diff --git a/astrbot/core/platform/sources/discord/discord_platform_adapter.py b/astrbot/core/platform/sources/discord/discord_platform_adapter.py
index 9c44691538a..de79150f9b6 100644
--- a/astrbot/core/platform/sources/discord/discord_platform_adapter.py
+++ b/astrbot/core/platform/sources/discord/discord_platform_adapter.py
@@ -22,7 +22,7 @@
 from astrbot.core.platform.astr_message_event import MessageSesion
 from astrbot.core.star.filter.command import CommandFilter
 from astrbot.core.star.filter.command_group import CommandGroupFilter
-from astrbot.core.star.star import star_map
+from astrbot.core.star.star import StarMetadata, star_map
 from astrbot.core.star.star_handler import StarHandlerMetadata, star_handlers_registry
 from astrbot.core.utils.media_utils import MediaResolver
 
@@ -466,13 +466,54 @@ def register_handler(self, handler_info) -> None:
         """注册处理器信息"""
         self.registered_handlers.append(handler_info)
 
+    @staticmethod
+    def _plugin_for_handler_module(handler_module_path: str) -> StarMetadata | None:
+        """Resolve the plugin that owns a handler module.
+
+        ``star_map`` is keyed by the plugin entry module
+        (``data.plugins.<plugin>.main``), so a handler defined in a submodule
+        (e.g. a mixin in ``data.plugins.<plugin>.foo``) never matches exactly.
+        Fall back to the plugin package root and return ``None`` only for
+        orphan modules that no plugin owns.
+
+        Args:
+            handler_module_path: Module path recorded on the handler metadata.
+
+        Returns:
+            The metadata of the owning plugin, or ``None`` if no plugin owns
+            the module.
+        """
+        plugin = star_map.get(handler_module_path)
+        if plugin is not None:
+            return plugin
+        for metadata in star_map.values():
+            if not metadata.root_dir_name:
+                continue
+            package_root = (
+                "astrbot.builtin_stars." if metadata.reserved else "data.plugins."
+            ) + metadata.root_dir_name
+            # Exact match covers handlers defined in the plugin's __init__.py,
+            # prefix match covers helper submodules.
+            if handler_module_path == package_root or handler_module_path.startswith(
+                package_root + "."
+            ):
+                return metadata
+        return None
+
     async def _collect_and_register_commands(self) -> None:
         """收集所有指令并注册到Discord"""
         logger.info("[Discord] Collecting and registering slash commands...")
         registered_commands = []
 
         for handler_md in star_handlers_registry:
-            if not star_map[handler_md.handler_module_path].activated:
+            # A handler may live in a plugin submodule (e.g. a mixin in
+            # `plugin/foo.py`). Resolve its owning plugin by package root
+            # instead of requiring an exact star_map key, so that activated
+            # plugins keep their slash commands. Skip only orphan handlers
+            # that no plugin owns, otherwise one unbound handler aborts the
+            # whole sync loop and no slash commands get registered at all.
+            plugin = self._plugin_for_handler_module(handler_md.handler_module_path)
+            if plugin is None or not plugin.activated:
                 continue
             if not handler_md.enabled:
                 continue
diff --git a/tests/test_discord_command_sync.py b/tests/test_discord_command_sync.py
index 2dee1cadb11..461609a5937 100644
--- a/tests/test_discord_command_sync.py
+++ b/tests/test_discord_command_sync.py
@@ -22,6 +22,12 @@ def _build_adapter(monkeypatch: pytest.MonkeyPatch):
     )
 
     monkeypatch.setattr(discord_platform_adapter, "star_handlers_registry", [])
+    # The real ``discord`` module may already be bound to this adapter when the
+    # rest of the suite imported it first. Stub the constructors the adapter
+    # calls so the tests do not depend on ``sys.modules["discord"]`` being mocked
+    # by ``mock_discord_modules``.
+    monkeypatch.setattr(discord_platform_adapter.discord, "SlashCommand", Mock())
+    monkeypatch.setattr(discord_platform_adapter.discord, "Option", Mock())
     monkeypatch.setattr(
         discord_platform_adapter.discord,
         "HTTPException",
@@ -55,3 +61,218 @@ async def test_discord_command_sync_ignores_daily_quota(monkeypatch):
     adapter.client.sync_commands.assert_awaited_once()
     warning.assert_called_once()
     assert "30034" in warning.call_args.args[0]
+
+
+@pytest.mark.asyncio
+async def test_discord_command_sync_keeps_going_after_unowned_handler(
+    monkeypatch,
+):
+    """A handler owned by no plugin must not abort the whole sync loop.
+
+    Regression test for https://github.com/AstrBotDevs/AstrBot/issues/10626:
+    the old code subscripted ``star_map`` directly and raised ``KeyError``
+    inside ``on_ready``, so no plugin's slash commands were registered at all.
+    The unowned handler must be skipped while active plugins still register.
+    """
+    from astrbot.core.platform.sources.discord import discord_platform_adapter
+
+    adapter = _build_adapter(monkeypatch)
+
+    orphan = Mock()
+    orphan.handler_module_path = "some.unrelated.toolkit.helpers"  # owned by no plugin
+    orphan.enabled = True
+    orphan.event_filters = [object()]
+
+    owned = Mock()
+    owned.handler_module_path = "data.plugins.demo.main"
+    owned.enabled = True
+    owned.event_filters = [object()]
+
+    plugin_md = Mock()
+    plugin_md.activated = True
+    plugin_md.reserved = False
+    plugin_md.root_dir_name = "demo"
+    monkeypatch.setattr(
+        discord_platform_adapter, "star_handlers_registry", [orphan, owned]
+    )
+    monkeypatch.setattr(
+        discord_platform_adapter,
+        "star_map",
+        {"data.plugins.demo.main": plugin_md},
+    )
+
+    cmd_info = ("demo_cmd", "demo description", object())
+    extract = Mock(return_value=cmd_info)
+    monkeypatch.setattr(adapter, "_extract_command_info", extract)
+
+    await adapter._collect_and_register_commands()  # must not raise KeyError
+
+    extract.assert_called_once()
+    adapter.client.add_application_command.assert_called_once()
+    adapter.client.sync_commands.assert_awaited_once()
+
+
+@pytest.mark.asyncio
+async def test_discord_command_sync_registers_submodule_handler_of_active_plugin(
+    monkeypatch,
+):
+    """A submodule handler whose owning plugin is activated must register.
+
+    ``star_map`` is keyed by the plugin entry module, so a handler living in
+    ``plugin/foo.py`` never matches exactly. The adapter resolves ownership by
+    plugin package root; the command must reach Discord instead of being
+    silently dropped.
+    """
+    from astrbot.core.platform.sources.discord import discord_platform_adapter
+
+    adapter = _build_adapter(monkeypatch)
+
+    submodule_handler = Mock()
+    submodule_handler.handler_module_path = "data.plugins.demo.mixin"
+    submodule_handler.enabled = True
+    submodule_handler.event_filters = [object()]
+
+    active_plugin_md = Mock()
+    active_plugin_md.activated = True
+    active_plugin_md.reserved = False
+    active_plugin_md.root_dir_name = "demo"
+    monkeypatch.setattr(
+        discord_platform_adapter,
+        "star_handlers_registry",
+        [submodule_handler],
+    )
+    monkeypatch.setattr(
+        discord_platform_adapter,
+        "star_map",
+        {"data.plugins.demo.main": active_plugin_md},
+    )
+
+    cmd_info = ("demo_cmd", "demo description", object())
+    extract = Mock(return_value=cmd_info)
+    monkeypatch.setattr(adapter, "_extract_command_info", extract)
+
+    await adapter._collect_and_register_commands()
+
+    extract.assert_called_once()
+    adapter.client.add_application_command.assert_called_once()
+    adapter.client.sync_commands.assert_awaited_once()
+
+
+@pytest.mark.asyncio
+async def test_discord_command_sync_registers_package_root_handler_of_active_plugin(
+    monkeypatch,
+):
+    """A handler defined in the plugin's ``__init__.py`` has a module path that
+    equals the plugin package root exactly (no trailing submodule). It must
+    still resolve to the plugin and register.
+    """
+    from astrbot.core.platform.sources.discord import discord_platform_adapter
+
+    adapter = _build_adapter(monkeypatch)
+
+    root_handler = Mock()
+    root_handler.handler_module_path = "data.plugins.demo"  # == package root
+    root_handler.enabled = True
+    root_handler.event_filters = [object()]
+
+    active_plugin_md = Mock()
+    active_plugin_md.activated = True
+    active_plugin_md.reserved = False
+    active_plugin_md.root_dir_name = "demo"
+    monkeypatch.setattr(
+        discord_platform_adapter,
+        "star_handlers_registry",
+        [root_handler],
+    )
+    monkeypatch.setattr(
+        discord_platform_adapter,
+        "star_map",
+        {"data.plugins.demo.main": active_plugin_md},
+    )
+
+    cmd_info = ("demo_cmd", "demo description", object())
+    extract = Mock(return_value=cmd_info)
+    monkeypatch.setattr(adapter, "_extract_command_info", extract)
+
+    await adapter._collect_and_register_commands()
+
+    extract.assert_called_once()
+    adapter.client.add_application_command.assert_called_once()
+
+
+@pytest.mark.asyncio
+async def test_discord_command_sync_skips_true_orphan_handler(monkeypatch):
+    """A handler owned by no plugin at all is skipped without aborting,
+    and must not accidentally resolve to an unrelated plugin.
+    """
+    from astrbot.core.platform.sources.discord import discord_platform_adapter
+
+    adapter = _build_adapter(monkeypatch)
+
+    orphan = Mock()
+    orphan.handler_module_path = "some.unrelated.toolkit.helpers"
+    orphan.enabled = True
+    orphan.event_filters = [object()]
+
+    active_plugin_md = Mock()
+    active_plugin_md.activated = True
+    active_plugin_md.reserved = False
+    active_plugin_md.root_dir_name = "demo"
+    monkeypatch.setattr(
+        discord_platform_adapter,
+        "star_handlers_registry",
+        [orphan],
+    )
+    monkeypatch.setattr(
+        discord_platform_adapter,
+        "star_map",
+        {"data.plugins.demo.main": active_plugin_md},
+    )
+
+    extract = Mock(return_value=None)
+    monkeypatch.setattr(adapter, "_extract_command_info", extract)
+
+    await adapter._collect_and_register_commands()
+
+    extract.assert_not_called()
+    adapter.client.add_application_command.assert_not_called()
+    adapter.client.sync_commands.assert_awaited_once()
+
+
+@pytest.mark.asyncio
+async def test_discord_command_sync_skips_submodule_handler_of_inactive_plugin(
+    monkeypatch,
+):
+    """A submodule handler of a deactivated plugin must not register."""
+    from astrbot.core.platform.sources.discord import discord_platform_adapter
+
+    adapter = _build_adapter(monkeypatch)
+
+    submodule_handler = Mock()
+    submodule_handler.handler_module_path = "data.plugins.demo.mixin"
+    submodule_handler.enabled = True
+    submodule_handler.event_filters = [object()]
+
+    inactive_plugin_md = Mock()
+    inactive_plugin_md.activated = False
+    inactive_plugin_md.reserved = False
+    inactive_plugin_md.root_dir_name = "demo"
+    monkeypatch.setattr(
+        discord_platform_adapter,
+        "star_handlers_registry",
+        [submodule_handler],
+    )
+    monkeypatch.setattr(
+        discord_platform_adapter,
+        "star_map",
+        {"data.plugins.demo.main": inactive_plugin_md},
+    )
+
+    extract = Mock(return_value=None)
+    monkeypatch.setattr(adapter, "_extract_command_info", extract)
+
+    await adapter._collect_and_register_commands()
+
+    extract.assert_not_called()
+    adapter.client.add_application_command.assert_not_called()
+    adapter.client.sync_commands.assert_awaited_once()