diff --git a/backend/app/api/settings.py b/backend/app/api/settings.py
index e61d7640..319c1c65 100644
--- a/backend/app/api/settings.py
+++ b/backend/app/api/settings.py
@@ -749,10 +749,24 @@ def get_data_source(name: str) -> dict:
 
 @router.post("/data-sources")
 def save_data_source(req: CustomSourceIn) -> dict:
-    """创建或更新一个自定义数据源 yaml, 保存后自动 reload。"""
+    """创建或更新一个自定义数据源 yaml, 保存后自动 reload。
+
+    先验后存 (对齐插件 Key 的先探后存语义): 用与加载同一套校验试建临时
+    provider, 不通过直接 400 且不落盘 — 否则 YAML 写入但 load_all 校验失败,
+    源从列表静默消失, 前端还弹"已保存"成功提示 (用户反馈: 全量分钟缺
+    amount 映射被拒, 以为存上了)。
+    """
     from app.data_providers import custom as custom_sources
     config = req.model_dump()
     config["name"] = (config.get("name") or "").lower()
+    probe = None
+    try:
+        probe = custom_sources.create_provider(config)  # 失败自抛 ValueError(含全部校验原因)
+    except ValueError as e:
+        raise HTTPException(status_code=400, detail=str(e)) from e
+    finally:
+        if probe is not None:
+            probe.close()  # 临时探针(仅校验用), 不留连接资源
     try:
         custom_sources.save_config(config["name"], config)
         custom_sources.load_all()
diff --git a/backend/app/data_providers/custom/provider.py b/backend/app/data_providers/custom/provider.py
index 14cfaa1d..a1d63466 100644
--- a/backend/app/data_providers/custom/provider.py
+++ b/backend/app/data_providers/custom/provider.py
@@ -31,9 +31,12 @@ _REQUIRED = {
     "daily": {"symbol", "date", "open", "high", "low", "close", "volume", "amount"},
     "adj_factor": {"symbol", "trade_date", "ex_factor"},
     "realtime": {"symbol", "last_price", "prev_close", "open", "high", "low", "volume"},
-    "minute": {"symbol", "datetime", "open", "high", "low", "close", "volume", "amount"},
+    "minute": {"symbol", "datetime", "open", "high", "low", "close", "volume"},
     # full_minute (全量分钟) 与 minute 同形: 当日窗口批量拉取, 字段映射一致
-    "full_minute": {"symbol", "datetime", "open", "high", "low", "close", "volume", "amount"},
+    "full_minute": {"symbol", "datetime", "open", "high", "low", "close", "volume"},
+    # minute/full_minute 的 amount(成交额)按契约可空 (docs/plugin-development.md:
+    # 无法提供可靠成交额时应返回 null 不得伪造, 均价线降级显示 —), 不列为必填 —
+    # 否则缺成交额的源整个被 validate 拒绝, 保存后源从列表消失
     # financial 字段由数据源决定, 只要求能映射出 symbol
     "financial": {"symbol"},
 }
diff --git a/backend/tests/test_custom_minute_config.py b/backend/tests/test_custom_minute_config.py
index ccdd1df8..b3040d6e 100644
--- a/backend/tests/test_custom_minute_config.py
+++ b/backend/tests/test_custom_minute_config.py
@@ -380,3 +380,107 @@ def test_full_minute_dataset_survives_config_and_registration(tmp_path: Path, mo
         custom_loader._PROVIDERS.clear()
         custom_loader._PROVIDERS.update(saved_providers)
         custom_loader._LOAD_ERRORS[:] = saved_errors
+
+
+# ================================================================
+# amount 可空契约 + 保存先验后存 (用户反馈: 自定义源配全量分钟"保存不好使")
+# ================================================================
+
+def _minute_dataset(*, drop_targets: tuple[str, ...] = ()) -> dict:
+    """minute/full_minute 形态的数据集配置; drop_targets 指定不映射的内部字段。"""
+    field_map = {
+        "code": "symbol", "ts": "datetime",
+        "o": "open", "h": "high", "lo": "low", "c": "close", "v": "volume",
+    }
+    field_map = {k: v for k, v in field_map.items() if v not in drop_targets}
+    return {
+        "url": "https://example.test/minutes",
+        "method": "POST",
+        "response_path": "data",
+        "field_map": field_map,
+        "symbols_param": "codes",
+    }
+
+
+def test_full_minute_without_amount_is_valid():
+    """契约: 分钟 amount(成交额)可空 — 缺成交额的源合法, 均价线降级显示 —。
+
+    修复前: _REQUIRED 把 amount 列为必填 → validate 报 missing mapped fields,
+    整个源被 load_all 拒绝, 用户保存后源从列表消失("保存不好使")。
+    """
+    from app.data_providers.custom import loader
+
+    provider = loader.create_provider({
+        "name": "fm_no_amount", "display_name": "fm",
+        "datasets": {"full_minute": _minute_dataset(drop_targets=("amount",))},
+    })
+    try:
+        assert not provider.validate(), provider.validate()
+        assert "full_minute" in provider.config.datasets
+    finally:
+        provider.close()
+
+
+def test_minute_without_amount_is_valid():
+    """minute 数据集同契约: amount 不映射也合法。"""
+    from app.data_providers.custom import loader
+
+    provider = loader.create_provider({
+        "name": "m_no_amount", "display_name": "m",
+        "datasets": {"minute": _minute_dataset(drop_targets=("amount",))},
+    })
+    try:
+        assert not provider.validate(), provider.validate()
+    finally:
+        provider.close()
+
+
+def test_minute_missing_core_field_still_rejected():
+    """必填集仍生效: 缺 volume(核心量字段)依旧拒绝, 不能矫枉过正。"""
+    from app.data_providers.custom import loader
+
+    with pytest.raises(ValueError, match="volume"):
+        loader.create_provider({
+            "name": "m_no_volume", "display_name": "m",
+            "datasets": {"minute": _minute_dataset(drop_targets=("volume",))},
+        })
+
+
+def test_save_data_source_validates_before_write(monkeypatch, tmp_path):
+    """保存先验后存: 校验不过 400 + 不落盘; 合法配置才写 YAML 并注册。
+
+    修复前: save_config 先写 YAML, load_all 校验失败仅记 _LOAD_ERRORS,
+    源从列表静默消失, 前端还弹"已保存"成功提示。
+    """
+    from app.api.settings import save_data_source
+    from app.data_providers.custom import loader
+
+    monkeypatch.setattr(loader, "data_sources_dir", lambda: tmp_path)
+    saved_providers = dict(loader._PROVIDERS)
+    saved_status = dict(loader._PLUGIN_STATUS)
+    monkeypatch.setattr(loader, "_load_builtin_plugins", lambda: None)
+    try:
+        # 合法: full_minute 缺 amount 映射 → 保存成功且源注册
+        ok = CustomSourceIn(
+            name="fm_ok",
+            datasets={"full_minute": DatasetConfigIn(**_minute_dataset())},
+        )
+        save_data_source(ok)
+        assert (tmp_path / "fm_ok.yaml").exists()
+        assert loader.provider_has_dataset("fm_ok", "full_minute")
+
+        # 非法: 缺 volume → HTTP 400 带原因, 且不写 YAML
+        bad = CustomSourceIn(
+            name="fm_bad",
+            datasets={"full_minute": DatasetConfigIn(**_minute_dataset(drop_targets=("volume",)))},
+        )
+        with pytest.raises(HTTPException) as ei:
+            save_data_source(bad)
+        assert ei.value.status_code == 400
+        assert "volume" in str(ei.value.detail)
+        assert not (tmp_path / "fm_bad.yaml").exists()
+    finally:
+        loader._PROVIDERS.clear()
+        loader._PROVIDERS.update(saved_providers)
+        loader._PLUGIN_STATUS.clear()
+        loader._PLUGIN_STATUS.update(saved_status)
diff --git a/docs/custom-data-source.md b/docs/custom-data-source.md
index 4368c156..981dc3a5 100644
--- a/docs/custom-data-source.md
+++ b/docs/custom-data-source.md
@@ -11,7 +11,7 @@
 | 日K | `daily` | 批量返回一组股票在指定区间内的日K |
 | 除权因子 | `adj_factor` | 批量返回一组股票的复权因子 |
 | 实时行情 | `realtime` | 返回全市场快照,用于盘中 enriched 增量计算 |
-| 分钟K | `minute` | 返回 1m 分钟K(需映射出 symbol / datetime / OHLC / 量额) |
+| 分钟K | `minute` | 返回 1m 分钟K(需映射出 symbol / datetime / OHLC / 量; amount 成交额可缺省, 缺省时均价线降级显示 —) |
 | 全量分钟 | `full_minute` | 与 `minute` 同形;声明后可被路由为「全量分钟」生效源,内置服务盘中按当日窗口全市场批量落盘(仅修复轮语义,节奏下限 60s) |
 | 财务数据 | `financial` | 一个配置覆盖全部财务表,请求时把表名作为参数传给上游;字段由数据源决定,仅需映射出 symbol |
 
@@ -295,7 +295,7 @@ cp docs/examples/custom-data-source/mock_source.yaml data/data_sources/mock_sour
   prev_close = 昨收价
   open / high / low = 当日 OHLC
   volume = 成交量
-  amount = 成交额
+  amount = 成交额 (可缺省)
   change_pct = 涨跌幅 (小数, 0.0366 = 3.66%)
   change_amount = 涨跌额
   amplitude = 振幅 (小数, 0.024 = 2.4%)
@@ -310,7 +310,7 @@ cp docs/examples/custom-data-source/mock_source.yaml data/data_sources/mock_sour
   datetime = 北京时间墙钟 (YYYY-MM-DD HH:MM:SS)
   open / high / low / close = OHLC
   volume = 成交量
-  amount = 成交额
+  amount = 成交额 (可缺省: 无法提供可靠成交额时不要映射, 前端均价线降级显示 —)
 
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