## Changes
Allow users to force hierarchical search mode without fallback to simple
search, enabling testing of hierarchical UI even when 0 summaries are found.
**Backend (flask_app.py):**
- Added `force_hierarchical` parameter to `hierarchical_search()`
- When True, never fallback to simple search (return empty hierarchical result)
- Added `fallback_reason` field to explain why no results
- Pass `force_hierarchical=True` when `force_mode == "hierarchical"`
- Applied to all fallback points:
- No Weaviate client
- No summaries found in Stage 1
- No sections after author/work filtering
- Exception during search
**Frontend (templates/search.html):**
- Display warning message when `fallback_reason` exists
- Yellow alert box with explanation and suggestions
- Works even when `results_data.results` is empty
## Usage
1. Select "🌳 Hiérarchique (2-étapes)" in Mode dropdown
2. Enter any query (even if no matching summaries)
3. See hierarchical UI with warning instead of fallback
## Example
Query: "Qu'est-ce que la justice ?" (not in Peirce corpus)
- Mode forced: Hierarchical
- Result: 0 sections, warning displayed
- No silent fallback to simple search
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
David Blanc Brioir
f6000de230