diff --git a/reme2/application.py b/reme2/application.py
index 82257aa2..676df50b 100644
--- a/reme2/application.py
+++ b/reme2/application.py
@@ -98,7 +98,7 @@ class Application(BaseComponent):
         in_degree: dict[tuple[ComponentEnum, str], int] = dict.fromkeys(nodes, 0)
         dependents: dict[tuple[ComponentEnum, str], list[tuple[ComponentEnum, str]]] = {k: [] for k in nodes}
         for key, comp in nodes.items():
-            for dep in comp.dependencies():
+            for dep in comp.dependencies:
                 dep_key = (dep.ctype, dep.name)
                 if dep_key in nodes:
                     dependents[dep_key].append(key)
diff --git a/reme2/component/base_component.py b/reme2/component/base_component.py
index 1ac9b29c..3cef1f92 100644
--- a/reme2/component/base_component.py
+++ b/reme2/component/base_component.py
@@ -3,7 +3,7 @@
 import asyncio
 from abc import ABC
 from pathlib import Path
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Any, Callable, TypeVar, cast
 
 from ..enumeration import ComponentEnum
 from ..utils import get_logger
@@ -11,21 +11,48 @@ from ..utils import get_logger
 if TYPE_CHECKING:
     from .application_context import ApplicationContext
 
+T = TypeVar("T", bound="BaseComponent")
+
+
+class Dependency:
+    """Declared dependency: bind() return value, instance attribute placeholder, and topological-sort edge."""
+
+    __slots__ = ("ctype", "name", "default_factory", "optional")
+
+    def __init__(
+            self,
+            ctype: ComponentEnum,
+            name: str,
+            default_factory: Callable[[], Any] | None = None,
+            optional: bool = True,
+    ) -> None:
+        self.ctype = ctype
+        self.name = name
+        self.default_factory = default_factory
+        self.optional = optional
+
+    def __repr__(self) -> str:
+        suffix = "?" if self.optional else ""
+        return f"<unresolved {self.ctype.value}:{self.name}{suffix}>"
+
+    def __getattr__(self, item: str) -> Any:
+        # Guard against using the dependency before start() resolves it.
+        raise RuntimeError(
+            f"Dependency {self.ctype.value}:{self.name} accessed before start() (attribute '{item}')",
+        )
+
 
 class BaseComponent(ABC):
-    """Async lifecycle base class with context manager support.
-
-    Subclasses must implement ``_start`` and ``_close``.
-    """
+    """Async lifecycle base class with bind-based dependency injection."""
 
     component_type = ComponentEnum.BASE
 
     def __init__(
-        self,
-        name: str | None = None,
-        backend: str = "",
-        app_context: "ApplicationContext | None" = None,
-        **kwargs,
+            self,
+            name: str | None = None,
+            backend: str = "",
+            app_context: "ApplicationContext | None" = None,
+            **kwargs,
     ) -> None:
         self.name: str = name or self.__class__.__name__
         self.backend: str = backend
@@ -37,11 +64,61 @@ class BaseComponent(ABC):
 
         self._is_started: bool = False
         self._lock: asyncio.Lock = asyncio.Lock()
+        # Components created from bind() default_factory in standalone mode (auto-managed lifecycle).
+        self._owned: list["BaseComponent"] = []
 
     @property
     def is_started(self) -> bool:
         return self._is_started
 
+    # ----- Dependency declaration ----------------------------------------
+
+    @staticmethod
+    def bind(
+            name: str | None,
+            base_cls: type[T],
+            *,
+            default_factory: Callable[[], T] | None = None,
+            optional: bool = True,
+    ) -> T | None:
+        """Declare a dependency on another component; resolved at start(). Empty name → None."""
+        if not name:
+            return None
+        ctype = getattr(base_cls, "component_type", None)
+        if not isinstance(ctype, ComponentEnum) or ctype is ComponentEnum.BASE:
+            raise TypeError(f"{base_cls.__name__} must declare a non-BASE ComponentEnum 'component_type'")
+        return cast(T, Dependency(ctype, name, default_factory, optional))
+
+    @property
+    def dependencies(self) -> list[Dependency]:
+        """All unresolved bindings declared on this instance."""
+        return [v for v in self.__dict__.values() if isinstance(v, Dependency)]
+
+    async def _resolve_bindings(self) -> None:
+        """Replace Dependency placeholders with real components (or default_factory / None for optional)."""
+        for attr, value in list(self.__dict__.items()):
+            if not isinstance(value, Dependency):
+                continue
+            if self.app_context is None:
+                # Standalone mode: factory or (optional → None) or keep placeholder.
+                if value.default_factory is not None:
+                    instance = value.default_factory()
+                    setattr(self, attr, instance)
+                    if isinstance(instance, BaseComponent):
+                        self._owned.append(instance)
+                elif value.optional:
+                    setattr(self, attr, None)
+            else:
+                target = self.app_context.components.get(value.ctype, {}).get(value.name)
+                if target is not None:
+                    setattr(self, attr, target)
+                elif value.optional:
+                    setattr(self, attr, None)
+                else:
+                    raise ValueError(f"{value.ctype.value} '{value.name}' not found.")
+
+    # ----- Lookup --------------------------------------------------------
+
     def get_component(self, component_type: ComponentEnum, name: str):
         """Get a component by type and name from app_context."""
         if self.app_context is None:
@@ -57,26 +134,39 @@ class BaseComponent(ABC):
             return Path.cwd()
         return Path(self.app_context.app_config.working_dir)
 
+    # ----- Lifecycle -----------------------------------------------------
+
     async def _start(self) -> None:
-        """Start the component."""
+        """Subclass hook: start logic."""
 
     async def _close(self) -> None:
-        """Close the component."""
+        """Subclass hook: close logic."""
 
     async def start(self) -> None:
-        """Start the component. No-op if already started."""
+        """Resolve bindings → start owned fallbacks → _start(). No-op if already started."""
         async with self._lock:
             if self._is_started:
                 return
+            await self._resolve_bindings()
+            for owned in self._owned:
+                try:
+                    await owned.start()
+                except Exception:
+                    self.logger.exception(f"Failed to start owned {owned.component_type.value}:{owned.name}")
             await self._start()
             self._is_started = True
 
     async def close(self) -> None:
-        """Close the component. No-op if not started."""
+        """_close() → close owned fallbacks in reverse. No-op if not started."""
         async with self._lock:
             if not self._is_started:
                 return
             await self._close()
+            for owned in reversed(self._owned):
+                try:
+                    await owned.close()
+                except Exception:
+                    self.logger.exception(f"Failed to close owned {owned.component_type.value}:{owned.name}")
             self._is_started = False
 
     async def restart(self) -> None:
diff --git a/reme2/component/file_store/base_file_store.py b/reme2/component/file_store/base_file_store.py
index e545fe1b..9f2ae8dc 100644
--- a/reme2/component/file_store/base_file_store.py
+++ b/reme2/component/file_store/base_file_store.py
@@ -19,28 +19,20 @@ class BaseFileStore(BaseComponent):
     ):
         super().__init__(**kwargs)
         self.store_name = store_name or self.name
-        self._embedding_model_name = embedding_model
-        self._keyword_index_name = keyword_index
-
-        self.embedding_model: BaseEmbeddingModel | None = None
-        self.keyword_index: BaseKeywordIndex | None = None
-        self.store_path = self.working_path / self.component_type.value / store_name
-        self.store_path.mkdir(parents=True, exist_ok=True)
         if not embedding_model and not keyword_index:
             raise ValueError("At least one of embedding_model or keyword_index must be set.")
 
+        self.embedding_model = self.bind(embedding_model, BaseEmbeddingModel)
+        self.keyword_index = self.bind(keyword_index, BaseKeywordIndex)
+        self.store_path = self.working_path / self.component_type.value / store_name
+        self.store_path.mkdir(parents=True, exist_ok=True)
+
         self.file_nodes: dict[str, FileNode] = {}
 
     async def _start(self) -> None:
-        if self._embedding_model_name:
-            self.embedding_model = self.get_component(ComponentEnum.EMBEDDING_MODEL, self._embedding_model_name)
-        if self._keyword_index_name:
-            self.keyword_index = self.get_component(ComponentEnum.KEYWORD_INDEX, self._keyword_index_name)
         await self.load_file_nodes()
 
     async def _close(self) -> None:
-        self.embedding_model = None
-        self.keyword_index = None
         await self.dump_file_nodes()
 
     async def load_file_nodes(self):
diff --git a/reme2/component/file_watcher/base_file_watcher.py b/reme2/component/file_watcher/base_file_watcher.py
index 144c852a..6d9367a3 100644
--- a/reme2/component/file_watcher/base_file_watcher.py
+++ b/reme2/component/file_watcher/base_file_watcher.py
@@ -36,18 +36,14 @@ class BaseFileWatcher(BaseComponent):
         self.force_polling: bool = force_polling
         self.debounce: int = debounce
         self.poll_delay_ms: int = poll_delay_ms
-        self.file_store_name: str = file_store
-        self.file_parser_name: str = file_parser
+        self.file_store = self.bind(file_store, BaseFileStore)
+        self.file_parser = self.bind(file_parser, BaseFileParser)
         self._stop_event: asyncio.Event = asyncio.Event()
         self._background_task: asyncio.Task | None = None
-        self.file_store: BaseFileStore | None = None
-        self.file_parser: BaseFileParser | None = None
         self._retry_interval: float = 10
 
     async def _start(self):
         self._stop_event = asyncio.Event()
-        self.file_store = self.get_component(ComponentEnum.FILE_STORE, self.file_store_name)
-        self.file_parser = self.get_component(ComponentEnum.FILE_PARSER, self.file_parser_name)
 
         async def background_task():
             await self.update_store()
diff --git a/reme2/component/keyword_index/base_keyword_index.py b/reme2/component/keyword_index/base_keyword_index.py
index 0ee134cd..9c29af25 100644
--- a/reme2/component/keyword_index/base_keyword_index.py
+++ b/reme2/component/keyword_index/base_keyword_index.py
@@ -15,23 +15,18 @@ class BaseKeywordIndex(BaseComponent):
 
     def __init__(self, tokenizer: str = "default", **kwargs):
         super().__init__(**kwargs)
-        self.tokenizer_name = tokenizer
-        self.tokenizer: BaseTokenizer | None = None
+        from ..tokenizer import RegexTokenizer
+
+        self.tokenizer = self.bind(
+            tokenizer,
+            BaseTokenizer,
+            default_factory=lambda: RegexTokenizer(filter_stopwords=False),
+        )
         self.index_path = self.working_path / self.component_type.value
         self.index_path.mkdir(parents=True, exist_ok=True)
 
     async def _start(self) -> None:
-        """Initialize tokenizer and load existing index if available."""
-        if self.app_context is None:
-            from ..tokenizer import RegexTokenizer
-
-            self.tokenizer = RegexTokenizer(filter_stopwords=False)
-        else:
-            self.tokenizer = self.get_component(ComponentEnum.TOKENIZER, self.tokenizer_name)
-
-        if self.tokenizer is not None:
-            await self.tokenizer.start()
-
+        """Load existing index if available. Tokenizer is injected and started by the owner lifecycle."""
         if self.index_file.exists():
             await self.load()
             self.logger.info(f"Loaded index from {self.index_path}")
@@ -41,9 +36,6 @@ class BaseKeywordIndex(BaseComponent):
         await self.dump()
         self.logger.info(f"Saved index to {self.index_path}")
 
-        if self.tokenizer is not None:
-            await self.tokenizer.close()
-
     @property
     def index_file(self) -> Path:
         """Path to the index pickle file based on tokenizer name."""