diff --git a/integration-tests/cli/simple-mcp-server.test.ts b/integration-tests/cli/simple-mcp-server.test.ts
index 3e50174d26..6d1651c9d3 100644
--- a/integration-tests/cli/simple-mcp-server.test.ts
+++ b/integration-tests/cli/simple-mcp-server.test.ts
@@ -168,6 +168,13 @@ describe('simple-mcp-server', () => {
   const rig = new TestRig();
 
   beforeAll(async () => {
+    // Force the pre-#3994 synchronous MCP discovery path: under progressive
+    // MCP availability the spawned CLI's first non-interactive `--prompt`
+    // request fires without the MCP `add` tool wired into the model's tool
+    // surface, so the model answers `15` directly and `foundToolCall` stays
+    // false. Remove once QwenLM/qwen-code#4163 is fixed.
+    process.env['QWEN_CODE_LEGACY_MCP_BLOCKING'] = '1';
+
     // Setup test directory with MCP server configuration
     await rig.setup('simple-mcp-server', {
       settings: {