Add CLAUDE.md and update RedisVL to fix Redis 8 compatibility

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+Redis Retrieval Optimizer is a scientific framework for benchmarking and optimizing information retrieval systems using Redis. It supports systematic evaluation of vector search, hybrid retrieval, BM25, and reranking strategies.
+
+## Development Commands
+
+### Setup
+```bash
+make install          # Install dependencies with Poetry
+make redis-start      # Start Redis Stack container (required for tests)
+make redis-stop       # Stop Redis container
+```
+
+### Testing & Quality
+```bash
+make test             # Run full pytest suite
+make check            # Run linting + tests
+make format           # Black + isort formatting
+make check-types      # MyPy type checking
+make lint             # Full linting (format + mypy)
+```
+
+### Single Test Execution
+```bash
+poetry run pytest tests/unit/test_cost_fn.py::test_specific_function
+poetry run pytest tests/integration/test_grid.py -v
+```
+
+## Architecture Overview
+
+### Core Study Types
+- **Grid Study** (`redis_retrieval_optimizer/grid_study.py`) - Systematic parameter exploration
+- **Bayesian Study** (`redis_retrieval_optimizer/bayes_study.py`) - Optuna-based optimization  
+- **Search Study** (`redis_retrieval_optimizer/search_study.py`) - Test methods on existing indices
+
+### Search Methods (`redis_retrieval_optimizer/search_methods/`)
+All methods follow `SearchMethodInput` → `SearchMethodOutput` interface:
+- **BM25** - Lexical search
+- **Vector** - Semantic search
+- **Hybrid** - Combined lexical + semantic
+- **Rerank** - Two-stage retrieval with cross-encoder
+- **Weighted RRF** - Reciprocal Rank Fusion
+
+### Configuration System
+- YAML-based study configurations
+- Pydantic schema validation (`redis_retrieval_optimizer/schema.py`)
+- Configuration examples in `tests/integration/*_data/`
+
+## Key Dependencies
+
+- **RedisVL** (>=0.8.1) - Primary Redis vector library
+- **Optuna** (>=4.3.0) - Bayesian optimization
+- **BEIR** (>=2.1.0) - IR benchmarking datasets
+- **RANX** (>=0.3.20) - Evaluation metrics (NDCG, precision, recall)
+- **Redis** (>=5.0) - Direct Redis client
+- **Poetry** - Dependency management (not uv)
+
+## Redis Requirements
+
+- **Redis Stack** container with vector search capabilities
+- Tests require Redis 7.0+ for full functionality
+- Use `make redis-start` to ensure proper Redis version
+
+## Testing Architecture
+
+- **Integration tests** require running Redis instance
+- **Unit tests** for isolated functionality
+- **Configuration-driven** tests with YAML fixtures
+- **pytest-asyncio** for async test support
+
+## Common Development Patterns
+
+### Adding New Search Methods
+1. Implement in `redis_retrieval_optimizer/search_methods/`
+2. Follow `SearchMethodInput` → `SearchMethodOutput` interface
+3. Add to method registry in appropriate study type
+4. Create unit tests and integration tests
+
+### Study Configuration
+```yaml
+embedding_models:
+  - type: "hf"
+    model: "sentence-transformers/all-MiniLM-L6-v2" 
+    dim: 384
+    embedding_cache_name: "vec-cache"
+
+search_methods: ["bm25", "vector", "hybrid"]
+vector_data_types: ["float16", "float32"]
+```
+
+### Data Requirements
+- **Corpus** - Documents to index (JSON format)
+- **Queries** - Search queries (JSON format)
+- **Qrels** - Relevance judgments (JSON format)
+
+## Performance Considerations
+
+- Use **RedisVL** for high-level operations
+- Use **redis-py** directly for custom low-level operations
+- Vector data types: float16 vs float32 trade-offs
+- Batch operations for large datasets
+
+## Troubleshooting
+
+### Redis Connection Issues
+- Ensure Redis Stack is running: `make redis-start`
+- Check Redis version compatibility (7.0+ recommended)
+- Verify RedisVL compatibility with Redis version
+
+### Test Failures
+- Run `make redis-start` before testing
+- Check for stale Redis indices from previous tests
+- Use `make clean` to clear build artifacts