fix(api): resolve zip-namespace collisions when merging drive mounts

api/oss/src/core/mounts/service.py

@@ -54,6 +54,11 @@
 # The single session-bound mount: the agent's durable working directory.
 _SESSION_CWD_NAME = "cwd"
 
+# The name the runner symlinks the agent mount into the cwd as (runner: `AGENT_FILES_LINK_NAME`).
+# geesefs degrades that symlink to a 0-byte OBJECT of the same name in the cwd store, so archiving
+# must skip it (see `build_archive_work_list`) — its real content comes from the folded agent mount.
+_AGENT_FILES_LINK_NAME = "agent-files"
+
 # Default TTL (seconds) for signed mount credentials. Covers the mount lifetime for a
 # turn; geesefs holds the creds without refresh, so a turn outliving this hits ExpiredToken.
 _CREDENTIALS_TTL_SECONDS = 3600
@@ -1240,6 +1245,15 @@ async def build_archive_work_list(
                     )
                     continue
                 zip_path = "/".join([*pfx_segments, *rel_segments])
+                # Skip the cwd mount's `agent-files` fold marker. The runner symlinks the agent mount
+                # into the cwd as `agent-files/`, but geesefs degrades that symlink to a 0-byte OBJECT
+                # named `agent-files`. Archived as a FILE it collides with the `agent-files/` DIRECTORY
+                # the folded agent-mount source contributes (passed as its own mount, prefix
+                # "agent-files"); on extraction the file blocks the directory and the agent's files are
+                # lost. The FE display filters the same marker (`isAgentFilesFold`); mirror it here so
+                # the real content survives.
+                if zip_path == _AGENT_FILES_LINK_NAME:
+                    continue
                 work.append((zip_path, obj.key, obj.size or 0, obj.mtime))
 
         return work

api/oss/tests/pytest/unit/test_mounts_file_ops.py

@@ -377,6 +377,34 @@ async def test_traversal_key_does_not_alias_a_real_entry(self):
         assert zip_paths == ["a/report.txt"]
 
 
+@pytest.mark.asyncio
+class TestArchiveAgentFilesFold:
+    async def test_agent_files_fold_marker_is_skipped(self):
+        # geesefs degrades the runner's `agent-files` symlink to a 0-byte OBJECT named `agent-files`
+        # in the cwd store. Archived as a FILE it collides with the `agent-files/` DIRECTORY the folded
+        # agent mount contributes, so on extraction the file blocks the directory and the agent's files
+        # are lost. The bare marker must be skipped; real files and any `agent-files/…` content ship.
+        mount = _make_mount()
+        storage = FakeMountStorage()
+        service = MountsService(
+            mounts_dao=_StubDAO(mount),
+            mounts_store=storage,
+            bucket=_BUCKET,
+        )
+        mount_base = service._storage_key(project_id=mount.project_id, mount=mount)
+        bucket_store = storage._store.setdefault(_BUCKET, {})
+        for key in ["notes.md", "agent-files", "agent-files/keep.txt"]:
+            bucket_store[f"{mount_base}{key}"] = b"x"
+
+        work = await service.build_archive_work_list(
+            project_id=mount.project_id,
+            mounts=[MountArchiveSource(mount_id=mount.id)],
+        )
+
+        zip_paths = {zip_path for zip_path, *_rest in work}
+        assert zip_paths == {"notes.md", "agent-files/keep.txt"}
+
+
 # ---------------------------------------------------------------------------
 # Roundtrip
 # ---------------------------------------------------------------------------