diff --git a/src/copilot.py b/src/copilot.py
index 62d2b8ca2..92c9c0a21 100644
--- a/src/copilot.py
+++ b/src/copilot.py
@@ -230,7 +230,10 @@ def request_flags(messages) -> tuple:
     """
     msgs = messages or []
     last = msgs[-1] if msgs else None
-    agent = bool(last) and last.get("role") != "user"
+    # A message element can be a non-dict (clients send `"messages": ["hi"]`);
+    # the vision loop below already guards each element with isinstance, so do
+    # the same here rather than call .get() on a bare string.
+    agent = isinstance(last, dict) and last.get("role") != "user"
     vision = False
     for m in msgs:
         content = m.get("content") if isinstance(m, dict) else None
diff --git a/tests/test_copilot.py b/tests/test_copilot.py
index 52d530af6..facf9a98f 100644
--- a/tests/test_copilot.py
+++ b/tests/test_copilot.py
@@ -89,6 +89,18 @@ def test_request_flags_vision():
     assert vision is True
 
 
+def test_request_flags_non_dict_last_message_does_not_crash():
+    # A client can send a bare-string (non-dict) last element; before the
+    # isinstance guard this raised AttributeError on last.get("role").
+    assert copilot.request_flags(["hi"]) == (False, False)
+    assert copilot.request_flags([{"role": "user"}, "trailing"]) == (False, False)
+
+
+def test_request_flags_empty_and_none():
+    assert copilot.request_flags([]) == (False, False)
+    assert copilot.request_flags(None) == (False, False)
+
+
 def test_apply_request_headers_mutates():
     h = {"X-GitHub-Api-Version": "v"}
     copilot.apply_request_headers(h, [{"role": "tool", "content": "x"}])