Routernitro forwarders
In Router Nitro’s November 2023 forwarder flow, forwarders paid destination recipients using assets from their own balances. Router Chain middleware verified those payments against transfer requests before forwarders could claim the corresponding source-chain funds.
Updated:
- Claim prerequisite
-
Middleware verified that the execution evidence matched the recorded request, then marked that request
Completed. - Claim initiation
- The forwarder initiated an outbound request on Router Chain after completion; gateway processing reached the source-chain Nitro contract for settlement.
- Design reference
- Router Protocol’s Router Nitro’s Architecture - Part One , published November 8, 2023.
CoinGabbar’s September 5, 2026 wind-down report described Router Protocol’s planned closure by September 30, 2026. An announced closure date does not confirm completion or establish whether a particular claim remains executable.
What unlocked the source-chain claim?
The source-chain Nitro contract validated the transfer request, collected the user’s funds and incremented its event nonce. It then emitted
FundsDeposited
, which orchestrators submitted to Router Chain with their attestations. After validation, Router Chain invoked middleware to store the request.
A forwarder could process the deposit event in parallel with that registration, paying on the destination chain. Destination Nitro transferred the specified assets from the forwarder’s address to the receiver and stored a request-field hash against replays. It also emitted
FundsPaid
to record execution.
Orchestrators submitted the destination payment event to Router Chain with attestations. Middleware checked that the message generated from request data matched the execution-event message hash. A match let it mark the request
Completed
and record the forwarder’s address and amount.
Did completion automatically reimburse the forwarder?
Completion enabled a claim, but the forwarder still needed to initiate an outbound request on Router Chain. Router Chain and the gateway contracts processed that request before source-chain Nitro settled the forwarder’s funds.
A destination
FundsPaid
event recorded payment to the recipient. That event alone did not establish middleware completion or show that the forwarder had received source-side reimbursement.
Did every forwarder advance liquidity?
Router Nitro’s November 2023 transfer designs assigned different duties to forwarders, depending on the path. The architecture article explicitly described its Cosmos integrations as conceptual work under development.
| Documented transfer path | Forwarder duty | Settlement dependency |
|---|---|---|
| EVM-to-EVM forwarder flow | Advanced assets from its own balance on the destination chain. | Middleware matched payment evidence to the request before enabling the source-chain claim. |
| EVM-to-Cosmos forwarder design, conceptual in November 2023 | Funded the recipient’s payment on the destination Cosmos chain. |
A destination
FundsPaid
IBC message reached middleware; successful verification enabled the forwarder’s withdrawal.
|
| Cosmos-to-Cosmos forwarder design, conceptual in November 2023 | Supplied the destination assets from its own account. | Middleware reverse-verified deposit and payment IBC messages before the forwarder could initiate source-side withdrawal through IBC. |
| Token-specific burn-and-mint flow, November 2023 | Did not front destination liquidity; this flow incurred no forwarder fee. | The bridge needed token mint/burn permissions on both chains; validated cross-chain messaging preceded destination minting. |
| USDC CCTP flow, November 2023 description | Polled Circle’s API for attestation and initiated destination execution. | Circle attestation preceded destination minting to the recipient specified in the source burn message. |
Source rollback exposure
The November 2023 architecture article identified fraud-proof-window rollbacks as a risk for transfers originating on an optimistic L2. A rollback could erase the source deposit, leaving a forwarder without reimbursement for a completed destination payment.
The article proposed comparing a reconstructed source-chain state root with the existing on-chain root before destination execution. Router described supporting Nitro modules as future work at publication.