Bayern and Tuchel agreed to part ways in February after the club lost three matches in a row and fell eight points behind eventual champions Bayer Leverkusen.
Bayern's run to the Champions League semi-finals, where they lost narrowly to Real Madrid, along with the club's failure to secure a replacement for Tuchel seemingly led to a change of heart among club bosses.
Tuchel confirmed he was in talks about continuing next season, but said would leave after Saturday's final game against Hoffenheim.
"We will stick to the agreement that we had in February. We had talks, as you reported, but we couldn't agree on terms," Tuchel told reporters.
"It's very difficult. The longer the season went on and the more you experience, the way we played against Arsenal and Real Madrid, it really glues you and the team together.
"These past few weeks were the basis to think about a U-turn, but we couldn't find an agreement to keep working together and I'm not going to elaborate on details and motivations.
"It stays behind closed doors."
Leverkusen's Bundesliga triumph, with former Bayern player Xabi Alonso as coach, broke Munich's 11-year stranglehold on the title.
"I'm a bit sad because I don't want to leave teams and the staff," Tuchel added. "There are 60-70 people you see around the team each day. You really connect with those people and work with them closely.
"This is always tough and a bit sad."
German media reported that Tuchel wanted an extension until 2026 should he agree to stay.
Tuchel's original deal was set to run until 2025 before his impending exit was first announced.
Tuchel at the time said he would have preferred to stay on but the announcement kick-started a fruitless search for a new boss.
Several candidates, including Alonso, former Bayern coach Julian Nagelsmann, former Manchester United interim boss Ralf Rangnick and others reportedly rebuffed approaches.
Tuchel also said striker Harry Kane was out of Saturday's match with Hoffenheim and had left Germany for treatment.
Tuchel said the England captain was struggling with a back injury and had been a doubt ahead of Bayern's semi-final second leg against Real Madrid.
"Harry is receiving treatment with his personal doctor. He's no longer here. He won't travel to Hoffenheim.
"It was really a borderline decision against Madrid. We tried it but it got worse with every move that he made, so there was no chance to take part in training."
Kane's absence ends his slim chances of breaking Robert Lewandowski's single-season Bundesliga goalscoring record. Kane has 36 goals in his first league season in Munich, trailing Lewandowski's record of 41.
"He won't make the squad, nor will Leroy (Sane) or Jamal (Musiala)."
Tuchel said Kim Min-jae, Eric Maxim Choupo-Moting, Kingsley Coman, Serge Gnabry, Raphael Guerreiro and Sacha Boey would also miss the match.
"It's a pretty long list."
