You operate an Avalanche L1 that accepts Interchain Messaging traffic from another L1. This tool answers the question your risk committee will ask about that arrangement: what is the smallest group of the source chain's validators that could get together and sign a message your chain would accept? Transcribe the source L1's validator stake distribution and the quorum your chain accepts, and the classifier sorts the weights, walks them from largest down, and returns the count at which the accepted quorum is first satisfied.
Avalanche reaches finality in under a second and offers no reorg window, so the challenge-period and dispute-window arithmetic that applies to optimistic rollup bridges has nothing to bite on here. The settlement risk does not disappear, it relocates: it moves to who signed the cross-chain message. A neutral finality classifier that reports a chain has no challenge window is telling you the risk moved off the timing axis, and this is the node that picks it up. The counterparty analogy is exact. A bank that accepts payment instructions from a correspondent has to say why it trusts that correspondent's authorisation controls, and a receiving L1 that accepts Interchain Messaging traffic has to say why it trusts a quorum of the source L1's stake.
The accepted quorum is an input and nothing is baked in. Interchain Messaging leaves the stake-weight threshold to the receiving chain, and it is your policy for this source, not a statute number. For context only, and not applied as a threshold here: the subnet-EVM Warp precompile ships a default quorum numerator of 67 with a permitted range of 33 to 100 against a denominator of 100. Quorum is treated as met when signed weight times 100 is greater than or equal to total weight times the quorum percentage, matching avalanchego's own Warp signature check, and the comparison is evaluated cross-multiplied so no division rounding can move the boundary. Verified against primary Avalanche sources on 2026-07-30.