## 2025-03-18: LLM-Based Query Classification Implementation

### Context
The project was using a keyword-based approach to classify queries into different domains (academic, code, current events). This approach had several limitations:
- Reliance on static keyword lists that needed constant maintenance
- Inability to understand the semantic meaning of queries
- False classifications for ambiguous queries or those containing keywords with multiple meanings
- Difficulty handling emerging topics without updating keyword lists

### Decision
1. Replace the keyword-based query classification with an LLM-based approach:
   - Implement a new `classify_query_domain` method in the `LLMInterface` class
   - Create a new query structuring method that uses the LLM classification results
   - Retain the keyword-based method as a fallback
   - Add confidence scores and reasoning to the classification results

2. Enhance the structured query format:
   - Add primary domain and confidence
   - Include secondary domains with confidence scores
   - Add classification reasoning
   - Maintain backward compatibility with existing search executor

3. Use a 0.3 confidence threshold for secondary domains:
   - Set domain flags (is_academic, is_code, is_current_events) based on primary domain
   - Also set flags for secondary domains with confidence scores above 0.3

### Rationale
- LLM-based approach provides better semantic understanding of queries
- Multi-domain classification with confidence scores handles complex queries better
- Self-explaining classifications with reasoning aids debugging and transparency
- The approach automatically adapts to new topics without code changes
- Retaining keyword-based fallback ensures system resilience

### Alternatives Considered
1. Expanding the keyword lists:
   - Would still lack semantic understanding
   - Increasing maintenance burden
   - False positives would still occur
   
2. Using embedding similarity to predefined domain descriptions:
   - Potentially more computationally expensive
   - Less explainable than the LLM's reasoning
   - Would require managing embedding models

3. Creating a custom classifier:
   - Would require labeled training data
   - More development effort
   - Less flexible than the LLM approach

### Impact
- More accurate query classification, especially for ambiguous or multi-domain queries
- Reduction in maintenance overhead for keyword lists
- Better search engine selection based on query domains
- Improved report generation due to more accurate query understanding
- Enhanced debugging capabilities with classification reasoning