Bridges & Portals

wstGBP bridges to L2s and sidechains using each chain’s own canonical bridge — there is no OFT / xERC20 / omnichain token today. That means five different architectures: OP Stack Standard Bridge, Arbitrum Nitro gateway, the Polygon PoS bridge, and the Gnosis OmniBridge. The L1 token is always the source of truth.

L1 token — Ethereum mainnet (chainId 1)

Live deployments

“Portals” — disambiguation

The word portal appears in three unrelated senses across the bridge ecosystem:

• OptimismPortal — the OP Stack L1 contract beneath the Standard Bridge that handles deposits and finalized withdrawals. End users normally interact with the L1StandardBridge, not the Portal directly.
• Polygon Portal — the Polygon bridge UI at portal.polygon.technology . Not a contract.
• FxPortal — Polygon’s permissionless mapping. Not used here; wstGBP uses Polygon’s native PoS mapping instead.

Base (OP Stack · chainId 8453)

RPC https://mainnet.base.org · Explorer https://basescan.org

Base runs its own factory 0xF10122… (v1.9.0), not the predeploy — its tooling and bridge UI expect tokens from that factory.

MegaETH “Frontier” (OP Stack · chainId 4326)

RPC https://mainnet.megaeth.com/rpc · Explorer https://megaeth.blockscout.com

Shared OP Stack L2 predeploys

Identical on every OP Stack L2 (Base, MegaETH, and future OP chains):

OP Stack flow

• Deposit (L1 → L2): approve the L1StandardBridge for wstGBP, then depositERC20(l1Token, l2Token, amount, minGasLimit = 200000, extraData = 0x). Use depositERC20To(..., to, ...) from a contract/Safe or to a different recipient (depositERC20 has an onlyEOA guard). Not payable — pay L1 gas only. Arrives in minutes.
• Withdraw (L2 → L1): bridgeERC20To on the L2 bridge 0x4200…0010, then finalize on L1 after the challenge period.

Arbitrum One — Nitro gateway (chainId 42161)

RPC https://arb1.arbitrum.io/rpc · Explorer https://arbiscan.io

L2 wstGBP 0x2c8CBe32da6feAECcF99eCeE2900556a17a529ED is a StandardArbERC20, auto‑deployed by the gateway on first deposit (no factory call, no predeploy).

Deposit: approve the L1ERC20Gateway (not the router) for wstGBP, then L1GatewayRouter.outboundTransferCustomRefund(...) — a payable call needing L2 gas params (maxGas, gasPriceBid, maxSubmissionCost). Prefer the bridge UI or Arbitrum SDK.

Polygon PoS — PoS bridge (chainId 137)

RPC https://polygon-rpc.com · Explorer https://polygonscan.com · UI portal.polygon.technology 

L2 wstGBP 0x3319d8A0A7f742AAC63D586E7bb846a9ee8218Ab is a native PoS‑bridge child ERC‑20 (the L1 ERC20Predicate locks, the L2 ChildChainManager mints/burns; backed 1:1).

Deposit (L1 → L2): approve the ERC20Predicate, then RootChainManager.depositFor(user, wstGBP, abi.encode(amount)). Arrives in ~20–30 min via state sync. Withdraw (L2 → L1): withdraw(amount) on the child token to burn, wait for the next Heimdall checkpoint, then RootChainManager.exit(burnProof) on L1 — the Portal UI assembles the proof.

Gnosis Chain — OmniBridge / AMB (chainId 100)

RPC https://rpc.gnosischain.com · Explorer https://gnosisscan.io · UI bridge.gnosischain.com 

L2 wstGBP 0x68115fFA8bF088289B80B1e17cD486B5752492aA is an ERC677 PermittableToken, auto‑deployed by the Home mediator on first deposit (backed 1:1 by tokens locked on L1).

Deposit (L1 → Gnosis): approve the Foreign mediator, then relayTokens(wstGBP, receiver, amount). Arrives in ~5–15 min. Withdraw (Gnosis → L1): relayTokens(...) on the Home mediator (or ERC677 transferAndCall(homeMediator, amount, "")) to burn, wait for validator signatures, then submit the signed claim on L1 — Gnosis→ Ethereum messages are not auto‑relayed, so the bridge UI (or you) must pay the L1 claim.

Roadmap — not yet live