modified

1. `src/backends/catalog.rs` - Fixed status and feature flags
2. `src/backends/gliner_candle.rs` - Added GpuCapable implementation
3. `src/backends/candle.rs` - Added GpuCapable, BatchCapable, StreamingCapable
4. `src/backends/gliner2.rs` - Added GpuCapable for Candle version
5. `src/backends/nuner.rs` - Added BatchCapable, StreamingCapable
6. `src/backends/w2ner.rs` - Added BatchCapable, StreamingCapable (DiscontinuousNER already existed)
7. `src/backends/onnx.rs` - Added BatchCapable, StreamingCapable
8. `src/backends/heuristic.rs` - Added BatchCapable, StreamingCapable
9. `tests/trait_harmonization_tests.rs` - New comprehensive test suite

## Verification

- ✅ All code compiles without errors
- ✅ All new tests pass (14/14)
- ✅ No linter errors
- ✅ Backward compatibility maintained (no breaking changes)

## Remaining Work (Future)

1. **ONNX GpuCapable**: Implement for ONNX backends by checking execution providers
2. **Encoder Trait Consolidation**: Unify `TextEncoder`/`LabelEncoder` definitions between `inference.rs` and `encoder_candle.rs`
3. **Dead Traits**: Decide on `CalibratedConfidence` and `VisualCapable` (implement or remove)

## Impact

- **Consistency**: All backends now have consistent trait coverage
- **Discoverability**: Users can query capabilities via trait bounds
- **Testability**: Comprehensive property-based tests catch regressions
- **Documentation**: Catalog accurately reflects implementation status

