fix: 岗位会商 handoff 将上游产物镜像到当前席位沙箱

席位线程隔离导致下游 read_file 找不到上游路径；镜像到 workspace/upstream 并改写 handoff 引用，附带安全路径校验与 SQL 回退测试。

Co-authored-by: Cursor <cursoragent@cursor.com>

offline-backend-20260512/backend/tests/test_position_roundtable_sessions.py

@@ -6,6 +6,7 @@ import asyncio
 import importlib.util
 import json
 import zipfile
+from pathlib import Path
 from types import SimpleNamespace
 from typing import Any
 
@@ -1244,8 +1245,11 @@ def test_activation_requires_a_structured_intent_snapshot() -> None:
 
 @pytest.mark.asyncio
 async def test_handoff_context_inlines_only_upstream_thread_text_artifacts(tmp_path, monkeypatch):
-    artifact = tmp_path / "handoff.md"
+    upstream_dir = tmp_path / "up" / "outputs"
+    upstream_dir.mkdir(parents=True)
+    artifact = upstream_dir / "handoff.md"
     artifact.write_text("上游产物正文：可供下一岗位直接参考。", encoding="utf-8")
+    mirror_root = tmp_path / "current" / "workspace" / "upstream"
     calls: list[tuple[str, str]] = []
 
     class StubStore:
@@ -1307,9 +1311,12 @@ async def test_handoff_context_inlines_only_upstream_thread_text_artifacts(tmp_p
 
     async def resolve(thread_id: str, path: str):
         calls.append((thread_id, path))
-        assert thread_id == "upstream-thread"
-        assert path == "mnt/user-data/outputs/handoff.md"
-        return artifact
+        if thread_id == "upstream-thread":
+            assert path == "mnt/user-data/outputs/handoff.md"
+            return artifact
+        assert thread_id == "current-thread"
+        assert path == "mnt/user-data/workspace/upstream/handoff.md"
+        return mirror_root / "handoff.md"
 
     monkeypatch.setattr(position_roundtable_router, "aresolve_thread_virtual_path", resolve)
     request = SimpleNamespace(
@@ -1325,8 +1332,102 @@ async def test_handoff_context_inlines_only_upstream_thread_text_artifacts(tmp_p
     assert len(context["upstream_nodes"]) == 1
     assert upstream["latest_answer"] == "上游问答结果"
     assert upstream["artifacts"][0]["content"] == "上游产物正文：可供下一岗位直接参考。"
+    assert upstream["artifacts"][0]["upstream_path"] == "mnt/user-data/outputs/handoff.md"
+    assert upstream["artifacts"][0]["path"] == "mnt/user-data/workspace/upstream/handoff.md"
+    assert upstream["artifacts"][0]["mirrored_to_sandbox"] is True
     assert "content" not in upstream["artifacts"][1]
-    assert calls == [("upstream-thread", "mnt/user-data/outputs/handoff.md")]
+    assert "mirrored_to_sandbox" not in upstream["artifacts"][1]
+    assert upstream["artifacts"][1]["path"] == "mnt/user-data/uploads/outside.md"
+    assert (mirror_root / "handoff.md").read_text(encoding="utf-8") == "上游产物正文：可供下一岗位直接参考。"
+    assert "/mnt/user-data/workspace/upstream/handoff.md" in context["instructions"]
+    assert set(calls) == {
+        ("upstream-thread", "mnt/user-data/outputs/handoff.md"),
+        ("current-thread", "mnt/user-data/workspace/upstream/handoff.md"),
+    }
+
+
+@pytest.mark.asyncio
+async def test_handoff_mirror_falls_back_to_persisted_content_and_skips_unsafe_paths(
+    tmp_path, monkeypatch
+):
+    mirror_root = tmp_path / "mirror"
+    resolved: list[tuple[str, str]] = []
+
+    class StubStore:
+        async def get_session(self, session_id, user_id):
+            assert (session_id, user_id) == ("session-a", "user-a")
+            return {"task_snapshot": {"title": "测试任务"}, "intent_snapshot": {}}
+
+        async def list_nodes(self, session_id, user_id):
+            return [
+                {
+                    "node_key": "stage-1-seat-1-agent-a",
+                    "stage_index": 0,
+                    "seat_index": 0,
+                    "agent_id": "agent-a",
+                    "position_id": "planning",
+                    "thread_id": "upstream-thread",
+                    "status": "done",
+                    "revision": 1,
+                    "latest_answer": "上游问答结果",
+                    "artifact_manifest": [
+                        {
+                            "name": "gone.md",
+                            "path": "mnt/user-data/outputs/gone.md",
+                            "mime_type": "text/markdown",
+                            "content": "数据库恢复正文",
+                        },
+                        {
+                            "name": "escape.md",
+                            "path": "mnt/user-data/outputs/../escape.md",
+                            "mime_type": "text/markdown",
+                            "content": "不应被镜像",
+                        },
+                    ],
+                },
+                {
+                    "node_key": "stage-2-seat-1-agent-b",
+                    "stage_index": 1,
+                    "seat_index": 0,
+                    "agent_id": "agent-b",
+                    "position_id": "solution",
+                    "thread_id": "current-thread",
+                    "status": "ready",
+                    "revision": 0,
+                    "latest_answer": None,
+                    "artifact_manifest": [],
+                },
+            ]
+
+    missing_source = tmp_path / "missing-source"
+
+    async def resolve(thread_id: str, path: str):
+        resolved.append((thread_id, path))
+        if thread_id == "upstream-thread":
+            return missing_source / "not-materialized.md"
+        assert thread_id == "current-thread"
+        return mirror_root / Path(path).name
+
+    monkeypatch.setattr(position_roundtable_router, "aresolve_thread_virtual_path", resolve)
+    request = SimpleNamespace(
+        app=SimpleNamespace(state=SimpleNamespace(position_roundtable_store=StubStore())),
+        state=SimpleNamespace(user=SimpleNamespace(id="user-a")),
+    )
+
+    context = await position_roundtable_router._handoff_context(
+        request, "session-a", "stage-2-seat-1-agent-b"
+    )
+
+    artifacts = context["upstream_nodes"][0]["artifacts"]
+    assert artifacts[0]["path"] == "mnt/user-data/workspace/upstream/gone.md"
+    assert artifacts[0]["mirrored_to_sandbox"] is True
+    assert (mirror_root / "gone.md").read_text(encoding="utf-8") == "数据库恢复正文"
+    # 持久化正文同时内嵌，沙箱磁盘丢失也不影响下一岗位读到内容。
+    assert artifacts[0]["content"] == "数据库恢复正文"
+    assert artifacts[1]["path"] == "mnt/user-data/outputs/../escape.md"
+    assert "mirrored_to_sandbox" not in artifacts[1]
+    assert not (mirror_root / "escape.md").exists()
+    assert all(".." not in path for _, path in resolved)
 
 
 @pytest.mark.asyncio