From c6af43b340a5855e669c8a285b8f57687a08198d Mon Sep 17 00:00:00 2001
From: fei <204683769+feiiiiii5@users.noreply.github.com>
Date: Mon, 17 Aug 2026 23:41:42 +0800
Subject: [PATCH] fix(memory): constrain search_nodes query length

The search_nodes tool accepted an unbounded query string (per
modelcontextprotocol/servers#3537, official servers should constrain
string parameters). An oversized query costs an O(graph) scan per
call with no value. Cap it at 2048 chars via an exported
SearchNodesQuerySchema, and add vitest coverage for the boundary
(at-limit accepted, over-limit rejected, non-string still rejected).

Signed-off-by: fei <204683769+feiiiiii5@users.noreply.github.com>
---
 .../__tests__/search-nodes-schema.test.ts     | 25 +++++++++++++++++++
 src/memory/index.ts                           |  9 ++++++-
 2 files changed, 33 insertions(+), 1 deletion(-)
 create mode 100644 src/memory/__tests__/search-nodes-schema.test.ts

diff --git a/src/memory/__tests__/search-nodes-schema.test.ts b/src/memory/__tests__/search-nodes-schema.test.ts
new file mode 100644
index 0000000000..c03f384ebb
--- /dev/null
+++ b/src/memory/__tests__/search-nodes-schema.test.ts
@@ -0,0 +1,25 @@
+import { describe, it, expect } from 'vitest';
+import { SearchNodesQuerySchema, SEARCH_QUERY_MAX_LENGTH } from '../index.js';
+
+describe('search_nodes input schema', () => {
+  it('should accept a normal query', () => {
+    expect(SearchNodesQuerySchema.safeParse('Alice').success).toBe(true);
+    expect(SearchNodesQuerySchema.safeParse('works at Acme Corp').success).toBe(true);
+  });
+
+  it('should accept a query at exactly the max length', () => {
+    const atLimit = 'a'.repeat(SEARCH_QUERY_MAX_LENGTH);
+    expect(SearchNodesQuerySchema.safeParse(atLimit).success).toBe(true);
+  });
+
+  it('should reject a query longer than the max length', () => {
+    const oversized = 'a'.repeat(SEARCH_QUERY_MAX_LENGTH + 1);
+    const result = SearchNodesQuerySchema.safeParse(oversized);
+    expect(result.success).toBe(false);
+  });
+
+  it('should still reject non-string input', () => {
+    expect(SearchNodesQuerySchema.safeParse(42).success).toBe(false);
+    expect(SearchNodesQuerySchema.safeParse(null).success).toBe(false);
+  });
+});
diff --git a/src/memory/index.ts b/src/memory/index.ts
index 9865c5318e..cea1cc35dd 100644
--- a/src/memory/index.ts
+++ b/src/memory/index.ts
@@ -486,6 +486,13 @@ server.registerTool(
   }
 );
 
+export const SEARCH_QUERY_MAX_LENGTH = 2048;
+
+export const SearchNodesQuerySchema = z
+  .string()
+  .max(SEARCH_QUERY_MAX_LENGTH)
+  .describe("The search query to match against entity names, types, and observation content");
+
 // Register search_nodes tool
 server.registerTool(
   "search_nodes",
@@ -493,7 +500,7 @@ server.registerTool(
     title: "Search Nodes",
     description: "Search for nodes in the knowledge graph based on a query",
     inputSchema: {
-      query: z.string().describe("The search query to match against entity names, types, and observation content")
+      query: SearchNodesQuerySchema
     },
     outputSchema: {
       entities: z.array(EntitySchema),