diff --git a/docs/BUG_HISTORY.md b/docs/BUG_HISTORY.md
index 6d552e5a..1191a78b 100644
--- a/docs/BUG_HISTORY.md
+++ b/docs/BUG_HISTORY.md
@@ -6429,6 +6429,22 @@
 - 复发自：BUG-403（候选卡、代表时间、可信区间必须共享 inference 投影，但读写口径未钉成同一函数）
 - 修复版本：待发布
 
+## BUG-424 | quarter/range 精度训练门计入、推断账本却标 unused
+
+- 状态：resolved
+- 首次发现：2026-08-28
+- 最近更新：2026-08-28
+- 影响面：`datedPrecision`、`buildCaseInferenceState` 的 `asPrecision`
+- 用户现象：账本允许 `quarter` / `range` 精度。训练门把它们当成带日期事件开门，推断状态却把同一批事件标成 `unknown`/`unused`，既不打分也不进 holdout。
+- 触发条件：录证据工具写入 `datePrecision: "quarter"` 或 `"range"` 后重建 `inference_state`。
+- 根因：`evidence-model.datedPrecision` 把 `quarter`/`range` 映射成 `year`，`inference-adapter.asPrecision` 映射成 `unknown`。
+- 修复：导出同一个 `datedPrecision`，推断适配器也走它。空值仍是 `unknown`。
+- 验证：`rectification-v9-contracts` 锁定 `quarter`/`range` → `year`。`rectification-credible-range-projection` 锁定 `quarter` 事件 `usage !== "unused"`。
+- 防复发：训练门与推断账本不得对同一 `datePrecision` 使用两套映射。
+- 相关记录：BUG-423
+- 复发自：无
+- 修复版本：待发布
+
 ## BUG-410 | 训练已齐仍因家人/职业方法层停在采集，Agent 只确认后截断
 
 - 状态：resolved
diff --git a/frontend/src/lib/rectification-agentic/v9/evidence-model.ts b/frontend/src/lib/rectification-agentic/v9/evidence-model.ts
index da46e488..05035212 100644
--- a/frontend/src/lib/rectification-agentic/v9/evidence-model.ts
+++ b/frontend/src/lib/rectification-agentic/v9/evidence-model.ts
@@ -165,7 +165,7 @@ export function datePrecisionRank(precision: string): number {
   return PRECISION_RANK[precision] ?? -1;
 }
 
-function datedPrecision(value: string): DatedEventInput["precision"] {
+export function datedPrecision(value: string): DatedEventInput["precision"] {
   if (value === "day" || value === "month" || value === "year" || value === "unknown") return value;
   return "year";
 }
diff --git a/frontend/src/lib/rectification-agentic/v9/inference-adapter.ts b/frontend/src/lib/rectification-agentic/v9/inference-adapter.ts
index bd222bd3..13767004 100644
--- a/frontend/src/lib/rectification-agentic/v9/inference-adapter.ts
+++ b/frontend/src/lib/rectification-agentic/v9/inference-adapter.ts
@@ -15,6 +15,7 @@ import { rankActive } from "../core/convergence-evaluator.ts";
 import { rangeFromTimes, unionStillValidRange } from "../core/credible-range.ts";
 import { previousInferenceFromReceipt } from "../core/compose-receipt.ts";
 import type { AnswerClass, ConflictProbe, InferenceState } from "../core/types.ts";
+import { datedPrecision } from "./evidence-model.ts";
 import {
   isHoldoutVerificationQuote,
   type ChoiceKey,
@@ -28,8 +29,8 @@ function yearFrom(value: string | null | undefined): number | null {
 }
 
 function asPrecision(value: string | null | undefined): EngineEventInput["precision"] {
-  if (value === "day" || value === "month" || value === "year") return value;
-  return "unknown";
+  if (!value) return "unknown";
+  return datedPrecision(value);
 }
 
 export function askedProbeKeysFromReceipt(
diff --git a/frontend/tests/rectification-credible-range-projection.test.ts b/frontend/tests/rectification-credible-range-projection.test.ts
index 7ab4b8c5..dbf59e2d 100644
--- a/frontend/tests/rectification-credible-range-projection.test.ts
+++ b/frontend/tests/rectification-credible-range-projection.test.ts
@@ -196,6 +196,24 @@ test("a corrupted receipt range outside the window still fail-closes", () => {
   assert.equal(projection.credibleRange, null);
 });
 
+test("quarter-precision evidence stays dated in the inference ledger", () => {
+  const state = buildCaseInferenceState({
+    range: { start_time: "05:00", end_time: "05:10" },
+    candidates: [
+      { candidateId: "05:00", time: "05:00", relativeSupport: 50 },
+      { candidateId: "05:10", time: "05:10", relativeSupport: 50 },
+    ],
+    evidence: [
+      { id: "q-career", domain: "career", occurredFrom: "2018-04-01", datePrecision: "quarter" },
+      { id: "y-edu", domain: "education", occurredFrom: "2016-01-01", datePrecision: "year" },
+    ],
+    probes: [],
+  });
+  const quarter = state.events.find((item) => item.id === "q-career");
+  assert.equal(quarter?.precision, "year");
+  assert.notEqual(quarter?.usage, "unused");
+});
+
 test("buildCaseInferenceState receipt is the producer of the projected range", () => {
   const state = buildCaseInferenceState({
     range: { start_time: "04:55", end_time: "05:02" },
diff --git a/frontend/tests/rectification-v9-contracts.test.ts b/frontend/tests/rectification-v9-contracts.test.ts
index 7e29a259..2dbe4f8a 100644
--- a/frontend/tests/rectification-v9-contracts.test.ts
+++ b/frontend/tests/rectification-v9-contracts.test.ts
@@ -29,6 +29,7 @@ import {
   isEvidenceDomain,
   isEvidenceKind,
   isEvidenceStatus,
+  datedPrecision,
   normalizeQuote,
   quoteIsGroundedInMessage,
 } from "../src/lib/rectification-agentic/v9/evidence-model.ts";
@@ -130,6 +131,10 @@ test("evidence model exposes the full kind/domain/precision/status sets", () =>
     assert.equal(isDatePrecision(precision), true);
   }
   assert.equal(isDatePrecision("exact_minute"), false);
+  assert.equal(datedPrecision("quarter"), "year");
+  assert.equal(datedPrecision("range"), "year");
+  assert.equal(datedPrecision("day"), "day");
+  assert.equal(datedPrecision("unknown"), "unknown");
   for (const status of ["draft", "pending_confirmation", "confirmed", "superseded", "rejected"]) {
     assert.equal(isEvidenceStatus(status), true);
   }