FuelLabs/fuel-core · error

The override height is zero. The override height should be g

Error message

The override height is zero. The override height should be greater than zero.

What it means

Thrown at node startup by make_database_compatible_with_config (crates/fuel-core/src/service.rs:335). For ConsensusConfig::PoAV2 the node iterates poa.get_all_overrides(); when the stored block's PoA seal at an override height fails verify_consensus against the startup config, it plans a rollback to override_height - 1 via BlockHeight::pred(). An override at height 0 makes pred() return None, and since there is no height before genesis to roll back to, startup aborts with this error.

Source

Thrown at crates/fuel-core/src/service.rs:335

                            start_up_consensus_config,
                            &header,
                            &poa_seal,
                        );

                        if !block_valid {
                            found_override_height = Some(override_height);
                        }
                    } else {
                        return Err(anyhow::anyhow!(
                            "The consensus at override height {override_height} is not PoA."
                        ));
                    };
                }
            }
        }

        if let Some(override_height) = found_override_height {
            let rollback_height = override_height.pred().ok_or(anyhow::anyhow!(
                "The override height is zero. \
                The override height should be greater than zero."
            ))?;
            tracing::warn!(
                "The consensus at override height {override_height} \
                does not match with the database. \
                Rollbacking the database to the height {rollback_height}"
            );
            combined_database.rollback_to(rollback_height, shutdown_listener)?;
        }

        Ok(())
    }

    fn override_chain_config_if_needed(&self) -> anyhow::Result<()> {
        let chain_config = self.shared.config.snapshot_reader.chain_config();
        let on_chain_view = self.shared.database.on_chain().latest_view()?;
        let chain_config_hash = chain_config.root()?.into();

View on GitHub (pinned to b9d4d170da)

Solutions

1. Move the PoAV2 override to a height greater than 0 (e.g., 1) so rollback to height-1 exists
2. Wipe/regenerate the on-chain database so genesis is re-executed under the new consensus instead of rolled back
3. If the goal was only new genesis keys, re-execute genesis with the new chain config rather than declaring an override at height 0
4. Add a config lint that rejects override keys equal to 0 before startup

Example fix

// before (chain config consensus.PoAV2):
//   overrides: { "0": { "signing_keys": [new_keys] } }
// after:
//   overrides: { "1": { "signing_keys": [new_keys] } }
//   (or start with a fresh database so the new keys apply at genesis)

fn overrides_rollbackable(poa: &PoAConfig) -> anyhow::Result<()> {
    for h in poa.get_all_overrides().keys() {
        anyhow::ensure!(!h.is_zero(),
            "override at height 0 cannot be rolled back; use height >= 1");
    }
    Ok(())
}
// run before node start, before make_database_compatible_with_config

match NodeProvider::start(&config).await {
    Err(e) if e.to_string().contains("The override height is zero") => {
        // config/DB mismatch at genesis: fix overrides or wipe DB, do not retry
        eprintln!("override at height 0 is unsupported; move it above 0 or re-init the DB");
        return Err(e);
    }
    other => other,
}

When it happens

Trigger: A PoAV2 chain config whose overrides map contains key height 0 (or BlockHeight::default()), used against a non-empty on-chain database whose genesis-block PoA seal no longer verifies under the new consensus config (e.g., changed/re-ordered signing keys).

Common situations: Editing PoAV2 signing-key overrides to take effect 'from genesis' while reusing an existing database; writing the first override height as 0 in a custom chain config; rotating compromised consensus keys without re-initializing the DB.

Related errors

• The consensus at override height {override_height} is not Po
• The genesis block height is not found in the database during
• Missing code for contract: {id}
• Missing utxo for contract: {id}
• Missing column. Check the schema!

AI-assisted analysis of FuelLabs/fuel-core@b9d4d170da (2026-08-16). Data as JSON: /api/errors/6f968f5d247260ae. Report an issue: GitHub.