diff --git a/src/anthropic/lib/streaming/_beta_messages.py b/src/anthropic/lib/streaming/_beta_messages.py
index 5a5a562a0..422ef7b7d 100644
--- a/src/anthropic/lib/streaming/_beta_messages.py
+++ b/src/anthropic/lib/streaming/_beta_messages.py
@@ -482,6 +482,8 @@ def accumulate_event(
             ),
         )
     elif event.type == "content_block_delta":
+        if event.index >= len(current_snapshot.content):
+            return current_snapshot
         content = current_snapshot.content[event.index]
         if event.delta.type == "text_delta":
             if content.type == "text":
@@ -530,6 +532,8 @@ def accumulate_event(
             if TYPE_CHECKING:  # type: ignore[unreachable]
                 assert_never(event.delta)
     elif event.type == "content_block_stop":
+        if event.index >= len(current_snapshot.content):
+            return current_snapshot
         content_block = current_snapshot.content[event.index]
         if content_block.type == "text" and is_given(output_format):
             content_block.parsed_output = parse_text(content_block.text, output_format)
diff --git a/src/anthropic/lib/streaming/_messages.py b/src/anthropic/lib/streaming/_messages.py
index 5c0da9992..5c370a42b 100644
--- a/src/anthropic/lib/streaming/_messages.py
+++ b/src/anthropic/lib/streaming/_messages.py
@@ -462,6 +462,8 @@ def accumulate_event(
             ),
         )
     elif event.type == "content_block_delta":
+        if event.index >= len(current_snapshot.content):
+            return current_snapshot
         content = current_snapshot.content[event.index]
         if event.delta.type == "text_delta":
             if content.type == "text":
@@ -497,6 +499,8 @@ def accumulate_event(
             if TYPE_CHECKING:  # type: ignore[unreachable]
                 assert_never(event.delta)
     elif event.type == "content_block_stop":
+        if event.index >= len(current_snapshot.content):
+            return current_snapshot
         content_block = current_snapshot.content[event.index]
         if content_block.type == "text" and is_given(output_format):
             content_block.parsed_output = parse_text(content_block.text, output_format)
diff --git a/src/anthropic/lib/tools/_beta_builtin_memory_tool.py b/src/anthropic/lib/tools/_beta_builtin_memory_tool.py
index edb948a26..f28c661fb 100644
--- a/src/anthropic/lib/tools/_beta_builtin_memory_tool.py
+++ b/src/anthropic/lib/tools/_beta_builtin_memory_tool.py
@@ -166,7 +166,7 @@ def clear_all_memory(self) -> BetaFunctionToolResultType:
 
 
 class BetaAsyncAbstractMemoryTool(BetaAsyncBuiltinFunctionTool):
-    """Abstract base class for memory tool implementations.
+    """Abstract base class for async memory tool implementations.
 
     This class provides the interface for implementing a custom memory backend for Claude.
 
@@ -175,25 +175,31 @@ class BetaAsyncAbstractMemoryTool(BetaAsyncBuiltinFunctionTool):
     Example usage:
 
     ```py
-    class MyMemoryTool(BetaAbstractMemoryTool):
-        def view(self, command: BetaMemoryTool20250818ViewCommand) -> BetaFunctionToolResultType:
+    import asyncio
+    from anthropic import AsyncAnthropic
+
+    class MyMemoryTool(BetaAsyncAbstractMemoryTool):
+        async def view(self, command: BetaMemoryTool20250818ViewCommand) -> BetaFunctionToolResultType:
             ...
             return "view result"
 
-        def create(self, command: BetaMemoryTool20250818CreateCommand) -> BetaFunctionToolResultType:
+        async def create(self, command: BetaMemoryTool20250818CreateCommand) -> BetaFunctionToolResultType:
             ...
             return "created successfully"
 
         # ... implement other abstract methods
 
 
-    client = Anthropic()
-    memory_tool = MyMemoryTool()
-    message = client.beta.messages.run_tools(
-        model="claude-sonnet-4-5",
-        messages=[{"role": "user", "content": "Remember that I like coffee"}],
-        tools=[memory_tool],
-    ).until_done()
+    async def main() -> None:
+        client = AsyncAnthropic()
+        memory_tool = MyMemoryTool()
+        message = await client.beta.messages.run_tools(
+            model="claude-sonnet-4-5",
+            messages=[{"role": "user", "content": "Remember that I like coffee"}],
+            tools=[memory_tool],
+        ).until_done()
+
+    asyncio.run(main())
     ```
     """