feat(llm): add Amazon Bedrock as a first-class provider

Bedrock uses the Converse API (langchain-aws) and the AWS credential chain, so
it has its own client like Anthropic/Google rather than the OpenAI-compatible
registry. langchain-aws is an optional dependency (pip install ".[bedrock]"),
lazy-imported with a clear install hint; importing the package never requires
it. The model name is a Bedrock model ID / inference profile ID.

tradingagents/llm_clients/bedrock_client.py

@@ -0,0 +1,69 @@
+import os
+from typing import Any
+
+from .base_client import BaseLLMClient, normalize_content
+from .validators import validate_model
+
+# Bedrock has no global default region; us-west-2 hosts the broadest model set.
+_DEFAULT_REGION = "us-west-2"
+_BEDROCK_CLASS = None
+
+
+def _bedrock_class():
+    """Lazily import langchain-aws (the optional ``[bedrock]`` extra) and return a
+    ChatBedrockConverse subclass with normalized content output.
+
+    Imported on demand so the optional dependency (and boto3) isn't required by
+    the rest of the package; cached after the first call.
+    """
+    global _BEDROCK_CLASS
+    if _BEDROCK_CLASS is not None:
+        return _BEDROCK_CLASS
+
+    try:
+        from langchain_aws import ChatBedrockConverse
+    except ImportError as exc:
+        raise ImportError(
+            "AWS Bedrock support requires the optional 'langchain-aws' dependency. "
+            'Install it with: pip install "tradingagents[bedrock]"'
+        ) from exc
+
+    class NormalizedChatBedrockConverse(ChatBedrockConverse):
+        """ChatBedrockConverse with normalized (string) content output."""
+
+        def invoke(self, input, config=None, **kwargs):
+            return normalize_content(super().invoke(input, config, **kwargs))
+
+    _BEDROCK_CLASS = NormalizedChatBedrockConverse
+    return _BEDROCK_CLASS
+
+
+class BedrockClient(BaseLLMClient):
+    """Client for Amazon Bedrock via the Converse API (langchain-aws).
+
+    Authentication uses the standard AWS credential chain (env vars,
+    ``~/.aws/credentials``, or an IAM role); set ``AWS_REGION`` /
+    ``AWS_DEFAULT_REGION`` and optionally ``AWS_PROFILE``. The model name is a
+    Bedrock model ID or cross-region inference profile ID, e.g.
+    ``us.anthropic.claude-opus-4-8-v1:0``.
+    """
+
+    def get_llm(self) -> Any:
+        """Return a configured ChatBedrockConverse instance."""
+        self.warn_if_unknown_model()
+        chat_cls = _bedrock_class()
+
+        region = (
+            os.environ.get("AWS_REGION")
+            or os.environ.get("AWS_DEFAULT_REGION")
+            or _DEFAULT_REGION
+        )
+        llm_kwargs = {"model": self.model, "region_name": region}
+        for key in ("temperature", "max_tokens", "max_retries", "callbacks"):
+            if key in self.kwargs:
+                llm_kwargs[key] = self.kwargs[key]
+        return chat_cls(**llm_kwargs)
+
+    def validate_model(self) -> bool:
+        """Validate model for Bedrock (any model ID accepted)."""
+        return validate_model("bedrock", self.model)