A fragile peace in war-weary Beirut.

As midnight struck in Beirut Sunday morning, the bells and carillons of churches roared into symphony to bring in Easter, the first in nine years celebrated peacefully.

But the sound signified more than a religious feast, for Lebanon was just completing separation of warring factions - for the first time without the assistance of foreign troops - and a new government was finally being shaped.

But as if to remind Lebanese of just how fragile is the latest peace effort, the velvet sky flared with fireworks, red tracers from the guns of the Christian Lebanese Forces shooting, for once, into the sky instead of at their Muslim rivals. And respecting, for once, the religious preferences of their foes, Muslim fighters kept their guns silent.

A narrow slit of a buffer zone now separates the two halves of the capital, where 2,000 internal security forces finished deployment over the weekend along the city's dividing ''green line'' and nearby mountains. The only reported incidents were the result of doubt among militiamen that the disengagement was really happening and curiosity, as gunmen emerged from crumbling buildings or from behind sandbags to eye the opposition.

''Those people have been fighting each other for a long time,'' said Lt. Ashraf Riffi, spokesman for the disengagement force. ''They would love to see each other's faces, and this is the only occasion they can get to do it without being shot.''

The massive barricades, both physical and psychological, are still standing, but on Easter there were traces of hope.

''Hope, yes. But not yet confidence in a safer and better future,'' commented Beirut's Daily Star. ''The path upwards to peace, self-respect, unity, and prosperity leads through a labyrinthine mine field of obstacles. . . . A breakdown of the truce or the failure to implement the understandings reached in Damascus (Thursday between President Amin Gemayel and President Hafez Assad) would plunge the country deeper than before into helpless self-destruction.''

There are already some political booby traps being planted around the effort to form a new government this week. Lebanese sources say former Prime Minister Rashid Karami is the favored to form a cabinet that will have equal representation of Christians and Muslims.

Under the still unannounced formula, a new cabinet would be charged with overseeing and then implementing constitutional changes to even the balance of power between Christians and Muslims over the next six months. Another part of the deal reportedly calls for increasing the number of parliamentary seats so that majority Muslims would gain equal representation with the minority Christian community that has dominated the government since independence 40 years ago.

But right-wing Christian quarters are already balking. Former President Camille Chamoun said he would not accept a parliamentary alteration, and threatened his party would not join a cabinet led by Mr. Karami, who served under Mr. Chamoun as prime minister in the 1950s, but then turned against him in 1958 as one of the main Muslim leaders behind Lebanon's first uprising.

Naoum Farah of the Lebanese Forces said, ''We will not participate in this new government because we consider (it to be) an instrument in the hands of Syria.''

Only Pierre Gemayel, the President's father and leader of the Christian Phalange Party, offered support. ''Let all know it's not the time for politicking. All should rally around the President and join the new government. Let's not talk. Let's do the job.''

The Christian reaction led Nabih Berri, leader of the Shiite Muslim ''Amal'' movement to charge ''the obstruction has begun.'' Druze leader Walid Jumblatt warned his fighters not to lay down their guard because the Lebanese crisis was still a long way from being settled.

Lebanese sources said the plan calls for Mr. Berri to be named deputy premier for economic issues, since his followers are generally the most underprivileged in Lebanon. Mr. Jumblatt would be deputy premier of national security.

The appointments are important for the Muslims as they would serve to elevate significantly the level of government jobs held by Shiite and Druze in a hierarchy which had been divided mainly by Maronite Christians and Sunni Muslims.

However, both men have indicated reluctance to accept direct roles, preferring to have other party officials join the government during what amounts to a six-month trial period for the peace formula. But the Syrians are likely to pressure them to participate, aware this would increase their cooperation and lead to stronger public acceptance of the government.

But as the various rival leaders maneuver to determine whether this will just be another lull in the long war or a permanent peace, the Lebanese began trying to pull their lives together yet again. A street merchant peddled his cart of music tapes through Beirut's quiet streets, his player blaring the sounds of a song not heard in years here, Lebanon's national anthem.