diff --git a/packages/agent-core-v2/src/agent/loop/machine/requester.ts b/packages/agent-core-v2/src/agent/loop/machine/requester.ts
index 3f60b90922d..1103330f777 100644
--- a/packages/agent-core-v2/src/agent/loop/machine/requester.ts
+++ b/packages/agent-core-v2/src/agent/loop/machine/requester.ts
@@ -3,6 +3,7 @@ import type {
   AgentLLMRequestSource,
   IAgentLLMRequesterService,
 } from '#/agent/llmRequester/llmRequester';
+import { ToolCallIdResponseNormalizer } from '#/agent/llmRequester/toolCallIdNormalizer';
 import { unwrapErrorCause } from '#/errors';
 import { llmMessageFromError } from '#/llm-adapter/contract/errors';
 import type { LLMRequestTrace } from '#/llm-adapter/contract/request-trace';
@@ -80,9 +81,17 @@ export function createMachineRequester(
       baseSource?.type === 'turn' && decision.step !== undefined
         ? { ...baseSource, step: decision.step }
         : baseSource;
+    const toolCallIds = new ToolCallIdResponseNormalizer(new Set());
     const task = service.start(
       { source },
-      (part) => control.onEvent?.({ type: 'llm.delta', part }),
+      (part) => {
+        if (part.type !== 'function') {
+          control.onEvent?.({ type: 'llm.delta', part });
+          return;
+        }
+        const id = toolCallIds.remapStreamedId(part.id, part._streamIndex);
+        control.onEvent?.({ type: 'llm.delta', part: id === part.id ? part : { ...part, id } });
+      },
       signal,
     );
     options?.onTrace?.(task.trace);