Within Mīmāṃsā, the seminal Mīmāṃsāsūtra by Jaimini has been commented upon by Śabara in his Bhāṣya. Next, Kumārila Bhaṭṭa commented upon different portions of the Mīmāṃsāsūtra and the Bhāṣya in four works, i.e., the Ślokavārttika, the lost Bṛhaṭṭīkā, the Tantravārttika and the Ṭupṭīkā. The general tendency in Sanskrit philosophy is to consider Kumārila or his interpreters as the final authority and to read Jaimini and Śabara through his lenses.
While working on a portion of Nyāyamañjarī 4 —the Sarvāgamaprāmāṇya— with Kei Kataoka, we could ascertain what follows as for his Mīmāṃsā sources. In an article, Alex Watson could detect a direct quote of Prabhākara and I would be glad to receive further hints concerning Jayanta's sources.
The main source of the Sarvāgamaprāmāṇya was the Tantravārttika commentary on Mīmāṃsāsūtra 1.3.1-4, by Kumārila Bhaṭṭa (as already ascertained in Kataoka 2004). To Kumārila we could add the role of Śabara as direct source of Jayanta, since in several cases Jayanta prefers Śabara's interpretation over Kumārila's one. As hinted at above, this contradicts a general tendency and is hence of particular significance.
Beside Śabara and Kumārila, we could ascertain that Jayanta also relied on a source within the opposed branch of Prābhākara Mīmāṃsā, although it has not been possible to find an exact textual parallel in the work of Prabhākara Miśra or of his first commentator, Śālikanātha Miśra.
Does this mean that Jayanta could read the work of a Prābhākara author before Prabhākara?
On Jayanta in general, see this post.