Tangshi lunduan 唐史論斷 "Discursive judgments on the History of the Tang Dynasty" is a historical critique of the dynastic history Tangshu 唐書 written by the Song period 宋 (960-1279) historian Sun Fu 孫甫 (998-1057). He was a very active politician and fought for favourable terms of the treatises of the Song court with the Western Xia empire 西夏 (1038-1227) and criticized Emperor Renzong 宋仁宗 (r. 1022-1063) for his negligence of realpolitcs. Sun Fu was very interested in history and compiled the books Tang shiji 唐史記 and Sansheng zhengfan 三聖政範.
His 3-juan long critique Tangshi lunduan is an evaluation of Liu Xu's 劉昫 (888–947) official dynastic history Tangshu (today known as Jiutangshu 舊唐書) that, he says, is much too confuse, in some parts too wide, and in some too brief.
Sun Fu also rearranged historiographical material from the Tangshu, which is written in a biographic-thematic style, into the shape of a chronicle. The result was the book 75-juan long Tangji 唐紀, in which praise and blame for political decisions and mechanism during the Tang period 唐 (618-907) were clearly laid out. For each of the 92 chapters, Sun Fu wrote a short discussion. This book is unfortunately lost.
The Tangshu lunduan was printed in 1157 in Jianzhou 劍州 (modern Jiange 劍閣, Sichuan), but this print is not transmitted. The earliest surviving print dates from 1235. The Tangshi lunduan is included in the reprint series Xuejin taoyuan 學津討原, Xuehai leibian 學海類編, Yueyatang congshu 粵雅堂叢書, Yihai zhenchen 藝海珠塵, Hanhai 函海 and Siku quanshu 四庫全書.