diff --git a/gptme/llm.py b/gptme/llm.py
index 99407480..bf2d647b 100644
--- a/gptme/llm.py
+++ b/gptme/llm.py
@@ -96,12 +96,15 @@ def print_clear():
             # need to flush stdout to get the print to show up
             sys.stdout.flush()
 
-            # TODO: make this more robust/general, maybe with a callback that runs on each char/chunk
-            # pause inference on finished code-block, letting user run the command before continuing
-            tooluses = list(ToolUse.iter_from_content(output))
-            if tooluses and any(tooluse.is_runnable for tooluse in tooluses):
-                logger.debug("Found tool use, breaking")
-                break
+            # Trigger the tool detection only if the line is finished.
+            # Helps to detect nested start code blocks.
+            if char == "\n":
+                # TODO: make this more robust/general, maybe with a callback that runs on each char/chunk
+                # pause inference on finished code-block, letting user run the command before continuing
+                tooluses = list(ToolUse.iter_from_content(output))
+                if tooluses and any(tooluse.is_runnable for tooluse in tooluses):
+                    logger.debug("Found tool use, breaking")
+                    break
     except KeyboardInterrupt:
         return Message("assistant", output + "... ^C Interrupted")
     finally:
diff --git a/tests/test_codeblock.py b/tests/test_codeblock.py
index aba2f98e..2705eb2b 100644
--- a/tests/test_codeblock.py
+++ b/tests/test_codeblock.py
@@ -58,6 +58,16 @@ def print_readme():
     ]
 
 
+def test_extract_codeblocks_unfinished_nested():
+    markdown = """
+```python
+def print_readme():
+    print('''Usage:
+```javascript
+"""
+    assert Codeblock.iter_from_markdown(markdown) == []
+
+
 def test_extract_codeblocks_empty():
     assert Codeblock.iter_from_markdown("") == []