Search Tool Hierarchy
When searching code, use this decision tree:
Decision Tree
code
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 directly
Tool 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 ProviderAdapter - •
def __init__ - •Regex patterns
LEANN Commands
bash
# 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