Search Tool Hierarchy
When searching code, use this decision tree:
Decision Tree
Need CONCEPTUAL/SEMANTIC search?
(how does X work, find patterns, understand architecture)
→ Use LEANN (/leann-search) - embedding-based semantic search
→ PreToolUse hook auto-redirects semantic Grep queries
Need to understand code STRUCTURE?
(find function calls, class usages, refactor patterns)
→ Use AST-grep (/ast-grep-find)
Need to find TEXT in code?
→ Use Morph (/morph-search) - 20x faster
→ If no Morph API key: fall back to Grep tool
Simple one-off search?
→ Use built-in Grep tool directlyTool Comparison
| Tool | Best For | Requires |
|---|---|---|
| LEANN | Semantic search: "how does caching work", "error handling patterns", conceptual queries | Index built |
| AST-grep | Structural patterns: "find all calls to foo()", refactoring, find usages by type | MCP server |
| Morph | Fast text search: "find files mentioning error", grep across codebase | API key |
| Grep | Literal patterns, class/function names, regex | Nothing (built-in) |
Examples
LEANN (semantic/conceptual):
- "how does authentication work"
- "find error handling patterns"
- "where is rate limiting implemented"
AST-grep (structural):
- "Find all functions that return a Promise"
- "Find all React components using useState"
- "Refactor all imports of X to Y"
Morph (text search):
- "Find all files mentioning 'authentication'"
- "Search for TODO comments"
Grep (literal):
class ProviderAdapterdef __init__- Regex patterns
LEANN Commands
# Search with semantic query
leann search opc-dev "how does blackboard communication work" --top-k 5
# List available indexes
leann list
# Rebuild index (when code changes)
leann build opc-dev --docs dir1 dir2 --no-recompute --no-compact --force