Python: Replace Pydantic Settings with TypedDict + load_settings() (#3843)

* Replace Pydantic Settings with TypedDict + load_settings()

- Remove pydantic-settings dependency, add python-dotenv
- Delete _pydantic.py (AFBaseSettings, HTTPsUrl)
- Add _settings.py with generic load_settings() function, SecretString,
  type coercion, and Required field validation (SettingNotFoundError)
- Convert all 13 settings classes from AFBaseSettings subclasses to
  TypedDict definitions with load_settings() calls
- Update all consumers from attribute access to dict access
- Add 20 unit tests for load_settings() covering basic loading, dotenv,
  SecretString, type coercion, and required field validation
- Update all existing tests for new settings patterns

* Fix mypy type errors from settings conversion

- Fix str | None attribute access in responses_client (walrus operator)
- Fix SecretString | None narrowing in bedrock (type: ignore after guard)
- Convert _context_provider.py attribute access to dict access (missed file)
- Fix endpoint type narrowing in search_provider and context_provider
- Fix purview: str | None .rstrip(), int | None defaults, urlparse bytes

* Address PR review: required_fields param, type validation, fixes

- Move required field validation from TypedDict annotations (Required)
  to a required_fields parameter on load_settings(), enabling runtime
  decisions about which fields are required
- Remove Required imports and restore from __future__ import annotations
  in ollama and foundry_local
- Add _check_override_type() for deterministic ServiceInitializationError
  on invalid override types (e.g. dict passed for str field)
- Fix all multi-exception test catches back to single exception type
- Fix Ollama host=None: use .get() so None is passed through to SDK default
- Fix Purview processor: use explicit is-None checks instead of or operator
- Remove unused BaseModel import from openai/_shared.py
- Add 4 new tests (24 total): required_fields param, type validation

* Fix type validation: allow int for float fields

_check_override_type now permits int values for float-typed fields,
matching Python's standard numeric promotion behavior.

* fix: wrap urlparse arg with str() to fix mypy bytes endswith error

python/packages/bedrock/agent_framework_bedrock/_chat_client.py

@@ -30,13 +30,13 @@ from agent_framework import (
     prepare_function_call_results,
     validate_tool_mode,
 )
-from agent_framework._pydantic import AFBaseSettings
+from agent_framework._settings import SecretString, load_settings
 from agent_framework.exceptions import ServiceInitializationError, ServiceInvalidResponseError
 from agent_framework.observability import ChatTelemetryLayer
 from boto3.session import Session as Boto3Session
 from botocore.client import BaseClient
 from botocore.config import Config as BotoConfig
-from pydantic import BaseModel, SecretStr, ValidationError
+from pydantic import BaseModel
 
 if sys.version_info >= (3, 13):
     from typing import TypeVar  # type: ignore # pragma: no cover
@@ -205,16 +205,14 @@ FINISH_REASON_MAP: dict[str, FinishReasonLiteral] = {
 }
 
 
-class BedrockSettings(AFBaseSettings):
+class BedrockSettings(TypedDict, total=False):
     """Bedrock configuration settings pulled from environment variables or .env files."""
 
-    env_prefix: ClassVar[str] = "BEDROCK_"
-
-    region: str = DEFAULT_REGION
-    chat_model_id: str | None = None
-    access_key: SecretStr | None = None
-    secret_key: SecretStr | None = None
-    session_token: SecretStr | None = None
+    region: str | None
+    chat_model_id: str | None
+    access_key: SecretString | None
+    secret_key: SecretString | None
+    session_token: SecretString | None
 
 
 class BedrockChatClient(
@@ -280,24 +278,25 @@ class BedrockChatClient(
                 client = BedrockChatClient[MyOptions](model_id="<model name>")
                 response = await client.get_response("Hello", options={"my_custom_option": "value"})
         """
-        try:
-            settings = BedrockSettings(
-                region=region,
-                chat_model_id=model_id,
-                access_key=access_key,  # type: ignore[arg-type]
-                secret_key=secret_key,  # type: ignore[arg-type]
-                session_token=session_token,  # type: ignore[arg-type]
-                env_file_path=env_file_path,
-                env_file_encoding=env_file_encoding,
-            )
-        except ValidationError as ex:
-            raise ServiceInitializationError("Failed to initialize Bedrock settings.", ex) from ex
+        settings = load_settings(
+            BedrockSettings,
+            env_prefix="BEDROCK_",
+            region=region,
+            chat_model_id=model_id,
+            access_key=access_key,
+            secret_key=secret_key,
+            session_token=session_token,
+            env_file_path=env_file_path,
+            env_file_encoding=env_file_encoding,
+        )
+        if not settings.get("region"):
+            settings["region"] = DEFAULT_REGION
 
         if client is None:
             session = boto3_session or self._create_session(settings)
             client = session.client(
                 "bedrock-runtime",
-                region_name=settings.region,
+                region_name=settings["region"],
                 config=BotoConfig(user_agent_extra=AGENT_FRAMEWORK_USER_AGENT),
             )
 
@@ -307,17 +306,17 @@ class BedrockChatClient(
             **kwargs,
         )
         self._bedrock_client = client
-        self.model_id = settings.chat_model_id
-        self.region = settings.region
+        self.model_id = settings["chat_model_id"]
+        self.region = settings["region"]
 
     @staticmethod
     def _create_session(settings: BedrockSettings) -> Boto3Session:
-        session_kwargs: dict[str, Any] = {"region_name": settings.region or DEFAULT_REGION}
-        if settings.access_key and settings.secret_key:
-            session_kwargs["aws_access_key_id"] = settings.access_key.get_secret_value()
-            session_kwargs["aws_secret_access_key"] = settings.secret_key.get_secret_value()
-        if settings.session_token:
-            session_kwargs["aws_session_token"] = settings.session_token.get_secret_value()
+        session_kwargs: dict[str, Any] = {"region_name": settings.get("region") or DEFAULT_REGION}
+        if settings.get("access_key") and settings.get("secret_key"):
+            session_kwargs["aws_access_key_id"] = settings["access_key"].get_secret_value()  # type: ignore[union-attr]
+            session_kwargs["aws_secret_access_key"] = settings["secret_key"].get_secret_value()  # type: ignore[union-attr]
+        if settings.get("session_token"):
+            session_kwargs["aws_session_token"] = settings["session_token"].get_secret_value()  # type: ignore[union-attr]
         return Boto3Session(**session_kwargs)
 
     @override

python/packages/bedrock/tests/test_bedrock_settings.py

@@ -11,6 +11,7 @@ from agent_framework import (
     FunctionTool,
     Message,
 )
+from agent_framework._settings import load_settings
 from pydantic import BaseModel
 
 from agent_framework_bedrock._chat_client import BedrockChatClient, BedrockSettings
@@ -33,9 +34,9 @@ def _dummy_weather(location: str) -> str:  # pragma: no cover - helper
 def test_settings_load_from_environment(monkeypatch: pytest.MonkeyPatch) -> None:
     monkeypatch.setenv("BEDROCK_REGION", "us-west-2")
     monkeypatch.setenv("BEDROCK_CHAT_MODEL_ID", "anthropic.claude-v2")
-    settings = BedrockSettings()
-    assert settings.region == "us-west-2"
-    assert settings.chat_model_id == "anthropic.claude-v2"
+    settings = load_settings(BedrockSettings, env_prefix="BEDROCK_")
+    assert settings["region"] == "us-west-2"
+    assert settings["chat_model_id"] == "anthropic.claude-v2"
 
 
 def test_build_request_includes_tool_config() -> None: