fix(secrets): route authz gate and pairing allowlist reads through the profile secret scope

- gateway/authz_mixin.py: group chat allowlists, {PLATFORM}_ALLOW_BOTS, and
  pairing-mode allowlist presence checks now go through the file's own
  _platform_gate_env helper (scoped-authoritative under multiplex).
- gateway/pairing.py: grant-mirror/revoke allowlist READS go through
  get_secret (Slack pattern for unscoped admin/CLI callers); writes still
  use save_env_value with a TODO for profile-aware writes.

gateway/authz_mixin.py

@@ -456,7 +456,7 @@ class GatewayAuthorizationMixin:
                 Platform.QQBOT: "QQ_GROUP_ALLOWED_USERS",
             }.get(source.platform, "")
             if chat_allowlist_env:
-                raw_chat_allowlist = os.getenv(chat_allowlist_env, "").strip()
+                raw_chat_allowlist = _platform_gate_env(chat_allowlist_env)
                 if raw_chat_allowlist:
                     allowed_group_ids = {
                         cid.strip()
@@ -498,7 +498,7 @@ class GatewayAuthorizationMixin:
         }
         if getattr(source, "is_bot", False):
             allow_bots_var = platform_allow_bots_map.get(source.platform)
-            if allow_bots_var and os.getenv(allow_bots_var, "none").lower().strip() in {"mentions", "all"}:
+            if allow_bots_var and _platform_gate_env(allow_bots_var, "none").lower().strip() in {"mentions", "all"}:
                 return True
 
         if not user_id:
@@ -876,13 +876,13 @@ class GatewayAuthorizationMixin:
                 ),
                 Platform.QQBOT: ("QQ_GROUP_ALLOWED_USERS",),
             }
-            if os.getenv(platform_env_map.get(platform, ""), "").strip():
+            if _platform_gate_env(platform_env_map.get(platform, "")).strip():
                 return "ignore"
             for env_key in platform_group_env_map.get(platform, ()):
-                if os.getenv(env_key, "").strip():
+                if _platform_gate_env(env_key).strip():
                     return "ignore"
 
-        if os.getenv("GATEWAY_ALLOWED_USERS", "").strip():
+        if _platform_gate_env("GATEWAY_ALLOWED_USERS").strip():
             return "ignore"
 
         return "pair"

gateway/pairing.py

@@ -146,6 +146,32 @@ def _user_ids_match(platform: str, left: str, right: str) -> bool:
     return bool(left_aliases and right_aliases and (left_aliases & right_aliases))
 
 
+def _read_allowlist_env(env_var: str) -> str:
+    """Read a platform allowlist env var through the profile secret scope.
+
+    Under multiplexing the process env may hold ANOTHER profile's allowlist
+    (first-writer-wins YAML→env bridges), so reads must honor the installed
+    scope's verdict — including a scoped miss returning empty rather than
+    borrowing the process value.  Unscoped callers (single-profile CLI /
+    admin endpoints) keep the legacy ``os.getenv`` read.
+
+    TODO(profile-secrets): the grant mirror below still WRITES through
+    ``hermes_cli.config.save_env_value`` / ``remove_env_value``, which target
+    the root ``.env`` — those writes need a profile-aware counterpart before
+    pairing grants can be mirrored correctly under multiplexing.
+    """
+    try:
+        from agent.secret_scope import UnscopedSecretError, get_secret
+
+        try:
+            return (get_secret(env_var) or "").strip()
+        except UnscopedSecretError:
+            pass
+    except Exception:
+        pass
+    return (os.getenv(env_var) or "").strip()
+
+
 def _sync_allowlist_add(platform: str, user_id: str) -> None:
     """Add ``user_id`` to the platform allowlist env var IF one is configured.
 
@@ -158,7 +184,7 @@ def _sync_allowlist_add(platform: str, user_id: str) -> None:
     env_var = _allowlist_env_for_platform(platform)
     if not env_var:
         return
-    current = os.getenv(env_var, "").strip()
+    current = _read_allowlist_env(env_var)
     if not current:
         return  # No allowlist configured — leave the gateway open (option i).
     ids = _split_allowlist(current)
@@ -278,7 +304,7 @@ def _sync_allowlist_remove(platform: str, user_id: str) -> None:
     env_var = _allowlist_env_for_platform(platform)
     if not env_var:
         return
-    current = os.getenv(env_var, "").strip()
+    current = _read_allowlist_env(env_var)
     if not current:
         return  # No allowlist configured — do not touch config-only snapshots.
     ids = _split_allowlist(current)