fix(dialogs): F04 载入已保存定义后把原定义带入可见对话上下文

- 载入定义时以“用户消息+助手确认”形式把名称、含义、范围、缺失处理和表达式
  写入对话，后续“把刚才公式改成乘以 100”等指代可关联到已载入定义；
  生成前仍需显式确认，不静默沿用旧定义
- 选择空选项时同步清理当前定义与上下文，选择状态与预览保持一致
- 服务端单条消息长度上限 1000→2000 以容纳完整定义上下文，超长仍拒绝
- E2E 覆盖：载入后请求包含原定义、修改后表达式为 (收入−成本)×100、
  空选项清理；单测覆盖 2000/2001 边界

finance/formula_views.py

@@ -22,7 +22,8 @@ def design_column(messages, ds, ctx):
         or set(item) != {"role", "content"}
         or item["role"] not in ("user", "assistant")
         or not isinstance(item["content"], str)
-        or len(item["content"]) > 1000
+        # 2000 字符容纳载入已保存定义后的完整对话上下文
+        or len(item["content"]) > 2000
         for item in messages
     ):
         raise APIError("对话消息内容无效")

frontend/src/dialogs.tsx

@@ -41,6 +41,19 @@ function describeExpression(expression: FormulaExpression): string {
   return `(${describeExpression(expression.left)} ${operators[expression.operator]} ${describeExpression(expression.right)})`;
 }
 
+function definitionSummary(definition: Record<string, unknown>): string {
+  const text = [
+    `已载入已保存定义「${String(definition.name)}」`,
+    `含义：${String(definition.meaning)}`,
+    `适用范围：${String(definition.scope)}`,
+    `缺失/零分母处理：${String(definition.missing)}`,
+    `计算表达式：${JSON.stringify(definition.expression)}`,
+  ].join("；");
+  return text.length <= 2000
+    ? text
+    : `${text.slice(0, 2000)}…（内容过长已截断）`;
+}
+
 export function Modal({
   title,
   onClose,
@@ -812,10 +825,26 @@ export function FormulaExportDialog({
   function loadDefinition(id: string) {
     setSelectedDefinition(id);
     const saved = definitions.find((item) => item.id === id);
-    if (!saved) return;
+    if (!saved) {
-    setColumn(saved.definition);
+      // 选择空选项时同步清理当前定义，避免下拉选择与预览不一致
+      setColumn(null);
       setMessages([]);
       setQuestions([]);
+      return;
+    }
+    setColumn(saved.definition);
+    // 载入定义后把原定义显式放进可见、经同意的对话上下文，
+    // 使“把刚才公式改成乘以 100”这类指代能关联到已载入表达式；
+    // 修改结果仍需重新确认，不会静默沿用旧定义。
+    setMessages([
+      { role: "user", content: definitionSummary(saved.definition) },
+      {
+        role: "assistant",
+        content:
+          "已载入该定义作为当前基准。请描述要调整的内容，我会在该定义基础上生成新的列定义，仍需你确认后再生成。",
+      },
+    ]);
+    setQuestions([]);
     setDraft("");
   }
   async function deleteDefinition() {

tests/e2e/formula-export.spec.ts

@@ -59,7 +59,18 @@ test("新增列：补充信息触发追问并重新确认后生成公式工作
                 meaning: "实际收入减成本",
                 scope: "所选分组与期间",
                 missing: "结果不可用（#N/A）；零分母不可用",
-                expression: {
+                expression:
+                  designCalls === 5
+                    ? {
+                        operator: "multiply",
+                        left: {
+                          operator: "subtract",
+                          left: { metric: "revenue" },
+                          right: { metric: "cost" },
+                        },
+                        right: { number: 100 },
+                      }
+                    : {
                         operator: "subtract",
                         left: { metric: "revenue" },
                         right: { metric: "cost" },
@@ -123,11 +134,33 @@ test("新增列：补充信息触发追问并重新确认后生成公式工作
   const reopened = page.getByRole("dialog", { name: "生成公式工作簿" });
   await reopened.getByLabel("已保存定义").selectOption({ label: "收入成本差" });
   await expect(reopened).toContainText("计算表达式：(实际收入 − 成本)");
-  await reopened
+  // F04 回归：载入定义后，原定义作为可见上下文进入对话
-    .getByRole("button", { name: "确认并生成公式工作簿" })
+  await expect(reopened).toContainText("已载入已保存定义「收入成本差」");
-    .click();
+  await expect(reopened).toContainText("我：已载入已保存定义");
+  await expect(reopened).toContainText("助手：已载入该定义作为当前基准");
+  // F04 回归：选择空选项时同步清理当前定义与上下文，选择状态与预览一致
+  await reopened.getByLabel("已保存定义").selectOption({ label: "选择定义" });
+  await expect(reopened.getByText("计算表达式：(实际收入 − 成本)")).toHaveCount(
+    0,
+  );
+  await expect(reopened.getByText("已载入已保存定义")).toHaveCount(0);
+
+  await reopened.getByLabel("已保存定义").selectOption({ label: "收入成本差" });
+  await reopened.getByRole("checkbox").check();
+  await reopened.getByLabel("列计算描述").fill("把刚才公式改成乘以 100");
+  await reopened.getByRole("button", { name: "发送描述" }).click();
+  await expect(reopened).toContainText(
+    "计算表达式：((实际收入 − 成本) × 100)",
+  );
+  // 模型请求必须包含载入的原定义上下文和新的修改描述
+  expect(sentMessages.at(0)?.content).toContain(
+    "已载入已保存定义「收入成本差」",
+  );
+  expect(sentMessages.at(0)?.content).toContain('"operator":"subtract"');
+  expect(sentMessages.at(-1)?.content).toBe("把刚才公式改成乘以 100");
+  await reopened.getByRole("button", { name: "确认并生成公式工作簿" }).click();
   await expect(reopened.getByRole("status")).toContainText("生成完成", {
     timeout: 30000,
   });
-  expect(designCalls).toBe(4);
+  expect(designCalls).toBe(5);
 });

tests/test_formula_columns.py

@@ -200,6 +200,54 @@ def test_design_column_preserves_clarification_branch_and_full_conversation(form
     assert payload["input"][1:] == messages
 
 
+def test_design_column_accepts_loaded_definition_context(formula_data, settings):
+    ds, _ = formula_data
+    settings.AI_ENABLED = True
+    settings.OPENAI_API_KEY = "test-key"
+    settings.OPENAI_MODEL = "test-model"
+    context = "已载入已保存定义「收入成本差」；计算表达式：" + '{"operator":"subtract",' * 45
+    assert 1000 < len(context) <= 2000
+    messages = [
+        {"role": "user", "content": context},
+        {"role": "assistant", "content": "已载入该定义作为当前基准。"},
+        {"role": "user", "content": "把刚才公式改成乘以 100"},
+    ]
+    clarification = {
+        "status": "completed",
+        "output": [
+            {
+                "content": [
+                    {
+                        "type": "output_text",
+                        "text": '{"complete":false,"questions":["要乘在整个表达式上吗？"],"column":null}',
+                    }
+                ]
+            }
+        ],
+    }
+    with patch("finance.formula_views.httpx.Client") as http:
+        http.return_value.__enter__.return_value.post.return_value = type(
+            "Response",
+            (),
+            {"raise_for_status": lambda self: None, "json": lambda self: clarification},
+        )()
+        result = design_column(
+            messages,
+            ds,
+            {"current": ["2026-08"], "baseline": ["2025-08"], "filters": {}, "group": "department"},
+        )
+    assert result["complete"] is False
+    payload = http.return_value.__enter__.return_value.post.call_args.kwargs["json"]
+    assert payload["input"][1:] == messages
+
+    with pytest.raises(Exception, match="对话消息内容无效"):
+        design_column(
+            [{"role": "user", "content": "y" * 2001}],
+            ds,
+            {"current": ["2026-08"], "baseline": ["2025-08"], "filters": {}, "group": "department"},
+        )
+
+
 def test_design_column_returns_only_validated_formula_definition(formula_data, settings):
     ds, _ = formula_data
     settings.AI_ENABLED = True