From 34fe60004d39da185a4f9eba6ac0f9a5ac279e13 Mon Sep 17 00:00:00 2001
From: Jinwoo-H <jinwoo0825@gmail.com>
Date: Sun, 23 Aug 2026 06:24:10 -0400
Subject: [PATCH] fix(native-chat): reject coarse-mtime rewrites

---
 .../native-chat/ssh-transcript-range-fs.test.ts     | 13 +++++++++++++
 src/main/native-chat/ssh-transcript-range-fs.ts     |  4 +++-
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/main/native-chat/ssh-transcript-range-fs.test.ts b/src/main/native-chat/ssh-transcript-range-fs.test.ts
index d0113912d76..13e981a2972 100644
--- a/src/main/native-chat/ssh-transcript-range-fs.test.ts
+++ b/src/main/native-chat/ssh-transcript-range-fs.test.ts
@@ -93,4 +93,17 @@ describe('SSH transcript range stability', () => {
       TranscriptRangeReadInvalidatedError
     )
   })
+
+  it('rejects a same-length rewrite even when remote mtime is coarse', async () => {
+    const remote = mutableProvider('old generation')
+    mocks.provider = remote.provider
+    const rangeFs = await createSshTranscriptRangeFs('ssh-owner')
+    const openingStamp = await rangeFs.stat(TRANSCRIPT_PATH, undefined, true)
+
+    remote.replace('new generation', false)
+
+    await expect(rangeFs.assertStable(TRANSCRIPT_PATH, openingStamp)).rejects.toBeInstanceOf(
+      TranscriptRangeReadInvalidatedError
+    )
+  })
 })
diff --git a/src/main/native-chat/ssh-transcript-range-fs.ts b/src/main/native-chat/ssh-transcript-range-fs.ts
index 92bb5e33cc2..de5027d9578 100644
--- a/src/main/native-chat/ssh-transcript-range-fs.ts
+++ b/src/main/native-chat/ssh-transcript-range-fs.ts
@@ -109,7 +109,9 @@ export async function createSshTranscriptRangeFs(
         if (versionChanged) {
           throw new TranscriptRangeReadInvalidatedError()
         }
-        return
+        if (openingStamp.size === 0) {
+          return
+        }
       }
       if (!openingStamp.boundaryFingerprint) {
         throw new TranscriptRangeReadInvalidatedError()