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Migrating to ibc-go

This file contains information on how to migrate from the IBC module contained in the SDK 0.41.x and 0.42.x lines to the IBC module in the ibc-go repository based on the 0.44 SDK version.

Import Changes

The most obvious changes is import name changes. We need to change:

  • applications -> apps
  • cosmos-sdk/x/ibc -> ibc-go

On my GNU/Linux based machine I used the following commands, executed in order:

grep -RiIl 'cosmos-sdk\/x\/ibc\/applications' | xargs sed -i 's/cosmos-sdk\/x\/ibc\/applications/ibc-go\/modules\/apps/g'
grep -RiIl 'cosmos-sdk\/x\/ibc' | xargs sed -i 's/cosmos-sdk\/x\/ibc/ibc-go\/modules/g'

ref: explanation of the above commands

Executing these commands out of order will cause issues.

Feel free to use your own method for modifying import names.

NOTE: Updating to the v0.44.0 SDK release and then running go mod tidy will cause a downgrade to v0.42.0 in order to support the old IBC import paths. Update the import paths before running go mod tidy.

Chain Upgrades

Chains may choose to upgrade via an upgrade proposal or genesis upgrades. Both in-place store migrations and genesis migrations are supported.

WARNING: Please read at least the quick guide for IBC client upgrades before upgrading your chain. It is highly recommended you do not change the chain-ID during an upgrade, otherwise you must follow the IBC client upgrade instructions.

Both in-place store migrations and genesis migrations will:

  • migrate the solo machine client state from v1 to v2 protobuf definitions
  • prune all solo machine consensus states
  • prune all expired tendermint consensus states

Chains must set a new connection parameter during either in place store migrations or genesis migration. The new parameter, max expected block time, is used to enforce packet processing delays on the receiving end of an IBC packet flow. Checkout the docs for more information.

In-Place Store Migrations

The new chain binary will need to run migrations in the upgrade handler. The fromVM (previous module version) for the IBC module should be 1. This will allow migrations to be run for IBC updating the version from 1 to 2.


func(ctx sdk.Context, _ upgradetypes.Plan, _ module.VersionMap) (module.VersionMap, error) {
// set max expected block time parameter. Replace the default with your expected value
app.IBCKeeper.ConnectionKeeper.SetParams(ctx, ibcconnectiontypes.DefaultParams())

fromVM := map[string]uint64{
... // other modules
"ibc": 1,
return, app.configurator, fromVM)

Genesis Migrations

To perform genesis migrations, the following code must be added to your existing migration code.

// add imports as necessary
import (
ibcv100 ""
ibchost ""


// add in migrate cmd function
// expectedTimePerBlock is a new connection parameter
newGenState, err = ibcv100.MigrateGenesis(newGenState, clientCtx, *genDoc, expectedTimePerBlock)
if err != nil {
return err

NOTE: The genesis chain-id, time and height MUST be updated before migrating IBC, otherwise the tendermint consensus state will not be pruned.

IBC Keeper Changes

The IBC Keeper now takes in the Upgrade Keeper. Please add the chains' Upgrade Keeper after the Staking Keeper:

// Create IBC Keeper
app.IBCKeeper = ibckeeper.NewKeeper(
- appCodec, keys[ibchost.StoreKey], app.GetSubspace(ibchost.ModuleName), app.StakingKeeper, scopedIBCKeeper,
+ appCodec, keys[ibchost.StoreKey], app.GetSubspace(ibchost.ModuleName), app.StakingKeeper, app.UpgradeKeeper, scopedIBCKeeper,



The UpdateClient has been modified to take in two client-identifiers and one initial height. Please see the documentation for more information.


A new IBC proposal type has been added, UpgradeProposal. This handles an IBC (breaking) Upgrade. The previous UpgradedClientState field in an Upgrade Plan has been deprecated in favor of this new proposal type.

Proposal Handler Registration

The ClientUpdateProposalHandler has been renamed to ClientProposalHandler. It handles both UpdateClientProposals and UpgradeProposals.

Add this import:

+  ibcclienttypes ""

Please ensure the governance module adds the correct route:

-  AddRoute(ibchost.RouterKey, ibcclient.NewClientUpdateProposalHandler(app.IBCKeeper.ClientKeeper))
+ AddRoute(ibcclienttypes.RouterKey, ibcclient.NewClientProposalHandler(app.IBCKeeper.ClientKeeper))

NOTE: Simapp registration was incorrect in the 0.41.x releases. The UpdateClient proposal handler should be registered with the router key belonging to ibc-go/core/02-client/types as shown in the diffs above.

Proposal CLI Registration

Please ensure both proposal type CLI commands are registered on the governance module by adding the following arguments to gov.NewAppModuleBasic():

Add the following import:

+  ibcclientclient ""

Register the cli commands:

paramsclient.ProposalHandler, distrclient.ProposalHandler, upgradeclient.ProposalHandler, upgradeclient.CancelProposalHandler,
+ ibcclientclient.UpdateClientProposalHandler, ibcclientclient.UpgradeProposalHandler,

REST routes are not supported for these proposals.

Proto file changes

The gRPC querier service endpoints have changed slightly. The previous files used v1beta1 gRPC route, this has been updated to v1.

The solo machine has replaced the FrozenSequence uint64 field with a IsFrozen boolean field. The package has been bumped from v1 to v2

IBC callback changes


Application developers need to update their OnRecvPacket callback logic.

The OnRecvPacket callback has been modified to only return the acknowledgement. The acknowledgement returned must implement the Acknowledgement interface. The acknowledgement should indicate if it represents a successful processing of a packet by returning true on Success() and false in all other cases. A return value of false on Success() will result in all state changes which occurred in the callback being discarded. More information can be found in the documentation.

The OnRecvPacket, OnAcknowledgementPacket, and OnTimeoutPacket callbacks are now passed the sdk.AccAddress of the relayer who relayed the IBC packet. Applications may use or ignore this information.

IBC Event changes

The packet_data attribute has been deprecated in favor of packet_data_hex, in order to provide standardized encoding/decoding of packet data in events. While the packet_data event still exists, all relayers and IBC Event consumers are strongly encouraged to switch over to using packet_data_hex as soon as possible.

The packet_ack attribute has also been deprecated in favor of packet_ack_hex for the same reason stated above. All relayers and IBC Event consumers are strongly encouraged to switch over to using packet_ack_hex as soon as possible.

The consensus_height attribute has been removed in the Misbehaviour event emitted. IBC clients no longer have a frozen height and misbehaviour does not necessarily have an associated height.

Relevant SDK changes

  • (codec) #9226 Rename codec interfaces and methods, to follow a general Go interfaces:
    • codec.Marshalercodec.Codec (this defines objects which serialize other objects)
    • codec.BinaryMarshalercodec.BinaryCodec
    • codec.JSONMarshalercodec.JSONCodec
    • Removed BinaryBare suffix from BinaryCodec methods (MarshalBinaryBare, UnmarshalBinaryBare, ...)
    • Removed Binary infix from BinaryCodec methods (MarshalBinaryLengthPrefixed, UnmarshalBinaryLengthPrefixed, ...)