Air with fire
The elements suit each other. Libra supplies the social framework and Sagittarius supplies the appetite for going somewhere with it, and the pairing tends to have a full diary and a wide circle without either party working at it.
The exchange is uneven in one respect. Sagittarius genuinely does not mind being disagreed with and treats a robust argument as entertainment. Libra minds a great deal and treats the same exchange as a rupture that has to be repaired afterwards, usually without saying so.
Cardinal and mutable
Libra initiates and Sagittarius adapts, which avoids most of the usual struggles over who decides. Sagittarius does not particularly want to run the arrangement and is content to go along with a plan that sounds interesting.
The problem is commitment rather than control. Libra's proposals are made with a settled partnership in view; Sagittarius agrees to the plan without necessarily agreeing to the frame around it. Both parties can leave the same conversation believing something different was decided.
Venus and Jupiter
Libra answers to Venus and Sagittarius to Jupiter, and classical astrology counts both as benefic. That is unusual and it accounts for the easy tone of the combination: neither ruler is inclined towards severity or grievance.
What two benefics do not supply is restraint. Venus avoids unpleasantness and Jupiter enlarges whatever it touches, so the pairing tends to overcommit socially and financially and to under-address anything difficult. The actual placements determine how pronounced that is.
Where it grinds
Bluntness. Sagittarius says the accurate thing in front of other people and considers the accuracy sufficient justification. Libra experiences public correction as a real injury and does not raise it at the time, which means Sagittarius often has no idea that damage occurred.
The second friction is freedom. Libra wants the partnership acknowledged and included; Sagittarius resists being defined by it and will occasionally make that point in a way that is heard as a rejection rather than as a preference.
A third strain is follow-through. Libra keeps arrangements because breaking them is unpleasant, while Sagittarius revises them when something better appears, and the cancelled evening costs more than Sagittarius assumes.
Why the suns are not the answer
A sun sign is shared by everyone born in the same stretch of the year, which makes any pairing account a statement about a tendency across millions of people rather than about a particular two.
The Moons tell you whether the two can be at home together, which neither sun sign addresses. Venus tells you what each expects from affection, and Mars tells you how the honesty problem behaves under pressure. Those are the placements worth comparing.
Questions people ask about this
Is Sagittarius too blunt for Libra?
Often, particularly in company. Libra rarely says so at the time, which means the injury goes unnoticed and repeats.
Do two benefic rulers make this easy?
They make it pleasant. Venus and Jupiter supply warmth and expansion and neither supplies restraint, which is the pairing's actual weakness.
Where does commitment go wrong?
Libra proposes with a partnership in mind and Sagittarius agrees to the plan rather than the frame. Both can leave believing different things were settled.
What should I look at beyond the suns?
Moon, Venus and Mars in both charts, and how they relate. They describe two people rather than two months of the year.