fix(providers): lazy-load provider exports

nanobot/providers/__init__.py

@@ -1,5 +1,30 @@
 """LLM provider abstraction module."""
 
+from __future__ import annotations
+
+from importlib import import_module
+from typing import TYPE_CHECKING
+
 from nanobot.providers.base import LLMProvider, LLMResponse
 
-__all__ = ["LLMProvider", "LLMResponse"]
+__all__ = ["LLMProvider", "LLMResponse", "LiteLLMProvider", "OpenAICodexProvider", "AzureOpenAIProvider"]
+
+_LAZY_IMPORTS = {
+    "LiteLLMProvider": ".litellm_provider",
+    "OpenAICodexProvider": ".openai_codex_provider",
+    "AzureOpenAIProvider": ".azure_openai_provider",
+}
+
+if TYPE_CHECKING:
+    from nanobot.providers.azure_openai_provider import AzureOpenAIProvider
+    from nanobot.providers.litellm_provider import LiteLLMProvider
+    from nanobot.providers.openai_codex_provider import OpenAICodexProvider
+
+
+def __getattr__(name: str):
+    """Lazily expose provider implementations without importing all backends up front."""
+    module_name = _LAZY_IMPORTS.get(name)
+    if module_name is None:
+        raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
+    module = import_module(module_name, __name__)
+    return getattr(module, name)