Methods and systems related to speculative resource allocation for routing on an interconnect fabric are disclosed herein. One disclosed method includes speculatively allocating a collection of resources to support a set of paths through an interconnect fabric. The method also includes aggregating a set of responses from the set of paths at a branch node on the set of paths. If a resource contention is detected, the set of responses will include an indicator of a resource contention. The method will then further include transmitting, from the branch node and in response to the indicator of the resource contention, a deallocate message downstream and the indicator of the resource contention upstream, and reallocating resources for the multicast after a hold period.