diff --git a/mcp_server.py b/mcp_server.py
index 2ea9667..1e4e0aa 100644
--- a/mcp_server.py
+++ b/mcp_server.py
@@ -44,10 +44,17 @@ _clients: Dict[str, CognitiveMemoryClient] = {}
 
 
 def get_client(graph: Optional[str] = None) -> CognitiveMemoryClient:
-    """Get or create a CognitiveMemoryClient for the given graph."""
-    key = graph or "default"
+    """Get or create a CognitiveMemoryClient for the given graph.
+
+    Resolution order: explicit graph param > COGNITIVE_MEMORY_GRAPH env var > "default".
+    Set COGNITIVE_MEMORY_GRAPH per-project via Claude Code's .claude/settings.json env overrides.
+    """
+    import os
+
+    effective_graph = graph or os.environ.get("COGNITIVE_MEMORY_GRAPH") or None
+    key = effective_graph or "default"
     if key not in _clients:
-        path = resolve_graph_path(graph)
+        path = resolve_graph_path(effective_graph)
         _clients[key] = CognitiveMemoryClient(memory_dir=path)
     return _clients[key]