fix(sandbox): sync same-size E2B output updates (#4329)

* fix(sandbox): detect same-size E2B output updates

* test(sandbox): cover E2B output modification times

* fix(sandbox): persist E2B output sync versions

* test(sandbox): cover E2B output sync manifest

* docs(backend): document E2B sync manifest

* fix(sandbox): scope E2B sync manifests

* test(sandbox): cover E2B sync manifest lifecycle

* docs(backend): describe E2B manifest lifecycle

* fix(sandbox): fall back from empty E2B sandbox ID

* test(sandbox): cover empty E2B sandbox IDs

* docs: clarify E2B output sync ownership

backend/AGENTS.md

@@ -464,6 +464,8 @@ Scheduled-task runtime note:
 
 Additional providers also live here (`boxlite`, `brave`, `browserless`, `crawl4ai`, `ddg_search`, `e2b_sandbox`, `exa`, `fastcrw`, `groundroute`, `infoquest`, `searxng`, `serper`); see each subpackage for specifics. E2B bootstrap is required. If it fails, the provider kills and closes the unusable remote sandbox. New sandbox creation raises an error. Warm-pool reclaim and remote discovery discard the sandbox and continue acquisition. E2B mounts remain optional.
 
+E2B output sync records remote file versions and actual host file metadata in a thread-local manifest. The manifest binds to the remote sandbox ID. A complete output listing removes entries for deleted files. This avoids repeat downloads when the host filesystem rounds modification times.
+
 **ACP agent tools**:
 - `invoke_acp_agent` - Invokes external ACP-compatible agents from `config.yaml`
 - ACP launchers must be real ACP adapters. The standard `codex` CLI is not ACP-compatible by itself; configure a wrapper such as `npx -y @zed-industries/codex-acp` or an installed `codex-acp` binary

backend/packages/harness/deerflow/community/e2b_sandbox/e2b_sandbox.py

@@ -74,7 +74,7 @@ class E2BSandbox(Sandbox):
     @property
     def sandbox_id(self) -> str:
         """e2b-side sandbox id (different from DeerFlow's ``self.id`` cache key)."""
-        return getattr(self._client, "sandbox_id", self.id)
+        return getattr(self._client, "sandbox_id", None) or self.id
 
     def close(self) -> None:
         with self._lock:

backend/packages/harness/deerflow/community/e2b_sandbox/e2b_sandbox_provider.py

@@ -26,6 +26,7 @@ from __future__ import annotations
 import asyncio
 import atexit
 import hashlib
+import json
 import logging
 import os
 import shlex
@@ -34,6 +35,7 @@ import threading
 import time
 import uuid
 from collections import OrderedDict
+from decimal import Decimal, InvalidOperation
 from pathlib import Path
 from typing import Any
 
@@ -716,6 +718,52 @@ class E2BSandboxProvider(SandboxProvider):
 
     # ── Output mirroring ────────────────────────────────────────────────
     _SYNC_BACK_SUBDIRS = ("outputs", "workspace")
+    _SYNC_MANIFEST_NAME = ".e2b-output-sync.json"
+
+    @staticmethod
+    def _load_sync_manifest(manifest_path: Path, sandbox_id: str) -> tuple[dict[str, dict[str, int]], bool]:
+        """Load verified remote and host versions from a prior output sync."""
+        try:
+            data = json.loads(manifest_path.read_text(encoding="utf-8"))
+        except FileNotFoundError:
+            return {}, False
+        except (OSError, json.JSONDecodeError) as e:
+            logger.warning("e2b sync: failed to load manifest %s: %s", manifest_path, e)
+            return {}, True
+
+        if not isinstance(data, dict) or data.get("version") != 1 or not isinstance(data.get("files"), dict):
+            logger.warning("e2b sync: ignoring invalid manifest %s", manifest_path)
+            return {}, True
+        if data.get("sandbox_id") != sandbox_id:
+            logger.debug("e2b sync: ignoring manifest from another sandbox %s", manifest_path)
+            return {}, True
+
+        files: dict[str, dict[str, int]] = {}
+        for key, value in data["files"].items():
+            if not isinstance(key, str) or not isinstance(value, dict):
+                continue
+            required = ("remote_size", "remote_mtime_ns", "host_size", "host_mtime_ns")
+            if all(isinstance(value.get(field), int) for field in required):
+                files[key] = {field: value[field] for field in required}
+        return files, False
+
+    @staticmethod
+    def _write_sync_manifest(
+        manifest_path: Path,
+        sandbox_id: str,
+        files: dict[str, dict[str, int]],
+    ) -> None:
+        """Atomically store output-sync versions after host files are written."""
+        try:
+            manifest_path.parent.mkdir(parents=True, exist_ok=True)
+            tmp_path = manifest_path.with_name(f"{manifest_path.name}.tmp")
+            tmp_path.write_text(
+                json.dumps({"version": 1, "sandbox_id": sandbox_id, "files": files}, sort_keys=True),
+                encoding="utf-8",
+            )
+            tmp_path.replace(manifest_path)
+        except OSError as e:
+            logger.warning("e2b sync: failed to write manifest %s: %s", manifest_path, e)
 
     def _sync_outputs_to_host(
         self,
@@ -733,11 +781,14 @@ class E2BSandboxProvider(SandboxProvider):
         local provider. The e2b VM has no shared host filesystem, so we
         explicitly pull artifacts back at release time.
 
-        We only mirror files whose host-side counterpart is missing or has a
-        different size — this gives an effective per-file dedup with a single
-        round-trip per release for unchanged trees, and avoids re-downloading
-        large generated files (e.g. PDFs, datasets) on every tool turn that
-        triggers a release.
+        We mirror files whose host-side counterpart is missing, has a different
+        size, or has a different remote modification time. A thread-local
+        manifest stores the remote version and the actual host metadata after
+        each write. This avoids false updates on host filesystems that round
+        modification times.
+
+        The remote file is the source of truth. The next sync overwrites a
+        host-side edit when its size or modification time differs.
 
         Failures are logged at WARNING level but never raised: artifact
         download is non-critical for sandbox lifecycle, and we already log
@@ -753,13 +804,17 @@ class E2BSandboxProvider(SandboxProvider):
         home_dir = sandbox.home_dir.rstrip("/") or "/home/user"
         paths = get_paths()
 
-        thread_root = paths.thread_dir(thread_id, user_id=user_id) / "user-data"
+        thread_dir = paths.thread_dir(thread_id, user_id=user_id)
+        thread_root = thread_dir / "user-data"
         host_targets: dict[str, Path] = {sub: thread_root / sub for sub in self._SYNC_BACK_SUBDIRS}
+        manifest_path = thread_dir / self._SYNC_MANIFEST_NAME
+        remote_sandbox_id = sandbox.sandbox_id
+        manifest, manifest_dirty = self._load_sync_manifest(manifest_path, remote_sandbox_id)
 
         # Build a single shell command that lists all files in the sync dirs
-        # with size + path, NUL-separated for safe parsing of weird filenames.
-        # find -printf '%s\t%p\0' keeps us to one round-trip regardless of
-        # how many subdirs we mirror.
+        # with size, modification time, and path, NUL-separated for safe
+        # parsing of weird filenames. This keeps us to one round-trip
+        # regardless of how many subdirs we mirror.
         #
         # We list using the *physical* /home/user paths (the bootstrap symlink
         # /mnt/user-data -> /home/user follows transparently), then translate
@@ -768,7 +823,7 @@ class E2BSandboxProvider(SandboxProvider):
         # that the path is under ``VIRTUAL_PATH_PREFIX`` (/mnt/user-data) and
         # internally re-resolves it to /home/user via ``_resolve_path``.
         find_targets = " ".join(shlex.quote(f"{home_dir}/{sub}") for sub in self._SYNC_BACK_SUBDIRS)
-        list_cmd = f'for d in {find_targets}; do   [ -d "$d" ] && find "$d" -type f -printf \'%s\\t%p\\0\' 2>/dev/null; done'
+        list_cmd = f'for d in {find_targets}; do   [ -d "$d" ] && find "$d" -type f -printf \'%s\\t%T@\\t%p\\0\' 2>/dev/null; done'
 
         try:
             result = client.commands.run(list_cmd)
@@ -781,10 +836,13 @@ class E2BSandboxProvider(SandboxProvider):
 
         stdout = getattr(result, "stdout", "") or ""
         if not stdout:
+            if manifest or manifest_dirty:
+                self._write_sync_manifest(manifest_path, remote_sandbox_id, {})
             return
 
         synced = 0
         skipped = 0
+        seen_manifest_keys: set[str] = set()
         from .e2b_sandbox import _MAX_DOWNLOAD_SIZE
 
         for entry in stdout.split("\0"):
@@ -792,22 +850,13 @@ class E2BSandboxProvider(SandboxProvider):
             if not entry:
                 continue
             try:
-                size_str, remote_path = entry.split("\t", 1)
+                size_str, remote_mtime_str, remote_path = entry.split("\t", 2)
                 remote_size = int(size_str)
-            except ValueError:
+                remote_mtime_ns = int(Decimal(remote_mtime_str) * 1_000_000_000)
+            except (InvalidOperation, ValueError):
                 logger.debug("e2b sync: unparseable entry %r", entry)
                 continue
 
-            if remote_size > _MAX_DOWNLOAD_SIZE:
-                logger.warning(
-                    "e2b sync: skipping oversize artefact %s (%d bytes > %d cap)",
-                    remote_path,
-                    remote_size,
-                    _MAX_DOWNLOAD_SIZE,
-                )
-                skipped += 1
-                continue
-
             # Determine which subdir this file belongs to so we can compute
             # the relative path on the host side.  remote_path is absolute,
             # e.g. /home/user/outputs/foo/bar.pdf
@@ -824,9 +873,28 @@ class E2BSandboxProvider(SandboxProvider):
             if sub_match is None:
                 continue
             _sub, host_path, virtual_path = sub_match
+            manifest_key = host_path.relative_to(thread_root).as_posix()
+            seen_manifest_keys.add(manifest_key)
+
+            if remote_size > _MAX_DOWNLOAD_SIZE:
+                logger.warning(
+                    "e2b sync: skipping oversize artefact %s (%d bytes > %d cap)",
+                    remote_path,
+                    remote_size,
+                    _MAX_DOWNLOAD_SIZE,
+                )
+                skipped += 1
+                continue
 
             try:
-                if host_path.exists() and host_path.stat().st_size == remote_size:
+                host_stat = host_path.stat()
+                entry = manifest.get(manifest_key)
+                if entry == {
+                    "remote_size": remote_size,
+                    "remote_mtime_ns": remote_mtime_ns,
+                    "host_size": host_stat.st_size,
+                    "host_mtime_ns": host_stat.st_mtime_ns,
+                }:
                     skipped += 1
                     continue
             except OSError:
@@ -847,11 +915,29 @@ class E2BSandboxProvider(SandboxProvider):
                 host_path.parent.mkdir(parents=True, exist_ok=True)
                 tmp_path = host_path.with_name(host_path.name + ".e2bsync.tmp")
                 tmp_path.write_bytes(data)
+                os.utime(tmp_path, ns=(remote_mtime_ns, remote_mtime_ns))
                 tmp_path.replace(host_path)
+                host_stat = host_path.stat()
+                manifest[manifest_key] = {
+                    "remote_size": remote_size,
+                    "remote_mtime_ns": remote_mtime_ns,
+                    "host_size": host_stat.st_size,
+                    "host_mtime_ns": host_stat.st_mtime_ns,
+                }
+                manifest_dirty = True
                 synced += 1
             except OSError as e:
                 logger.warning("e2b sync: failed to write %s on host: %s", host_path, e)
 
+        stale_keys = set(manifest) - seen_manifest_keys
+        if stale_keys:
+            for key in stale_keys:
+                manifest.pop(key)
+            manifest_dirty = True
+
+        if manifest_dirty:
+            self._write_sync_manifest(manifest_path, remote_sandbox_id, manifest)
+
         if synced or skipped:
             logger.info(
                 "e2b sync: sandbox=%s thread=%s synced=%d skipped=%d",

backend/tests/test_e2b_sandbox_provider.py

@@ -3,6 +3,8 @@
 from __future__ import annotations
 
 import importlib
+import json
+import os
 import threading
 from collections import OrderedDict
 from types import SimpleNamespace
@@ -210,6 +212,13 @@ def test_thread_key_returns_user_thread_tuple():
     assert p._thread_key("t1", "u1") == ("u1", "t1")
 
 
+def test_sandbox_id_falls_back_when_client_id_is_none():
+    client = FakeClient(sandbox_id=None)
+    sandbox = _make_sandbox(client, sandbox_id="fallback-id")
+
+    assert sandbox.sandbox_id == "fallback-id"
+
+
 def test_stable_seed_is_deterministic_and_user_scoped():
     p = _make_provider()
     s_a = p._stable_seed("t1", "u1")
@@ -817,7 +826,7 @@ def _setup_paths(monkeypatch, tmp_path):
 def test_sync_outputs_to_host_writes_new_files(monkeypatch, tmp_path):
     p = _make_provider()
     _setup_paths(monkeypatch, tmp_path)
-    listing = "13\t/home/user/outputs/random.pdf\x00"
+    listing = "13\t2.000000000\t/home/user/outputs/random.pdf\x00"
     files = FakeFilesAPI(store={"/home/user/outputs/random.pdf": b"%PDF-1.4hello"})
     cmds = FakeCommandsAPI([SimpleNamespace(stdout=listing, stderr="", exit_code=0)])
     client = FakeClient(commands=cmds, files=files)
@@ -830,23 +839,243 @@ def test_sync_outputs_to_host_writes_new_files(monkeypatch, tmp_path):
     assert expected.read_bytes() == b"%PDF-1.4hello"
 
 
-def test_sync_outputs_to_host_skips_unchanged_files(monkeypatch, tmp_path):
+def test_sync_outputs_to_host_updates_changed_same_size_file(monkeypatch, tmp_path):
     p = _make_provider()
     _setup_paths(monkeypatch, tmp_path)
     out_dir = Paths(base_dir=tmp_path).thread_dir("t1", user_id="u1") / "user-data" / "outputs"
     out_dir.mkdir(parents=True, exist_ok=True)
     target = out_dir / "random.pdf"
     target.write_bytes(b"%PDF-1.4hello")
+    os.utime(target, ns=(1_000_000_000, 1_000_000_000))
 
-    listing = "13\t/home/user/outputs/random.pdf\x00"
-    files = FakeFilesAPI(store={"/home/user/outputs/random.pdf": b"DIFFERENT-SAME-LEN"})
+    listing = "13\t2.000000000\t/home/user/outputs/random.pdf\x00"
+    files = FakeFilesAPI(store={"/home/user/outputs/random.pdf": b"changed-value"})
     cmds = FakeCommandsAPI([SimpleNamespace(stdout=listing, stderr="", exit_code=0)])
     client = FakeClient(commands=cmds, files=files)
     sb = _make_sandbox(client, sandbox_id="sb-sync-2")
 
     p._sync_outputs_to_host(sb, thread_id="t1", user_id="u1")
 
-    assert files.read_calls == [], "size match should skip the download round-trip"
+    assert files.read_calls, "same-size files must be checked for updates"
+    assert target.read_bytes() == b"changed-value"
+    assert target.stat().st_mtime_ns == 2_000_000_000
+
+
+def test_sync_outputs_to_host_skips_file_when_manifest_matches(monkeypatch, tmp_path):
+    p = _make_provider()
+    _setup_paths(monkeypatch, tmp_path)
+    out_dir = Paths(base_dir=tmp_path).thread_dir("t1", user_id="u1") / "user-data" / "outputs"
+    out_dir.mkdir(parents=True, exist_ok=True)
+    target = out_dir / "random.pdf"
+    target.write_bytes(b"%PDF-1.4hello")
+    os.utime(target, ns=(2_000_000_000, 2_000_000_000))
+
+    listing = "13\t2.000000000\t/home/user/outputs/random.pdf\x00"
+    files = FakeFilesAPI(store={"/home/user/outputs/random.pdf": b"%PDF-1.4hello"})
+    cmds = FakeCommandsAPI(
+        [
+            SimpleNamespace(stdout=listing, stderr="", exit_code=0),
+            SimpleNamespace(stdout=listing, stderr="", exit_code=0),
+        ]
+    )
+    client = FakeClient(commands=cmds, files=files)
+    sb = _make_sandbox(client, sandbox_id="sb-sync-unchanged")
+
+    p._sync_outputs_to_host(sb, thread_id="t1", user_id="u1")
+    files.read_calls.clear()
+    p._sync_outputs_to_host(sb, thread_id="t1", user_id="u1")
+
+    assert files.read_calls == []
+    assert target.read_bytes() == b"%PDF-1.4hello"
+
+
+def test_sync_outputs_to_host_uses_manifest_when_host_mtime_is_rounded(monkeypatch, tmp_path):
+    p = _make_provider()
+    _setup_paths(monkeypatch, tmp_path)
+    paths = Paths(base_dir=tmp_path)
+    thread_dir = paths.thread_dir("t1", user_id="u1")
+    target = thread_dir / "user-data" / "outputs" / "random.pdf"
+    target.parent.mkdir(parents=True, exist_ok=True)
+    target.write_bytes(b"%PDF-1.4hello")
+    rounded_host_mtime_ns = 1_720_000_000_123_456_800
+    os.utime(target, ns=(rounded_host_mtime_ns, rounded_host_mtime_ns))
+    (thread_dir / ".e2b-output-sync.json").write_text(
+        json.dumps(
+            {
+                "version": 1,
+                "sandbox_id": "sb-sync-manifest",
+                "files": {
+                    "outputs/random.pdf": {
+                        "remote_size": 13,
+                        "remote_mtime_ns": 1_720_000_000_123_456_789,
+                        "host_size": 13,
+                        "host_mtime_ns": rounded_host_mtime_ns,
+                    }
+                },
+            }
+        ),
+        encoding="utf-8",
+    )
+
+    listing = "13\t1720000000.1234567890\t/home/user/outputs/random.pdf\x00"
+    files = FakeFilesAPI(store={"/home/user/outputs/random.pdf": b"%PDF-1.4hello"})
+    cmds = FakeCommandsAPI([SimpleNamespace(stdout=listing, stderr="", exit_code=0)])
+    client = FakeClient(sandbox_id="sb-sync-manifest", commands=cmds, files=files)
+    sb = _make_sandbox(client, sandbox_id="sb-sync-manifest")
+
+    p._sync_outputs_to_host(sb, thread_id="t1", user_id="u1")
+
+    assert files.read_calls == []
+
+
+def test_sync_outputs_to_host_records_variable_precision_remote_mtime(monkeypatch, tmp_path):
+    p = _make_provider()
+    _setup_paths(monkeypatch, tmp_path)
+    listing = "13\t1720000000.1234567890\t/home/user/outputs/random.pdf\x00"
+    files = FakeFilesAPI(store={"/home/user/outputs/random.pdf": b"%PDF-1.4hello"})
+    cmds = FakeCommandsAPI([SimpleNamespace(stdout=listing, stderr="", exit_code=0)])
+    client = FakeClient(commands=cmds, files=files)
+    sb = _make_sandbox(client, sandbox_id="sb-sync-precision")
+
+    p._sync_outputs_to_host(sb, thread_id="t1", user_id="u1")
+
+    manifest_path = Paths(base_dir=tmp_path).thread_dir("t1", user_id="u1") / ".e2b-output-sync.json"
+    manifest = json.loads(manifest_path.read_text(encoding="utf-8"))
+    assert manifest["files"]["outputs/random.pdf"]["remote_mtime_ns"] == 1_720_000_000_123_456_789
+
+
+def test_sync_outputs_to_host_removes_manifest_entries_for_deleted_files(monkeypatch, tmp_path):
+    p = _make_provider()
+    _setup_paths(monkeypatch, tmp_path)
+    paths = Paths(base_dir=tmp_path)
+    thread_dir = paths.thread_dir("t1", user_id="u1")
+    thread_dir.mkdir(parents=True, exist_ok=True)
+    (thread_dir / ".e2b-output-sync.json").write_text(
+        json.dumps(
+            {
+                "version": 1,
+                "sandbox_id": "sb-sync-cleanup",
+                "files": {
+                    "outputs/deleted.txt": {
+                        "remote_size": 3,
+                        "remote_mtime_ns": 1,
+                        "host_size": 3,
+                        "host_mtime_ns": 1,
+                    }
+                },
+            }
+        ),
+        encoding="utf-8",
+    )
+    listing = "5\t1720000000.1234567890\t/home/user/outputs/live.txt\x00"
+    files = FakeFilesAPI(store={"/home/user/outputs/live.txt": b"alive"})
+    cmds = FakeCommandsAPI([SimpleNamespace(stdout=listing, stderr="", exit_code=0)])
+    client = FakeClient(commands=cmds, files=files)
+    sb = _make_sandbox(client, sandbox_id="sb-sync-cleanup")
+
+    p._sync_outputs_to_host(sb, thread_id="t1", user_id="u1")
+
+    manifest = json.loads((thread_dir / ".e2b-output-sync.json").read_text(encoding="utf-8"))
+    assert set(manifest["files"]) == {"outputs/live.txt"}
+
+
+def test_sync_outputs_to_host_discards_manifest_from_another_sandbox(monkeypatch, tmp_path):
+    p = _make_provider()
+    _setup_paths(monkeypatch, tmp_path)
+    paths = Paths(base_dir=tmp_path)
+    thread_dir = paths.thread_dir("t1", user_id="u1")
+    target = thread_dir / "user-data" / "outputs" / "random.pdf"
+    target.parent.mkdir(parents=True, exist_ok=True)
+    target.write_bytes(b"%PDF-1.4hello")
+    remote_mtime_ns = 1_720_000_000_123_456_789
+    os.utime(target, ns=(remote_mtime_ns, remote_mtime_ns))
+    (thread_dir / ".e2b-output-sync.json").write_text(
+        json.dumps(
+            {
+                "version": 1,
+                "sandbox_id": "sb-old",
+                "files": {
+                    "outputs/random.pdf": {
+                        "remote_size": 13,
+                        "remote_mtime_ns": remote_mtime_ns,
+                        "host_size": 13,
+                        "host_mtime_ns": remote_mtime_ns,
+                    }
+                },
+            }
+        ),
+        encoding="utf-8",
+    )
+    listing = "13\t1720000000.1234567890\t/home/user/outputs/random.pdf\x00"
+    files = FakeFilesAPI(store={"/home/user/outputs/random.pdf": b"%PDF-1.4hello"})
+    cmds = FakeCommandsAPI([SimpleNamespace(stdout=listing, stderr="", exit_code=0)])
+    client = FakeClient(sandbox_id="sb-new", commands=cmds, files=files)
+    sb = _make_sandbox(client, sandbox_id="sb-new")
+
+    p._sync_outputs_to_host(sb, thread_id="t1", user_id="u1")
+
+    assert files.read_calls
+    manifest = json.loads((thread_dir / ".e2b-output-sync.json").read_text(encoding="utf-8"))
+    assert manifest["sandbox_id"] == "sb-new"
+
+
+def test_sync_outputs_to_host_resets_empty_manifest_for_new_sandbox(monkeypatch, tmp_path):
+    p = _make_provider()
+    _setup_paths(monkeypatch, tmp_path)
+    thread_dir = Paths(base_dir=tmp_path).thread_dir("t1", user_id="u1")
+    thread_dir.mkdir(parents=True, exist_ok=True)
+    manifest_path = thread_dir / ".e2b-output-sync.json"
+    manifest_path.write_text(
+        json.dumps(
+            {
+                "version": 1,
+                "sandbox_id": "sb-old",
+                "files": {
+                    "outputs/stale.txt": {
+                        "remote_size": 1,
+                        "remote_mtime_ns": 1,
+                        "host_size": 1,
+                        "host_mtime_ns": 1,
+                    }
+                },
+            }
+        ),
+        encoding="utf-8",
+    )
+    client = FakeClient(
+        sandbox_id="sb-new",
+        commands=FakeCommandsAPI([SimpleNamespace(stdout="", stderr="", exit_code=0)]),
+    )
+    sb = _make_sandbox(client, sandbox_id="sb-new")
+
+    p._sync_outputs_to_host(sb, thread_id="t1", user_id="u1")
+
+    manifest = json.loads(manifest_path.read_text(encoding="utf-8"))
+    assert manifest == {"version": 1, "sandbox_id": "sb-new", "files": {}}
+
+
+def test_sync_outputs_to_host_restores_externally_modified_file(monkeypatch, tmp_path):
+    p = _make_provider()
+    _setup_paths(monkeypatch, tmp_path)
+    listing = "13\t1720000000.1234567890\t/home/user/outputs/random.pdf\x00"
+    files = FakeFilesAPI(store={"/home/user/outputs/random.pdf": b"%PDF-1.4hello"})
+    cmds = FakeCommandsAPI(
+        [
+            SimpleNamespace(stdout=listing, stderr="", exit_code=0),
+            SimpleNamespace(stdout=listing, stderr="", exit_code=0),
+        ]
+    )
+    client = FakeClient(commands=cmds, files=files)
+    sb = _make_sandbox(client, sandbox_id="sb-sync-local-change")
+
+    p._sync_outputs_to_host(sb, thread_id="t1", user_id="u1")
+    target = Paths(base_dir=tmp_path).thread_dir("t1", user_id="u1") / "user-data" / "outputs" / "random.pdf"
+    target.write_bytes(b"changed-value")
+    os.utime(target, ns=(1_720_000_001_000_000_000, 1_720_000_001_000_000_000))
+
+    p._sync_outputs_to_host(sb, thread_id="t1", user_id="u1")
+
+    assert len(files.read_calls) == 2
     assert target.read_bytes() == b"%PDF-1.4hello"
 
 
@@ -869,7 +1098,7 @@ def test_sync_outputs_to_host_uses_virtual_path_for_download(monkeypatch, tmp_pa
     p = _make_provider()
     _setup_paths(monkeypatch, tmp_path)
 
-    listing = "5\t/home/user/outputs/sub/x.txt\x00"
+    listing = "5\t2.000000000\t/home/user/outputs/sub/x.txt\x00"
     files = FakeFilesAPI(store={"/home/user/outputs/sub/x.txt": b"hello"})
     cmds = FakeCommandsAPI([SimpleNamespace(stdout=listing, stderr="", exit_code=0)])
     client = FakeClient(commands=cmds, files=files)
@@ -990,7 +1219,7 @@ def test_sync_outputs_to_host_skips_oversize_files(monkeypatch, tmp_path):
     _setup_paths(monkeypatch, tmp_path)
 
     oversize = e2b_sb_mod._MAX_DOWNLOAD_SIZE + 1
-    listing = f"{oversize}\t/home/user/outputs/huge.bin\x00"
+    listing = f"{oversize}\t2.000000000\t/home/user/outputs/huge.bin\x00"
     files = FakeFilesAPI()  # no store entry: any read attempt would raise
     cmds = FakeCommandsAPI([SimpleNamespace(stdout=listing, stderr="", exit_code=0)])
     client = FakeClient(commands=cmds, files=files)