diff --git a/app/main.js b/app/main.js
index 42e9fed..d1d2b19 100644
--- a/app/main.js
+++ b/app/main.js
@@ -46,10 +46,12 @@ async function main() {
   }
 
   step('Step2', 'PR 對話收斂');
-  let reconcile = { resolvedFindings: [], carriedFindings: [], resolvedCount: 0, unresolvedCount: 0 };
+  let reconcile = { resolvedFindings: [], carriedFindings: [], resolvedCount: 0, duplicateCount: 0, unresolvedCount: 0 };
   try {
-    reconcile = await reconcileConversations();
-    ok(`Step2 完成: resolved=${reconcile.resolvedCount} unresolved=${reconcile.unresolvedCount} 加回=${reconcile.carriedFindings.length}`);
+    // 載入來源分支既有的舊問題，供對話收斂判斷「未修復但已存在於舊問題」的情況
+    const oldFindingsForReconcile = loadOldFindings(WORKSPACE);
+    reconcile = await reconcileConversations({ oldFindings: oldFindingsForReconcile });
+    ok(`Step2 完成: resolved=${reconcile.resolvedCount} duplicate=${reconcile.duplicateCount} 加回=${reconcile.carriedFindings.length}`);
   } catch (e) {
     warn(`Step2 對話收斂失敗（繼續執行）: ${e.message}`);
   }
diff --git a/app/resolve.js b/app/resolve.js
index 1ddac94..409fc31 100644
--- a/app/resolve.js
+++ b/app/resolve.js
@@ -134,11 +134,12 @@ function isSafeRepoPath(p) {
 }
 
 /**
- * 對話收斂主流程：
- * 1. 取得 PR 所有行內 review comment，收斂成對話，跳過已 resolve 的；
- * 2. 取每個對話所在檔案的最新內容，請 AI 判斷問題是否已解決；
- * 3. 已解決者呼叫 Gitea resolve API 解決對話，並記錄其 finding（供移除舊問題）；
- * 4. 未解決且可解析為 bot finding 者，收集為「加回問題列表」清單。
+ * 對話收斂主流程：取得 PR 所有行內 review comment、收斂成對話、跳過已 resolve 的，
+ * 取最新程式碼請 AI 判斷後，對每個待判斷對話做下列處置：
+ * 1. 程式碼已修復（AI 判定已解決）→ 解決對話，並記錄其 finding 供從舊問題移除；
+ * 2. 未修復但已存在於舊問題（以檔案＋建議簽章比對）→ 解決對話（已被追蹤，不重複加回）；
+ * 3. 未修復且不在舊問題 → 不解決對話，將其 finding 加入舊問題集合（carriedFindings）。
+ * deps.oldFindings 提供來源分支既有的舊問題清單以供第 2 步比對。
  * 任一外部呼叫失敗都降級處理（保守視為未解決），不中斷整體 pipeline。
  */
 export async function reconcileConversations(deps = {}) {
@@ -147,6 +148,7 @@ export async function reconcileConversations(deps = {}) {
     resolveComment = resolvePullReviewComment,
     getFileContent = getFileContentAtRef,
     judge = judgeConversationsResolved,
+    oldFindings = [],
   } = deps;
 
   let comments;
@@ -196,39 +198,63 @@ export async function reconcileConversations(deps = {}) {
     verdicts = items.map(it => ({ idx: it.idx, resolved: false }));
   }
   const resolvedSet = new Set(verdicts.filter(v => v.resolved).map(v => v.idx));
+  const oldSigs = new Set((oldFindings || []).map(findingSig));
 
-  const resolvedFindings = [];
-  const carriedFindings = [];
+  // 分類每個待判斷對話：
+  // - 'resolved'：程式碼已修復 → 解決對話，並從舊問題移除
+  // - 'duplicate'：未修復但已存在於舊問題 → 解決對話（不重複加回）
+  // - 'carry'：未修復且不在舊問題 → 加入舊問題集合（不解決對話）
+  const dispositions = open.map((c, i) => {
+    if (resolvedSet.has(i)) return 'resolved';
+    const sig = c.botFinding ? findingSig(c.botFinding) : null;
+    if (sig && oldSigs.has(sig)) return 'duplicate';
+    return 'carry';
+  });
 
-  // 並行 resolve 所有 AI 判定已解決的對話（allSettled：個別失敗不中斷其他）
+  // 並行對 resolved 與 duplicate 的對話呼叫 resolve API（allSettled：個別失敗不中斷其他）
   const resolveTargets = open
     .map((c, i) => ({ c, i }))
-    .filter(({ i }) => resolvedSet.has(i));
+    .filter(({ i }) => dispositions[i] === 'resolved' || dispositions[i] === 'duplicate');
   const settled = await Promise.allSettled(
     resolveTargets.map(({ c }) => resolveComment(c.commentIds[0])),
   );
   const resolveOutcome = new Map();
   resolveTargets.forEach(({ i }, j) => resolveOutcome.set(i, settled[j]));
 
+  const resolvedFindings = [];
+  const carriedFindings = [];
   let resolvedCount = 0;
+  let duplicateCount = 0;
   for (let i = 0; i < open.length; i++) {
     const c = open[i];
-    const outcome = resolveOutcome.get(i);
-    if (outcome?.status === 'fulfilled') {
-      resolvedCount += 1;
-      if (c.botFinding) resolvedFindings.push({ ...c.botFinding, is_new: false });
-      ok(`對話已解決並 resolve: ${c.path}:${c.line}`);
+    const disp = dispositions[i];
+
+    if (disp === 'carry') {
+      pushCarried(carriedFindings, c);
       continue;
     }
-    if (outcome?.status === 'rejected') {
-      warn(`resolve 對話失敗（保留為未解決）: ${c.path}:${c.line} error=${outcome.reason?.message}`);
+
+    const outcome = resolveOutcome.get(i);
+    if (outcome?.status === 'fulfilled') {
+      if (disp === 'resolved') {
+        resolvedCount += 1;
+        if (c.botFinding) resolvedFindings.push({ ...c.botFinding, is_new: false });
+        ok(`對話已解決並 resolve（程式碼已修復）: ${c.path}:${c.line}`);
+      } else {
+        duplicateCount += 1;
+        ok(`對話已解決並 resolve（已存在於舊問題）: ${c.path}:${c.line}`);
+      }
+      continue;
     }
-    pushCarried(carriedFindings, c);
+
+    warn(`resolve 對話失敗: ${c.path}:${c.line} error=${outcome?.reason?.message}`);
+    // resolved 但無法關閉對話時，保守加回舊問題避免遺漏；duplicate 本就在舊問題中，無須加回
+    if (disp === 'resolved') pushCarried(carriedFindings, c);
   }
 
   const unresolvedCount = open.length - resolvedCount;
-  ok(`對話收斂完成: resolved=${resolvedCount} unresolved=${unresolvedCount} 加回 findings=${carriedFindings.length}`);
-  return { resolvedFindings, carriedFindings, resolvedCount, unresolvedCount };
+  ok(`對話收斂完成: 已修復 resolved=${resolvedCount} 已存在舊問題 duplicate=${duplicateCount} 加入舊問題 carried=${carriedFindings.length}`);
+  return { resolvedFindings, carriedFindings, resolvedCount, duplicateCount, unresolvedCount };
 }
 
 function fileOf(location) {