diff --git a/nanobot/utils/helpers.py b/nanobot/utils/helpers.py
index a8681b8f..eebee792 100644
--- a/nanobot/utils/helpers.py
+++ b/nanobot/utils/helpers.py
@@ -526,6 +526,9 @@ def split_message(content: str, max_len: int = 2000) -> list[str]:
     """
     if not content:
         return []
+    # Non-positive max_len cannot advance the cut pointer; return unsplit.
+    if max_len <= 0:
+        return [content]
     if len(content) <= max_len:
         return [content]
     chunks: list[str] = []
diff --git a/tests/utils/test_helpers.py b/tests/utils/test_helpers.py
index 483eb77e..3d7daf96 100644
--- a/tests/utils/test_helpers.py
+++ b/tests/utils/test_helpers.py
@@ -12,6 +12,13 @@ def test_split_message_no_code_blocks_unchanged():
     assert split_message(content, max_len=12) == ["alpha beta", "gamma delta"]
 
 
+def test_split_message_nonpositive_maxlen_returns_unsplit():
+    content = "alpha beta gamma delta"
+
+    assert split_message(content, max_len=0) == [content]
+    assert split_message(content, max_len=-1) == [content]
+
+
 def test_truncate_text_to_tokens_keeps_text_within_budget():
     text = "hello world " * 100