Rational homotopy type and computability

Given a simplicial pair $(X,A)$, a simplicial complex $Y$, and a map $f:A \to Y$,does$f$haveanextensionto$X$?Weshowthatforafixed$Y$, this question is algorithmically decidable for all $X$, $A$, and $f$ if $Y$ has the rational homotopy type of an H-space. As a corollary, many questions related to bundle structures over a finite complex are likely decidable. Conversely, for all other $Y$, the question is at least as hard as certain special cases of Hilbert’s tenth problem which are known or suspected to be undecidable.