fix(sftp): omit stale listing size after re-stat failure

When source re-stat fails, clear child totalBytes/mtime so
startStreamTransfer omits an explicit snapshot and the bridge
re-stats on the dedicated session instead of truncating to the
stale listing size.

Co-authored-by: 陈大猫 <binaricat@users.noreply.github.com>

application/state/sftp/transferDirectoryFileBatch.test.ts

@@ -111,6 +111,8 @@ test("transferDiscoveredFiles does not skip when source re-stat fails", async ()
   } as MutableRefObject<Map<string, Set<string>>>;
   let transfers = transfersRef.current;
   let transferCalls = 0;
+  let transferredTotalBytes: number | undefined;
+  let transferredSourceLastModified: number | undefined;
   const mtime = 1_700_000_000_000;
 
   await transferDiscoveredFiles({
@@ -140,8 +142,10 @@ test("transferDiscoveredFiles does not skip when source re-stat fails", async ()
     },
     waitWhileTransferPaused: async () => {},
     isPauseLatched: () => false,
-    transferFile: async () => {
+    transferFile: async (task) => {
       transferCalls += 1;
+      transferredTotalBytes = task.totalBytes;
+      transferredSourceLastModified = task.sourceLastModified;
     },
     tryStatTarget: async () => ({
       size: 10,
@@ -152,6 +156,12 @@ test("transferDiscoveredFiles does not skip when source re-stat fails", async ()
   });
 
   assert.equal(transferCalls, 1, "missing fresh source meta must not skip");
+  assert.equal(transferredTotalBytes, 0, "must not pass stale listing size after re-stat failure");
+  assert.equal(
+    transferredSourceLastModified,
+    undefined,
+    "must clear stale listing mtime after re-stat failure",
+  );
 });
 
 test("transferDiscoveredFiles skips only when fresh source still matches", async () => {

application/state/sftp/transferDirectoryFileBatch.ts

@@ -147,6 +147,12 @@ export async function transferDiscoveredFiles(
             lastModified: skipSourceLastModified,
           });
           freshSourceOk = true;
+        } else {
+          // Do not pass stale pre-scan size as an explicit snapshot (Codex P2).
+          // Child totalBytes 0 is omitted at startStreamTransfer via `|| undefined`,
+          // so the dedicated transfer session re-stats the source itself.
+          skipSourceSize = 0;
+          skipSourceLastModified = 0;
         }
       }
       if (skipUnchanged && !file.isSymlink && freshSourceOk) {
@@ -224,7 +230,7 @@ export async function transferDiscoveredFiles(
         progressMode: "bytes",
         parentTaskId: rootTaskId,
         totalBytes: skipSourceSize,
-        sourceLastModified: skipSourceLastModified,
+        sourceLastModified: skipSourceLastModified || undefined,
         directoryEntryIndex,
         directoryEntryIdentity,
         retryable: rootTask.retryable,

application/state/sftp/transferDirectoryOps.ts

@@ -895,6 +895,13 @@ export function useSftpDirectoryTransferOps({
                 lastModified: transferLastModified,
               });
               freshSourceOk = true;
+            } else {
+              // Do not pass stale listing size as an explicit snapshot: the
+              // dedicated transfer session may still read a grown file (Codex P2).
+              // Child totalBytes 0 is omitted at startStreamTransfer via
+              // `|| undefined`, so the bridge re-stats instead of truncating.
+              transferSize = 0;
+              transferLastModified = 0;
             }
           }
 
@@ -984,7 +991,7 @@ export function useSftpDirectoryTransferOps({
             progressMode: "bytes",
             parentTaskId: rootTaskId,
             totalBytes: transferSize,
-            sourceLastModified: transferLastModified,
+            sourceLastModified: transferLastModified || undefined,
             directoryEntryIndex,
             directoryEntryIdentity,
             // Inherit retryable from parent - downloadToLocal sets retryable: false