傳統 Graph:
  cfg80211_p2p_init() ──→ cfg80211_get_bss()
  （不知道這個 function 需要什麼條件才能存在）

CRAG Graph:
  cfg80211_p2p_init()
    active_conditions: {"WIFI_P2P_SUPPORT": "y"}
    ──→ cfg80211_get_bss()
  
  Query: preprocess_config({"WIFI_P2P_SUPPORT": "n"})
  Result: cfg80211_p2p_init() 被自動過濾掉
  
  Query: preprocess_config({"WIFI_P2P_SUPPORT": "y"})
  Result: cfg80211_p2p_init() 出現

crag-mcp/
├── crag_mcp/
│   ├── core/
│   │   ├── workspace.py          # Workspace 掃描
│   │   └── config_context.py     # Config / #ifdef 管理
│   ├── parsers/
│   │   └── tree_sitter_parser.py # AST + #ifdef 條件提取
│   ├── llm/
│   │   └── small_llm.py           # Semantic analysis
│   ├── graph/
│   │   └── kuzu_graph.py         # Kùzu + active_conditions
│   └── server/
│       └── mcp_server.py         # 7 tools
├── pyproject.toml
└── README.md

/ws/A/.crag-mcp/
├── graph.kuzu/           # Kùzu DB（函式 + 呼叫關係）
└── file_cache/           # parse cache

configure(workspace_path="/path/to/project")
query_graph("authentication flow")
# 無條件過濾，所有 code 都出現

configure(workspace_path="/path/to/linux")
preprocess_config(
    config_path="/path/to/linux/.config",
    define_overrides={"WIFI_P2P_SUPPORT": "y"}
)
query_graph("WIFI P2P implementation")
# 只有 WIFI_P2P_SUPPORT=y 的 code 會出現

# 改 config，重新查詢
preprocess_config(
    config_path="/path/to/linux/.config",
    define_overrides={"WIFI_P2P_SUPPORT": "n"}
)
query_graph("WIFI P2P implementation")
# P2P 相關 code 被自動過濾掉

configure(workspace_path="/ws/A")
preprocess_config(config_path="/ws/A/.config", workspace_path="/ws/A")

configure(workspace_path="/ws/B")
preprocess_config(config_path="/ws/B/.config", workspace_path="/ws/B")

result_a = query_graph("wifi p2p flow", workspace_path="/ws/A")
result_b = query_graph("wifi p2p flow", workspace_path="/ws/B")

# Agent 自行比較，再決定要不要查 C
result_c = query_graph("wifi p2p flow", workspace_path="/ws/C")

# Graph node 儲存
{
    "name": "cfg80211_p2p_init",
    "active_conditions": {"WIFI_P2P_SUPPORT": "y"}
}

# Query 時比對
preprocess_config(define_overrides={"WIFI_P2P_SUPPORT": "n"})
# → cfg80211_p2p_init 被過濾（條件不滿足）

preprocess_config(define_overrides={"WIFI_P2P_SUPPORT": "y"})
# → cfg80211_p2p_init 出現（條件滿足）

# 無 active_conditions → 永遠出現（always active）

/path/to/project/.crag-mcp/
├── graph.kuzu/           # Kùzu DB（二進制目錄）
└── file_cache/           # parse cache（JSON）

.crag-mcp/

cd /path/to/crag-mcp/
pip install -e .

cd /path/to/crag-mcp/
uv pip install -e .

{
  "mcpServers": {
    "crag": {
      "command": "uv",
      "args": ["run", "--directory", "/path/to/crag-mcp", "-m", "crag_mcp.server.mcp_server"],
      "env": {
        "CRAG_WORKSPACE": "${workspaceFolder}",
        "CRAG_SMALL_LLM": "gemma4:31b-cloud"
      }
    }
  }
}

Agent 看到專案:
├── 有 .config / Kconfig / #ifdef → 呼叫 preprocess_config()
├── 純 Python / JS / Go → 不呼叫（無條件編譯）
└── 使用者提到 "kernel" / "config" → 詢問是否 preprocess