Is it safe to combine sodium hypochlorite (bleach) sodium triphosphate (TSP) for cleaning?
Actually, the more complete answer is that Na3PO4 is a recommended stabilizer for bleach.
Also, per a ScienceDirect source, to quote:

Trisodium phosphate hydrolyzes to produce hydroxide ions. Phosphate acts as buffer...'coordinated phosphate pH control.'

where pH control prolongs the shelf life of chlorine bleach, as supported by the statement (same source):

One down-side of chlorinated products is a limited storage stability. This instability reduces the chlorine benefit which the detergent can deliver, but also reduces the benefit of the other active ingredients which are destroyed by bleach action.

Further, more advanced radical-based bleaching is suggested by the comment:

For dyeing with vinyl sulphone dyes, dyebath is prepared with trisodium phosphate (2%) and dye.

So, the scavenging of light (or transition metal contamination) induced radicals (which can lead to unwanted chlorate formation), is likely also an advantage of employing Na3PO4, in my opinion.