/code-graph

name: code-graph
description: AST-based code graph for fast symbol lookup, dependency analysis, and blast radius via codebase-memory-mcp MCP server
when-to-use: "Before reading files — query the graph first for symbol lookup, call tracing, and blast radius"
user-invocable: false
effort: medium

Code Graph Skill

**Purpose:** Use the code graph (codebase-memory-mcp) for sub-millisecond symbol lookup, function search, dependency analysis, and blast radius detection. This replaces brute-force grep and file reading for code navigation.

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Core Principle

**Graph first, file second.** Before reading files or grepping, query the code graph. Only read full files when you need to modify them or need context beyond what the graph provides.

**Consider graph when planning.** When planning any change — feature, refactor, bug fix — start by querying the graph to understand scope, dependencies, and blast radius. This applies to thinking and planning phases, not just implementation. Grep is still the right tool for searching string literals, log messages, config values, and content that lives outside code structure.

┌────────────────────────────────────────────────────────────────┐
│  GRAPH FIRST, FILE SECOND                                      │
│  ─────────────────────────────────────────────────────────────│
│  The code graph indexes your entire codebase as a persistent   │
│  knowledge graph. Claude queries it via MCP for instant         │
│  symbol lookup, dependency chains, and blast radius — instead   │
│  of reading hundreds of files.                                 │
│                                                                │
│  14 MCP tools │ 64 languages │ sub-ms queries │ zero deps      │
│  ~99% fewer tokens for navigation vs brute-force file reads    │
├────────────────────────────────────────────────────────────────┤
│  AUTO-UPDATED                                                  │
│  ─────────────────────────────────────────────────────────────│
│  File watcher keeps graph in sync. Post-commit hook ensures    │
│  freshness. No manual rebuild needed.                          │
└────────────────────────────────────────────────────────────────┘

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When to Use Graph vs Direct Read

| Task | Use Graph Tool | Use Direct Read? | |------|---------------|------------------| | Find function/class definition | `search_graph` | No | | Get function signature + docs | `get_code_snippet` | No | | Find all callers of a function | `trace_call_path` | No | | Trace dependency chain | `query_graph` | No | | Determine blast radius of change | `detect_changes` | No | | Understand project architecture | `get_architecture` | No | | Search for code patterns | `search_code` | No | | Read full implementation to modify | `search_graph` to locate, then Read file | Yes | | Understand business logic context | `get_code_snippet` for overview, then Read | Yes |

**Rule:** If a graph tool can answer the question, use it. Only open files when you need the full source to make edits.

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Available MCP Tools

Indexing & Status

| Tool | Purpose | When to Use | |------|---------|-------------| | `index_repository` | Build/rebuild graph for a project | First setup, or after major restructure | | `index_status` | Check if graph is current | Before querying, if unsure of freshness | | `list_projects` | List all indexed projects | Multi-project navigation |

Querying & Navigation

| Tool | Purpose | When to Use | |------|---------|-------------| | `search_graph` | Find symbols by name (fuzzy) | "Find auth-related functions" | | `search_code` | Text search across indexed codebase | "Find TODO comments", pattern matching | | `get_code_snippet` | Get source code for a specific symbol | Need signature, docstring, implementation | | `get_graph_schema` | Understand graph structure and relationships | Exploring what data is available | | `query_graph` | Run structured graph queries | Complex dependency/relationship queries |

Analysis

| Tool | Purpose | When to Use | |------|---------|-------------| | `trace_call_path` | Trace caller/callee chains | "Who calls sendEmail?", "What does init() trigger?" | | `detect_changes` | Identify changed files and blast radius | Before/after code changes, PR review | | `get_architecture` | High-level module/package structure | Onboarding, understanding project layout |

Management

| Tool | Purpose | When to Use | |------|---------|-------------| | `delete_project` | Remove a project from the graph | Cleanup, project restructure | | `manage_adr` | Architecture decision records | Document architectural decisions | | `ingest_traces` | Import runtime traces | Performance analysis, dead code detection |

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Workflow: Before Any Code Change

0. PLAN       → get_architecture + search_graph to understand scope before planning
1. LOCATE     → search_graph to find the symbol
2. UNDERSTAND → get_code_snippet for context
3. BLAST      → detect_changes to assess impact
4. TRACE      → trace_call_path to find all affected callers
5. CHANGE     → Read file, make edit
6. VERIFY     → detect_changes again to confirm scope

**Step 0 applies to planning, not just coding.** When the user asks you to plan a feature, refactor, or fix — query the graph first to understand what exists, what depends on what, and what the scope looks like. This prevents plans based on wrong assumptions about the codebase.

**Never skip step 3.** Blast radius analysis prevents unexpected breakage from changes to shared code.

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Graph Data & Freshness

The graph stays fresh automatically through 3 layers — no manual rebuild needed:

| Layer | Trigger | What Happens | |-------|---------|-------------| | **File watcher** | Every file save | codebase-memory-mcp detects changes and re-indexes affected files in real-time | | **Auto-index** | Session start | `auto_index: true` ensures graph is current when Claude Code starts | | **Post-commit hook** | Every `git comm