Composed in Sanskrit, or Assembled in Chinese?

The most consequential modern argument about the text is where it was written, and it is genuinely unresolved.

Jan Nattier published a study in 1992 arguing that the Heart Sutra was composed in China rather than India. The core of the argument is textual: the sutra's central passage corresponds closely to a section of the Large Perfection of Wisdom Sutra, but the correspondence is much tighter with Kumarajiva's Chinese translation of that text than with the surviving Sanskrit. Nattier argued that the Chinese Heart Sutra was extracted from Kumarajiva's Chinese, that the mantra and framing were added, and that the Sanskrit text we have is a back-translation from Chinese, pointing to places where the Sanskrit renders the Chinese in wording that differs from the Sanskrit the Chinese was translated from.

The proposal was and remains contested. Some scholars, including Japanese specialists in the field, have argued against it on the basis of the Sanskrit manuscript tradition and of parallels Nattier's account has to explain away. Others have accepted it. It has not been settled, and it should be described as an open question with a strong argument on one side rather than as a conclusion.

Nothing in it affects the text's standing in practice. A text composed in China in the seventh century is not thereby less Buddhist, and the Chinese Buddhist canon contains a great deal of material composed in China. But the question of whether the most-chanted text in East Asia originated in India bears directly on how the transmission of Buddhism eastward is understood, which is why the argument matters beyond philology.