diff --git a/src/main/mcpServers/hub/__tests__/hub.test.ts b/src/main/mcpServers/hub/__tests__/hub.test.ts
index 92a5b65578..51ec727ee9 100644
--- a/src/main/mcpServers/hub/__tests__/hub.test.ts
+++ b/src/main/mcpServers/hub/__tests__/hub.test.ts
@@ -176,6 +176,7 @@ describe('HubServer Integration', () => {
 
       const execOutput = JSON.parse(execResult.content[0].text)
       expect(execOutput.error).toBe('test error')
+      expect(execOutput.isError).toBe(true)
     })
   })
 
@@ -213,6 +214,7 @@ describe('HubServer Integration', () => {
 
       expect(execOutput.error).toBe('Execution timed out after 60000ms')
       expect(execOutput.result).toBeUndefined()
+      expect(execOutput.isError).toBe(true)
       expect(execOutput.logs).toContain('[log] starting')
       expect(vi.mocked(mcpService.abortTool)).toHaveBeenCalled()
     })
diff --git a/src/main/mcpServers/hub/__tests__/runtime.test.ts b/src/main/mcpServers/hub/__tests__/runtime.test.ts
index 86664a2021..5268aa6dec 100644
--- a/src/main/mcpServers/hub/__tests__/runtime.test.ts
+++ b/src/main/mcpServers/hub/__tests__/runtime.test.ts
@@ -85,6 +85,7 @@ describe('Runtime', () => {
 
       expect(result.result).toBeUndefined()
       expect(result.error).toBe('test error')
+      expect(result.isError).toBe(true)
     })
 
     it('supports parallel helper', async () => {
@@ -139,5 +140,20 @@ describe('Runtime', () => {
 
       expect(result.result).toBe(30)
     })
+
+    it('stops execution when a tool throws', async () => {
+      const runtime = new Runtime()
+      const tools = [
+        createMockTool({
+          functionName: 'server__failing_tool'
+        })
+      ]
+
+      const result = await runtime.execute('return await server__failing_tool({})', tools)
+
+      expect(result.result).toBeUndefined()
+      expect(result.error).toBe('Tool failed')
+      expect(result.isError).toBe(true)
+    })
   })
 })
diff --git a/src/main/mcpServers/hub/index.ts b/src/main/mcpServers/hub/index.ts
index c3abbd517c..6647a3c803 100644
--- a/src/main/mcpServers/hub/index.ts
+++ b/src/main/mcpServers/hub/index.ts
@@ -175,7 +175,8 @@ export class HubServer {
           type: 'text',
           text: JSON.stringify(result, null, 2)
         }
-      ]
+      ],
+      isError: result.isError
     }
   }
 }
diff --git a/src/main/mcpServers/hub/mcp-bridge.ts b/src/main/mcpServers/hub/mcp-bridge.ts
index b759d83b35..9e45eeba0d 100644
--- a/src/main/mcpServers/hub/mcp-bridge.ts
+++ b/src/main/mcpServers/hub/mcp-bridge.ts
@@ -4,7 +4,7 @@
  */
 import mcpService from '@main/services/MCPService'
 import { generateMcpToolFunctionName } from '@shared/mcp'
-import type { MCPTool } from '@types'
+import type { MCPCallToolResponse, MCPTool, MCPToolResultContent } from '@types'
 
 import type { GeneratedTool } from './types'
 
@@ -47,10 +47,12 @@ export const callMcpTool = async (functionName: string, params: unknown, callId?
     }
     const toolId = `${retryToolInfo.serverId}__${retryToolInfo.toolName}`
     const result = await mcpService.callToolById(toolId, params, callId)
+    throwIfToolError(result)
     return extractToolResult(result)
   }
   const toolId = `${toolInfo.serverId}__${toolInfo.toolName}`
   const result = await mcpService.callToolById(toolId, params, callId)
+  throwIfToolError(result)
   return extractToolResult(result)
 }
 
@@ -58,7 +60,7 @@ export const abortMcpTool = async (callId: string): Promise<boolean> => {
   return mcpService.abortTool(null as unknown as Electron.IpcMainInvokeEvent, callId)
 }
 
-function extractToolResult(result: { content: Array<{ type: string; text?: string }> }): unknown {
+function extractToolResult(result: MCPCallToolResponse): unknown {
   if (!result.content || result.content.length === 0) {
     return null
   }
@@ -74,3 +76,21 @@ function extractToolResult(result: { content: Array<{ type: string; text?: strin
 
   return result.content
 }
+
+function throwIfToolError(result: MCPCallToolResponse): void {
+  if (!result.isError) {
+    return
+  }
+
+  const textContent = extractTextContent(result.content)
+  throw new Error(textContent ?? 'Tool execution failed')
+}
+
+function extractTextContent(content: MCPToolResultContent[] | undefined): string | undefined {
+  if (!content || content.length === 0) {
+    return undefined
+  }
+
+  const textBlock = content.find((item) => item.type === 'text' && item.text)
+  return textBlock?.text
+}
diff --git a/src/main/mcpServers/hub/runtime.ts b/src/main/mcpServers/hub/runtime.ts
index c266157a09..dd33fc9ff0 100644
--- a/src/main/mcpServers/hub/runtime.ts
+++ b/src/main/mcpServers/hub/runtime.ts
@@ -103,7 +103,8 @@ export class Runtime {
           {
             result: undefined,
             logs: resolvedLogs.length > 0 ? resolvedLogs : undefined,
-            error: errorMessage
+            error: errorMessage,
+            isError: true
           },
           terminateWorker
         )
diff --git a/src/main/mcpServers/hub/types.ts b/src/main/mcpServers/hub/types.ts
index 2bff26b8dc..1c24ac7e77 100644
--- a/src/main/mcpServers/hub/types.ts
+++ b/src/main/mcpServers/hub/types.ts
@@ -26,10 +26,11 @@ export interface ExecInput {
   code: string
 }
 
-export interface ExecOutput {
+export type ExecOutput = {
   result: unknown
   logs?: string[]
   error?: string
+  isError?: boolean
 }
 
 export interface ToolRegistryOptions {
diff --git a/src/main/services/MCPService.ts b/src/main/services/MCPService.ts
index f106dd9faf..013bdb6ad7 100644
--- a/src/main/services/MCPService.ts
+++ b/src/main/services/MCPService.ts
@@ -195,11 +195,7 @@ class McpService {
    * Call a tool by its full ID (serverId__toolName format).
    * Used by Hub server's runtime.
    */
-  public async callToolById(
-    toolId: string,
-    params: unknown,
-    callId?: string
-  ): Promise<{ content: Array<{ type: string; text?: string }> }> {
+  public async callToolById(toolId: string, params: unknown, callId?: string): Promise<MCPCallToolResponse> {
     const parts = toolId.split('__')
     if (parts.length < 2) {
       throw new Error(`Invalid tool ID format: ${toolId}`)