The exact details are still sketchy, but the series of deliberate leaks are enough to confirm the Israeli air strike inside Syrian borders on Wednesday. Syrian regime officials insist that it was only a weapons-research facility that was hit, while US officials are saying that an arms convoy headed for Lebanon (and perhaps for Hizbollah) was also targeted.
The immediate reaction has been a fear of escalation, and for good reason. The countries have fought three wars, and carried on an intermittent proxy battle in Lebanon for decades. While the Assad regime's narrative of "resistance" was largely just a justification for the repression of its own people, there is no doubt that Syria's incendiary civil war threatens to burn its neighbours. For Lebanon, in particular, that would be a disaster.
The risk of escalation is greater than before - it should be remembered that the Golan border was relatively quiet from the end of the 1973 October War until the uprising in 2011 - but it is not in the interests of either side.
Syrian authorities admitted yesterday that there had been an attack on "a scientific research centre for defence" - the same term it used to describe the suspected nuclear facilities near Deir Ezzor that Israeli jets hit in 2007. At this point, claims about arms convoys and speculation about chemical weapons are still unsubstantiated.
Despite the real concerns about a regional backlash, recent precedent argues against escalation. Damascus has consistently reacted with self-restraint after previous Israeli incursions such as the 2007 strike, saying that it reserved the right to respond but never doing so. Israel, for all its bluster, also knows that it is in an uncertain situation, surrounded by uprisings and isolated by its own actions.
This is not the first time that Israeli forces have carried out attacks on Syrian soil since the uprising started. In early November, IDF forces fired "warning shots" into Syria for two consecutive days. The situation was contained after Syria promised, through the UN, to halt "accidental shelling" of Israeli territory.
Lastly, this week's strike comes as western countries appear to scale back support for Syrian rebels. France has reached out to the former Syrian ambassador and the UN has announced an aid programme that benefits the regime. The Assads are unlikely to risk this reprieve in a fight with Israel.
Of course, escalation cannot be discounted. The Israeli strike embarrassed the regime as its own jets target civilian neighbourhoods and bakeries. On both sides, brinkmanship risks a cross-border conflict, although neither government would like to see it.