diff --git a/plugins/platforms/telegram/adapter.py b/plugins/platforms/telegram/adapter.py
index 6a6fb549c3..0dcd279b49 100644
--- a/plugins/platforms/telegram/adapter.py
+++ b/plugins/platforms/telegram/adapter.py
@@ -1437,22 +1437,44 @@ class TelegramAdapter(BasePlatformAdapter):
                     pass
 
         if authorized is None:
+            # Resolve through the runner's full auth chain (platform + group
+            # allowlists, pairing store, allow-all flags). Prefer the
+            # platform-bound callback registered via set_authorization_check:
+            # it routes to GatewayRunner._is_user_authorized AND survives
+            # multiplex handler wrapping, whereas the bound-handler __self__
+            # lookup is None when the primary handler is a profile closure —
+            # which silently dropped the chat allowlist and default-denied
+            # allowlisted group members under multiplex_profiles (#87132). Fall
+            # back to the bound handler for setups without a registered callback.
             runner = getattr(getattr(self, "_message_handler", None), "__self__", None)
             auth_fn = getattr(runner, "_is_user_authorized", None)
-            if callable(auth_fn):
-                # Only make an early decision via the runner when an allowlist
-                # actually exists; otherwise unknown DMs must reach the pairing
-                # flow rather than being default-denied here.
+            has_callback = getattr(self, "_authorization_check", None) is not None
+            if has_callback or callable(auth_fn):
+                # Only make an early decision when an allowlist actually exists;
+                # otherwise unknown DMs must reach the pairing flow rather than
+                # being default-denied here.
                 if not self._telegram_auth_env_configured():
                     return True
-                try:
-                    authorized = bool(auth_fn(source))
-                except Exception:
-                    logger.debug(
-                        "[Telegram] Falling back to env-only auth for user %s",
+                decision = (
+                    self._is_sender_authorized(
                         user_id,
-                        exc_info=True,
+                        chat_type=source.chat_type,
+                        chat_id=source.chat_id,
                     )
+                    if has_callback
+                    else None
+                )
+                if decision is not None:
+                    authorized = decision
+                elif callable(auth_fn):
+                    try:
+                        authorized = bool(auth_fn(source))
+                    except Exception:
+                        logger.debug(
+                            "[Telegram] Falling back to env-only auth for user %s",
+                            user_id,
+                            exc_info=True,
+                        )
 
         if authorized is None:
             allowed_csv = _scoped_gate_env("TELEGRAM_ALLOWED_USERS").strip()
diff --git a/tests/gateway/test_telegram_auth_check.py b/tests/gateway/test_telegram_auth_check.py
index 47ab755251..293d437a59 100644
--- a/tests/gateway/test_telegram_auth_check.py
+++ b/tests/gateway/test_telegram_auth_check.py
@@ -313,3 +313,60 @@ async def test_unmentioned_group_location_from_removed_user_not_observed():
     await adapter._handle_location_message(update, SimpleNamespace())
 
     assert observed == []
+
+
+def test_group_allowlist_authorized_under_multiplex_closure_handler(monkeypatch):
+    """group_allowed_chats must authorize a chat member under multiplex_profiles.
+
+    Regression for #87132: with gateway.multiplex_profiles the primary message
+    handler is a closure, so its ``__self__`` is absent and the early intake
+    filter could not reach GatewayRunner._is_user_authorized — it fell back to
+    env-only auth and default-denied every non-global sender in an explicitly
+    allowlisted group. The platform-bound callback registered via
+    set_authorization_check survives the closure wrapping and must be consulted.
+    """
+    monkeypatch.setenv("TELEGRAM_GROUP_ALLOWED_CHATS", "-100123")
+
+    adapter = _make_adapter(group_allowed_chats=["-100123"])
+
+    # Multiplex: the primary handler is a closure with no ``__self__`` runner.
+    def closure_handler(event):
+        return None
+
+    adapter._message_handler = closure_handler
+    assert getattr(closure_handler, "__self__", None) is None
+
+    # The runner installs this callback at adapter registration; it routes
+    # through the full auth chain (here: the chat allowlist) regardless of how
+    # the message handler is wrapped.
+    def auth_check(user_id, chat_type=None, chat_id=None):
+        return str(chat_id) in {"-100123"}
+
+    adapter.set_authorization_check(auth_check)
+
+    # A sender absent from any user allowlist, posting in the allowlisted group,
+    # is authorized via the chat allowlist.
+    allowed = _make_message(from_user_id=555, chat_id=-100123, chat_type="group")
+    assert adapter._is_user_authorized_from_message(allowed) is True
+
+    # The same sender in a NON-allowlisted group is still rejected.
+    denied = _make_message(from_user_id=555, chat_id=-100999, chat_type="group")
+    assert adapter._is_user_authorized_from_message(denied) is False
+
+
+def test_multiplex_closure_handler_without_callback_falls_back_to_env(monkeypatch):
+    """No registered callback + a closure handler (no runner) must not raise and
+    falls back to env-only auth — the getattr guard keeps the legacy path safe."""
+    monkeypatch.setenv("TELEGRAM_GROUP_ALLOWED_CHATS", "-100123")
+    monkeypatch.setenv("TELEGRAM_ALLOWED_USERS", "111")
+
+    adapter = _make_adapter(group_allowed_chats=["-100123"])
+    adapter._message_handler = lambda event: None  # closure, no __self__
+    # No set_authorization_check() → _authorization_check is absent/None.
+
+    assert adapter._is_user_authorized_from_message(
+        _make_message(from_user_id=111, chat_id=-100123, chat_type="group")
+    ) is True
+    assert adapter._is_user_authorized_from_message(
+        _make_message(from_user_id=555, chat_id=-100123, chat_type="group")
+    ) is False