diff --git a/finance/formula_views.py b/finance/formula_views.py
index afcf4f8..9ad469f 100644
--- a/finance/formula_views.py
+++ b/finance/formula_views.py
@@ -3,14 +3,17 @@ from pathlib import Path
 
 import httpx
 from django.conf import settings
+from django.db import IntegrityError, transaction
 from django.http import FileResponse, JsonResponse
 from django.utils import timezone
 
 from .analysis import METRICS, context, dimensions
 from .formula_columns import available_metrics, ensure_available_metrics, validate_column
-from .models import FormulaDefinition, FormulaExport
+from .models import FormulaDefinition, FormulaExport, Membership
 from .views import APIError, audit, body, dataset, endpoint, limit
 
+MAX_DEFINITIONS_PER_DATASET = 50
+
 
 def design_column(messages, ds, ctx):
     if not (settings.AI_ENABLED and settings.OPENAI_API_KEY and settings.OPENAI_MODEL):
@@ -198,6 +201,7 @@ def formula_definitions(request, dataset_id):
                     {
                         "id": str(item.pk),
                         "definition": item.definition,
+                        "revision": item.revision,
                         "updated_at": item.updated_at.isoformat(),
                     }
                     for item in items
@@ -205,28 +209,52 @@ def formula_definitions(request, dataset_id):
             }
         )
 
-    definition = validate_column(body(request).get("definition"))
+    data = body(request)
+    definition = validate_column(data.get("definition"))
     try:
         ensure_available_metrics(ds, definition)
     except ValueError as exc:
         raise APIError(str(exc)) from exc
     normalized_name = definition["name"].strip().casefold()
-    existing = FormulaDefinition.objects.filter(
-        dataset=ds, user=request.user, normalized_name=normalized_name
-    ).first()
-    if not existing and FormulaDefinition.objects.filter(dataset=ds, user=request.user).count() >= 50:
-        raise APIError("每个数据集最多保存 50 个公式定义")
-    item, created = FormulaDefinition.objects.update_or_create(
-        dataset=ds,
-        user=request.user,
-        normalized_name=normalized_name,
-        defaults={"definition": definition},
-    )
-    audit(request, "formula_definition.save", item.pk, {"dataset": str(ds.pk), "name": definition["name"]})
+    limit(f"formula-definition:{request.user.pk}", 30, 3600)
+    with transaction.atomic():
+        # 锁定稳定的用户所属行序列化同一用户的并发保存，使配额检查与写入原子化。
+        Membership.objects.select_for_update().get(pk=request.member.pk)
+        existing = (
+            FormulaDefinition.objects.select_for_update()
+            .filter(dataset=ds, user=request.user, normalized_name=normalized_name)
+            .first()
+        )
+        if existing:
+            # 同名更新按 revision 做乐观并发控制，避免两个窗口相互静默覆盖。
+            if data.get("revision") != existing.revision:
+                raise APIError("定义已在其他窗口更新，请刷新后重试", 409)
+            existing.definition, existing.revision = definition, existing.revision + 1
+            existing.save(update_fields=["definition", "revision", "updated_at"])
+            item, created = existing, False
+        else:
+            if (
+                FormulaDefinition.objects.filter(dataset=ds, user=request.user).count()
+                >= MAX_DEFINITIONS_PER_DATASET
+            ):
+                raise APIError(f"每个数据集最多保存 {MAX_DEFINITIONS_PER_DATASET} 个公式定义")
+            try:
+                item = FormulaDefinition.objects.create(
+                    dataset=ds,
+                    user=request.user,
+                    normalized_name=normalized_name,
+                    definition=definition,
+                )
+            except IntegrityError as exc:
+                raise APIError("定义保存发生并发冲突，请重试", 409) from exc
+            created = True
+        # 审计与定义变更在同一事务内提交；审计失败时变更一并回滚。
+        audit(request, "formula_definition.save", item.pk, {"dataset": str(ds.pk), "name": definition["name"]})
     return JsonResponse(
         {
             "id": str(item.pk),
             "definition": item.definition,
+            "revision": item.revision,
             "updated_at": item.updated_at.isoformat(),
         },
         status=201 if created else 200,
@@ -242,8 +270,9 @@ def formula_definition_delete(request, dataset_id, definition_id):
     if not item:
         raise APIError("公式定义不存在", 404)
     name = item.definition.get("name", "")
-    audit(request, "formula_definition.delete", item.pk, {"dataset": str(ds.pk), "name": name})
-    item.delete()
+    with transaction.atomic():
+        item.delete()
+        audit(request, "formula_definition.delete", item.pk, {"dataset": str(ds.pk), "name": name})
     return JsonResponse({"deleted": True})
 
 
diff --git a/finance/migrations/0005_formuladefinition_revision.py b/finance/migrations/0005_formuladefinition_revision.py
new file mode 100644
index 0000000..40be6c8
--- /dev/null
+++ b/finance/migrations/0005_formuladefinition_revision.py
@@ -0,0 +1,18 @@
+# Generated by Django 5.2.17 on 2026-09-25 17:30
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('finance', '0004_formuladefinition'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='formuladefinition',
+            name='revision',
+            field=models.PositiveIntegerField(default=1),
+        ),
+    ]
diff --git a/finance/models.py b/finance/models.py
index 1de5920..e84caf7 100644
--- a/finance/models.py
+++ b/finance/models.py
@@ -121,6 +121,7 @@ class FormulaDefinition(models.Model):
     user = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
     normalized_name = models.CharField(max_length=320)
     definition = models.JSONField()
+    revision = models.PositiveIntegerField(default=1)
     created_at = models.DateTimeField(auto_now_add=True)
     updated_at = models.DateTimeField(auto_now=True)
 
diff --git a/frontend/src/dialogs.tsx b/frontend/src/dialogs.tsx
index 21329b1..6e5e96b 100644
--- a/frontend/src/dialogs.tsx
+++ b/frontend/src/dialogs.tsx
@@ -31,6 +31,7 @@ type FormulaExpression =
 type SavedFormulaDefinition = {
   id: string;
   definition: Record<string, unknown>;
+  revision: number;
   updated_at: string;
 };
 
@@ -802,10 +803,18 @@ export function FormulaExportDialog({
     setBusy(true);
     setError("");
     try {
+      // 同名保存按服务端匹配规则覆盖旧版本；带上已知版本的 revision，
+      // 其他窗口先更新过则服务端返回 409，避免静默覆盖。
+      const normalizedName = (value: string) => value.trim().toLowerCase();
+      const existing = definitions.find(
+        (item) =>
+          normalizedName(String(item.definition.name)) ===
+          normalizedName(String(column.name)),
+      );
       const saved = await api<SavedFormulaDefinition>(
         `/datasets/${ds.id}/formula-definitions`,
         "POST",
-        { definition: column },
+        { definition: column, revision: existing?.revision },
       );
       setDefinitions((items) =>
         [...items.filter((item) => item.id !== saved.id), saved].sort((a, b) =>
@@ -914,6 +923,11 @@ export function FormulaExportDialog({
             </button>
           </div>
         )}
+        {definitions.length > 0 && !task && (
+          <p className="muted">
+            保存同名定义会覆盖原版本；若已在其他窗口被修改，保存将提示刷新后重试。
+          </p>
+        )}
         <label className="check">
           <input
             type="checkbox"
diff --git a/tests/test_assistant_api.py b/tests/test_assistant_api.py
index 62d9895..deea87e 100644
--- a/tests/test_assistant_api.py
+++ b/tests/test_assistant_api.py
@@ -168,16 +168,21 @@ def test_formula_definition_library_is_private_validated_and_audited(workspace):
     saved = client.post(url, data={"definition": definition}, content_type="application/json")
     assert saved.status_code == 201
     definition_id = saved.json()["id"]
+    assert saved.json()["revision"] == 1
     assert client.get(url).json()["items"][0]["definition"] == definition
 
     updated = client.post(
         url,
-        data={"definition": {**definition, "name": "  收入成本差  ", "meaning": "更新说明"}},
+        data={
+            "definition": {**definition, "name": "  收入成本差  ", "meaning": "更新说明"},
+            "revision": 1,
+        },
         content_type="application/json",
     )
     assert updated.status_code == 200
     assert FormulaDefinition.objects.filter(dataset=ds, user=ds.created_by).count() == 1
     assert updated.json()["definition"]["meaning"] == "更新说明"
+    assert updated.json()["revision"] == 2
 
     other = Client()
     other_user = ds.created_by.__class__.objects.create_user(
diff --git a/tests/test_formula_definitions_concurrency.py b/tests/test_formula_definitions_concurrency.py
new file mode 100644
index 0000000..d0c8483
--- /dev/null
+++ b/tests/test_formula_definitions_concurrency.py
@@ -0,0 +1,123 @@
+from unittest.mock import patch
+
+import pytest
+from django.db import connection
+
+from finance.models import FormulaDefinition
+
+pytestmark = pytest.mark.django_db
+
+
+def column_definition(name="收入成本差"):
+    return {
+        "name": name,
+        "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": {
+            "operator": "subtract",
+            "left": {"metric": "revenue"},
+            "right": {"metric": "cost"},
+        },
+    }
+
+
+def _post(client, url, definition, revision=None):
+    return client.post(
+        url,
+        data={"definition": definition, **({"revision": revision} if revision is not None else {})},
+        content_type="application/json",
+    )
+
+
+def test_same_name_update_requires_matching_revision(workspace):
+    ds, _, client, *_ = workspace
+    url = f"/api/datasets/{ds.pk}/formula-definitions"
+
+    saved = _post(client, url, column_definition())
+    assert saved.status_code == 201
+    item_id, revision = saved.json()["id"], saved.json()["revision"]
+
+    # 缺失或过期的 revision 都不能静默覆盖其他窗口的修改
+    assert _post(client, url, column_definition()).status_code == 409
+    assert _post(client, url, column_definition(), revision=999).status_code == 409
+
+    updated = _post(client, url, column_definition(), revision=revision)
+    assert updated.status_code == 200
+    assert updated.json()["revision"] == revision + 1
+
+    # 基于旧版本的再次更新必须被拒绝，两个标签页不互相静默丢失
+    stale = _post(client, url, column_definition(), revision=revision)
+    assert stale.status_code == 409
+    current = FormulaDefinition.objects.get(pk=item_id)
+    assert current.revision == revision + 1
+    # 列表接口暴露当前 revision 供前端携带
+    listed = client.get(url).json()["items"]
+    assert listed[0]["revision"] == revision + 1
+
+
+def test_definition_quota_is_enforced_and_release_allows_new_save(workspace):
+    ds, _, client, *_ = workspace
+    url = f"/api/datasets/{ds.pk}/formula-definitions"
+    for index in range(50):
+        FormulaDefinition.objects.create(
+            dataset=ds,
+            user=ds.created_by,
+            normalized_name=f"定义{index:02d}",
+            definition=column_definition(f"定义{index:02d}"),
+        )
+
+    rejected = _post(client, url, column_definition("第 51 个不同名定义"))
+    assert rejected.status_code == 400
+    assert "50" in rejected.json()["error"]
+    assert FormulaDefinition.objects.filter(dataset=ds).count() == 50
+
+    # 同名更新不受配额限制；删除后名额释放可再保存新名称
+    assert _post(client, url, column_definition("定义00"), revision=1).status_code == 200
+    FormulaDefinition.objects.filter(normalized_name="定义00").delete()
+    assert _post(client, url, column_definition("第 51 个不同名定义")).status_code == 201
+
+
+def test_audit_failure_rolls_back_definition_change(workspace):
+    ds, _, client, *_ = workspace
+    url = f"/api/datasets/{ds.pk}/formula-definitions"
+
+    with patch("finance.formula_views.audit", side_effect=RuntimeError("audit unavailable")):
+        with pytest.raises(RuntimeError, match="audit unavailable"):
+            _post(client, url, column_definition())
+
+    assert FormulaDefinition.objects.filter(dataset=ds).count() == 0
+
+
+def test_concurrent_distinct_saves_cannot_exceed_quota_on_postgres(workspace):
+    if connection.vendor != "postgresql":
+        pytest.skip("并发配额依赖 PostgreSQL 行锁语义，生产库单独验证")
+    import threading
+
+    from django.test import Client
+
+    ds, member, *_ = workspace
+    user = ds.created_by
+    for index in range(49):
+        FormulaDefinition.objects.create(
+            dataset=ds,
+            user=user,
+            normalized_name=f"定义{index:02d}",
+            definition=column_definition(f"定义{index:02d}"),
+        )
+
+    barrier = threading.Barrier(4)
+
+    def save(index):
+        client = Client()
+        assert client.login(username=user.username, password="Finance-TestPassword991!")
+        barrier.wait()
+        _post(client, f"/api/datasets/{ds.pk}/formula-definitions", column_definition(f"并发{index}"))
+
+    threads = [threading.Thread(target=save, args=(index,)) for index in range(4)]
+    for thread in threads:
+        thread.start()
+    for thread in threads:
+        thread.join()
+
+    assert FormulaDefinition.objects.filter(dataset=ds).count() == 50