Can we get an official citation or unofficial consensus as to the effect of a failed concentration check and attacks of opportunity?
I've been under the impression for years that when a caster casts defensively to avoid an AoO and fails, the spell is lost but no AoO is provoked.
However, some members of my new group argue that the rule is ambiguous as written in the core book and come down on the side that a failed check means an opponent gets an AoO.
Thoughts and friendly opinions?