diff --git a/backend/app/data/caliber_identity.py b/backend/app/data/caliber_identity.py
index ece0af6c..c496bc9f 100644
--- a/backend/app/data/caliber_identity.py
+++ b/backend/app/data/caliber_identity.py
@@ -25,7 +25,7 @@ from collections.abc import Iterable
 from typing import Any
 
 #: 指标的语义字段：只有这几样算定义，运行时值（value、rendered、inputs……）不参与哈希
-SEMANTIC_FIELDS = ("id", "name", "expression", "unit", "decimals", "format", "kind", "definition", "params")
+SEMANTIC_FIELDS = ("id", "name", "expression", "unit", "decimals", "format", "kind", "definition", "params", "external")
 
 
 def _blank(value: Any) -> bool:
diff --git a/backend/app/engine/issuance.py b/backend/app/engine/issuance.py
index bd87cfc8..32a60a56 100644
--- a/backend/app/engine/issuance.py
+++ b/backend/app/engine/issuance.py
@@ -475,6 +475,17 @@ def incomplete_gaps(metrics: list[dict[str, Any]]) -> list[str]:
             for m in metrics if isinstance(m, dict) and m.get("incomplete")]
 
 
+def external_stale_gaps(metrics: list[dict[str, Any]]) -> list[str]:
+    """外部常量过期：过了 stale_after_days 天，值还是那个值，但它已经不能代表现在。"""
+    out: list[str] = []
+    for m in metrics:
+        external = m.get("external") if isinstance(m, dict) else None
+        if isinstance(external, dict) and external.get("stale"):
+            out.append(f"指标「{m.get('name') or m.get('id')}」的外部常量已过期"
+                       f"（来源：{external.get('source') or '未写'}，生效日期 {external.get('as_of') or '未写'}）")
+    return out
+
+
 def no_data_gaps(metrics: list[dict[str, Any]]) -> list[str]:
     """契约收来的指标里，输入取自「查询区间里这张表没有数据」的列的（口径卡标了 no_data，data/coverage.py），每个一句缺口。
 
diff --git a/backend/app/engine/nodes/io.py b/backend/app/engine/nodes/io.py
index 948ff862..03b84196 100644
--- a/backend/app/engine/nodes/io.py
+++ b/backend/app/engine/nodes/io.py
@@ -151,7 +151,9 @@ def _apply_contract(
     from datetime import datetime, timezone
 
     from app.engine.governance import board_only
-    from app.engine.issuance import decide_tier, incomplete_gaps, no_data_gaps, sql_check_findings, trace_numbers
+    from app.engine.issuance import (
+        decide_tier, external_stale_gaps, incomplete_gaps, no_data_gaps, sql_check_findings, trace_numbers,
+    )
 
     nodes = state.get("nodes") or {}
     # 写了 report_from 就是引用模式：按报告文档逐段复核，不再按数值回指叙述
@@ -194,6 +196,8 @@ def _apply_contract(
     gaps.extend(incomplete_gaps(metrics))
     # 输入取自「查询区间里这张表没有数据」的列的指标：数回指得上、复算一致，但那个 0 不代表真的是 0，不能完整出具
     gaps.extend(no_data_gaps(metrics))
+    # 外部常量过了有效期：值还是那个值，但已经不能代表现在
+    gaps.extend(external_stale_gaps(metrics))
     # 来源查询没通过 SQL 检查（error 级：重复计算、存量跨期加总）：口径卡复算得一致，算的却是错数。
     # 报告直接引用的查询要等引用核对之后才知道，缺口放在这个位置，下面一起算
     sql_at = len(gaps)
diff --git a/backend/app/engine/nodes/metrics.py b/backend/app/engine/nodes/metrics.py
index 57ec6784..9b86ea4e 100644
--- a/backend/app/engine/nodes/metrics.py
+++ b/backend/app/engine/nodes/metrics.py
@@ -5,6 +5,7 @@ import asyncio
 import json
 import math
 import re
+from datetime import date, timedelta
 from typing import Any
 
 from app.core import artifact_store
@@ -97,14 +98,40 @@ async def run_metrics(state: GraphState, ctx: NodeContext) -> dict[str, Any]:
     comparing = _Comparing()
     for definition in definitions:
         metric_id = str(definition.get("id") or "").strip()
-        expr = str(definition.get("expression") or "").strip()
-        if not metric_id or not expr:
-            errors.append(f"指标定义不完整（缺少 ID 或计算表达式）：{definition}")
+        if not metric_id:
+            errors.append(f"指标定义不完整（缺少 ID）：{definition}")
             continue
         display, problem = _display_of(definition)
         if problem:
             errors.append(f"指标「{metric_id}」：{problem}")
             continue
+        if str(definition.get("kind") or "formula") == "external":
+            value, external, problem = _external_of(definition)
+            if problem:
+                errors.append(f"指标「{metric_id}」：{problem}")
+                continue
+            decimals = display["decimals"]
+            value = round_metric(value, decimals)
+            metrics.append({
+                "id": metric_id,
+                "name": definition.get("name") or metric_id,
+                "unit": definition.get("unit") or "",
+                "value": value,
+                "expression": "",
+                "decimals": decimals,
+                "format": display["format"],
+                "rendered": _rendered(value, definition, display),
+                "inputs": [],
+                "substituted": str(value),
+                "recompute_ok": True,
+                "status": "ok",
+                "external": external,
+            })
+            continue
+        expr = str(definition.get("expression") or "").strip()
+        if not expr:
+            errors.append(f"指标定义不完整（缺少计算表达式）：{definition}")
+            continue
         try:
             tree, _, _ = parse_expression(expr)
         except ExpressionError as e:
@@ -414,6 +441,33 @@ def source_expression(expression: str, source: Any) -> str:
 _DECIMALS_RANGE = 15
 
 
+def _external_of(definition: dict[str, Any]) -> tuple[Any, dict[str, Any], str | None]:
+    """外部常量指标：{value, external: {source, as_of, stale_after_days, stale}}，以及写错时的一句话。
+
+    外部常量不来自查询，但也不能没有出处：来源和生效日期必填；过了 stale_after_days 天标 stale，出具契约据此降档。
+    值只收数（布尔不算），单位的换算、取整仍交给 decimals/format。
+    """
+    external = definition.get("external")
+    if not isinstance(external, dict):
+        return None, {}, "外部常量指标需要 external 对象（value / source / as_of / stale_after_days）"
+    value = external.get("value")
+    if isinstance(value, bool) or not isinstance(value, (int, float)):
+        return None, {}, "external.value 需要是数"
+    source = str(external.get("source") or "").strip()
+    if not source:
+        return None, {}, "external.source 需要写明来源"
+    raw_as_of = external.get("as_of")
+    try:
+        as_of = date.fromisoformat(str(raw_as_of))
+    except (TypeError, ValueError):
+        return None, {}, "external.as_of 需要是 YYYY-MM-DD"
+    days = external.get("stale_after_days")
+    if days is not None and (isinstance(days, bool) or not isinstance(days, int) or days < 0):
+        return None, {}, "external.stale_after_days 需要是非负整数"
+    stale = days is not None and date.today() > as_of + timedelta(days=days)
+    return value, {"source": source, "as_of": as_of.isoformat(), "stale_after_days": days, "stale": stale}, None
+
+
 def _display_of(definition: dict[str, Any]) -> tuple[dict[str, Any], str | None]:
     """指标的显示格式：{decimals, format, bad_decimals}，以及写错时的一句话。
 
diff --git a/backend/app/engine/schema.py b/backend/app/engine/schema.py
index 9fa996ba..47d137f4 100644
--- a/backend/app/engine/schema.py
+++ b/backend/app/engine/schema.py
@@ -1088,7 +1088,7 @@ def _check_challenge(node: GraphNode, spec: GraphSpec, result: ValidationResult)
 
 #: 指标定义的类型。现在只有公式（表达式）这一种在运行时能算；规则、评估、外部常量还没实现，
 #: 先在校验里挡住，免得写进图里以后被当成能算的指标
-METRIC_KINDS = ("formula",)
+METRIC_KINDS = ("formula", "external")
 #: 定义卡参数的标量类型（和入口表单的字段类型同一套子集）
 METRIC_PARAM_TYPES = ("string", "number", "integer", "boolean")
 
@@ -1108,10 +1108,32 @@ def metric_definition_issues(node: GraphNode, metric: Any, index: int) -> list[V
         add(f"指标定义缺少 ID：{field}", code="metrics.id_missing")
     kind = str(metric.get("kind") or "formula")
     if kind not in METRIC_KINDS:
-        add(f"指标「{metric.get('id') or index + 1}」的类型「{kind}」还没有实现：现在只支持「公式」（formula）。"
-            "规则、评估、外部常量请先在定义卡里写成说明，等对应的执行方式上线后再发布",
+        add(f"指标「{metric.get('id') or index + 1}」的类型「{kind}」还没有实现：现在支持「公式」（formula）和"
+            "「外部常量」（external）。规则、评估请先在定义卡里写成说明，等对应的执行方式上线后再发布",
             f"{field}.kind", code="metrics.kind_unsupported")
-    if not metric.get("expression"):
+    if kind == "external":
+        external = metric.get("external")
+        if not isinstance(external, dict):
+            add("外部常量指标需要 external 对象（value / source / as_of / stale_after_days）",
+                f"{field}.external", code="metrics.external_invalid")
+        else:
+            value = external.get("value")
+            if isinstance(value, bool) or not isinstance(value, (int, float)):
+                add("external.value 需要是数", f"{field}.external.value", code="metrics.external_invalid")
+            if not isinstance(external.get("source"), str) or not external["source"].strip():
+                add("external.source 需要写明来源", f"{field}.external.source", code="metrics.external_invalid")
+            raw = external.get("as_of")
+            try:
+                from datetime import date
+
+                date.fromisoformat(str(raw))
+            except (TypeError, ValueError):
+                add("external.as_of 需要是 YYYY-MM-DD", f"{field}.external.as_of", code="metrics.external_invalid")
+            days = external.get("stale_after_days")
+            if days is not None and (isinstance(days, bool) or not isinstance(days, int) or days < 0):
+                add("external.stale_after_days 需要是非负整数", f"{field}.external.stale_after_days",
+                    code="metrics.external_invalid")
+    elif not metric.get("expression"):
         add(f"指标定义缺少表达式：{metric.get('id') or '（空）'}", code="metrics.expression_missing")
 
     definition = metric.get("definition")
diff --git a/backend/app/ledger/descriptor.py b/backend/app/ledger/descriptor.py
index 5ebca863..983a7b9d 100644
--- a/backend/app/ledger/descriptor.py
+++ b/backend/app/ledger/descriptor.py
@@ -28,7 +28,7 @@ from app.look.calibers import card_inputs
 from app.tools.datasource import QUERY_PREFIX
 
 #: 指标只写口径卡配置里真有的这几个键
-METRIC_KEYS = ("id", "name", "unit", "decimals", "format", "kind", "definition", "params")
+METRIC_KEYS = ("id", "name", "unit", "decimals", "format", "kind", "definition", "params", "external")
 
 
 async def list_calibers(session: AsyncSession, *, workflow_id: str | None = None) -> list[dict[str, Any]]:
diff --git a/backend/app/ledger/labels.py b/backend/app/ledger/labels.py
index 32a70125..f1b15f45 100644
--- a/backend/app/ledger/labels.py
+++ b/backend/app/ledger/labels.py
@@ -34,7 +34,7 @@ from typing import Any
 from app.analysis.contract import LEDGER_KIND
 
 #: 标签的四种、认法的两种
-KINDS = ("caliber", "related", "reasoning", "unknown")
+KINDS = ("caliber", "external", "related", "reasoning", "unknown")
 HOWS = ("independent", "composed")
 #: 界面上标签要写明的两句：比对在封存之后做，不在封存范围内；事后补比的是按现在的口径回看
 POST_SEAL_NOTE = "封存后比对，不在封存范围内"
@@ -300,6 +300,12 @@ def metric_label(card: Mapping[str, Any] | None, metric_id: Any, queries: Mappin
     metric = next((m for m in card.get("metrics") or [] if isinstance(m, dict) and m.get("id") == metric_id), None)
     if metric is None:
         return _unknown(METRIC_GONE)
+    external = metric.get("external")
+    if isinstance(external, dict):
+        # 外部常量不来自查询：没有等价证明可做，标签单独一类；带来源和生效日期，过期照实标
+        return {"kind": "external", "source": external.get("source"), "as_of": external.get("as_of"),
+                "stale": bool(external.get("stale")),
+                **({"definition_hash": card.get("definition_hash")} if card.get("definition_hash") else {})}
     inputs = [i for i in metric.get("inputs") or [] if isinstance(i, dict)]
     from_queries = [i for i in inputs if i.get("artifact") and i.get("via") in _SNAPSHOT_VIAS]
     if not from_queries:
diff --git a/backend/tests/test_analysis_judge_ledger.py b/backend/tests/test_analysis_judge_ledger.py
index c7fb4360..5f549d30 100644
--- a/backend/tests/test_analysis_judge_ledger.py
+++ b/backend/tests/test_analysis_judge_ledger.py
@@ -88,7 +88,7 @@ def test_analysis_numbers_get_no_caliber_label_and_are_not_counted():
     labelled = {s["id"]: s.get("ref") for s in iter_segments(doc) if s["id"] in labels}
     assert list(labelled.values()) == ["v:Q1.r0.gmv"]
     whole = ledger_labels.whole_of(labels, {})
-    assert whole["counts"] == {"caliber": 0, "related": 0, "reasoning": 1, "unknown": 0}
+    assert whole["counts"] == {"caliber": 0, "external": 0, "related": 0, "reasoning": 1, "unknown": 0}
     assert ledger_labels.referenced_columns([doc], lambda _: None) == {q: {"gmv"}}
 
 
diff --git a/backend/tests/test_ledger_cells.py b/backend/tests/test_ledger_cells.py
index a2d18a31..46fc0451 100644
--- a/backend/tests/test_ledger_cells.py
+++ b/backend/tests/test_ledger_cells.py
@@ -273,8 +273,8 @@ async def test_last_weeks_sales_labels_only_the_sales_number_as_from_the_caliber
     assert cols["销售额"]["binding"] == {"start": "2026-10-05", "end": "2026-10-11"}
     assert {c: cols[c]["kind"] for c in COLUMNS[1:]} == {c: "related" for c in COLUMNS[1:]}
     whole = content["whole"]
-    assert whole["equivalent"] is False and whole["counts"] == {"caliber": 1, "related": 3, "reasoning": 0,
-                                                                 "unknown": 0}
+    assert whole["equivalent"] is False and whole["counts"] == {"caliber": 1, "external": 0, "related": 3,
+                                                                 "reasoning": 0, "unknown": 0}
     # 工件 meta：逐格证明了的口径也记上（召回按旧版本反查只读它）
     from sqlalchemy import select
 
diff --git a/backend/tests/test_metric_definition.py b/backend/tests/test_metric_definition.py
index d3ef5fd2..a798439c 100644
--- a/backend/tests/test_metric_definition.py
+++ b/backend/tests/test_metric_definition.py
@@ -44,3 +44,51 @@ def test_params_must_be_named_and_typed_once_each():
 def test_definition_must_be_an_object_with_text_fields():
     errors = _errors(_graph(definition={"text": 1, "exclusions": "新客"}))
     assert [i.code for i in errors].count("metrics.definition_invalid") >= 2
+
+
+async def test_an_external_constant_metric_runs_without_a_query():
+    from app.engine.runner import run_manager
+    from tests import ledger_samples as S
+
+    await run_manager.setup()
+    try:
+        graph = S.chain(
+            S.node("start", "input"),
+            S.node("card", "metrics", caliber="年度目标", caliber_version="v1", metrics=[{
+                "id": "target", "name": "年度目标", "unit": "元", "decimals": 0, "kind": "external",
+                "definition": {"text": "董事会批准的年度目标", "owner": "财务"},
+                "external": {"value": 120000000, "source": "2026 年度预算决议", "as_of": "2026-01-01",
+                             "stale_after_days": 365},
+            }]),
+            S.node("out", "output", fields=[{"name": "v", "value": "{{ nodes.card.metrics[0].rendered }}"}]))
+        started = await run_manager.start(graph=graph, input_payload={})
+        row = await S.wait(started.id)
+        assert row.status == "succeeded", row.error
+        assert row.output["v"] == "120,000,000元"
+        from app.api.evidence import _sealed, _sealed_cards
+
+        sealed = await _sealed(row.id)
+        [card] = [c for _, _, c in _sealed_cards(sealed)]
+        metric = card["metrics"][0]
+        assert metric["external"]["source"] == "2026 年度预算决议"
+        assert metric["external"]["stale"] is False
+    finally:
+        await run_manager.shutdown()
+
+
+def test_an_external_constant_needs_a_source_and_an_effective_date():
+    errors = _errors(_graph(kind="external", external={"value": 10, "as_of": "not-a-date"}))
+    codes = [i.code for i in errors]
+    assert codes.count("metrics.external_invalid") >= 2
+    assert _errors(_graph(kind="external", external={
+        "value": 10, "source": "预算", "as_of": "2026-01-01", "stale_after_days": 30})) == []
+
+
+def test_an_external_metric_is_labelled_external_not_reasoning():
+    from app.ledger.labels import metric_label
+
+    card = {"definition_hash": "abc", "metrics": [{"id": "target", "external": {
+        "source": "预算", "as_of": "2026-01-01", "stale": True}}]}
+    label = metric_label(card, "target", {}, {})
+    assert label == {"kind": "external", "source": "预算", "as_of": "2026-01-01", "stale": True,
+                     "definition_hash": "abc"}
diff --git a/frontend/src/run/LedgerStep.tsx b/frontend/src/run/LedgerStep.tsx
index 4d247e7d..a80a1eed 100644
--- a/frontend/src/run/LedgerStep.tsx
+++ b/frontend/src/run/LedgerStep.tsx
@@ -348,6 +348,16 @@ export function LedgerPart({ runId, runClass, report, segId, segText, segLedger,
             i.workflow_id === issue.workflow_id && i.version === issue.version) }} />}
         </div>
       )}
+      {label.kind === 'external' && (
+        <div className="space-y-1" data-ledger-external="">
+          <p className="font-medium">外部常量</p>
+          <p className="text-2xs text-dim">
+            来源：{label.source || '未写'} · 生效日期：{label.as_of || '未写'}
+            {label.stale && <span className="ml-1.5 text-[var(--warn)]">已过期</span>}
+          </p>
+          <p className="text-2xs text-faint">不来自查询，没有等价证明；正式出具前请核对来源和有效期。</p>
+        </div>
+      )}
       {label.kind === 'related' && (
         <div className="space-y-2">
           <p className="text-2xs text-dim">{LEDGER_UI.step.relatedSub}{label.reason ? `：${label.reason}` : ''}</p>
diff --git a/frontend/src/typesLedger.ts b/frontend/src/typesLedger.ts
index 6e152424..29ac215e 100644
--- a/frontend/src/typesLedger.ts
+++ b/frontend/src/typesLedger.ts
@@ -53,8 +53,11 @@ export interface LedgerRelated {
  * - unknown：没比对（reason 写为什么）
  */
 export interface LedgerLabel {
-  kind: 'caliber' | 'related' | 'reasoning' | 'unknown'
+  kind: 'caliber' | 'external' | 'related' | 'reasoning' | 'unknown'
   how?: 'independent' | 'composed'
+  source?: string
+  as_of?: string
+  stale?: boolean
   caliber?: string
   workflow_id?: string
   version?: number