diff --git a/src/anthropic/lib/tools/_beta_builtin_memory_tool.py b/src/anthropic/lib/tools/_beta_builtin_memory_tool.py
index edb948a2..f5b4620a 100644
--- a/src/anthropic/lib/tools/_beta_builtin_memory_tool.py
+++ b/src/anthropic/lib/tools/_beta_builtin_memory_tool.py
@@ -327,6 +327,8 @@ def _read_file_content(full_path: Path, memory_path: str) -> str:
         raise ToolError(
             f"The file {memory_path} no longer exists (may have been deleted or renamed concurrently)."
         ) from err
+    except UnicodeDecodeError as err:
+        raise ToolError(f"The file {memory_path} is not a valid UTF-8 text file and cannot be read as memory.") from err
 
 
 def _format_file_size(bytes_size: int) -> str:
@@ -620,6 +622,8 @@ async def _async_read_file_content(full_path: AsyncPath, memory_path: str) -> st
         raise ToolError(
             f"The file {memory_path} no longer exists (may have been deleted or renamed concurrently)."
         ) from err
+    except UnicodeDecodeError as err:
+        raise ToolError(f"The file {memory_path} is not a valid UTF-8 text file and cannot be read as memory.") from err
 
 
 class BetaAsyncLocalFilesystemMemoryTool(BetaAsyncAbstractMemoryTool):
diff --git a/tests/lib/tools/memory_tools/test_filesystem.py b/tests/lib/tools/memory_tools/test_filesystem.py
index 9a9398f4..cbfffe26 100644
--- a/tests/lib/tools/memory_tools/test_filesystem.py
+++ b/tests/lib/tools/memory_tools/test_filesystem.py
@@ -164,6 +164,16 @@ def test_view_error_for_non_existent_file(self, sync_local_filesystem_tool: Beta
                 BetaMemoryTool20250818ViewCommand(command="view", path="/memories/nonexistent.txt")
             )
 
+    def test_view_error_for_non_utf8_file(self, sync_local_filesystem_tool: BetaLocalFilesystemMemoryTool) -> None:
+        memory_root = sync_local_filesystem_tool.memory_root
+        memory_root.mkdir(parents=True, exist_ok=True)
+        (memory_root / "binary.dat").write_bytes(b"\xff\xfe\x80 not utf-8")
+
+        with pytest.raises(ToolError, match="is not a valid UTF-8 text file"):
+            sync_local_filesystem_tool.view(
+                BetaMemoryTool20250818ViewCommand(command="view", path="/memories/binary.dat")
+            )
+
     def test_view_error_for_files_with_too_many_lines(
         self, sync_local_filesystem_tool: BetaLocalFilesystemMemoryTool
     ) -> None:
@@ -635,6 +645,18 @@ async def test_view_error_for_non_existent_file(
                 BetaMemoryTool20250818ViewCommand(command="view", path="/memories/nonexistent.txt")
             )
 
+    async def test_view_error_for_non_utf8_file(
+        self, async_local_filesystem_tool: BetaAsyncLocalFilesystemMemoryTool
+    ) -> None:
+        memory_root = Path(str(async_local_filesystem_tool.memory_root))
+        memory_root.mkdir(parents=True, exist_ok=True)
+        (memory_root / "binary.dat").write_bytes(b"\xff\xfe\x80 not utf-8")
+
+        with pytest.raises(ToolError, match="is not a valid UTF-8 text file"):
+            await async_local_filesystem_tool.view(
+                BetaMemoryTool20250818ViewCommand(command="view", path="/memories/binary.dat")
+            )
+
     async def test_view_error_for_files_with_too_many_lines(
         self, async_local_filesystem_tool: BetaAsyncLocalFilesystemMemoryTool
     ) -> None: