Parse XML tool-use repl blocks in find_code_blocks

Claude models often emit native XML tool-use syntax
(<invoke name="repl"><parameter name="code">...</parameter></invoke>)
instead of ```repl``` fences, so none of their code was executed.
Fall back to parsing those blocks when no fenced block is present.

Fixes #179

Author: MohammadHijjawi97

rlm/utils/parsing.py

@@ -10,7 +10,8 @@
 def find_code_blocks(text: str) -> list[str]:
     """
     Find REPL code blocks in text wrapped in triple backticks and return List of content(s).
-    Returns None if no code blocks are found.
+    If there are none, fall back to XML tool-use blocks (`<invoke name="repl">`), which
+    Claude models often emit instead of fences. Returns an empty list if nothing is found.
     """
     pattern = r"```repl\s*\n(.*?)\n```"
     results = []
@@ -19,6 +20,11 @@ def find_code_blocks(text: str) -> list[str]:
         code_content = match.group(1).strip()
         results.append(code_content)
 
+    if not results:
+        xml_pattern = r'<invoke\s+name="repl">\s*<parameter\s+name="code">(.*?)</parameter>'
+        for match in re.finditer(xml_pattern, text, re.DOTALL):
+            results.append(match.group(1).strip())
+
     return results
 
 

tests/test_parsing.py

@@ -74,6 +74,52 @@ def factorial(n):
         assert "def factorial(n):" in blocks[0]
         assert "return n * factorial(n - 1)" in blocks[0]
 
+    def test_xml_tool_call_block(self):
+        """Claude models may emit native XML tool-use syntax instead of ```repl``` fences."""
+        text = """I'll inspect the context first.
+
+<function_calls>
+<invoke name="repl">
+<parameter name="code">
+print("Length of context:", len(context))
+print(context[:500])
+</parameter>
+</invoke>
+</function_calls>"""
+        blocks = find_code_blocks(text)
+        assert blocks == ['print("Length of context:", len(context))\nprint(context[:500])']
+
+    def test_multiple_xml_tool_call_blocks(self):
+        text = """<function_calls>
+<invoke name="repl">
+<parameter name="code">a = 1</parameter>
+</invoke>
+<invoke name="repl">
+<parameter name="code">
+b = a + 1
+</parameter>
+</invoke>
+</function_calls>"""
+        blocks = find_code_blocks(text)
+        assert blocks == ["a = 1", "b = a + 1"]
+
+    def test_xml_tool_call_for_other_tool_ignored(self):
+        text = """<function_calls>
+<invoke name="search">
+<parameter name="code">x = 1</parameter>
+</invoke>
+</function_calls>"""
+        assert find_code_blocks(text) == []
+
+    def test_fenced_blocks_take_precedence_over_xml(self):
+        text = """```repl
+y = 2
+```
+<invoke name="repl">
+<parameter name="code">x = 1</parameter>
+</invoke>"""
+        assert find_code_blocks(text) == ["y = 2"]
+
 
 class TestAnswerDictFinalAnswer:
     """Tests for the ``answer`` dict completion signal surfaced via REPLResult.final_answer."""