fix: shared MCP truncate() crashes on None/non-string tool output (#1605)

mcp_servers/_common.py

@@ -13,6 +13,10 @@ SEARCH_TIMEOUT = 30
 
 def truncate(text: str, limit: int = MAX_OUTPUT_CHARS) -> str:
     """Truncate text to *limit* characters with a suffix note."""
+    if not isinstance(text, str):
+        # Tool output is occasionally None or a non-string; len(None) would
+        # raise. Coerce so this shared helper never crashes a tool response.
+        text = "" if text is None else str(text)
     if len(text) > limit:
         return text[:limit] + f"\n... (truncated, {len(text)} chars total)"
     return text

tests/test_mcp_common_truncate.py

@@ -0,0 +1,27 @@
+"""Regression: the shared MCP truncate() must tolerate non-string input."""
+import importlib.machinery
+import importlib.util
+from pathlib import Path
+
+_PATH = Path(__file__).resolve().parents[1] / "mcp_servers" / "_common.py"
+
+
+def _load():
+    loader = importlib.machinery.SourceFileLoader("odysseus_mcp_common", str(_PATH))
+    spec = importlib.util.spec_from_loader(loader.name, loader)
+    module = importlib.util.module_from_spec(spec)
+    loader.exec_module(module)
+    return module
+
+
+def test_truncate_handles_none_and_nonstring():
+    c = _load()
+    assert c.truncate(None) == ""
+    assert c.truncate(12345) == "12345"
+
+
+def test_truncate_string_behaviour_unchanged():
+    c = _load()
+    assert c.truncate("hello", limit=100) == "hello"
+    out = c.truncate("x" * 50, limit=10)
+    assert out.startswith("x" * 10) and "truncated" in out