KABUL, Afghanistan — It is always hard to gauge what diplomats really think unless one of their cables ends up on WikiLeaks, but every once in a while, the barriers fall and a bit of truth slips into public view.

That is especially true in Afghanistan, where diplomats painstakingly weigh every word against political goals back home.

The positive spin from the Americans has been running especially hard the last few weeks, as Congressional committees in Washington focus on spending bills and the Obama administration, trying to secure money for a few more years here, talks up the country’s progress. The same is going on at the European Union, where the tone has been sterner than in the past, but still glosses predictions of Afghanistan’s future with upbeat words like “promise” and “potential.”

Despite that, one of those rare truth-telling moments came at a farewell cocktail party last week hosted by the departing French ambassador to Kabul: Bernard Bajolet, who is leaving to head France’s Direction Génerale de la Sécurité Extérieure, its foreign intelligence service.