Table of Contents

Monitoring Misbehaviour and Evidence Submission

Use the mishbehaviour command to monitor the updates for a given client, detect certain types of misbehaviour and submit evidence to the chain. If the evidence passes the on-chain validation, the client is frozen. Further packets cannot be relayed using the frozen client.

    hermes misbehaviour <OPTIONS>

    Listen to client update IBC events and handles misbehaviour

    chain_id                  identifier of the chain where client updates are monitored for misbehaviour
    client_id                 identifier of the client to be monitored for misbehaviour

The misbehaviour monitor starts by analyzing all headers used in prior client updates. Once finished it registers for update client events and checks any new headers for misbehaviour. If it detects evidence of misbehaviour, it submits a transaction with the evidence to the chain. If the chain validates the transaction then the monitor exits.

This is an experimental feature.

The following types of misbehaviour are handled:

  1. Fork

    Assumes at least one consensus state before the fork point exists. Let existing consensus states on chain B be: [Sn,.., Sf, Sf-1, S0] with Sf-1 being the most recent state before the fork. Chain A is queried for a header Hf' at Sf.height and if it is different than the Hf in the event for the client update (the one that has generated Sf on chain), then the two headers are included in the evidence and submitted. Note that in this case the headers are different but have the same height.

  2. BFT time violation for an unavailable header

    Some header with a height that is higher than the latest height on chain A has been accepted and a consensus state was created on B. Note that this implies that the timestamp of this header must be within the clock_drift of the client. Assume the client on B has been updated with h2(not present on/ produced by chain A) and it has a timestamp of t2 that is at most clock_drift in the future. Then the latest header from A is fetched, let it be h1, with a timestamp of t1. If t1 >= t2 then evidence of misbehavior is submitted to A.


The hermes misbehaviour outputs an error message displaying MISBEHAVIOUR DETECTED:

hermes misbehaviour ibc-0 07-tendermint-0
Apr 13 20:04:03.347  INFO ibc_relayer::foreign_client: checking misbehaviour for consensus state heights [Height { revision: 1, height: 195 }, Height { revision: 1, height: 85 }, Height { revision: 1, height: 28 }]
Apr 13 20:04:04.425 ERROR ibc_relayer::foreign_client: MISBEHAVIOUR DETECTED ClientId("07-tendermint-0") h1: Height { revision: 1, height: 195 }-Height { revision: 1, height: 85 } h2: Height { revision: 1, height: 195 }-Height { revision: 1, height: 85 }, sending evidence
Apr 13 20:04:05.070  INFO ibc_relayer_cli::commands::misbehaviour: evidence submission result [ClientMisbehaviour(ClientMisbehaviour(Attributes { height: Height { revision: 0, height: 1521 }, client_id: ClientId("07-tendermint-0"), client_type: Tendermint, consensus_height: Height { revision: 1, height: 195 } }))]

Success: Some(
            Attributes {
                height: Height {
                    revision: 0,
                    height: 1521,
                client_id: ClientId(
                client_type: Tendermint,
                consensus_height: Height {
                    revision: 1,
                    height: 195,

Querying client state from this point will show the client is in frozen state, with frozen_height indicating the height at which the client was frozen:

hermes query client state ibc-0 07-tendermint-0 | jq
  "result": {
    "allow_update_after_expiry": true,
    "allow_update_after_misbehaviour": true,
    "chain_id": "ibc-1",
    "frozen_height": {
      "revision_height": 16,
      "revision_number": 1
    "latest_height": {
      "revision_height": 16,
      "revision_number": 1
    "max_clock_drift": {
      "nanos": 0,
      "secs": 3
    "trust_level": {
      "denominator": "3",
      "numerator": "1"
    "trusting_period": {
      "nanos": 0,
      "secs": 1209600
    "unbonding_period": {
      "nanos": 0,
      "secs": 1814400
    "upgrade_path": [
  "status": "success"