Why was the Senate restored in Poland in 1989?

The Senate was restored in Poland in 1989 as part of a series of constitutional reforms negotiated between the communist government and the Solidarity movement.1

Following a period of severe economic and political instability, the government recognized the need for broad reforms and entered into "roundtable negotiations" with the opposition. These discussions led to the agreement to legalize Solidarity and hold partially free elections for a new bicameral parliament. As part of this transition, the Sejm (the existing legislature) became the lower house, and the Senate was reinstated as the upper house with 100 members. This move, along with the replacement of the Council of State with the office of president, was intended to restructure the government and facilitate the country's transition away from the communist model.231