Some Steam users received a notification yesterday that advertised a Half-Life: Alyx event before vanishing. The notification claimed that the Half-Life Collection would be free until the launch of the VR spin-off, except there is no such thing as the Half-Life Collection, and right now all the Half-Life games have prices.
Source: N4G PC Half-Life might be going free-to-play until the launch of Half-Life: Alyx