diff --git a/backend/packages/harness/deerflow/mcp/tools.py b/backend/packages/harness/deerflow/mcp/tools.py
index 9f7d4bc5f..148f82b49 100644
--- a/backend/packages/harness/deerflow/mcp/tools.py
+++ b/backend/packages/harness/deerflow/mcp/tools.py
@@ -70,7 +70,10 @@ def _local_path_from_uri(uri: str, *, base_dir: Path | None = None) -> Path | No
     """
     if not uri:
         return None
-    parsed = urlparse(uri)
+    try:
+        parsed = urlparse(uri)
+    except ValueError:
+        return None
     if parsed.scheme == "file":
         raw = unquote(parsed.path)
     elif parsed.scheme == "":
diff --git a/backend/tests/test_mcp_file_migration.py b/backend/tests/test_mcp_file_migration.py
index 615008b63..235be193e 100644
--- a/backend/tests/test_mcp_file_migration.py
+++ b/backend/tests/test_mcp_file_migration.py
@@ -46,6 +46,9 @@ class TestLocalPathFromUri:
         assert mcp_tools._local_path_from_uri("https://example.com/a.png") is None
         assert mcp_tools._local_path_from_uri("data:image/png;base64,AAAA") is None
 
+    def test_malformed_uri_is_ignored(self):
+        assert mcp_tools._local_path_from_uri("//[::1/foo.png") is None
+
     def test_relative_path_is_ignored_without_base_dir(self):
         assert mcp_tools._local_path_from_uri("relative/path.txt") is None
 
@@ -192,6 +195,14 @@ class TestRewriteLocalPathsInText:
 
         assert result == text
 
+    def test_malformed_path_like_text_is_left_untouched(self, paths: Paths):
+        text = "Saved at //[::1/foo.png"
+
+        with _patch_paths(paths):
+            result = mcp_tools._rewrite_local_paths_in_text(text, thread_id="t1", user_id="u1")
+
+        assert result == text
+
     def test_playwright_markdown_path_is_rewritten_twice_without_copy(self, paths: Paths):
         workspace = paths.sandbox_work_dir("t1", user_id="u1")
         _workspace_file(paths, ".playwright-mcp/page.png", content=b"png")
@@ -508,6 +519,15 @@ class TestConvertCallToolResultRewrites:
         assert content[0]["type"] == "text"
         assert content[0]["text"] == "hello"
 
+    def test_malformed_path_like_text_result_does_not_raise(self, paths: Paths):
+        result = CallToolResult(content=[TextContent(type="text", text="Saved at //[::1/foo.png")], isError=False)
+
+        with _patch_paths(paths):
+            content, _ = mcp_tools._convert_call_tool_result(result, thread_id="t1", user_id="u1")
+
+        assert content[0]["type"] == "text"
+        assert content[0]["text"] == "Saved at //[::1/foo.png"
+
     def test_image_content_passthrough(self, paths: Paths):
         from mcp.types import ImageContent