diff --git a/chat-history.js b/chat-history.js
new file mode 100644
index 0000000..9f8e28c
--- /dev/null
+++ b/chat-history.js
@@ -0,0 +1,189 @@
+// ST-BME: 聊天历史纯函数
+// 此模块中的函数均不依赖 index.js 模块级可变状态，
+// 可被 index.js 及其他模块安全导入。
+
+import { clampInt } from "./ui-status.js";
+import { rollbackBatch } from "./runtime-state.js";
+
+export function isAssistantChatMessage(message) {
+  return Boolean(message) && !message.is_user && !message.is_system;
+}
+
+export function getAssistantTurns(chat) {
+  const assistantTurns = [];
+  // 从 index 1 开始：index 0 是角色卡首条消息（greeting），不参与提取
+  for (let index = 1; index < chat.length; index++) {
+    if (isAssistantChatMessage(chat[index])) {
+      assistantTurns.push(index);
+    }
+  }
+  return assistantTurns;
+}
+
+export function getMinExtractableAssistantFloor(chat) {
+  const assistantTurns = getAssistantTurns(chat);
+  return assistantTurns.length > 0 ? assistantTurns[0] : null;
+}
+
+export function buildExtractionMessages(chat, startIdx, endIdx, settings) {
+  const contextTurns = clampInt(settings.extractContextTurns, 2, 0, 20);
+  const contextStart = Math.max(0, startIdx - contextTurns * 2);
+  const messages = [];
+
+  for (
+    let index = contextStart;
+    index <= endIdx && index < chat.length;
+    index++
+  ) {
+    const msg = chat[index];
+    if (msg.is_system) continue;
+    messages.push({
+      seq: index,
+      role: msg.is_user ? "user" : "assistant",
+      content: msg.mes || "",
+    });
+  }
+
+  return messages;
+}
+
+export function getChatIndexForPlayableSeq(chat, playableSeq) {
+  if (!Array.isArray(chat) || !Number.isFinite(playableSeq)) return null;
+
+  let currentSeq = -1;
+  for (let index = 0; index < chat.length; index++) {
+    const message = chat[index];
+    if (message?.is_system) continue;
+    currentSeq++;
+    if (currentSeq >= playableSeq) {
+      return index;
+    }
+  }
+
+  return chat.length;
+}
+
+export function getChatIndexForAssistantSeq(chat, assistantSeq) {
+  if (!Array.isArray(chat) || !Number.isFinite(assistantSeq)) return null;
+
+  let currentSeq = -1;
+  for (let index = 0; index < chat.length; index++) {
+    if (!isAssistantChatMessage(chat[index])) continue;
+    currentSeq++;
+    if (currentSeq >= assistantSeq) {
+      return index;
+    }
+  }
+
+  return chat.length;
+}
+
+export function resolveDirtyFloorFromMutationMeta(trigger, primaryArg, meta, chat) {
+  if (!meta || typeof meta !== "object") return null;
+
+  const candidates = [];
+  const isDeleteTrigger = String(trigger || "").includes("message-deleted");
+  const minExtractableFloor = getMinExtractableAssistantFloor(chat);
+
+  // 删除后 chat 已是收缩后的状态，删除事件携带的 seq 更接近“被删区间起点”，
+  // 因此这里额外向前退一层，避免恢复仍停留在被删楼层对应的旧图谱边界。
+  if (!isDeleteTrigger && Number.isFinite(meta.messageId)) {
+    candidates.push({
+      floor: meta.messageId,
+      source: `${trigger}-meta`,
+    });
+  }
+  if (Number.isFinite(meta.deletedPlayableSeqFrom)) {
+    const floor = getChatIndexForPlayableSeq(chat, meta.deletedPlayableSeqFrom);
+    if (Number.isFinite(floor)) {
+      candidates.push({
+        floor: Number.isFinite(minExtractableFloor)
+          ? Math.max(minExtractableFloor, floor - 1)
+          : Math.max(0, floor - 1),
+        source: `${trigger}-meta-delete-boundary`,
+      });
+    }
+  }
+  if (Number.isFinite(meta.deletedAssistantSeqFrom)) {
+    const floor = getChatIndexForAssistantSeq(
+      chat,
+      meta.deletedAssistantSeqFrom,
+    );
+    if (Number.isFinite(floor)) {
+      candidates.push({
+        floor: Number.isFinite(minExtractableFloor)
+          ? Math.max(minExtractableFloor, floor - 1)
+          : Math.max(0, floor - 1),
+        source: `${trigger}-meta-delete-boundary`,
+      });
+    }
+  }
+  if (!isDeleteTrigger && Number.isFinite(meta.playableSeq)) {
+    const floor = getChatIndexForPlayableSeq(chat, meta.playableSeq);
+    if (Number.isFinite(floor)) {
+      candidates.push({
+        floor,
+        source: `${trigger}-meta`,
+      });
+    }
+  }
+  if (!isDeleteTrigger && Number.isFinite(meta.assistantSeq)) {
+    const floor = getChatIndexForAssistantSeq(chat, meta.assistantSeq);
+    if (Number.isFinite(floor)) {
+      candidates.push({
+        floor,
+        source: `${trigger}-meta`,
+      });
+    }
+  }
+  if (!isDeleteTrigger && Number.isFinite(primaryArg)) {
+    candidates.push({
+      floor: primaryArg,
+      source: `${trigger}-meta`,
+    });
+  }
+
+  if (candidates.length === 0) return null;
+  const validCandidates = Number.isFinite(minExtractableFloor)
+    ? candidates.filter((c) => c.floor >= minExtractableFloor)
+    : candidates;
+  if (validCandidates.length === 0) return null;
+  return validCandidates.reduce((earliest, current) =>
+    current.floor < earliest.floor ? current : earliest,
+  );
+}
+
+export function clampRecoveryStartFloor(chat, floor) {
+  if (!Number.isFinite(floor)) return floor;
+
+  const minExtractableFloor = getMinExtractableAssistantFloor(chat);
+  if (!Number.isFinite(minExtractableFloor)) {
+    return floor;
+  }
+
+  return Math.max(floor, minExtractableFloor);
+}
+
+export function rollbackAffectedJournals(graph, affectedJournals = []) {
+  for (let index = affectedJournals.length - 1; index >= 0; index--) {
+    rollbackBatch(graph, affectedJournals[index]);
+  }
+  graph.batchJournal = Array.isArray(graph.batchJournal)
+    ? graph.batchJournal.slice(
+        0,
+        Math.max(0, graph.batchJournal.length - affectedJournals.length),
+      )
+    : [];
+}
+
+export function pruneProcessedMessageHashesFromFloor(graph, fromFloor) {
+  if (!graph?.historyState?.processedMessageHashes) return;
+  if (!Number.isFinite(fromFloor)) return;
+
+  const hashes = graph.historyState.processedMessageHashes;
+  for (const key of Object.keys(hashes)) {
+    if (Number(key) >= fromFloor) {
+      delete hashes[key];
+    }
+  }
+}
diff --git a/index.js b/index.js
index 000e173..4d92da7 100644
--- a/index.js
+++ b/index.js
@@ -123,6 +123,18 @@ import {
   writeChatMetadataPatch,
   writeGraphShadowSnapshot,
 } from "./graph-persistence.js";
+import {
+  buildExtractionMessages,
+  clampRecoveryStartFloor,
+  getAssistantTurns,
+  getChatIndexForAssistantSeq,
+  getChatIndexForPlayableSeq,
+  getMinExtractableAssistantFloor,
+  isAssistantChatMessage,
+  pruneProcessedMessageHashesFromFloor,
+  resolveDirtyFloorFromMutationMeta,
+  rollbackAffectedJournals,
+} from "./chat-history.js";
 
 // 操控面板模块（动态加载，防止加载失败崩溃整个扩展）
 let _panelModule = null;
@@ -3540,174 +3552,6 @@ async function handleExtractionSuccess(
   };
 }
 
-function isAssistantChatMessage(message) {
-  return Boolean(message) && !message.is_user && !message.is_system;
-}
-
-function getAssistantTurns(chat) {
-  const assistantTurns = [];
-  // 从 index 1 开始：index 0 是角色卡首条消息（greeting），不参与提取
-  for (let index = 1; index < chat.length; index++) {
-    if (isAssistantChatMessage(chat[index])) {
-      assistantTurns.push(index);
-    }
-  }
-  return assistantTurns;
-}
-
-function buildExtractionMessages(chat, startIdx, endIdx, settings) {
-  const contextTurns = clampInt(settings.extractContextTurns, 2, 0, 20);
-  const contextStart = Math.max(0, startIdx - contextTurns * 2);
-  const messages = [];
-
-  for (
-    let index = contextStart;
-    index <= endIdx && index < chat.length;
-    index++
-  ) {
-    const msg = chat[index];
-    if (msg.is_system) continue;
-    messages.push({
-      seq: index,
-      role: msg.is_user ? "user" : "assistant",
-      content: msg.mes || "",
-    });
-  }
-
-  return messages;
-}
-
-function getChatIndexForPlayableSeq(chat, playableSeq) {
-  if (!Array.isArray(chat) || !Number.isFinite(playableSeq)) return null;
-
-  let currentSeq = -1;
-  for (let index = 0; index < chat.length; index++) {
-    const message = chat[index];
-    if (message?.is_system) continue;
-    currentSeq++;
-    if (currentSeq >= playableSeq) {
-      return index;
-    }
-  }
-
-  return chat.length;
-}
-
-function getChatIndexForAssistantSeq(chat, assistantSeq) {
-  if (!Array.isArray(chat) || !Number.isFinite(assistantSeq)) return null;
-
-  let currentSeq = -1;
-  for (let index = 0; index < chat.length; index++) {
-    if (!isAssistantChatMessage(chat[index])) continue;
-    currentSeq++;
-    if (currentSeq >= assistantSeq) {
-      return index;
-    }
-  }
-
-  return chat.length;
-}
-
-function resolveDirtyFloorFromMutationMeta(trigger, primaryArg, meta, chat) {
-  if (!meta || typeof meta !== "object") return null;
-
-  const candidates = [];
-  const isDeleteTrigger = String(trigger || "").includes("message-deleted");
-  const minExtractableFloor = getMinExtractableAssistantFloor(chat);
-
-  // 删除后 chat 已是收缩后的状态，删除事件携带的 seq 更接近“被删区间起点”，
-  // 因此这里额外向前退一层，避免恢复仍停留在被删楼层对应的旧图谱边界。
-  if (!isDeleteTrigger && Number.isFinite(meta.messageId)) {
-    candidates.push({
-      floor: meta.messageId,
-      source: `${trigger}-meta`,
-    });
-  }
-  if (Number.isFinite(meta.deletedPlayableSeqFrom)) {
-    const floor = getChatIndexForPlayableSeq(chat, meta.deletedPlayableSeqFrom);
-    if (Number.isFinite(floor)) {
-      candidates.push({
-        floor: Number.isFinite(minExtractableFloor)
-          ? Math.max(minExtractableFloor, floor - 1)
-          : Math.max(0, floor - 1),
-        source: `${trigger}-meta-delete-boundary`,
-      });
-    }
-  }
-  if (Number.isFinite(meta.deletedAssistantSeqFrom)) {
-    const floor = getChatIndexForAssistantSeq(
-      chat,
-      meta.deletedAssistantSeqFrom,
-    );
-    if (Number.isFinite(floor)) {
-      candidates.push({
-        floor: Number.isFinite(minExtractableFloor)
-          ? Math.max(minExtractableFloor, floor - 1)
-          : Math.max(0, floor - 1),
-        source: `${trigger}-meta-delete-boundary`,
-      });
-    }
-  }
-  if (!isDeleteTrigger && Number.isFinite(meta.playableSeq)) {
-    const floor = getChatIndexForPlayableSeq(chat, meta.playableSeq);
-    if (Number.isFinite(floor)) {
-      candidates.push({
-        floor,
-        source: `${trigger}-meta`,
-      });
-    }
-  }
-  if (!isDeleteTrigger && Number.isFinite(meta.assistantSeq)) {
-    const floor = getChatIndexForAssistantSeq(chat, meta.assistantSeq);
-    if (Number.isFinite(floor)) {
-      candidates.push({
-        floor,
-        source: `${trigger}-meta`,
-      });
-    }
-  }
-  if (!isDeleteTrigger && Number.isFinite(primaryArg)) {
-    candidates.push({
-      floor: primaryArg,
-      source: `${trigger}-meta`,
-    });
-  }
-
-  if (candidates.length === 0) return null;
-  const validCandidates = Number.isFinite(minExtractableFloor)
-    ? candidates.filter((c) => c.floor >= minExtractableFloor)
-    : candidates;
-  if (validCandidates.length === 0) return null;
-  return validCandidates.reduce((earliest, current) =>
-    current.floor < earliest.floor ? current : earliest,
-  );
-}
-
-function getLastProcessedAssistantFloor() {
-  ensureCurrentGraphRuntimeState();
-  return Number.isFinite(
-    currentGraph?.historyState?.lastProcessedAssistantFloor,
-  )
-    ? currentGraph.historyState.lastProcessedAssistantFloor
-    : -1;
-}
-
-function getMinExtractableAssistantFloor(chat) {
-  const assistantTurns = getAssistantTurns(chat);
-  return assistantTurns.length > 0 ? assistantTurns[0] : null;
-}
-
-function clampRecoveryStartFloor(chat, floor) {
-  if (!Number.isFinite(floor)) return floor;
-
-  const minExtractableFloor = getMinExtractableAssistantFloor(chat);
-  if (!Number.isFinite(minExtractableFloor)) {
-    return floor;
-  }
-
-  return Math.max(floor, minExtractableFloor);
-}
-
 function notifyHistoryDirty(dirtyFrom, reason) {
   updateStageNotice(
     "history",
@@ -4152,30 +3996,6 @@ function applyRecoveryPlanToVectorState(
     : "历史恢复后需要修复受影响后缀的向量索引";
 }
 
-function rollbackAffectedJournals(graph, affectedJournals = []) {
-  for (let index = affectedJournals.length - 1; index >= 0; index--) {
-    rollbackBatch(graph, affectedJournals[index]);
-  }
-  graph.batchJournal = Array.isArray(graph.batchJournal)
-    ? graph.batchJournal.slice(
-        0,
-        Math.max(0, graph.batchJournal.length - affectedJournals.length),
-      )
-    : [];
-}
-
-function pruneProcessedMessageHashesFromFloor(graph, fromFloor) {
-  if (!graph?.historyState?.processedMessageHashes) return;
-  if (!Number.isFinite(fromFloor)) return;
-
-  const hashes = graph.historyState.processedMessageHashes;
-  for (const key of Object.keys(hashes)) {
-    if (Number(key) >= fromFloor) {
-      delete hashes[key];
-    }
-  }
-}
-
 async function rollbackGraphForReroll(targetFloor, context = getContext()) {
   ensureCurrentGraphRuntimeState();
   const chatId = getCurrentChatId(context);
diff --git a/tests/p0-regressions.mjs b/tests/p0-regressions.mjs
index 101676c..5a810f6 100644
--- a/tests/p0-regressions.mjs
+++ b/tests/p0-regressions.mjs
@@ -42,6 +42,17 @@ import {
   writeChatMetadataPatch,
   writeGraphShadowSnapshot,
 } from "../graph-persistence.js";
+import {
+  buildExtractionMessages,
+  clampRecoveryStartFloor,
+  getAssistantTurns,
+  getChatIndexForAssistantSeq,
+  getChatIndexForPlayableSeq,
+  getMinExtractableAssistantFloor,
+  isAssistantChatMessage,
+  pruneProcessedMessageHashesFromFloor,
+  rollbackAffectedJournals,
+} from "../chat-history.js";
 
 const extensionsShimSource = [
   "export const extension_settings = globalThis.__p0ExtensionSettings || {};",
@@ -180,7 +191,7 @@ const schema = [
 
 function createBatchStageHarness() {
   return fs.readFile(indexPath, "utf8").then((source) => {
-    const marker = "function isAssistantChatMessage(message) {";
+    const marker = "function notifyHistoryDirty(dirtyFrom, reason) {";
     const start = source.indexOf("function shouldAdvanceProcessedHistory(");
     const end = source.indexOf(marker);
     if (start < 0 || end < 0 || end <= start) {
@@ -309,26 +320,21 @@ function createGenerationRecallHarness() {
 
 function createRerollHarness() {
   return fs.readFile(indexPath, "utf8").then((source) => {
-    const helperStart = source.indexOf(
-      "function pruneProcessedMessageHashesFromFloor(",
-    );
-    const helperEnd = source.indexOf("async function recoverHistoryIfNeeded(");
+    const rollbackStart = source.indexOf("async function rollbackGraphForReroll(");
+    const rollbackEnd = source.indexOf("async function recoverHistoryIfNeeded(");
     const rerollStart = source.indexOf("async function onReroll(");
     const rerollEnd = source.indexOf("async function onManualSleep()");
     if (
-      helperStart < 0 ||
-      helperEnd < 0 ||
+      rollbackStart < 0 ||
+      rollbackEnd < 0 ||
       rerollStart < 0 ||
       rerollEnd < 0 ||
-      helperEnd <= helperStart ||
+      rollbackEnd <= rollbackStart ||
       rerollEnd <= rerollStart
     ) {
       throw new Error("无法从 index.js 提取 reroll 定义");
     }
-    const snippet = [
-      source.slice(helperStart, helperEnd),
-      source.slice(rerollStart, rerollEnd),
-    ]
+    const snippet = [source.slice(rollbackStart, rollbackEnd), source.slice(rerollStart, rerollEnd)]
       .join("\n")
       .replace(/^export\s+/gm, "");
     const context = {
@@ -414,6 +420,9 @@ function createRerollHarness() {
       async deleteBackendVectorHashesForRecovery(...args) {
         context.deletedHashesCalls.push(args);
       },
+      pruneProcessedMessageHashesFromFloor(graph, fromFloor) {
+        return pruneProcessedMessageHashesFromFloor(graph, fromFloor);
+      },
       async prepareVectorStateForReplay(...args) {
         context.prepareVectorStateCalls.push(args);
       },
@@ -459,7 +468,7 @@ function createRerollHarness() {
     };
     vm.createContext(context);
     vm.runInContext(
-      `${snippet}\nresult = { pruneProcessedMessageHashesFromFloor, rollbackGraphForReroll, onReroll };`,
+      `${snippet}\nresult = { rollbackGraphForReroll, onReroll };`,
       context,
       { filename: indexPath },
     );