Thanks Cedrik — really appreciate the thoughtful response. It’s great to see someone who shares the same enthusiasm for this idea and immediately gets the distinction between a visibility layer and a verification + execution-trigger layer.
On the technical blocker: you’re right that VerifyMembership exposure is the key unlock. I’ve opened cosmos/gaia#4023 for this — it’s been labeled as an epic by the team, which is encouraging. It’s a configuration change, not a protocol change, so it could land in any Gaia upgrade. In the meantime, the POC works end-to-end with off-chain AppHash verification — the proof math is real, just the trust anchor needs to move on-chain.
On the economic design — this is where the real conversation starts, and I don’t think there’s an obvious answer yet:
Watcher economy: Should watchers be a public Hub service — operated by validators or funded by the community pool as shared infrastructure — or should they be private businesses building on top of a free protocol? Both models have precedents in Cosmos: relayers are largely treated as public goods, while indexers are private businesses. The answer probably shapes the entire value capture model.
Fee model: Do gas fees from increased Hub usage provide enough value by themselves, or does the protocol need its own fee layer? Options range from keeping the primitive entirely free (maximizing adoption, letting value accrue indirectly through ATOM demand), to a protocol fee per verification feeding the community pool, to a staking requirement where only addresses staking a minimum amount of ATOM can create subscriptions. Each has different trade-offs between adoption speed and direct value capture. This is a discussion the community should have.
Watchable state standard: Beyond just consuming existing chain state, we could see a standard emerge — something like an ICS for observable state — where chains structure specific keys for cross-chain consumption: incremental indexes, structured event keys, predictable paths. Chains that adopt the standard become easier to integrate, which creates a network effect around the Hub.
Event propagation: On a more speculative note, you could imagine hubs watching each other, propagating verified state across a network. A proof verified on the Cosmos Hub could be re-proven on another hub, creating a mesh of cross-chain awareness without requiring every chain to maintain light clients for every other chain.
Hydro connection: Your parallel with Hydro is spot on. Hydro proved that Hub-native coordination can matter. Interchain Events generalizes that pattern — any cross-chain state becomes a trigger for on-chain logic. The Hydro contract itself could be a great candidate for being watched by other chains reacting to round results.
Would love to hear your thoughts on the watcher model especially — that feels like the most consequential design decision for how this scales."