“I'm literally looking at like okay if they have enough data and the cost per trial for example is low enough then we can do it based on that that's the ideal if it's not or if they're a very new app and they don't have big budgets then I'll look on clickthrough rates.”

Use Cost-Per-Trial as the Proper Messaging Signal — CTR Only as a Budget-Constrained Proxy

CTR measures curiosity; cost-per-trial measures intent. When budget allows, Daphne optimizes messaging tests for cost-per-trial because a message that attracts clicks but not subscribers is a false signal. For early-stage apps with small budgets, CTR is the practical proxy — but results should be corroborated across at least two channels before treating them as directionally reliable.