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Adding the Module

Opening a connection from a CometBFT-based chain is a straightforward process. Until the recent release of wasm light clients, the traditional way of having a light client on a Cosmos-SDK chain was to implement a light client with Go and bundling it with the chain which meant modifying the light client code requires a binary upgrade to the chain. After IBC proved its capability to be extended into other platforms, the wasm light client module was introduced for chains to easily, deploy and modify light clients. Union supports a native, Golang-based light client, and a modular and flexible wasm light client.

Add the 08-wasm Module

Firstly, your chain needs to support wasm clients. The official docs have an extensive guide on enabling this integration. Before diving into this documentation, note that the 08-wasm module requires your chain to be on IBC-go v7 or v8. And also note that adding this module will also add the dependency to libwasmvm to your chain which is already there if you are already using CosmWasm.

Upload the CometBLS Client

By default, the wasm light client module is gated through governance. Storing a contract requires you to submit a store-code proposal:

  1. Download the latest CometBLS light client:
Terminal window
wget https://github.com/unionlabs/union/releases/download/v0.24.0/cometbls-light-client.wasm

This will create a file locally, called ‘cometbls-light-client.wasm’, which is the compiled binary for the CometBLS light client.

  1. Submit a proposal to store the CometBLS light client:
Terminal window
$NODE_BIN tx ibc-wasm store-code cometbls-light-client.wasm \
  --title "Upload CometBLS Wasm client" \
  --summary "Upload CometBLS Wasm client" \
  --deposit 100000$DENOM \
  --from $KEY \
  --gas auto \
  --gas-adjustment 2
  1. Add a deposit for the proposal:
Terminal window
$NODE_BIN tx gov deposit $PROPOSAL_ID 1000000000$DENOM \
  --from $KEY \
  --gas auto \
  --gas-adjustment 2
  1. Vote yes on the proposal:
Terminal window
$NODE_BIN tx gov vote "$PROPOSAL_ID" yes \
  --from $KEY \
  -y \
  --gas auto \
  --gas-adjustment 2

After the proposal passes, query for the stored light client’s checksum:

Terminal window
$NODE_BIN query ibc-wasm checksums

Read more in the official docs.