The most influential form is the short Chinese one, in 260 characters, attributed to Xuanzang, the pilgrim-translator who travelled to India and returned in 645. His version, dated 649, is the text chanted across East Asia; longer recensions exist in Sanskrit and Tibetan with a conventional narrative frame, an audience and a closing approval by the Buddha, which the short Chinese text lacks. Traditional accounts hold that Xuanzang received the sutra before his journey and recited it for protection in the desert, a legend, but one that shows how early the text was treated as talismanic rather than merely doctrinal.
In 1992 the Buddhologist Jan Nattier published an argument that reversed the assumed direction of transmission. Comparing the Heart Sutra's core section with the corresponding passage in Kumarajiva's Chinese translation of the Large Perfection of Wisdom Sutra, she found the Chinese wording of the two nearly identical, while the Sanskrit of the Heart Sutra differs from the Sanskrit the Large Sutra passage is drawn from in ways a shared Indian original would not explain. Her conclusion: the Heart Sutra was assembled in China, probably in the seventh century, from Kumarajiva's Chinese, and afterwards back-translated into Sanskrit.
The thesis is genuinely contested rather than settled. It has been widely accepted among Western scholars and has shaped subsequent work, but it has been rejected in detail by Harada Waso, Fukui Fumimasa, Ishii Kosei and others, largely on the evidence of the seventh-century commentaries by Xuanzang's pupils Woncheuk and Kuiji and of Sanskrit manuscript material. Nothing in the dispute affects the sutra's standing in practice, and no tradition that chants it has treated the question as devotional.