The allegation against Batista upended the already dramatic corruption saga, which has left Temer fighting to remain in power and has damaged JBS. It also marks a radical change of fate for Batista himself.
The businessman and his brother Wesley admitted to prosecutors that they had bribed no less than 1,900 politicians.
It was the kind of large-scale graft network similar to those uncovered at other major Brazilian companies. But the bombshell allegation involved Temer.
To bolster the evidence, Batista met with Temer at his Brasilia residence in March and secretly recorded the president allegedly discussing payment of hush money to keep a former ally from testifying.
That recording and the Batistas' testimony then became key weapons in efforts by chief prosecutor Rodrigo Janot to put Temer behind bars. In return for their testimony, the Batista brothers appeared set to avoid prison.
A first criminal charge against Temer of bribe-taking lodged in June was rejected by Congress. However, Janot has been expected to file a second charge of obstruction of justice -- based partly on the Batista recording -- within days.
But the plea deal agreement, lambasted by Temer as a get-out-of-jail card for a "notorious bandit," is now under question.
And the confusion apparently started with what appears to have been a blunder by the tycoon's lawyers.
They were meant to send prosecutors more evidence under the plea deal but seemingly sent by error a recording in which Joesley Batista is said to be heard discussing with a former company director, Ricardo Saud, how he withheld important information from prosecutors.