fix(ui): skip incomplete tool calls during replay

src/ai/ui/ai_sdk/inbound_messages.py

@@ -245,6 +245,8 @@ def _parse(
                     )
 
                 case ui_messages_.UIToolInvocationPart() as inv:
+                    if inv.state == "input-streaming":
+                        continue
                     tool_args = json.dumps(inv.args) if inv.args else "{}"
                     is_completed = (
                         inv.state in _TOOL_RESULT_STATES
@@ -297,6 +299,8 @@ def _parse(
                         | ui_messages_.UIDynamicToolPart()
                     ) as tp
                 ):
+                    if tp.state == "input-streaming":
+                        continue
                     tool_input = (
                         tp.raw_input
                         if tp.state == "output-error" and tp.input is None

tests/ui/ai_sdk/test_inbound_messages.py

@@ -71,6 +71,39 @@ def test_to_messages_splits_at_tool_boundary() -> None:
     assert messages[1].tool_results[0].tool_call_id == "tc1"
 
 
+@pytest.mark.parametrize(
+    "tool_part",
+    [
+        _tool("search", "tc1", "input-streaming", input={"q": "par"}),
+        {
+            "type": "dynamic-tool",
+            "toolName": "search",
+            "toolCallId": "tc1",
+            "state": "input-streaming",
+            "input": {"q": "par"},
+        },
+        {
+            "type": "tool-invocation",
+            "toolName": "search",
+            "toolInvocationId": "tc1",
+            "state": "input-streaming",
+            "args": {"q": "par"},
+        },
+    ],
+)
+def test_to_messages_skips_incomplete_tool_calls(
+    tool_part: dict[str, Any],
+) -> None:
+    messages, approvals = to_messages(
+        [_ui("assistant", _text("Searching"), tool_part)]
+    )
+
+    assert approvals == []
+    assert len(messages) == 1
+    assert messages[0].text == "Searching"
+    assert messages[0].tool_calls == []
+
+
 def test_to_messages_keeps_deferred_approval_tombstone() -> None:
     """Deferred approvals carry no response — leave the tombstone in history."""
     messages, _ = to_messages(