  We introduce a principle of local collection for compositional truth
predicates and show that it is conservative over the classically compositional
theory of truth in the arithmetical setting. This axiom states that upon
restriction to formulae of any syntactic complexity, the resulting predicate
satisfies full collection. In particular, arguments using collection for the
truth predicate applied to sentences occurring in any given (code of a) proof
do not suffice to show that the conclusion of that proof is true, in stark
contrast to the case of induction scheme. We analyse various further results
concerning end-extensions of models of compositional truth and the collection
scheme for the compositional truth predicate.
