diff --git a/src/core/tools/NewTaskTool.ts b/src/core/tools/NewTaskTool.ts
index 827a63c95c3..f406774eae4 100644
--- a/src/core/tools/NewTaskTool.ts
+++ b/src/core/tools/NewTaskTool.ts
@@ -126,22 +126,31 @@ export class NewTaskTool extends BaseTool<"new_task"> {
 			// Preserve the current mode so we can resume with it later.
 			task.pausedModeSlug = (await provider.getState()).mode ?? defaultModeSlug
 
+			// For native protocol, set the pending tool call ID BEFORE starting the subtask.
+			// This prevents a race condition where the subtask completes (during the delay
+			// in startSubtask) before we set the ID, which would cause completeSubtask to
+			// not push the tool_result, breaking the API conversation structure.
+			if (toolProtocol === "native" && toolCallId) {
+				task.pendingNewTaskToolCallId = toolCallId
+			}
+
 			const newTask = await task.startSubtask(unescapedMessage, todoItems, mode)
 
 			if (!newTask) {
+				// Clear the pending ID since the subtask wasn't created
+				if (toolProtocol === "native" && toolCallId) {
+					task.pendingNewTaskToolCallId = undefined
+				}
 				pushToolResult(t("tools:newTask.errors.policy_restriction"))
 				return
 			}
 
-			// For native protocol, defer the tool_result until the subtask completes.
+			// For native protocol with toolCallId, don't push tool_result here.
 			// The actual result (including what the subtask accomplished) will be pushed
 			// by completeSubtask. This gives the parent task useful information about
 			// what the subtask actually did.
-			if (toolProtocol === "native" && toolCallId) {
-				task.pendingNewTaskToolCallId = toolCallId
-				// Don't push tool_result here - it will come from completeSubtask with the actual result.
-				// The task loop will stay alive because isPaused is true (see Task.ts stack push condition).
-			} else {
+			// The task loop will stay alive because isPaused is true (see Task.ts stack push condition).
+			if (toolProtocol !== "native" || !toolCallId) {
 				// For XML protocol, push the result immediately (existing behavior)
 				pushToolResult(
 					`Successfully created new task in ${targetMode.name} mode with message: ${unescapedMessage} and ${todoItems.length} todo items`,