diff --git a/src/mcp/cli-suffix.test.ts b/src/mcp/cli-suffix.test.ts
index f0435d430..9e8d60ab6 100644
--- a/src/mcp/cli-suffix.test.ts
+++ b/src/mcp/cli-suffix.test.ts
@@ -29,4 +29,21 @@ describe("hasCliSuffix", () => {
     // then
     expect(result).toBe(false)
   })
+
+  // regression: issue #4220 — ast_grep MCP failed on Windows because the older
+  // dist used `path.endsWith("dist/cli.js")`. `hasCliSuffix` must match Windows
+  // backslash paths against the POSIX-shaped `dist/cli.js` suffix.
+  it("matches the ast_grep dist cli suffix on Windows path separators", () => {
+    // given
+    const windowsPath = "C:\\Users\\test\\AppData\\Local\\cache\\oh-my-opencode\\dist\\packages\\ast-grep-mcp\\dist\\cli.js"
+
+    // when: matched against just the trailing `dist/cli.js` segment
+    const matchesShortSuffix = hasCliSuffix(windowsPath, "dist/cli.js")
+    // and the fully-qualified package suffix
+    const matchesPackageSuffix = hasCliSuffix(windowsPath, "packages/ast-grep-mcp/dist/cli.js")
+
+    // then: both must succeed despite the backslashes
+    expect(matchesShortSuffix).toBe(true)
+    expect(matchesPackageSuffix).toBe(true)
+  })
 })