In a first phase, "the framework agreement lays the groundwork for establishing a transitional civilian authority," said the Forces for Freedom and Change, noting that other civilian groups also signed.
"The goals of the agreement are establishing a fully civilian authority, creating a free climate for politics, and reaching a final agreement with the widest political participation," Al-Wathiq al-Barir, a spokesman for the FFC, said.
The military has been pushing a separate, smaller FFC faction to get behind the deal, though one of its members, former rebel and Finance Minister Jibril Ibrahim, criticized it on Twitter as "exclusionary."
A final deal tackling issues including transitional justice and reforms to the military should be completed "within weeks," it said.
However, that part is far thornier, with observers questioning whether the military would be willing to give up economic interests and wider powers that it views as its privileged domain.
Monday's deal was signed by al-Burhan, paramilitary commander Mohamed Hamdan Dagalo and multiple civilian groups, most notably the Forces for Freedom and Change -- the main civilian faction that was ousted in the coup.
The deal -- based on a proposal by the Sudanese Bar Association -- was negotiated in the presence of officials from the United Nations, Western diplomats as well as Saudi Arabia and the United Arab Emirates, according to the FFC.
The signing was attended by UN special representative Volker Perthes and AU ambassador Mohamed Belaish.
Phase one of the deal "is a very low level commitment on al-Burhan's part... allowing him to survive" politically, said Kholood Khair founder of the Confluence Advisory, a Khartoum-based think-tank.
But the signatories will likely face "a real political crisis as they start talking in earnest about security sector reforms, transitional justice (and) financial accountability," she added.
Monday's signing comes months after al-Burhan pledged that the military would step aside and make way for factions to agree on a civilian government.
Pro-democracy activists reject the latest effort and are calling for new street protests demanding the military return to barracks.
On Monday security officers fired tear gas and stun grenades to disperse protesters about 1-1/2km from the presidential palace, a Reuters witness said.
"We will defeat this agreement because it is an extension of the coup," one protester, 36-year-old state employee Ahmed Fateh al-Rahman, said. "We want justice for our martyrs, trial for the military, and civilian rule."
Several former rebels who signed peace deals with Sudan in 2020 also voiced their opposition to the deal.
Mohamed Zakaraia, spokesman for former rebel group the Justice and Equality movement, told AFP that it "will bring about dire consequences and further complicate the political scene."
The United States and allies on Monday welcomed the signing. .
A joint statement issued by the US State Department said the United States, Norway, Saudi Arabia, the United Arab Emirates and Britain "welcome the agreement of an initial political framework."
This report was sourced from data provided by Reuters and Agence France-Presse.