fix(server): schema preflight for tool call (#15172)

packages/backend/server/src/plugins/copilot/runtime/tool/bridge.ts

@@ -1,3 +1,5 @@
+import { z } from 'zod';
+
 import {
   type LlmBackendConfig,
   llmDispatchToolLoopStream,
@@ -63,7 +65,7 @@ export function createToolExecutionCallback(
   };
 }
 
-async function executeToolCall(
+export async function executeToolCall(
   tools: CopilotToolSet,
   request: LlmToolCallbackRequest,
   options: CopilotToolExecuteOptions
@@ -103,7 +105,11 @@ async function executeToolCall(
   }
 
   try {
-    const output = await tool.execute(request.args, options);
+    const args =
+      tool.inputSchema instanceof z.ZodType
+        ? tool.inputSchema.parse(request.args)
+        : request.args;
+    const output = await tool.execute(args, options);
     return {
       callId: request.callId,
       name: request.name,
@@ -173,3 +179,7 @@ export function createToolLoopBridge(
     );
   };
 }
+
+// re-export for test consumers
+export type { LlmToolCallbackRequest } from '../../../../native';
+export type { CopilotToolSet, CopilotToolExecuteOptions } from '../../tools';