From 83eb00719d611907dac11f6e2e8d3d4daba9bb7f Mon Sep 17 00:00:00 2001
From: Spencer <spencertang@google.com>
Date: Fri, 24 Apr 2026 18:49:25 +0000
Subject: [PATCH] fix(core): prevent MCP tool wiping on background discovery
 failures

---
 packages/core/src/tools/mcp-client.test.ts | 4 ++--
 packages/core/src/tools/mcp-client.ts      | 1 +
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/packages/core/src/tools/mcp-client.test.ts b/packages/core/src/tools/mcp-client.test.ts
index 50b17aa735..956fe6ee3e 100644
--- a/packages/core/src/tools/mcp-client.test.ts
+++ b/packages/core/src/tools/mcp-client.test.ts
@@ -1461,8 +1461,8 @@ describe('mcp-client', () => {
       // Trigger notification - should fail internally but catch the error
       await notificationCallback();
 
-      // Should try to remove tools
-      expect(mockedToolRegistry.removeMcpToolsByServer).toHaveBeenCalled();
+      // Should NOT try to remove tools when discovery fails
+      expect(mockedToolRegistry.removeMcpToolsByServer).not.toHaveBeenCalled();
 
       // Should NOT emit success feedback
       expect(coreEvents.emitFeedback).not.toHaveBeenCalledWith(
diff --git a/packages/core/src/tools/mcp-client.ts b/packages/core/src/tools/mcp-client.ts
index 0441063f81..b7bb588448 100644
--- a/packages/core/src/tools/mcp-client.ts
+++ b/packages/core/src/tools/mcp-client.ts
@@ -1344,6 +1344,7 @@ export async function discoverTools(
         error,
         mcpServerName,
       );
+      throw error;
     }
     return [];
   }