fix(agent): parse misfenced read_file calls (#4799)

tests/test_misfenced_read_file_tool_call.py

@@ -0,0 +1,70 @@
+import json
+
+import src.agent_tools  # noqa: F401  (break agent_tools<->tool_parsing import cycle)
+from src.tool_parsing import parse_tool_blocks, strip_tool_blocks
+
+
+def test_bash_fenced_read_file_function_call_runs_as_read_file():
+    blocks = parse_tool_blocks('```bash\nread_file("notes/todo.md")\n```')
+
+    assert len(blocks) == 1
+    assert blocks[0].tool_type == "read_file"
+    assert blocks[0].content == "notes/todo.md"
+
+
+def test_python_fenced_read_file_function_call_runs_as_read_file():
+    blocks = parse_tool_blocks('```python\nread_file(path="notes/todo.md", offset=3, limit=2)\n```')
+
+    assert len(blocks) == 1
+    assert blocks[0].tool_type == "read_file"
+    assert json.loads(blocks[0].content) == {
+        "path": "notes/todo.md",
+        "offset": 3,
+        "limit": 2,
+    }
+
+
+def test_bash_fenced_read_file_command_runs_as_read_file():
+    blocks = parse_tool_blocks('```bash\nread_file "notes/todo.md"\n```')
+
+    assert len(blocks) == 1
+    assert blocks[0].tool_type == "read_file"
+    assert blocks[0].content == "notes/todo.md"
+
+
+def test_bash_fenced_read_file_json_command_runs_as_read_file():
+    blocks = parse_tool_blocks('```bash\nread_file {"path":"notes/todo.md","offset":1,"limit":4}\n```')
+
+    assert len(blocks) == 1
+    assert blocks[0].tool_type == "read_file"
+    assert json.loads(blocks[0].content) == {
+        "path": "notes/todo.md",
+        "offset": 1,
+        "limit": 4,
+    }
+
+
+def test_multiline_bash_read_file_block_stays_bash():
+    blocks = parse_tool_blocks('```bash\nread_file notes/todo.md\necho done\n```')
+
+    assert len(blocks) == 1
+    assert blocks[0].tool_type == "bash"
+    assert "read_file notes/todo.md" in blocks[0].content
+
+
+def test_nontrivial_python_read_file_name_stays_python_code():
+    blocks = parse_tool_blocks('```python\nprint(read_file("notes/todo.md"))\n```')
+
+    assert len(blocks) == 1
+    assert blocks[0].tool_type == "python"
+
+
+def test_strip_tool_blocks_removes_rescued_read_file_fence():
+    text = 'Opening file:\n```bash\nread_file "notes/todo.md"\n```\nDone.'
+
+    cleaned = strip_tool_blocks(text)
+
+    assert "```" not in cleaned
+    assert "read_file" not in cleaned
+    assert "Opening file:" in cleaned
+    assert "Done." in cleaned