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 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

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