The traction trebuchet is dated only to "by the 4th century BC" in China with no named inventor, and the later counterweight trebuchet only to "around the 12th century" in Christian and Muslim lands around the Mediterranean; no primary source in this research gives an exact year or a single inventor for either device.
What would resolve this A dated primary text or archaeological find establishing a specific year and place for the first traction trebuchet in China, or for the first counterweight trebuchet, would resolve this.
OpenHistory of military technologyTrebuchet (Wikipedia)