diff --git a/src/components/image-editor/model3d-generation/Model3dGenerationSubmission.ts b/src/components/image-editor/model3d-generation/Model3dGenerationSubmission.ts
index 01f579827..21f2c59c3 100644
--- a/src/components/image-editor/model3d-generation/Model3dGenerationSubmission.ts
+++ b/src/components/image-editor/model3d-generation/Model3dGenerationSubmission.ts
@@ -30,6 +30,13 @@ export const MODEL3D_GENERATION_TIMEOUT_MESSAGE =
 
 export type Model3dSubmissionPlan = {
   endpoint: Model3dPricingEndpoint;
+  /**
+   * 本次提交使用的尝试代次；调用方必须把它写回 dialog 状态。
+   *
+   * 老快照恢复出来的 dialog 可能没有代次，这里兜底铸一个；如果调用方不写回，
+   * 每次提交都会换键，双击去重与重复计费保护就静默失效。
+   */
+  attemptNonce: string;
   requestKey: string;
   title: string;
   body: Record<string, unknown>;
@@ -109,6 +116,7 @@ export function buildModel3dSubmissionPlan({
     return { ok: false, message: MODEL3D_IMAGE_SOURCE_REQUIRED_MESSAGE };
   }
   const endpoint = resolveModel3dEndpoint(dialog.mode);
+  const attemptNonce = resolveModel3dAttemptNonce(dialog.model3dAttemptNonce);
   const body: Record<string, unknown> = {
     ...(source ? { source } : {}),
     // 价格相关参数永远全量给出：provider 的隐式默认值会直接改变价格，
@@ -136,8 +144,9 @@ export function buildModel3dSubmissionPlan({
     ok: true,
     plan: {
       endpoint,
+      attemptNonce,
       requestKey: resolveModel3dRequestKey({
-        attemptNonce: dialog.model3dAttemptNonce,
+        attemptNonce,
         endpoint,
         body,
       }),
@@ -165,10 +174,17 @@ export function resolveModel3dRequestKey({
   endpoint: Model3dPricingEndpoint;
   body: Record<string, unknown>;
 }): string {
-  const nonce = attemptNonce?.trim() || mintModel3dAttemptNonce();
+  const nonce = resolveModel3dAttemptNonce(attemptNonce);
   return `${nonce}-${fingerprintModel3dRequest(endpoint, body)}`;
 }
 
+/** 取本次提交使用的代次：已有代次直接用，缺失（例如老快照）才现场铸造。 */
+export function resolveModel3dAttemptNonce(
+  attemptNonce?: string | null,
+): string {
+  return attemptNonce?.trim() || mintModel3dAttemptNonce();
+}
+
 /** 键排序只求稳定，不承载任何业务语义：同一份内容必须算出同一个键。 */
 function compareModel3dRequestEntryKeys(
   [left]: [string, unknown],
diff --git a/src/components/image-editor/model3d-generation/useModel3dGenerationTask.test.tsx b/src/components/image-editor/model3d-generation/useModel3dGenerationTask.test.tsx
index d251ece37..a67b977f9 100644
--- a/src/components/image-editor/model3d-generation/useModel3dGenerationTask.test.tsx
+++ b/src/components/image-editor/model3d-generation/useModel3dGenerationTask.test.tsx
@@ -178,6 +178,26 @@ describe('useModel3dGenerationTask', () => {
     expect(result.current.dialog.composerOpen).toBe(false);
   });
 
+  it('缺代次的老快照兜底铸一个并写回，幂等键跟着这个代次走', async () => {
+    submitModel3dGenerationRequestMock.mockResolvedValue({
+      operationId: 'task-1',
+      jobKind: 'model3d_text_to_model',
+      status: QUEUED_STATUS,
+      statusUrl: '/api/runtime/external-generation/jobs/task-1',
+    });
+    const legacyDialog = createDialog({ model3dAttemptNonce: undefined });
+    const { result } = renderTask({ dialog: legacyDialog });
+
+    await act(async () => {
+      await result.current.submitModel3dGeneration(legacyDialog);
+    });
+
+    const request = submitModel3dGenerationRequestMock.mock.calls[0][0];
+    const persistedNonce = result.current.dialog.model3dAttemptNonce;
+    expect(persistedNonce).toBeTruthy();
+    expect(request.idempotencyKey.startsWith(`${persistedNonce}-`)).toBe(true);
+  });
+
   it('排队链路没接手时回到可再次提交的空闲态', async () => {
     submitModel3dGenerationRequestMock.mockResolvedValue({
       operationId: 'task-1',
diff --git a/src/components/image-editor/model3d-generation/useModel3dGenerationTask.ts b/src/components/image-editor/model3d-generation/useModel3dGenerationTask.ts
index 609cb97a1..d19517121 100644
--- a/src/components/image-editor/model3d-generation/useModel3dGenerationTask.ts
+++ b/src/components/image-editor/model3d-generation/useModel3dGenerationTask.ts
@@ -93,6 +93,8 @@ export function useModel3dGenerationTask({
       }
       updateCanvasGenerationDialogById(dialogId, (currentDialog) => ({
         ...currentDialog,
+        // 兜底铸的代次要写回状态：否则老快照每次提交都换幂等键，去重保护失效。
+        model3dAttemptNonce: planResult.plan.attemptNonce,
         status: 'generating',
         composerOpen: false,
         errorMessage: undefined,