diff --git a/src/claude_code_sdk/_internal/client.py b/src/claude_code_sdk/_internal/client.py
index 9e8ceac..ef1070d 100644
--- a/src/claude_code_sdk/_internal/client.py
+++ b/src/claude_code_sdk/_internal/client.py
@@ -47,11 +47,9 @@ class InternalClient:
 
         match data["type"]:
             case "user":
-                # Extract just the content from the nested structure
                 return UserMessage(content=data["message"]["content"])
 
             case "assistant":
-                # Parse content blocks
                 content_blocks: list[ContentBlock] = []
                 for block in data["message"]["content"]:
                     match block["type"]:
@@ -79,20 +77,18 @@ class InternalClient:
             case "system":
                 return SystemMessage(
                     subtype=data["subtype"],
-                    data=data,  # Pass through all data
+                    data=data,
                 )
 
             case "result":
-                # Map total_cost to total_cost_usd for consistency
                 return ResultMessage(
                     subtype=data["subtype"],
-                    cost_usd=data["cost_usd"],
                     duration_ms=data["duration_ms"],
                     duration_api_ms=data["duration_api_ms"],
                     is_error=data["is_error"],
                     num_turns=data["num_turns"],
                     session_id=data["session_id"],
-                    total_cost_usd=data["total_cost"],
+                    total_cost_usd=data.get("total_cost_usd"),
                     usage=data.get("usage"),
                     result=data.get("result"),
                 )
diff --git a/src/claude_code_sdk/_internal/transport/subprocess_cli.py b/src/claude_code_sdk/_internal/transport/subprocess_cli.py
index 564bc94..f63732a 100644
--- a/src/claude_code_sdk/_internal/transport/subprocess_cli.py
+++ b/src/claude_code_sdk/_internal/transport/subprocess_cli.py
@@ -190,7 +190,11 @@ class SubprocessCLITransport(Transport):
 
                     try:
                         data = json.loads(line_str)
-                        yield data
+                        try:
+                            yield data
+                        except GeneratorExit:
+                            # Handle generator cleanup gracefully
+                            return
                     except json.JSONDecodeError as e:
                         if line_str.startswith("{") or line_str.startswith("["):
                             raise SDKJSONDecodeError(line_str, e) from e
@@ -198,8 +202,6 @@ class SubprocessCLITransport(Transport):
 
             except anyio.ClosedResourceError:
                 pass
-            finally:
-                tg.cancel_scope.cancel()
 
         await self._process.wait()
         if self._process.returncode is not None and self._process.returncode != 0:
diff --git a/src/claude_code_sdk/types.py b/src/claude_code_sdk/types.py
index a80510b..21ae8ff 100644
--- a/src/claude_code_sdk/types.py
+++ b/src/claude_code_sdk/types.py
@@ -75,13 +75,12 @@ class ResultMessage:
     """Result message with cost and usage information."""
 
     subtype: str
-    cost_usd: float
     duration_ms: int
     duration_api_ms: int
     is_error: bool
     num_turns: int
     session_id: str
-    total_cost_usd: float
+    total_cost_usd: float | None = None
     usage: dict[str, Any] | None = None
     result: str | None = None