fix(providers): lazy-load provider exports

tests/test_providers_init.py

@@ -0,0 +1,37 @@
+"""Tests for lazy provider exports from nanobot.providers."""
+
+from __future__ import annotations
+
+import importlib
+import sys
+
+
+def test_importing_providers_package_is_lazy(monkeypatch) -> None:
+    monkeypatch.delitem(sys.modules, "nanobot.providers", raising=False)
+    monkeypatch.delitem(sys.modules, "nanobot.providers.litellm_provider", raising=False)
+    monkeypatch.delitem(sys.modules, "nanobot.providers.openai_codex_provider", raising=False)
+    monkeypatch.delitem(sys.modules, "nanobot.providers.azure_openai_provider", raising=False)
+
+    providers = importlib.import_module("nanobot.providers")
+
+    assert "nanobot.providers.litellm_provider" not in sys.modules
+    assert "nanobot.providers.openai_codex_provider" not in sys.modules
+    assert "nanobot.providers.azure_openai_provider" not in sys.modules
+    assert providers.__all__ == [
+        "LLMProvider",
+        "LLMResponse",
+        "LiteLLMProvider",
+        "OpenAICodexProvider",
+        "AzureOpenAIProvider",
+    ]
+
+
+def test_explicit_provider_import_still_works(monkeypatch) -> None:
+    monkeypatch.delitem(sys.modules, "nanobot.providers", raising=False)
+    monkeypatch.delitem(sys.modules, "nanobot.providers.litellm_provider", raising=False)
+
+    namespace: dict[str, object] = {}
+    exec("from nanobot.providers import LiteLLMProvider", namespace)
+
+    assert namespace["LiteLLMProvider"].__name__ == "LiteLLMProvider"
+    assert "nanobot.providers.litellm_provider" in sys.modules