What happened
Mitterrand's Africa policy operated on a doctrine of preserving French influence across its former colonies ("Françafrique"), and Rwanda — though a former Belgian colony — was drawn into this sphere because its Hutu-led government was seen as a bulwark against Anglophone-backed Tutsi rebels advancing from Uganda.
French military advisers trained and armed the Rwandan government's forces throughout the early 1990s. When the Rwandan Patriotic Front (RPF) invaded from Uganda in 1990, France intervened militarily to prop up Habyarimana. Declassified documents and a 2021 French government-commissioned inquiry (the Duclert Commission) found Paris bore "serious and overwhelming responsibilities" for the disaster, though it stopped short of finding complicity in the genocide itself.
What is well established: French officials were briefed on ethnic massacres of Tutsi civilians beginning in 1990 and escalating sharply from February 1993, a full year before the genocide. Despite this, military cooperation continued. When the genocide began in April 1994, France's Operation Turquoise (June–August 1994) established a so-called safe zone, but it arrived after most of the killing had already happened, and some officers were later accused of allowing perpetrators to escape through it into Zaire.
This is one of the starkest examples in modern European history of a democracy's foreign policy establishment treating a client regime's internal atrocities as secondary to geopolitical positioning.