From e58f995faebbe9eb29b83048a26ff74c1e0f0b09 Mon Sep 17 00:00:00 2001
From: ytahdn <1294726970@qq.com>
Date: Thu, 23 Jul 2026 16:37:35 +0800
Subject: [PATCH] fix(core): avoid empty transcript history pages (#7582)
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Co-authored-by: 钉萁 <dingqi.jww@alibaba-inc.com>
---
 .../session-transcript-reader.test.ts         | 26 +++++++++++++
 .../src/services/session-transcript-reader.ts | 38 +++++++++++++------
 2 files changed, 52 insertions(+), 12 deletions(-)

diff --git a/packages/core/src/services/session-transcript-reader.test.ts b/packages/core/src/services/session-transcript-reader.test.ts
index e0435446d4..7eed032326 100644
--- a/packages/core/src/services/session-transcript-reader.test.ts
+++ b/packages/core/src/services/session-transcript-reader.test.ts
@@ -329,6 +329,32 @@ describe('SessionTranscriptReader', () => {
     });
   });
 
+  it('includes leading session metadata with the first backward page', async () => {
+    const sessionSource = {
+      ...record('source', null, 'session source'),
+      type: 'system' as const,
+      subtype: 'session_source' as const,
+    };
+    await writeRecords([
+      sessionSource,
+      record('u1', 'source', 'first prompt'),
+      record('a1', 'u1', 'first answer'),
+    ]);
+
+    const page = await new SessionTranscriptReader(workspaceDir).readPage(
+      sessionId,
+      { direction: 'backward', limit: 100 },
+    );
+
+    expect(page.records.map((item) => item.uuid)).toEqual([
+      'source',
+      'u1',
+      'a1',
+    ]);
+    expect(page.hasMore).toBe(false);
+    expect(page.nextCursorState).toBeUndefined();
+  });
+
   it('keeps backward pages within a normal user turn boundary', async () => {
     const toolCall = record('a-tool', 'u1', 'call tool');
     const toolResult = {
diff --git a/packages/core/src/services/session-transcript-reader.ts b/packages/core/src/services/session-transcript-reader.ts
index 14a0e3673b..e3ef8ffcf3 100644
--- a/packages/core/src/services/session-transcript-reader.ts
+++ b/packages/core/src/services/session-transcript-reader.ts
@@ -517,24 +517,38 @@ function selectBackwardPageUuids(
       break;
     }
   }
-  if (!alignedToReplayBoundary) {
+  let expandedSelection = false;
+  if (alignedToReplayBoundary && selectedStart > 0) {
+    let previousTurnStart = selectedStart - 1;
+    while (
+      previousTurnStart >= 0 &&
+      !isReplayTurnStart(index, index.activeUuids[previousTurnStart]!)
+    ) {
+      previousTurnStart--;
+    }
+    if (previousTurnStart < 0) {
+      selectedStart = 0;
+      expandedSelection = true;
+    }
+  } else if (!alignedToReplayBoundary) {
     while (
       selectedStart > 0 &&
       !isReplayTurnStart(index, index.activeUuids[selectedStart]!)
     ) {
       selectedStart--;
     }
-    if (maxBytes !== undefined) {
-      const alignedBytes = index.activeUuids
-        .slice(selectedStart, position)
-        .reduce((total, uuid) => total + recordSegmentBytes(index, uuid), 0);
-      if (alignedBytes > maxBytes) {
-        throw new SessionTranscriptPageTooLargeError(
-          sessionId,
-          alignedBytes,
-          maxBytes,
-        );
-      }
+    expandedSelection = true;
+  }
+  if (expandedSelection && maxBytes !== undefined) {
+    const alignedBytes = index.activeUuids
+      .slice(selectedStart, position)
+      .reduce((total, uuid) => total + recordSegmentBytes(index, uuid), 0);
+    if (alignedBytes > maxBytes) {
+      throw new SessionTranscriptPageTooLargeError(
+        sessionId,
+        alignedBytes,
+        maxBytes,
+      );
     }
   }