From 6495bece3a354c642f6570ee0d691c8b7d8b76f0 Mon Sep 17 00:00:00 2001
From: Lebing Xie <pingp76@yahoo.com>
Date: Mon, 15 Jun 2026 16:37:07 +0800
Subject: [PATCH] fix compressor summary duplication

---
 src/compressor.test.ts | 32 ++++++++++++++++++++++++++++++++
 src/compressor.ts      | 13 ++++++-------
 2 files changed, 38 insertions(+), 7 deletions(-)

diff --git a/src/compressor.test.ts b/src/compressor.test.ts
index a85e5da..ec9b97a 100644
--- a/src/compressor.test.ts
+++ b/src/compressor.test.ts
@@ -89,6 +89,11 @@ function makeSummaryBlock(summaryText: string, round?: number): MessageBlock {
   return block;
 }
 
+/** 统计子串出现次数，用于断言 P2 不会把同一段摘要重复拼接。 */
+function countOccurrences(text: string, needle: string): number {
+  return text.split(needle).length - 1;
+}
+
 // ---------------------------------------------------------------------------
 // P0 衰减压缩
 // ---------------------------------------------------------------------------
@@ -562,6 +567,33 @@ describe("compactHistory (P2)", () => {
       const content = (summaryBlock.user as { content: string }).content;
       // 第二次 summary 应该包含第一次 summary 的内容
       expect(content).toContain("[Context Summary]");
+      // 但不能同时从 lastSummary 闭包和 summary block 各拼一次。
+      expect(countOccurrences(content, "User: q1")).toBe(1);
+    }
+  });
+
+  it("does not duplicate cached summary when raw history is compacted again", () => {
+    const compressor = createContextCompressor({ compactKeepRecent: 1 });
+
+    // prepareMessages 路径只压缩本次请求视图，不会把 summary 写回 history。
+    // 因此第二次压缩时传入的仍是完整原始 history；如果再拼 lastSummary，
+    // q1/q2 会既来自闭包摘要，又来自原始 oldBlocks，造成重复膨胀。
+    compressor.compactHistory([
+      makeTextBlock("q1", "a1", 1),
+      makeTextBlock("q2", "a2", 2),
+    ]);
+
+    const result = compressor.compactHistory([
+      makeTextBlock("q1", "a1", 1),
+      makeTextBlock("q2", "a2", 2),
+      makeTextBlock("q3", "a3", 3),
+    ]);
+
+    const summaryBlock = result.blocks[0]!;
+    if (summaryBlock.type === "summary") {
+      const content = (summaryBlock.user as { content: string }).content;
+      expect(countOccurrences(content, "User: q1")).toBe(1);
+      expect(countOccurrences(content, "User: q2")).toBe(1);
     }
   });
 
diff --git a/src/compressor.ts b/src/compressor.ts
index 8233092..75c8113 100644
--- a/src/compressor.ts
+++ b/src/compressor.ts
@@ -345,12 +345,6 @@ export function createContextCompressor(
       // 按类型遍历旧块，提取关键信息构建摘要文本
       const summaryLines: string[] = [];
 
-      // 如果之前已有摘要，先加入，实现多层摘要的级联压缩
-      if (lastSummary) {
-        summaryLines.push(lastSummary);
-        summaryLines.push("---");
-      }
-
       for (const block of oldBlocks) {
         if (block.type === "text") {
           const userContent = block.user ? extractText(block.user) : "";
@@ -386,7 +380,12 @@ export function createContextCompressor(
             }
           });
         } else if (block.type === "summary") {
-          // 之前的 summary 块：保留其文本，纳入新摘要
+          // 之前的 summary 块：保留其文本，纳入新摘要。
+          // 注意：lastSummary 只作为 getState() 的状态快照，不再作为摘要输入源。
+          // compactHistory(blocks) 的语义是“总结本次传入的完整 block 视图”：
+          // - prepareMessages 路径不会写回 history，下一次传入的 blocks 仍包含原始旧消息；
+          // - recovery 写回路径会把旧摘要作为 summary block 放回 history。
+          // 如果再额外拼闭包缓存，就会把同一段旧摘要重复写入新 summary。
           summaryLines.push(extractText(block.user));
         }
       }