Channel Rebalancing

What Is Channel Rebalancing?

Channel rebalancing is a way to move liquidity between your existing channels without opening or closing a channel. Fiber sends a circular payment that leaves through one channel and returns through another, so your total balance stays the same except for routing fees. This helps move local balance to the channel where you need more outbound liquidity.

When to Rebalance

Suppose a node has two channels:

You --[Channel A]--> Peer A    (local: 90, remote: 10)
You --[Channel B]--> Peer B    (local: 10, remote: 90)

Channel A has more local balance, while Channel B has more remote balance. If the node needs to send payments through Channel B, the low local balance on that channel may limit outbound payments. Rebalancing can shift liquidity from Channel A toward Channel B.

A real-world case is a merchant that receives many customer payments through one public node, then later needs to send payouts through a different channel. Rebalancing can move liquidity into the payout channel without closing or reopening channels.

How Fiber Handles Rebalancing

Fiber supports two rebalancing methods:

Automatic rebalancing: use this when you want Fiber to find the circular route for you. It is simpler, but you cannot control which channels are used.
Manual rebalancing: use this when you want to target specific channels or hops. It gives more control, but you need to know the route.

Automatic Rebalancing

Use send_payment with target_pubkey set to your own node pubkey, keysend: true, and allow_self_payment: true. Fiber will try to find a circular path automatically.

{
  "jsonrpc": "2.0",
  "method": "send_payment",
  "params": [
    {
      "target_pubkey": "<your_own_pubkey>",
      "amount": "0x5F5E100",
      "keysend": true,
      "allow_self_payment": true
    }
  ],
  "id": 1
}

This method is easiest to use, but the routing algorithm chooses the path. allow_self_payment is not compatible with trampoline routing.

Manual Rebalancing

Use build_router and send_payment_with_router when you want to control the exact circular route.

First, build a route that starts from your node, passes through the peers you want to use, and returns to your own node:

{
  "jsonrpc": "2.0",
  "method": "build_router",
  "params": [
    {
      "amount": "0x5F5E100",
      "hops_info": [
        { "pubkey": "<peer_A_pubkey>" },
        { "pubkey": "<peer_B_pubkey>" },
        { "pubkey": "<your_own_pubkey>" }
      ]
    }
  ],
  "id": 1
}

build_router returns router_hops, which includes the route, fees, and expiry deltas.

Then send the payment with the returned router:

{
  "jsonrpc": "2.0",
  "method": "send_payment_with_router",
  "params": [
    {
      "router": "<router_hops from build_router>",
      "keysend": true
    }
  ],
  "id": 2
}

To force a specific channel at a hop, include channel_outpoint in hops_info.

Tips

Use dry_run: true first to check whether the route can be built and how much fee it will cost.
Make sure the rebalance amount plus routing fees does not exceed your local balance in the outbound channel.
Use max_fee_amount with send_payment to cap the total routing fee.
Use list_channels after a successful rebalance to confirm the updated balances.