feat(node): an upload lands in the folder it was sent to

There is no `uploads/` subdirectory any more, and the client names the folder
rather than the root.

It was the last of v5's quarantine — the per-user layer went on 2026-08-14 for
the same reason — and it goes on the same grounds: a folder appearing beside
the operator's library because somebody sent a file is the node deciding how
their disk is arranged. Somebody dropping a file into the folder they are
looking at expects it to be in that folder.

**What made the quarantine worth having was never the subdirectory.** It is the
filename allowlist, the size cap, the chunk ordering and the no-overwrite rule,
and all four are untouched: an existing file is never replaced, the second
sender of IMG_1234.jpg gets a free name, and the check still sits at the write.

Letting the client choose the destination is safe for one reason and only one:
it is resolved through `RootSet.resolve()`, which refuses `..`, absolute
segments and anything whose resolved form escapes its root, symlinks included.
A member answers "which of this group's folders", never "which path on the
operator's disk" — and the test that used to assert the node chose now asserts
that, with six shapes of escape.

`direct` goes with it. Its only job was to say "no subdirectory for this root",
which is now every root, and a config flag that does nothing is worse than none.

Chat's attachment folder finally does something: the directory the operator
picks in the Chat settings pane is where attachments are written, falling back
to the first writable root while they have not chosen one, or if the one they
chose has since been made read-only or ejected — a stale choice should not
become a refusal at send time.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011pvMdvLBG92jyhvD5pD6us

1 files changed, 42 insertions, 13 deletions

diff --git a/packages/meshbay-node/src/meshbay_node/transport/webrtc_server.py b/packages/meshbay-node/src/meshbay_node/transport/webrtc_server.py
index d341d8c..61458f2 100644
--- a/packages/meshbay-node/src/meshbay_node/transport/webrtc_server.py
+++ b/packages/meshbay-node/src/meshbay_node/transport/webrtc_server.py
@@ -214,7 +214,6 @@ JOIN_FAILURE_WINDOW = 600  # seconds
 # attachments from the chat alike. One visible directory the operator can look
 # into, back up or empty — rather than a hidden tree of per-user uuids that
 # nobody could read, or files scattered wherever someone happened to be looking.
-UPLOAD_DIR_NAME = "uploads"
 
 
 def _extract_dtls_fingerprint(sdp: str) -> bytes:
@@ -4016,7 +4015,12 @@ class WebRTCPeerSession:
         # later — the same reason the old single upload root was never guessed.
         # A client that names nothing is an MNP 1.0 one, and there was exactly
         # one destination in its world: the first writable root.
-        target_root_name = str(msg.get("root") or "").strip()
+        # `dir` is the folder being browsed, as a virtual path
+        # (`Media/Films/1999`); `root` is the older, coarser form and is what
+        # its first segment means on its own.
+        target_rel = str(msg.get("dir") or "").strip().strip("/")
+        target_root_name = (target_rel.split("/")[0] if target_rel
+                            else str(msg.get("root") or "").strip())
         upload_root = None
         if target_root_name:
             upload_root = roots.by_name(target_root_name)
@@ -4052,18 +4056,43 @@ class WebRTCPeerSession:
                         "filename": filename})
             return
 
-        if upload_root.direct:
-            rel_dir = upload_root.name
-            target_dir = upload_root.path
+        # The folder the sender is looking at, and no subdirectory of the node's
+        # invention.
+        #
+        # Uploads used to be confined to `<root>/uploads/`, created on demand.
+        # That was the last of v5's quarantine (the per-user layer went on
+        # 2026-08-14, for the same reason): a shared directory nobody can
+        # organise is not a shared directory, and a folder appearing beside the
+        # operator's library because somebody sent a file is the node deciding
+        # how their disk is arranged.
+        #
+        # What made the quarantine worth having is not the subdirectory — it is
+        # the filename allowlist, the size cap, the chunk ordering, and the
+        # no-overwrite rule below. All four are unchanged.
+        #
+        # `resolve()` and not a join: it refuses `..`, absolute segments and
+        # anything whose resolved form escapes its root, symlinks included. The
+        # client names *where among the group's own folders*, never a path on
+        # the operator's filesystem.
+        if target_rel:
+            target_dir = roots.resolve(target_rel)
+            if target_dir is None or not target_dir.is_dir():
+                self._send({"type": "error",
+                            "detail": "Not a directory in this group",
+                            "code": "no_such_directory",
+                            "filename": filename})
+                return
+            rel_dir = target_rel
         else:
-            rel_dir = f"{upload_root.name}/{UPLOAD_DIR_NAME}"
-            target_dir = upload_root.path / UPLOAD_DIR_NAME
-            try:
-                target_dir.mkdir(parents=True, exist_ok=True)
-            except OSError as e:
-                log.warning("Cannot create upload folder in root %r: %s",
-                            upload_root.name, e)
-                self._send({"type": "error", "detail": "Upload folder unavailable",
+            # An MNP 1.0 client names nothing; the root itself is where its one
+            # destination now is.
+            target_dir = upload_root.path
+            rel_dir = upload_root.name
+            if not target_dir.is_dir():
+                self._send({"type": "error",
+                            "detail": f"Directory '{upload_root.name}' is "
+                                      f"currently unavailable",
+                            "code": "root_unavailable",
                             "filename": filename})
                 return