[Vasanthdev2004]

Stacked on #132. Phase 8 of the bridge update.

What it does

The bridge panel (header dialog and /bridge) gains a "Funds on an exchange?" link under the amount. It swaps the form for a four-step guide that uses only routes the bridge already checks:

1. Address. The connected wallet's full address with a copy button. If the clipboard is refused, the button selects the text instead. Without a wallet, the step offers Connect wallet.
2. Network. Withdraw ETH or USDC to Base, Ethereum, Arbitrum or Optimism. Base is marked "No bridge needed" when Base is the destination. The step says to choose native USDC (not USDC.e) and to withdraw a little ETH beside USDC for gas. It makes no claim about which exchange supports which network.
3. Watch. Reads ETH and Circle's USDC on those four networks every 15 seconds. The reads are read-only and pause while the tab is hidden. Arrivals are measured from the lowest balance seen since the watch began, so funds already in the wallet never count. Rises below the existing dust floors ($1 USDC, 0.0005 ETH) are ignored.
4. Bridge. Each arrival gets a "Bridge … from …" button. It sets the origin network, the asset and, for a token, the amount, using the same guarded setters the pickers use. You then quote and confirm as usual. A token that landed with no ETH on its network gets a gas warning. Funds that land on the destination itself are reported as ready to use.

The watch and the open guide are kept in this tab's session storage for two hours. Closing the panel, or connecting a wallet from the guide, resumes the guide without taking focus.

Why not Relay deposit addresses

These were evaluated first. Relay can attach a one-time deposit address to a quote, but in production these addresses are Lit-derived EOAs. They are built from derivation inputs the quote does not return plus an unpublished root key, so an address cannot be tied to its order. On Base, fresh accounts were seen sweeping into the depository at nonce 0 and 1. Tracking also needs an API key, and an Ethereum USDC route quoted about 3.3% at $25. docs/bridge.md records the findings and the tx hashes. relay.ts never requests a deposit address, and validation.ts still refuses any quote that carries one.

Code

• lib/bridge/exchange.ts: networks, baseline, arrivals, gas check, the route an arrival opens, and session persistence (all pure).
• components/bridge/useExchangeWatch.ts: the polling hook.
• fund.ts: readHoldingsOn now holds the shared read code; readBridgeHoldings calls it.
• BridgeDialog.tsx: the ExchangeGuide view, the link, and focus handling. Opening moves focus to the guide title. Back and Bridge return focus to the link or the amount.
• /ui-review-bridge: six guide states, and the review dialog's guide wired to a synthetic arrival.
• /bridge "Good to know" bullet, and a docs section.

Verification

• exchange.test.ts (8 tests) and a UI guard in bridge-ui.test.ts. The guard checks that the guide only reads, opens the bridge through the guarded setters, calls out missing gas, and keeps deposit addresses off.
• Full suite: 1548 tests, 28 failures, the same 28 as the baseline. No new failures.
• tsc (app and tests) and eslint on the bridge paths are clean.
• Browser checks:
  • every guide state on /ui-review-bridge;
  • the review dialog's arrival opens Arbitrum USDC to Arc with 25 filled in;
  • /bridge without a wallet;
  • a reload resumes the guide;
  • 375px width with no overflow.
• No wallet signed anything. No real exchange withdrawal has been watched yet.

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[Vasanthdev2004]

Closed in favour of #135, which holds the whole bridge update in one PR. The commits from this PR are in it unchanged.