security: validate tool_use_id path component; drop --reload in network mode

backend/run-network.sh

@@ -37,16 +37,16 @@ if [ -z "${VC_AUTH_TOKEN:-}" ]; then
   exit 1
 fi
 
-# --reload: hot-reload on backend code changes. With detach-on-shutdown the
-# reload preserves running CLI sessions (they're rehydrated on the restart).
-# --reload-dir . limits the watcher to backend/ so the session store under the
-# project root (rapidly-written events.jsonl) never triggers reloads.
+# NOTE: unlike the localhost run.sh, this network-exposed (0.0.0.0) mode does
+# NOT enable uvicorn --reload. The autoreloader's file-watcher and child-process
+# supervisor are extra attack surface that shouldn't run on a LAN-reachable
+# service (and any writable-code scenario would become reload-triggered RCE).
 # --timeout-graceful-shutdown: long-lived SSE/poll/terminal-WS connections
-# never drain on their own, so a reload (or stop) would hang on "Waiting for
-# connections to close". 3s lets an in-flight request finish, then force-closes.
+# never drain on their own, so a stop would hang on "Waiting for connections to
+# close". 3s lets an in-flight request finish, then force-closes.
 exec .venv/bin/python -m uvicorn main:app \
   --host 0.0.0.0 --port 8000 \
   --ssl-keyfile ../frontend/.certs/dev-key.pem \
   --ssl-certfile ../frontend/.certs/dev-cert.pem \
   --log-level info \
-  --reload --reload-dir . --timeout-graceful-shutdown 3
+  --timeout-graceful-shutdown 3

backend/tmux_hooks/_common.py

@@ -12,11 +12,25 @@
 
 import json
 import os
+import re
 import sys
 import time
 
 CTRL = os.environ.get("VC_CTRL", "")
 
+# tool_use_id is interpolated into a decisions/<id>.json path that reaches
+# open()/os.remove()/os.replace(). It is normally a CLI-minted `toolu_*` token,
+# but — like every other externally-derived path component in this codebase
+# (session_id/handle, validated via tmux_runner._SESSION_ID_RE) — it must be
+# validated so it can never escape the decisions/ dir via traversal or
+# separators. Same charset/length bound as validate_session_id.
+_SAFE_ID_RE = re.compile(r"^[A-Za-z0-9][A-Za-z0-9_-]{0,127}$")
+
+
+def safe_id(value: str) -> str:
+    """Return value if it is a safe single path component, else 'none'."""
+    return value if value and _SAFE_ID_RE.match(value) else "none"
+
 
 def read_input() -> dict:
     try:
@@ -38,7 +52,7 @@ def append_event(event: dict) -> None:
 
 
 def decision_path(tool_use_id: str) -> str:
-    return os.path.join(CTRL, "decisions", f"{tool_use_id or 'none'}.json")
+    return os.path.join(CTRL, "decisions", f"{safe_id(tool_use_id)}.json")
 
 
 def read_mode() -> str:

backend/tmux_runner.py

@@ -671,7 +671,12 @@ def _write_decision(self, s: _TmuxSession, choice: str) -> bool | None:
                               "tool_use_id": s.pending_tool_use_id})
             return None
         allow = decision == "allow"
-        path = os.path.join(s.ctrl, "decisions", f"{s.pending_tool_use_id or 'none'}.json")
+        # pending_tool_use_id is interpolated into a filesystem path, so validate
+        # it as a safe single path component (matches the hook's _common.safe_id);
+        # fall back to 'none' rather than letting a malformed id escape decisions/.
+        tu_id = (s.pending_tool_use_id or "").strip()
+        decision_id = tu_id if _SESSION_ID_RE.match(tu_id) else "none"
+        path = os.path.join(s.ctrl, "decisions", f"{decision_id}.json")
         tmp = path + ".tmp"
         with open(tmp, "w") as f:
             json.dump({"decision": decision,