Observed in a live checkpoint: the pending scenario_validate tool call
carried a scenario_json that the LLM stream cut mid-document (ended
inside the unclosed outer object, len 3837). _parse_json_value failed
with a generic 'Could not extract JSON value' that neither the operator
nor the LLM could act on. Add _looks_truncated (unbalanced structure /
unterminated string at end) and report 'truncated/incomplete JSON' with
input length, so the model regenerates the full document.
busya
614f675f64