fix: a V4 swap action not in the deployed shape is shown as not decoded (closes #358)

The four V4 swap actions are read only as the parameter structs deployed
on mainnet and Sepolia. ethers decoded the newer v4-periphery structs,
which add minHopPriceX36, as the deployed ones without an error, and the
newer multi-hop exact-in struct showed the offset of its hop-price array
as the swap amount. A decode now counts only when encoding it again gives
back the same bytes. When a swap action fails that, its step is listed as
"V4 Swap (could not be decoded)", and a token line left without a
currency reads "Unknown (could not be decoded)" rather than "not named in
the calldata". The README records both.

Model: opus-5-5

README.md

@@ -239,8 +239,12 @@ provide:
   `make check` stays non-mutating. Linting runs only in the container, because
   an ESLint result that depends on whichever ESLint the host happens to have is
   not a result, so docker is required to lint.
-- `script/fmt` — format all files (writes), on the host
+- `script/fmt` — format all files (writes), on the host, with the `prettier`
-- `script/fmt-check` — check formatting (read-only), on the host
+  that `script/bootstrap` installs in `node_modules/`; when that one is missing
+  it fails and says to run `script/bootstrap`, instead of using a `prettier`
+  from the `PATH`
+- `script/fmt-check` — check formatting (read-only), on the host, with the same
+  `prettier` and the same refusal
 - `script/check` — run `script/test`, `script/lint` and `script/fmt-check`
 - `script/check-censored` — assert the competitor name RULES.md bars appears
   nowhere in the working tree or under `dist/` outside its documented
@@ -414,17 +418,20 @@ content script, the inpage provider, the background worker and the approval
 popup all have to work together. A local test page is served by the route
 handler on a reserved-TLD origin, gets `window.ethereum` from the shipped
 `MAIN`-world content script like any other page, and drives
-`eth_requestAccounts`, `personal_sign`, `eth_signTypedData_v4` and
+`eth_requestAccounts`, `personal_sign`, `eth_signTypedData_v4`,
-`eth_sendTransaction` through the real prompts. Every signature is recovered in
+`eth_sendTransaction` and `wallet_switchEthereumChain` through the real prompts.
-the runner and compared against the active address, the transaction assertions
+Every signature is recovered in the runner and compared against the active
-run against the raw signed transaction captured at `eth_sendRawTransaction`
+address, the transaction assertions run against the raw signed transaction
-rather than against anything the extension reported, rejecting each prompt is
+captured at `eth_sendRawTransaction` rather than against anything the extension
-required to return a rejection to the page rather than hang or resolve, a prompt
+reported, rejecting each prompt is required to return a rejection to the page
-raised while another approval window has focus is required to open a window of
+rather than hang or resolve, a network switch request is required to leave the
-its own, and the password is required to be absent from every message the
+stored network unchanged and send no `chainChanged` until it is approved, a
-approval window sends to the background — with the message that would carry it
+network switch in Settings is required to send the page `chainChanged` with the
-required to be present, so that check cannot pass by observing nothing. That
+new chain id, a prompt raised while another approval window has focus is
-last one is the standing floor under
+required to open a window of its own, and the password is required to be absent
+from every message the approval window sends to the background — with the
+message that would carry it required to be present, so that check cannot pass by
+observing nothing. That last one is the standing floor under
 [#157](https://git.eeqj.de/sneak/AutistMask/issues/157).
 
 The limits of that coverage and of the rest of the Chrome suite, none of them
@@ -525,10 +532,11 @@ Chrome that ever changes this fails the run instead of passing it.
 `make test-e2e-firefox` builds `dist/firefox/` and drives the **real popup in a
 real Firefox**, installed as an unpacked MV2 temporary add-on via geckodriver.
 It covers popup load, the StateRecovery screen (the same cases as the Chrome
-suite), wallet creation through the UI, the Add Token screen, and the four dApp
+suite), wallet creation through the UI, the Add Token screen, and the dApp round
-round trips — `eth_requestAccounts`, `personal_sign`, `eth_sendTransaction`, and
+trips — `eth_requestAccounts`, `personal_sign`, `wallet_switchEthereumChain`
-a closed approval window rejecting with EIP-1193 4001 — driven through the real
+rejected and then approved, `eth_sendTransaction`, and a closed approval window
-content script, background page and approval windows.
+rejecting with EIP-1193 4001 — driven through the real content script,
+background page and approval windows.
 
 The suite lives in `tests/e2e/firefox/`. Its WebDriver client (`driver.js`) has
 **no npm dependencies at all**: it is built on global `fetch` and
@@ -1102,14 +1110,16 @@ read:
 
 The swap's `Token In` and `Token Out` lines name a currency, not an amount; each
 reads `Unknown (not named in the calldata)` when the decoder found no token for
-that side. An `UNWRAP_WETH` step makes `Token Out` ETH only when the output side
+that side, or `Unknown (could not be decoded)` instead when a V4 swap action in
-is WETH, on mainnet or Sepolia, or when no step set the output side; a WETH
+the transaction could not be read (see Transaction Decoding below). An
-`Min. received` figure then reads in ETH. Otherwise `Token Out` and
+`UNWRAP_WETH` step makes `Token Out` ETH only when the output side is WETH, on
-`Min. received` keep the output side's own token and figure, whether the swap
+mainnet or Sepolia, or when no step set the output side; a WETH `Min. received`
-was paid in ETH or in a token: a V2 exact-out swap that buys USDC and then
+figure then reads in ETH. Otherwise `Token Out` and `Min. received` keep the
-unwraps the WETH it did not spend shows USDC. The token permission warning on
+output side's own token and figure, whether the swap was paid in ETH or in a
-the signature screen has its own amount wording, including `Unknown`; the
+token: a V2 exact-out swap that buys USDC and then unwraps the WETH it did not
-SignApproval section below describes it.
+spend shows USDC. The token permission warning on the signature screen has its
+own amount wording, including `Unknown`; the SignApproval section below
+describes it.
 
 The swap's `Deadline` line is the router's deadline as a UTC date and time, e.g.
 `2026-02-27 08:25:51`. A JavaScript date reaches only to 275760-09-13 00:00:00
@@ -1782,8 +1792,12 @@ view would leave a wallet one click from deletion.
       plus a "+ Add token" button
     - Display: "Show tracked tokens with zero balance" checkbox, "UTC
       Timestamps" checkbox, and a Theme selector (System / Light / Dark)
-    - Network: network selector (Ethereum Mainnet / Sepolia Testnet); switching
+    - Network: network selector (Ethereum Mainnet / Sepolia Testnet). The
-      resets the RPC and Blockscout endpoints to that network's defaults
+      network changes only here, or when the user approves a site's request on
+      **NetworkApproval**; either way, switching restores the RPC and Blockscout
+      endpoints last used on that network, or that network's defaults if it has
+      none, and sends `chainChanged` with the new chain id to every open tab.
+      Choosing the network already active changes nothing and sends nothing
     - Ethereum RPC: endpoint URL input + "Save" button (validated against
       `eth_chainId` before being saved)
     - Blockscout API: endpoint URL input + "Save" button (validated against
@@ -2071,7 +2085,10 @@ view would leave a wallet one click from deletion.
   no window and takes no nonce, and the site can send it again once the pending
   one is answered. The window is centred on the browser window the user was last
   in; if that was another approval window, or the browser refuses the centred
-  position, the browser picks the position.
+  position, the browser picks the position. The network shown is the one the
+  transaction was populated on, and a site cannot switch it without the user:
+  its `wallet_switchEthereumChain` request changes the network only when the
+  user approves it on **NetworkApproval**.
 - **Elements**:
     - "Transaction Request" heading
     - Phishing warning banner (shown when the hostname is on the phishing
@@ -2149,6 +2166,13 @@ view would leave a wallet one click from deletion.
     - Typed data that states no primary type, or one other than the type it
       would be signed as, or that cannot be read → shown with the error line
       saying so and "Sign" disabled; only "Reject" remains
+    - Typed data whose domain `chainId` names a chain other than the active
+      network's → shown with the error line naming both chain ids and "Sign"
+      disabled; only "Reject" remains. EIP-712 asks for this, because the
+      signature is valid on the chain the domain names. Typed data with no
+      `chainId` is not refused. The background refuses such a signature too,
+      against the network active when the signature reaches it, and answers the
+      site with the same sentence
     - A `personal_sign` or `eth_sign` message that is not hex (`0x` or `0X` and
       an even number of hex digits, the form ethers' `getBytes` reads when
       signing) → shown as plain text, with the error line "This message is plain
@@ -2162,6 +2186,40 @@ view would leave a wallet one click from deletion.
     - Popup window closed without answering → the request is rejected with
       EIP-1193 code 4001
 
+#### NetworkApproval (`approve-network`)
+
+- **When**: A connected website asks to switch the network with
+  `wallet_switchEthereumChain`, naming a supported network other than the active
+  one. Only the user switches the network: until the user approves the request
+  here, it changes nothing — not the network, the RPC and Blockscout endpoints,
+  the balances or the cached token data — and no page is sent `chainChanged`.
+  Opened the same way as TxApproval, in a separate popup window. Only one exists
+  per site at a time: a further switch request from a site whose switch request
+  is still unanswered is refused with EIP-1193 code `-32002` and opens no
+  window. A request naming the network already active is answered at once and
+  opens nothing; one naming an unsupported chain is refused with code `4902`,
+  and one from a site that is not connected with code `4100`.
+  `wallet_addEthereumChain` never switches the network.
+- **Elements**:
+    - "Network Switch Request" heading
+    - Phishing warning banner (shown when the hostname is on the phishing
+      blocklist)
+    - Site origin (bold, scheme and port included) + "wants to switch the
+      wallet's network."
+    - Current network: its name
+    - Requested network: its name
+    - A line saying that switching changes the network for the whole wallet and
+      for every site
+    - "Switch" / "Reject" buttons
+- **Transitions**:
+    - "Switch" → closes popup; the background switches the network as
+      **Settings** does, restoring the RPC and Blockscout endpoints last used on
+      that network (or that network's defaults if it has none), sends
+      `chainChanged` to every open tab, and answers the site with success
+    - "Reject" → closes popup; the site is answered with EIP-1193 code 4001 and
+      nothing changes
+    - Popup window closed without answering → the same as "Reject"
+
 #### StateRecovery (`state-recovery`)
 
 - **When**: the stored profile fails `assertStateUsable()`. At open, that is
@@ -2456,6 +2514,8 @@ logged.
 - Sign transactions requested by connected sites (`eth_sendTransaction`)
 - Sign messages (`personal_sign`, `eth_sign`)
 - Sign typed data (`eth_signTypedData_v4`, `eth_signTypedData`)
+- Switch network at a connected site's request, once the user approves it
+  (`wallet_switchEthereumChain`)
 - Human-readable transaction decoding (ERC-20, Uniswap Universal Router)
 - ETH/USD and token/USD price display
 - Configurable RPC endpoint and Blockscout API
@@ -2605,7 +2665,8 @@ plaintext list of anyone's domain names.
 When a dApp on a blocklisted domain requests a wallet connection, transaction
 approval, or signature, the approval popup displays a prominent red warning
 banner alerting the user. The domain checker matches exact hostnames and all
-parent domains (subdomain matching).
+parent domains (subdomain matching), and checks a hostname written with a
+trailing dot (`name.`) as `name`.
 
 #### Transaction Decoding
 
@@ -2631,7 +2692,11 @@ Currently supported:
   or recipient, and amount.
 - **Uniswap Universal Router**: `execute()` calls — shows swap direction (e.g.
   "Swap USDT → ETH"), token addresses, amounts, execution steps, and deadline.
-  Decodes Permit2, V2/V3/V4 swaps, wrap/unwrap, and balance checks.
+  Decodes Permit2, V2/V3/V4 swaps, wrap/unwrap, and balance checks. A V4 swap
+  action is read only in the parameter shape deployed on mainnet and Sepolia,
+  not in the newer one on `v4-periphery` `main`, which adds a `minHopPriceX36`
+  field. An action in any other shape is not read, and its step is listed as
+  `V4 Swap (could not be decoded)`.
 
 ### Non-Goals Forever
 

TODO.md

@@ -2,10 +2,9 @@
 
 - `git pull` `next` and cut a branch from it — one branch per issue, named
   `issue-<N>-<slug>`. Never branch from `main`.
-- Do the work as one commit whose title ends with ` (closes #N)`, with the
+- Do the work as one commit whose title ends with ` (closes #N)`.
-  `TODO.md` update in that same commit.
+- Add no entry to Completed Steps. What landed is recorded on the tracker and in
-- Move Next Step to the top of Completed Steps; move the top item of Future
+  `git log`, where each commit title names the issue it closes.
-  Steps into Next Step.
 - Run `make fmt`, then `make check`. A feature branch may be red; `next` and
   `main` may not.
 - Rebase onto current `next` immediately before pushing — other branches land on
@@ -44,6 +43,39 @@ then continue tagging as milestones land.
 
 # Completed Steps
 
+- 2026-10-08: The browser suites no longer read a screen before the page has
+  shown it ([#502](https://git.eeqj.de/sneak/AutistMask/issues/502)). Their wait
+  for a screen used to pass as soon as the element laid out, which every view
+  does until the page's stylesheet has applied, so an approval test could read
+  the prompt's fields before the page's script had filled them. `visible()` in
+  `tests/e2e/harness.js` and `waitVisible()` in `tests/e2e/firefox/driver.js`
+  now also wait for the page to finish loading and for neither the element nor
+  anything around it to carry the `hidden` class that `showView()` puts on every
+  view but the current one. No caller changed.
+
+- 2026-10-08: Switching the network in Settings now tells open pages
+  ([#500](https://git.eeqj.de/sneak/AutistMask/issues/500)). Once the switch is
+  saved, Settings asks the background to send `chainChanged` with the new chain
+  id to every open tab, through the same function an approved site request uses.
+  Choosing the network already active changes nothing and sends nothing. Only
+  the extension's own pages can ask for this. `tests/chainSwitchGate.test.js`
+  drives the real Settings view against the background, and the Chrome suite
+  checks that the test page hears both switches.
+
+- 2026-10-07: A site can no longer switch the wallet's network by itself
+  ([#408](https://git.eeqj.de/sneak/AutistMask/issues/408)). A connected site's
+  `wallet_switchEthereumChain` request for the other supported network opens a
+  prompt in its own window, through the same approval machinery as the
+  transaction and signature prompts, naming the site, the current network and
+  the requested one. The network, its endpoints, the balances and the caches
+  change, and `chainChanged` is sent, only when the user approves it; rejecting
+  or closing the prompt answers 4001. One such prompt per site at a time. The
+  approval window no longer shows the connection prompt while it waits for the
+  background to describe the approval, because that prompt's "Allow" answers on
+  the same port as the new one; `tests/approvalWindow.test.js` checks that it
+  shows no screen until then. `tests/chainSwitchGate.test.js` and both browser
+  suites drive the prompt.
+
 - 2026-10-07: Two contradictions between the documents and the code are resolved
   as ruled on [#165](https://git.eeqj.de/sneak/AutistMask/issues/165). The
   README's 1.0 non-goal now puts Ethereum mainnet and the Sepolia testnet in

script/fmt

@@ -25,6 +25,13 @@ run_yarn() {
 
 main() {
     cd "$ROOT"
+    # Without the repo's own prettier, yarn runs whatever prettier is on
+    # the PATH, which may be a version that formats files differently.
+    if [ ! -x node_modules/.bin/prettier ]; then
+        echo "fmt: this repo's prettier is not installed in node_modules/," \
+            "so run script/bootstrap first." >&2
+        exit 1
+    fi
     echo "Formatting..."
     run_yarn run fmt
 }

script/fmt-check

@@ -26,6 +26,13 @@ run_yarn() {
 
 main() {
     cd "$ROOT"
+    # Without the repo's own prettier, yarn runs whatever prettier is on
+    # the PATH, which may be a version that formats files differently.
+    if [ ! -x node_modules/.bin/prettier ]; then
+        echo "fmt-check: this repo's prettier is not installed in" \
+            "node_modules/, so run script/bootstrap first." >&2
+        exit 1
+    fi
     echo "Checking formatting..."
     run_yarn run fmt-check
 }

src/background/index.js

@@ -22,6 +22,7 @@ const { debugFetch, log } = require("../shared/log");
 const {
     verifySignedTx,
     verifySignature,
+    typedDataChainRefusal,
     failureIsRetryable,
     describeTxFailure,
     sameAddress,
@@ -137,11 +138,12 @@ function releaseTxApprovalSlotFor(approvalId) {
     }
 }
 
-// One site-connection approval and one sign approval per site at a time: a
+// One site-connection approval, one sign approval and one network-switch
-// page that asks again before the user has answered is refused with the code
+// approval per site at a time: a page that asks again before the user has
-// above instead of opening another window, so it cannot bury the user in
+// answered is refused with the code above instead of opening another window,
-// prompts. The pending approval itself holds the place, so a caller must test
+// so it cannot bury the user in prompts. The pending approval itself holds the
-// this and raise its approval with nothing awaited in between.
+// place, so a caller must test this and raise its approval with nothing awaited
+// in between.
 function findPendingApproval(origin, type) {
     return Object.values(pendingApprovals).find(
         (approval) => approval.origin === origin && approval.type === type,
@@ -348,8 +350,9 @@ function settleApproval(id, result, options) {
 
 // What a pending approval resolves to when it is given up on rather than
 // answered: the window was closed, or could not be opened at all. A tx or sign
-// approval answers the requesting page in EIP-1193 shape; a site-connection
+// approval answers the requesting page in EIP-1193 shape; a site-connection or
-// approval answers the connection handler in its own.
+// network-switch approval answers its handler in the shape the popup's
+// decision has, as a refusal.
 function abandonedResult(approval, code, message) {
     if (approval.type === "tx" || approval.type === "sign") {
         return { error: { code, message } };
@@ -588,6 +591,26 @@ function requestSignApproval(origin, signParams, approvedFrom) {
     });
 }
 
+// Open a network-switch approval popup and return a promise that resolves with
+// { approved }. Opened in a window, as tx and sign approvals are, because a
+// site's request is not a user gesture. The popup answers on the approval port,
+// as a site-connection approval does.
+function requestNetworkApproval(origin, currentNetworkId, requestedNetworkId) {
+    return new Promise((resolve) => {
+        const id = crypto.randomUUID();
+        pendingApprovals[id] = {
+            id,
+            origin,
+            currentNetworkId,
+            requestedNetworkId,
+            resolve,
+            type: "network",
+        };
+
+        openApprovalWindow(id);
+    });
+}
+
 // Anything only the extension's own pages may say. A content script speaks
 // with the page's URL, so this is what separates the popup from the site the
 // popup is being asked about.
@@ -597,8 +620,8 @@ function isExtensionSender(sender) {
 }
 
 // The approval popup's port: it carries the user's decision on a
-// site-connection approval, and its disconnect is how that approval learns the
+// site-connection or network-switch approval, and its disconnect is how that
-// popup closed without one.
+// approval learns the popup closed without one.
 //
 // The decision travels this port rather than a one-off runtime.sendMessage()
 // for exactly one reason: the port is also what the popup's window.close()
@@ -610,8 +633,9 @@ function isExtensionSender(sender) {
 // had refused.
 //
 // TX and sign approvals do not decide here. They stay pending across a
-// disconnect — the user can reopen the toolbar popup — and are rejected by the
+// disconnect. When their window closes, the windows.onRemoved listener below
-// windows.onRemoved listener below.
+// rejects them, unless an approved attempt is still running, in which case
+// that attempt answers the page.
 runtime.onConnect.addListener((port) => {
     if (port.name.startsWith("approval:")) {
         const id = port.name.split(":")[1];
@@ -639,7 +663,9 @@ runtime.onConnect.addListener((port) => {
             const approval = pendingApprovals[id];
             if (approval) {
                 if (approval.type === "tx" || approval.type === "sign") {
-                    // Keep pending — user can reopen the toolbar popup
+                    // When its window closes, windows.onRemoved rejects it,
+                    // unless an approved attempt is still running, in which
+                    // case that attempt answers the page.
                     return;
                 }
                 settleApproval(id, { approved: false, remember: false });
@@ -806,6 +832,10 @@ async function handleRpc(method, params, origin) {
         // tab is served from, so a page the user never connected to must
         // not be able to do it. Ungated, any page could clear the
         // [TESTNET] banner under a user who believed they were on Sepolia.
+        //
+        // A connected site does not switch it either: only the user does,
+        // by approving the request on the prompt below
+        // (https://git.eeqj.de/sneak/AutistMask/issues/408).
         const s = await getState();
         const activeAddress = activeAddressOf(s);
         const allowed = s.allowedSites[activeAddress] || [];
@@ -827,6 +857,27 @@ async function handleRpc(method, params, origin) {
         }
         if (SUPPORTED_CHAIN_IDS.has(chainId)) {
             const target = networkByChainId(chainId);
+            if (findPendingApproval(origin, "network")) {
+                return {
+                    error: {
+                        code: APPROVAL_PENDING_CODE,
+                        message: APPROVAL_PENDING_MESSAGE,
+                    },
+                };
+            }
+            const decision = await requestNetworkApproval(
+                origin,
+                s.networkId,
+                target.id,
+            );
+            if (!decision.approved) {
+                return {
+                    error: {
+                        code: APPROVAL_REJECTED_CODE,
+                        message: APPROVAL_REJECTED_MESSAGE,
+                    },
+                };
+            }
             // Read-modify-write against storage. The old path went through
             // onChainSwitch(), which mutates the singleton and then persists
             // every field of it — on an unloaded worker that wrote empty
@@ -1345,20 +1396,21 @@ startBackgroundJobs();
 // which then fails retryably settles instead of waiting in a window that no
 // longer exists.
 //
-// A site-connection approval whose popup connected its port is not decided
+// A site-connection or network-switch approval whose popup connected its port
-// here. That popup approves and closes in the same breath, and this event
+// is not decided here. That popup approves and closes in the same breath, and
-// races the decision on a channel of its own — the same race the port exists
+// this event races the decision on a channel of its own — the same race the
-// to end. Its port disconnect says the same thing this event does, in an order
+// port exists to end. Its port disconnect says the same thing this event does,
-// that is defined, so the disconnect is left to say it. The window closing
+// in an order that is defined, so the disconnect is left to say it. The window
-// before any port connected is the one case with nothing else to speak for it,
+// closing before any port connected is the one case with nothing else to speak
-// and is rejected here so the dApp is not left waiting on a window that is
+// for it, and is rejected here so the dApp is not left waiting on a window that
-// gone.
+// is gone.
 if (windowsNs && windowsNs.onRemoved) {
     windowsNs.onRemoved.addListener((windowId) => {
         for (const [id, approval] of Object.entries(pendingApprovals)) {
             if (approval.windowId !== windowId) continue;
-            const isSite = approval.type !== "tx" && approval.type !== "sign";
+            const decidedOnPort =
-            if (isSite && approval.portConnected) continue;
+                approval.type !== "tx" && approval.type !== "sign";
+            if (decidedOnPort && approval.portConnected) continue;
             const rejection = abandonedResult(
                 approval,
                 APPROVAL_REJECTED_CODE,
@@ -1423,6 +1475,7 @@ runtime.onMessage.addListener((msg, sender, sendResponse) => {
         "AUTISTMASK_ADDRESSES_REMOVED",
         "AUTISTMASK_GET_CONNECTED_SITES",
         "AUTISTMASK_REMOVE_SITE",
+        "AUTISTMASK_NETWORK_CHANGED",
     ];
     if (POPUP_ONLY_TYPES.includes(msg.type) && !isExtensionSender(sender)) {
         sendResponse({ error: "Unauthorized sender" });
@@ -1446,6 +1499,11 @@ runtime.onMessage.addListener((msg, sender, sendResponse) => {
                 resp.signParams = approval.signParams;
                 resp.approvedFrom = approval.approvedFrom;
             }
+            if (approval.type === "network") {
+                resp.type = "network";
+                resp.currentNetworkId = approval.currentNetworkId;
+                resp.requestedNetworkId = approval.requestedNetworkId;
+            }
             // Flag if the requesting domain is on the phishing blocklist.
             resp.isPhishingDomain = isPhishingDomain(
                 extractHostname(approval.origin),
@@ -1710,7 +1768,8 @@ runtime.onMessage.addListener((msg, sender, sendResponse) => {
 
         (async () => {
             try {
-                const activeAddress = await getActiveAddress();
+                const s = await getState();
+                const activeAddress = activeAddressOf(s);
                 // Same as the transaction path: the address the approval named
                 // is the one that must have signed, and a switch since then is
                 // a refusal rather than a signature from another account.
@@ -1729,6 +1788,20 @@ runtime.onMessage.addListener((msg, sender, sendResponse) => {
                     signature,
                     approval.approvedFrom,
                 );
+                // The sign screen refuses typed data whose domain names
+                // another chain. A signature for it that arrives anyway is
+                // refused here, against the network active now.
+                const sp = approval.signParams;
+                if (
+                    sp.method === "eth_signTypedData_v4" ||
+                    sp.method === "eth_signTypedData"
+                ) {
+                    const refusal = typedDataChainRefusal(
+                        JSON.parse(sp.typedData).domain,
+                        networkById(s.networkId),
+                    );
+                    if (refusal) throw new ApprovalMismatchError(refusal);
+                }
                 settleApproval(msg.id, { signature }, { holdsClaim: true });
                 sendResponse({ signature });
             } catch (e) {
@@ -1801,6 +1874,13 @@ runtime.onMessage.addListener((msg, sender, sendResponse) => {
         broadcastSiteRemoved(msg.origin);
         return false;
     }
+
+    // Settings switched the network and has saved it. Open tabs are told the
+    // new chain id the same way as after a site's approved switch request.
+    if (msg.type === "AUTISTMASK_NETWORK_CHANGED") {
+        broadcastChainChanged(msg.chainId);
+        return false;
+    }
 });
 
 module.exports = { PROXY_METHODS };

src/popup/index.html

@@ -7,9 +7,10 @@
         <link rel="stylesheet" href="styles.css" />
     </head>
     <!-- Chrome gives extension pages a stylesheet of its own that sets the
-         font on body, and a Tailwind class beats it only when marked
+         font and its size on body, and a Tailwind class beats it only when
-         important: hence font-mono! rather than font-mono. -->
+         marked important: hence font-mono! and text-sm! rather than
-    <body class="bg-bg text-fg font-mono! text-sm">
+         font-mono and text-sm. -->
+    <body class="bg-bg text-fg font-mono! text-sm!">
         <div id="app" class="p-2 pr-5 overflow-x-hidden">
             <!-- ============ GLOBAL TITLE BAR ============ -->
             <div
@@ -87,11 +88,14 @@
 
                 <!-- Mnemonic form section -->
                 <div id="add-wallet-section-mnemonic">
-                    <p class="mb-2">
+                    <!-- The die button shares the instruction's row: on a row
-                        Enter your 12 or 24 word recovery phrase below, or click
+                         of its own it pushes Import below the fold at
-                        the button to roll the die for a new one.
+                         360x600. -->
-                    </p>
+                    <div class="mb-2 flex justify-between items-start gap-2">
-                    <div class="mb-1 flex justify-end">
+                        <p>
+                            Enter your 12 or 24 word recovery phrase below, or
+                            click the button to roll the die for a new one.
+                        </p>
                         <button
                             id="btn-generate-phrase"
                             class="border border-border px-2 py-1 hover:bg-fg hover:text-bg cursor-pointer text-xs"
@@ -1741,6 +1745,54 @@
                 </div>
             </div>
 
+            <!-- ============ NETWORK SWITCH APPROVAL ============ -->
+            <div id="view-approve-network" class="view hidden">
+                <h2 class="font-bold mb-2">Network Switch Request</h2>
+                <div
+                    id="approve-network-phishing-warning"
+                    class="mb-3 p-2 text-xs font-bold hidden bg-red-100 text-red-800 border-2 border-red-600 rounded-md"
+                >
+                    ⚠️ PHISHING WARNING: This site is on a known phishing
+                    blocklist. Proceed with extreme caution.
+                </div>
+                <p class="mb-2">
+                    <span id="approve-network-origin" class="font-bold"></span>
+                    wants to switch the wallet's network.
+                </p>
+                <div class="mb-3">
+                    <div class="text-xs text-muted mb-1">Current network</div>
+                    <div
+                        id="approve-network-current"
+                        class="text-xs font-bold"
+                    ></div>
+                </div>
+                <div class="mb-3">
+                    <div class="text-xs text-muted mb-1">Requested network</div>
+                    <div
+                        id="approve-network-requested"
+                        class="text-xs font-bold"
+                    ></div>
+                </div>
+                <p class="mb-3 text-xs">
+                    Switching changes the network for the whole wallet and for
+                    every site, not only for this one.
+                </p>
+                <div class="flex justify-between">
+                    <button
+                        id="btn-approve-network"
+                        class="border border-border px-2 py-1 hover:bg-fg hover:text-bg cursor-pointer"
+                    >
+                        Switch
+                    </button>
+                    <button
+                        id="btn-reject-network"
+                        class="border border-border px-2 py-1 hover:bg-fg hover:text-bg cursor-pointer"
+                    >
+                        Reject
+                    </button>
+                </div>
+            </div>
+
             <!-- ============ STATE RECOVERY ============ -->
             <!--
                 Shown when the stored profile cannot be read at all. Every

src/popup/index.js

@@ -238,9 +238,9 @@ async function init() {
         // rejection rather than an uncaught error — measured as still failing
         // the run on both harnesses (Playwright `pageerror`, and the Firefox
         // driver's console-service drain), so nothing is lost by leaving it
-        // on that path.
+        // on that path. show() puts the approval's own screen up once the
+        // background has described it.
         approval.show(approvalId);
-        showView("approve-site");
         return;
     }
 

src/popup/views/approval.js

@@ -12,8 +12,9 @@ const {
     formatFee,
     tokenLabel,
 } = require("./helpers");
-const { state, saveState } = require("../../shared/state");
+const { state, saveState, currentNetwork } = require("../../shared/state");
 const {
+    networkById,
     networkByChainId,
     nativeCurrencyByChainId,
 } = require("../../shared/networks");
@@ -45,7 +46,10 @@ const {
 const { decryptWithPassword } = require("../../shared/vault");
 const { getSignerForAddress } = require("../../shared/wallet");
 const { walletDefect } = require("../../shared/walletDefects");
-const { describeSigningFailure } = require("../../shared/approvalVerify");
+const {
+    describeSigningFailure,
+    typedDataChainRefusal,
+} = require("../../shared/approvalVerify");
 const txStatus = require("./txStatus");
 const uniswap = require("../../shared/uniswap");
 const { notify, runtimeApi, sendMessage } = require("../../shared/browserApi");
@@ -328,9 +332,9 @@ function showTxApproval(details) {
     const ethUsd = ethPrice ? parseFloat(ethValueFormatted) * ethPrice : null;
     const usdStr = formatUsd(ethUsd);
     // In the native currency of the network the transaction is for, which the
-    // Network line names, not the active network's: a site can switch the
+    // Network line names, not the active network's: the active network can
-    // active network after this transaction is prepared and back before it is
+    // change, in Settings or when the user approves a site's request, after
-    // signed.
+    // this transaction is prepared and change back before it is signed.
     $("approve-tx-value").textContent =
         ethValueFormatted +
         " " +
@@ -442,7 +446,8 @@ function signedPrimaryType(types) {
 // Why a signature request cannot be signed, as a sentence for the error line,
 // or null when it can. Only typed data is refused: the `primaryType` the page
 // states has to be the type ethers will sign, or this screen would name one
-// message while another is signed.
+// message while another is signed. Its domain may name no chain but the active
+// network's.
 function typedDataRefusal(sp) {
     if (sp.method === "personal_sign" || sp.method === "eth_sign") return null;
     let data;
@@ -465,7 +470,7 @@ function typedDataRefusal(sp) {
             ", so it cannot be signed."
         );
     }
-    return null;
+    return typedDataChainRefusal(data.domain, currentNetwork());
 }
 
 // The largest amount a Permit2 allowance can hold, a uint160. Permit2 treats
@@ -752,9 +757,29 @@ function showSignApproval(details) {
     );
 }
 
+function showNetworkApproval(details) {
+    showPhishingWarning(
+        "approve-network-phishing-warning",
+        details.isPhishingDomain,
+    );
+    $("approve-network-origin").textContent = details.origin;
+    $("approve-network-current").textContent = networkById(
+        details.currentNetworkId,
+    ).name;
+    $("approve-network-requested").textContent = networkById(
+        details.requestedNetworkId,
+    ).name;
+    showView("approve-network");
+}
+
 // Awaited by nobody: the popup entry point calls this and moves on. It
 // therefore has to absorb its own failure, and a background that cannot
 // describe the approval is the same outcome as an approval that is gone.
+//
+// Nothing is on screen until the background has described the approval, so
+// the screen shown is always the one for the approval this window answers:
+// the connection prompt's "Allow" and the network switch prompt's "Switch"
+// answer on the same port, and either would approve the other.
 async function show(id) {
     approvalId = id;
     approvalPort = runtimeApi().connect({ name: "approval:" + id });
@@ -778,6 +803,10 @@ async function show(id) {
         showSignApproval(details);
         return;
     }
+    if (details.type === "network") {
+        showNetworkApproval(details);
+        return;
+    }
     // Site connection approval
     showPhishingWarning(
         "approve-site-phishing-warning",
@@ -787,6 +816,7 @@ async function show(id) {
     $("approve-address").innerHTML = approvalAddressHtml(state.activeAddress);
     attachCopyHandlers("view-approve-site");
     $("approve-remember").checked = state.rememberSiteChoice;
+    showView("approve-site");
 }
 
 let approvalId = null;
@@ -866,20 +896,21 @@ function clearSignPassword() {
     hideError("approve-sign-error");
 }
 
-// Answer a site-connection approval and close. The decision goes out on the
+// Answer a site-connection or network-switch approval and close. The decision
-// approval port — see approvalPort above for why — and carries no approval id,
+// goes out on the approval port — see approvalPort above for why — and carries
-// because the port name already names the approval the background will settle.
+// no approval id, because the port name already names the approval the
-// The post is guarded because a throw must not cost the close: posting on a
+// background will settle. `remember` means something only for a site
-// port whose background worker has been torn down throws, and the approval it
+// connection. The post is guarded because a throw must not cost the close:
-// would have settled died with that worker, so the only thing left to do is
+// posting on a port whose background worker has been torn down throws, and the
-// what the user asked for — go away.
+// approval it would have settled died with that worker, so the only thing left
-function decideSite(approved) {
+// to do is what the user asked for — go away.
+function decide(approved, remember) {
     if (approvalPort) {
         try {
             approvalPort.postMessage({
                 type: "AUTISTMASK_APPROVAL_DECISION",
                 approved,
-                remember: $("approve-remember").checked,
+                remember,
             });
         } catch {
             // Nothing to report it to; the window closes either way.
@@ -898,11 +929,19 @@ function init(_ctx) {
     });
 
     $("btn-approve").addEventListener("click", () => {
-        decideSite(true);
+        decide(true, $("approve-remember").checked);
     });
 
     $("btn-reject").addEventListener("click", () => {
-        decideSite(false);
+        decide(false, $("approve-remember").checked);
+    });
+
+    $("btn-approve-network").addEventListener("click", () => {
+        decide(true, false);
+    });
+
+    $("btn-reject-network").addEventListener("click", () => {
+        decide(false, false);
     });
 
     $("btn-approve-tx").addEventListener("click", async () => {

src/popup/views/helpers.js

@@ -51,6 +51,7 @@ const VIEWS = [
     "approve-site",
     "approve-tx",
     "approve-sign",
+    "approve-network",
     "export-privkey",
     "show-phrase",
     // Shown by src/popup/views/stateRecovery.js when the stored profile

src/popup/views/settings.js

@@ -316,7 +316,11 @@ function init(ctx) {
     const networkSelect = $("settings-network");
     networkSelect.addEventListener("change", async () => {
         const newId = networkSelect.value;
+        if (newId === state.networkId) return;
         const net = await onChainSwitch(newId);
+        // Open pages are told by the background, as after a site's approved
+        // switch request.
+        notify({ type: "AUTISTMASK_NETWORK_CHANGED", chainId: net.chainId });
         $("settings-rpc").value = state.rpcUrl;
         $("settings-blockscout").value = state.blockscoutUrl;
         showFlash("Switched to " + net.name + ".");

src/popup/views/transactionDetail.js

@@ -84,8 +84,9 @@ function show(tx) {
             contractAddress: tx.contractAddress || null,
             // The network the history entry was read from. The type line and
             // the fee are in its native currency, not the active network's:
-            // a site can switch the active network before a later popup
+            // the active network can change, in Settings or when the user
-            // shows this screen again.
+            // approves a site's request, before a later popup shows this
+            // screen again.
             chainId: tx.chainId,
         },
     };

src/popup/views/txStatus.js

@@ -89,8 +89,9 @@ function startWait(txInfo, txHash, broadcastTime, pollNow) {
 
     // A native amount, here and on the success and error screens, is in the
     // native currency of txInfo.chainId, the network the transaction was sent
-    // on, not the active network's: a site can switch the active network
+    // on, not the active network's: the active network can change, in
-    // while this screen is open or before a later popup resumes it.
+    // Settings or when the user approves a site's request, while this screen
+    // is open or before a later popup resumes it.
     const symbol =
         txInfo.token === "ETH"
             ? nativeCurrencyByChainId(txInfo.chainId)

src/shared/approvalVerify.js

@@ -53,6 +53,7 @@ const {
     accessListify,
     formatEther,
     getAddress,
+    getBigInt,
     getBytes,
     toQuantity,
     verifyMessage,
@@ -635,6 +636,33 @@ function verifySignature(signParams, signature, expectedFrom) {
     return recovered;
 }
 
+// Why typed data cannot be signed while `network` is the active network, as a
+// sentence, or null when it can. EIP-712 has a wallet refuse typed data whose
+// domain names another chain, because the signature is valid on that chain.
+// ethers signs no chain id when the domain's is null or absent, and reads any
+// other with getBigInt(), so 1, "1" and "0x1" are the same chain here too.
+function typedDataChainRefusal(domain, network) {
+    const chainId = domain?.chainId;
+    if (chainId === undefined || chainId === null) return null;
+    let named;
+    try {
+        named = getBigInt(chainId);
+    } catch {
+        return "This typed data cannot be read, so it cannot be signed.";
+    }
+    const active = getBigInt(network.chainId);
+    if (named === active) return null;
+    return (
+        "This typed data is for chain id " +
+        named +
+        ", but the active network is " +
+        network.name +
+        " (chain id " +
+        active +
+        "), so it cannot be signed."
+    );
+}
+
 // The stage a transaction approval failed at. Which stage it is decides
 // whether the approval survives the failure.
 const TX_STAGE_SIGN = "sign";
@@ -796,6 +824,7 @@ function describeSigningFailure(response, fallbackMessage) {
 module.exports = {
     verifySignedTx,
     verifySignature,
+    typedDataChainRefusal,
     assertNoForbiddenFields,
     assertNothingUnchecked,
     assertCanonicalBytes,

src/shared/phishingDomains.js

@@ -110,11 +110,14 @@ function hashListed(hash) {
  * Generate hostname variants for subdomain matching.
  * "sub.evil.com" yields ["sub.evil.com", "evil.com"].
  *
+ * A trailing dot is dropped: "evil.com." is the fully qualified spelling of
+ * "evil.com", and the browser loads the same site from either.
+ *
  * @param {string} hostname
  * @returns {string[]}
  */
 function hostnameVariants(hostname) {
-    const h = hostname.toLowerCase();
+    const h = hostname.toLowerCase().replace(/\.$/, "");
     const variants = [h];
     const parts = h.split(".");
     // Parent domains: a.b.c.d -> b.c.d, c.d

src/shared/uniswap.js

@@ -53,6 +53,11 @@ function formatAmount(raw, decimals) {
 // on a scale — not as a token name, and not as a quantity.
 const UNNAMED_CURRENCY = "Unknown (not named in the calldata)";
 
+// The same refusal when a V4 swap action could not be read (see
+// decodeExactly()). That action names both of its currencies, so saying the
+// calldata did not name one would be false.
+const UNDECODED_CURRENCY = "Unknown (could not be decoded)";
+
 // Explicit presence, never truthiness. Every gate in this file that guards a
 // decoded value goes through here: an address is never falsy once set, but an
 // amount of 0n is, and a gate that cannot tell a genuine zero from an absent
@@ -295,6 +300,24 @@ function v4ExactInAmount(raw) {
     return raw === 0n ? OPEN_DELTA : raw;
 }
 
+// The V4 swap actions are read only in the parameter structs V4Router has
+// deployed on mainnet and Sepolia. v4-periphery `main` has since added a
+// `minHopPriceX36` field to all four (`src/interfaces/IV4Router.sol`), and
+// reading a shape nobody has deployed would be guessing. ethers alone would
+// read the newer structs anyway: it takes whatever word sits where a
+// deployed field would be, ignores bytes left over, and holds back an error
+// in a field until that field is used. The newer multi-hop exact-in struct
+// then yields the offset of its hop-price array as `amountIn`. So a decode
+// counts only when encoding the result again gives back the same bytes;
+// otherwise this throws, and decodeV4Swap() marks the step as not decoded.
+function decodeExactly(types, data) {
+    const decoded = coder.decode(types, data);
+    if (coder.encode(types, decoded) !== data) {
+        throw new Error("Not in the deployed V4 parameter shape.");
+    }
+    return decoded;
+}
+
 // Decode V4_SWAP (command 0x10) input bytes.
 // The input is ABI-encoded as (bytes actions, bytes[] params).
 // We extract token addresses from SETTLE (input) and TAKE (output) sub-actions,
@@ -309,6 +332,10 @@ function decodeV4Swap(input) {
         let takeToken = null;
         let amountIn = null;
         let amountOutMin = null;
+        // Set when a swap action's parameters are not in the deployed shape
+        // (see decodeExactly()), so nothing was read from that action. SETTLE
+        // and TAKE may still name both currencies.
+        let swapUndecoded = false;
 
         for (let i = 0; i < actions.length; i++) {
             const actionId = actions[i];
@@ -337,7 +364,7 @@ function decodeV4Swap(input) {
                         //   tuple(address,uint24,int24,address,bytes)[] path,
                         //   uint128 amountIn, uint128 amountOutMin)
                         try {
-                            const s = coder.decode(
+                            const s = decodeExactly(
                                 [
                                     "tuple(address,tuple(address,uint24,int24,address,bytes)[],uint128,uint128)",
                                 ],
@@ -355,13 +382,13 @@ function decodeV4Swap(input) {
                                 amountOutMin = s[0][3];
                             }
                         } catch {
-                            // Fall through — SETTLE/TAKE will provide tokens
+                            swapUndecoded = true;
                         }
                     } else {
                         // ExactInputSingleParams: (tuple(address,address,uint24,int24,address) poolKey,
                         //   bool zeroForOne, uint128 amountIn, uint128 amountOutMin, bytes hookData)
                         try {
-                            const s = coder.decode(
+                            const s = decodeExactly(
                                 [
                                     "tuple(tuple(address,address,uint24,int24,address),bool,uint128,uint128,bytes)",
                                 ],
@@ -384,7 +411,7 @@ function decodeV4Swap(input) {
                                 amountOutMin = s[0][3];
                             }
                         } catch {
-                            // Fall through
+                            swapUndecoded = true;
                         }
                     }
                 } else if (
@@ -393,7 +420,7 @@ function decodeV4Swap(input) {
                 ) {
                     if (actionId === V4_SWAP_EXACT_OUT) {
                         try {
-                            const s = coder.decode(
+                            const s = decodeExactly(
                                 [
                                     "tuple(address,tuple(address,uint24,int24,address,bytes)[],uint128,uint128)",
                                 ],
@@ -405,11 +432,11 @@ function decodeV4Swap(input) {
                                 settleToken = path[path.length - 1][0];
                             }
                         } catch {
-                            // Fall through
+                            swapUndecoded = true;
                         }
                     } else {
                         try {
-                            const s = coder.decode(
+                            const s = decodeExactly(
                                 [
                                     "tuple(tuple(address,address,uint24,int24,address),bool,uint128,uint128,bytes)",
                                 ],
@@ -426,7 +453,7 @@ function decodeV4Swap(input) {
                                     ? poolKey[1]
                                     : poolKey[0];
                         } catch {
-                            // Fall through
+                            swapUndecoded = true;
                         }
                     }
                 }
@@ -440,6 +467,7 @@ function decodeV4Swap(input) {
             tokenOut: takeToken,
             amountIn,
             amountOutMin,
+            swapUndecoded,
         };
     } catch {
         return null;
@@ -465,6 +493,7 @@ function decode(data, toAddress, sources) {
         let minOutput = null;
         let hasUnwrapWeth = false;
         let hasV2ExactOut = false;
+        let swapUndecoded = false;
         const commandNames = [];
 
         // THE INVARIANT: an amount and the token it is counted in always come
@@ -568,6 +597,12 @@ function decode(data, toAddress, sources) {
                 if (cmdId === 0x10) {
                     const v4 = decodeV4Swap(inputs[i]);
                     if (v4) {
+                        // Without this, a swap action that went unread would
+                        // look like one that had nothing to show.
+                        if (v4.swapUndecoded) {
+                            swapUndecoded = true;
+                            commandNames[i] += " (could not be decoded)";
+                        }
                         setInputOnce(v4.tokenIn, v4.amountIn);
                         // Always update output: last swap step wins. A step
                         // that carries the Min. received figure but decoded no
@@ -591,12 +626,13 @@ function decode(data, toAddress, sources) {
             }
         }
 
-        // Resolve token info. A null token on either side means the calldata
+        // Resolve token info. A null token on either side means no step that
-        // named no currency for it; tokenInfo() refuses rather than calling it
+        // was read named a currency for it; tokenInfo() refuses rather than
-        // ETH. UNWRAP_WETH turns WETH into ETH, so it makes the output ETH
+        // calling it ETH. UNWRAP_WETH turns WETH into ETH, so it makes the
-        // when the output side is WETH, or when no step set the output side.
+        // output ETH when the output side is WETH, or when no step set the
-        // Any other output keeps its own token and figure: a swap that buys
+        // output side. Any other output keeps its own token and figure: a swap
-        // USDC and then unwraps the WETH it did not spend receives USDC.
+        // that buys USDC and then unwraps the WETH it did not spend receives
+        // USDC.
         const outputIsWeth =
             present(outputToken) &&
             WETH_ADDRESSES.includes(outputToken.toLowerCase());
@@ -640,7 +676,10 @@ function decode(data, toAddress, sources) {
             // rather than going missing or naming a token by default. Same
             // wording as the Token Out refusal below: the two sides of this
             // screen must not describe the same condition in two ways.
-            details.push({ label: "Token In", value: UNNAMED_CURRENCY });
+            details.push({
+                label: "Token In",
+                value: swapUndecoded ? UNDECODED_CURRENCY : UNNAMED_CURRENCY,
+            });
         }
 
         if (present(inputAmount)) {
@@ -703,7 +742,10 @@ function decode(data, toAddress, sources) {
             // rather than going missing or naming a token by default, and a
             // Min. received figure below it is never attached to a token the
             // calldata did not state.
-            details.push({ label: "Token Out", value: UNNAMED_CURRENCY });
+            details.push({
+                label: "Token Out",
+                value: swapUndecoded ? UNDECODED_CURRENCY : UNNAMED_CURRENCY,
+            });
         }
 
         if (present(minOutput)) {

tests/approvalOrigin.test.js

@@ -1,5 +1,5 @@
-// The connection, transaction and signature prompts name the site by its full
+// The connection, transaction, signature and network switch prompts name the
-// origin, scheme and port included, not by its bare hostname
+// site by its full origin, scheme and port included, not by its bare hostname
 // (https://git.eeqj.de/sneak/AutistMask/issues/402). A page served over http,
 // or on another port, of a host the user trusts over https must not raise a
 // prompt that reads as that trusted site.
@@ -104,6 +104,7 @@ beforeEach(() => {
 test("the connection prompt shows the origin", async () => {
     await openApproval({});
     expect(node("approve-origin").textContent).toBe(ORIGIN);
+    expect(node("view-approve-site").classList.contains("hidden")).toBe(false);
 });
 
 test("the transaction prompt shows the origin", async () => {
@@ -138,3 +139,24 @@ test("the signature prompt shows the origin", async () => {
     });
     expect(node("approve-sign-origin").textContent).toBe(ORIGIN);
 });
+
+test("the network switch prompt shows the origin and both networks", async () => {
+    await openApproval({
+        type: "network",
+        currentNetworkId: "mainnet",
+        requestedNetworkId: "sepolia",
+    });
+    expect(node("approve-network-origin").textContent).toBe(ORIGIN);
+    expect(node("approve-network-current").textContent).toBe(
+        "Ethereum Mainnet",
+    );
+    expect(node("approve-network-requested").textContent).toBe(
+        "Sepolia Testnet",
+    );
+    // Its own screen, and not the connection prompt, whose "Allow" answers
+    // on the same port.
+    expect(node("view-approve-network").classList.contains("hidden")).toBe(
+        false,
+    );
+    expect(node("view-approve-site").classList.contains("hidden")).toBe(true);
+});

tests/approvalWindow.test.js

@@ -0,0 +1,47 @@
+// The approval window shows no screen until the background has described the
+// approval it answers (https://git.eeqj.de/sneak/AutistMask/issues/408). The
+// connection prompt's "Allow" and the network switch prompt's "Switch" answer
+// on the same port, so a window that showed the connection prompt while it
+// waited could approve a network switch.
+//
+// Booted through the real popup entry point, which is where the connection
+// prompt used to be put up before the background had answered.
+
+const {
+    bootPopup,
+    cleanupPopup,
+    settle,
+    unversionedValidProfile,
+} = require("./support/popupBoot");
+
+afterEach(cleanupPopup);
+
+test("the approval window shows no screen until the background describes the approval", async () => {
+    // The background's answer, held until the test gives it.
+    let answer = null;
+    const env = await bootPopup(unversionedValidProfile(), {
+        search: "?approval=approval-1",
+        runtime: {
+            connect: () => ({ postMessage: () => {} }),
+            sendMessage: (msg, reply) => {
+                if (msg.type === "AUTISTMASK_GET_APPROVAL") answer = reply;
+            },
+        },
+    });
+
+    expect(answer).not.toBeNull();
+    // No screen at all, the connection prompt included.
+    expect(env.visibleViews()).toEqual([]);
+
+    answer({
+        type: "network",
+        origin: "https://dapp.example",
+        currentNetworkId: "mainnet",
+        requestedNetworkId: "sepolia",
+        isPhishingDomain: false,
+    });
+    await settle();
+
+    expect(env.visibleViews()).toEqual(["approve-network"]);
+    expect(env.pageErrors).toEqual([]);
+});

tests/backgroundApproval.test.js

@@ -397,7 +397,13 @@ function loadBackground(options) {
                 rpcResult = r;
             },
         );
-        return { result: () => rpcResult };
+        return {
+            id: () =>
+                new URL(created[created.length - 1].url).searchParams.get(
+                    "approval",
+                ),
+            result: () => rpcResult,
+        };
     }
 
     // A dApp asking to connect. The origin defaults to one the persisted
@@ -1484,6 +1490,55 @@ describe("what the approval is verified against", () => {
         });
     });
 
+    // Typed data whose domain names another chain is refused on the sign
+    // screen; a signature for it that reaches the background anyway is not
+    // handed to the page (https://git.eeqj.de/sneak/AutistMask/issues/519).
+    // TYPED_DATA names mainnet.
+    async function answerTypedData(bg, pending) {
+        const { domain, types, message } = JSON.parse(TYPED_DATA);
+        delete types.EIP712Domain;
+        const signature = await signer.signTypedData(domain, types, message);
+        const answer = bg.send(
+            {
+                type: "AUTISTMASK_SIGN_RESPONSE",
+                id: pending.id(),
+                approved: true,
+                signature,
+            },
+            { url: bg.fromPopup.url },
+        );
+        await settle();
+        return { answer, signature };
+    }
+
+    test("typed data for the active chain is handed back signed", async () => {
+        const bg = loadBackground();
+        const pending = bg.requestTypedData();
+        await settle();
+
+        const { answer, signature } = await answerTypedData(bg, pending);
+
+        expect(answer.sendResponse).toHaveBeenCalledWith({ signature });
+        expect(pending.result()).toEqual({ result: signature });
+    });
+
+    test("typed data for another chain is refused, not handed back", async () => {
+        const bg = loadBackground();
+        bg.setNetwork(SEPOLIA);
+        const pending = bg.requestTypedData();
+        await settle();
+
+        const { answer } = await answerTypedData(bg, pending);
+
+        const refusal =
+            "This typed data is for chain id 1, but the active network is Sepolia Testnet (chain id 11155111), so it cannot be signed.";
+        expect(answer.sendResponse).toHaveBeenCalledWith({
+            error: refusal,
+            retryable: false,
+        });
+        expect(pending.result()).toEqual({ error: { message: refusal } });
+    });
+
     test("a sign request from another address raises no approval at all", async () => {
         const bg = loadBackground();
         const pending = bg.requestSign(other.address);

tests/backgroundStateIsolation.test.js

@@ -25,6 +25,7 @@
 
 const { Wallet } = require("ethers");
 const { networkById } = require("../src/shared/networks");
+const { applyChainSwitchFields } = require("../src/shared/chainSwitchFields");
 const { makeStorageStub } = require("./support/storageStub");
 
 const SIGNER_KEY =
@@ -240,8 +241,8 @@ describe("a chain switch under a transaction already committed to a chain", () =
     // The artifact is verified against the chain read at the top of the
     // attempt. Whatever endpoint it is then broadcast to has to be that same
     // chain's — otherwise the wallet checks a transaction against Sepolia and
-    // sends it to a mainnet node. A connected site can switch the chain at any
+    // sends it to a mainnet node. The user can switch the network in Settings
-    // moment, including this one.
+    // at any moment, including this one.
     test("the artifact is broadcast to the endpoint of the chain it was verified against", async () => {
         const bg = loadWorker("sepolia");
 
@@ -264,9 +265,9 @@ describe("a chain switch under a transaction already committed to a chain", () =
             populated(Number(SEPOLIA.networkVersion)),
         );
 
-        // A connected site switches the chain while the attempt is running,
+        // The user switches the network in Settings while the attempt is
-        // and the switch is committed to storage in full before the attempt
+        // running: the popup writes the switched record to storage in full
-        // goes any further.
+        // before the attempt goes any further.
         //
         // It is fired from inside the attempt's SECOND state read, because
         // that is where the window used to be: the chain id was captured at
@@ -277,18 +278,18 @@ describe("a chain switch under a transaction already committed to a chain", () =
         // this to fire on, and the switch below runs after the attempt is
         // done instead — which is the point.
         let reads = 0;
-        let switched = null;
+        let switched = false;
-        const doSwitch = async () => {
+        const doSwitch = () => {
-            switched = bg.rpc("wallet_switchEthereumChain", [
+            const record = bg.persisted();
-                { chainId: MAINNET.chainId },
+            applyChainSwitchFields(record, MAINNET.id);
-            ]);
+            global.chrome.storage.write("autistmask", record);
-            await settle();
+            switched = true;
         };
         bg.setGetHook(async () => {
             reads++;
             if (reads !== 2) return;
             bg.setGetHook(null);
-            await doSwitch();
+            doSwitch();
         });
 
         const attempt = bg.send(
@@ -303,8 +304,7 @@ describe("a chain switch under a transaction already committed to a chain", () =
         await settle();
 
         bg.setGetHook(null);
-        if (!switched) await doSwitch();
+        if (!switched) doSwitch();
-        expect(switched.result()).toEqual({ result: null });
         expect(bg.persisted().networkId).toBe("mainnet");
         await settle();
 

tests/chainSwitchGate.test.js

@@ -1,16 +1,24 @@
-// Who may move the active chain.
+// Who may move the active chain, and when.
 //
 // wallet_switchEthereumChain used to be answered for any origin at all, with
 // no connection check and no prompt, so a page the user had never connected
 // to could clear the [TESTNET] banner under someone who believed they were
-// on Sepolia (https://git.eeqj.de/sneak/AutistMask/issues/308). The refusal
+// on Sepolia (https://git.eeqj.de/sneak/AutistMask/issues/308). Gated on the
-// is asserted as a refusal to ACT — the state unmoved and no chainChanged
+// connection, a connected site could still move the wallet between mainnet and
-// broadcast — because an error code alone would not distinguish a gate from
+// Sepolia without asking. Only the user switches the network: a connected
-// a switch that happened and then reported a failure.
+// site's request opens a prompt, and nothing changes unless the user approves
+// it there (https://git.eeqj.de/sneak/AutistMask/issues/408).
 //
-// The endpoint half of that issue lives in tests/networkEndpoints.test.js,
+// Every refusal is asserted as a refusal to ACT — the stored record unmoved
-// which covers the popup's chain switch; this file covers the background's,
+// and no chainChanged broadcast — because an error code alone would not
-// which goes through storage rather than the shared state singleton.
+// distinguish a refusal from a switch that happened and then reported a
+// failure.
+//
+// The endpoint half of #308 lives in tests/networkEndpoints.test.js, which
+// covers the popup's chain switch; this file covers the background's, which
+// goes through storage rather than the shared state singleton. The last block
+// covers what the background tells open tabs when the user switches the
+// network in Settings.
 
 const { networkById } = require("../src/shared/networks");
 const { makeStorageStub } = require("./support/storageStub");
@@ -21,18 +29,23 @@ const ADDRESS = "0x66133E8ea0f5D1d612D2502a968757D1048c214a";
 const CONNECTED_ORIGIN = "https://dapp.example";
 const STRANGER_ORIGIN = "https://stranger.example";
 
+const EXT_URL = "chrome-extension://autistmask/";
+
 const MAINNET = networkById("mainnet");
 const SEPOLIA = networkById("sepolia");
 
 // The user's own node, so a switch that happens is visible as the loss of it.
 const CUSTOM_RPC = "http://127.0.0.1:8545";
 
+// A balance a switch would clear, so a switch that happens is visible here too.
 function walletFixture() {
     return [
         {
             name: "Wallet 1",
             type: "hd",
-            addresses: [{ address: ADDRESS, balance: "0", tokenBalances: [] }],
+            addresses: [
+                { address: ADDRESS, balance: "1.5", tokenBalances: [] },
+            ],
         },
     ];
 }
@@ -47,10 +60,6 @@ afterEach(() => {
     delete global.chrome;
 });
 
-// ---------------------------------------------------------------------------
-// The gate: which origins the background will switch the chain for.
-// ---------------------------------------------------------------------------
-
 // Load the background worker against stubbed browser APIs, with the real
 // chain-switch and persistence modules behind it, and return the handles to
 // drive it.
@@ -91,30 +100,46 @@ function loadBackground() {
     const storage = makeStorageStub({ autistmask: persisted });
 
     let messageListener = null;
+    let connectListener = null;
+    let windowRemovedListener = null;
+    // The URL of every approval window the background opened. The approval id
+    // is in it, and that is how the popup learns which approval it answers.
+    const opened = [];
     // Every message the background pushed at a content script. chainChanged
-    // is what tells a page the wallet moved, so an ungated switch is visible
+    // is what tells a page the wallet moved, so a switch is visible here as
-    // here as well as in the state.
+    // well as in the state.
     const toTabs = [];
 
     global.chrome = {
         storage,
         runtime: {
-            getURL: (path) => "chrome-extension://autistmask/" + path,
+            getURL: (path) => EXT_URL + path,
             onMessage: {
                 addListener: (fn) => {
                     messageListener = fn;
                 },
             },
-            onConnect: { addListener: () => {} },
+            onConnect: {
+                addListener: (fn) => {
+                    connectListener = fn;
+                },
+            },
             lastError: null,
         },
         windows: {
             getLastFocused: (cb) => cb(null),
-            create: (options, cb) => cb({ id: 1 }),
+            create: (options, cb) => {
+                opened.push(options.url);
+                cb({ id: opened.length });
+            },
             remove: (id, cb) => {
                 if (cb) cb();
             },
-            onRemoved: { addListener: () => {} },
+            onRemoved: {
+                addListener: (fn) => {
+                    windowRemovedListener = fn;
+                },
+            },
         },
         tabs: {
             query: (queryInfo, cb) => cb([{ id: 1 }]),
@@ -128,6 +153,8 @@ function loadBackground() {
 
     require("../src/background/index");
 
+    // A page's request. Its answer is read with result(), which is null for as
+    // long as the request is waiting on the user.
     async function switchChain(chainId, origin) {
         let result = null;
         messageListener(
@@ -142,55 +169,309 @@ function loadBackground() {
             },
         );
         await settle();
-        return result;
+        return { result: () => result };
+    }
+
+    function promptId() {
+        return new URL(opened[opened.length - 1]).searchParams.get("approval");
+    }
+
+    // What the popup is told to show for the prompt.
+    function describePrompt() {
+        let reply = null;
+        messageListener(
+            { type: "AUTISTMASK_GET_APPROVAL", id: promptId() },
+            { url: EXT_URL + "src/popup/index.html" },
+            (r) => {
+                reply = r;
+            },
+        );
+        return reply;
+    }
+
+    // The user's answer, as the popup sends it: on the port named for the
+    // approval, from the extension's own page, and then the window closes.
+    async function answerPrompt(approved) {
+        const onMessage = [];
+        const onDisconnect = [];
+        const port = {
+            name: "approval:" + promptId(),
+            sender: { url: EXT_URL + "src/popup/index.html" },
+            onMessage: { addListener: (fn) => onMessage.push(fn) },
+            onDisconnect: { addListener: (fn) => onDisconnect.push(fn) },
+        };
+        connectListener(port);
+        for (const fn of onMessage) {
+            fn(
+                {
+                    type: "AUTISTMASK_APPROVAL_DECISION",
+                    approved,
+                    remember: false,
+                },
+                port,
+            );
+        }
+        for (const fn of onDisconnect) fn(port);
+        await settle();
+    }
+
+    // The user closes the prompt window without answering it.
+    async function closePrompt() {
+        windowRemovedListener(opened.length);
+        await settle();
     }
 
     return {
         switchChain,
+        describePrompt,
+        answerPrompt,
+        closePrompt,
+        opened,
+        // A message to the background from `sender`, and its answer.
+        send: (msg, sender) => {
+            let reply = null;
+            messageListener(msg, sender, (r) => {
+                reply = r;
+            });
+            return reply;
+        },
         walletState: () => storage.read("autistmask"),
         chainChangedEvents: () =>
             toTabs.filter((m) => m.eventName === "chainChanged"),
     };
 }
 
+const USER_REJECTED = { code: 4001, message: "User rejected the request." };
+
 describe("wallet_switchEthereumChain is gated on the connection", () => {
     test("an origin the wallet was never connected to is refused with 4100", async () => {
         const bg = loadBackground();
+        const before = bg.walletState();
 
-        const result = await bg.switchChain(SEPOLIA.chainId, STRANGER_ORIGIN);
+        const request = await bg.switchChain(SEPOLIA.chainId, STRANGER_ORIGIN);
 
-        expect(result.error).toEqual({ code: 4100, message: "Unauthorized" });
+        expect(request.result().error).toEqual({
-        expect(result.result).toBeUndefined();
+            code: 4100,
+            message: "Unauthorized",
+        });
+        expect(request.result().result).toBeUndefined();
         // The refusal has to be a refusal to ACT, not just an error string:
         // the wallet is still on mainnet, still on the user's own node, and
-        // no page was told the chain moved.
+        // no page was told the chain moved. Nor was the user asked.
-        expect(bg.walletState().networkId).toBe("mainnet");
+        expect(bg.walletState()).toEqual(before);
-        expect(bg.walletState().rpcUrl).toBe(CUSTOM_RPC);
         expect(bg.chainChangedEvents()).toEqual([]);
+        expect(bg.opened).toEqual([]);
     });
 
     test("an unconnected origin is refused even for the chain already active", async () => {
         const bg = loadBackground();
 
-        const result = await bg.switchChain(MAINNET.chainId, STRANGER_ORIGIN);
+        const request = await bg.switchChain(MAINNET.chainId, STRANGER_ORIGIN);
 
-        expect(result.error).toEqual({ code: 4100, message: "Unauthorized" });
+        expect(request.result().error).toEqual({
+            code: 4100,
+            message: "Unauthorized",
+        });
     });
 
     test("an unconnected origin is refused before the unsupported-chain answer", async () => {
         const bg = loadBackground();
 
-        const result = await bg.switchChain("0x89", STRANGER_ORIGIN);
+        const request = await bg.switchChain("0x89", STRANGER_ORIGIN);
 
-        expect(result.error.code).toBe(4100);
+        expect(request.result().error.code).toBe(4100);
+    });
+});
+
+describe("only the user switches the network", () => {
+    test("a connected site's request changes nothing while the prompt is open", async () => {
+        const bg = loadBackground();
+        const before = bg.walletState();
+
+        const request = await bg.switchChain(SEPOLIA.chainId, CONNECTED_ORIGIN);
+
+        // Waiting on the user, with one prompt on screen naming the site and
+        // both networks.
+        expect(request.result()).toBeNull();
+        expect(bg.opened).toHaveLength(1);
+        expect(bg.describePrompt()).toMatchObject({
+            origin: CONNECTED_ORIGIN,
+            type: "network",
+            currentNetworkId: "mainnet",
+            requestedNetworkId: "sepolia",
+        });
+
+        // The network, the endpoints and the balances are as they were, and
+        // no page was told otherwise.
+        expect(bg.walletState()).toEqual(before);
+        expect(bg.chainChangedEvents()).toEqual([]);
     });
 
-    test("a connected origin switches the chain", async () => {
+    test("approving the prompt switches the network", async () => {
         const bg = loadBackground();
 
-        const result = await bg.switchChain(SEPOLIA.chainId, CONNECTED_ORIGIN);
+        const request = await bg.switchChain(SEPOLIA.chainId, CONNECTED_ORIGIN);
+        await bg.answerPrompt(true);
+
+        expect(request.result()).toEqual({ result: null });
+        const after = bg.walletState();
+        expect(after.networkId).toBe("sepolia");
+        expect(after.rpcUrl).toBe(SEPOLIA.defaultRpcUrl);
+        expect(after.wallets[0].addresses[0].balance).toBe("0");
+        expect(bg.chainChangedEvents()).toEqual([
+            {
+                type: "AUTISTMASK_EVENT",
+                eventName: "chainChanged",
+                data: SEPOLIA.chainId,
+            },
+        ]);
+    });
+
+    test("rejecting the prompt changes nothing and answers 4001", async () => {
+        const bg = loadBackground();
+        const before = bg.walletState();
+
+        const request = await bg.switchChain(SEPOLIA.chainId, CONNECTED_ORIGIN);
+        await bg.answerPrompt(false);
+
+        expect(request.result()).toEqual({ error: USER_REJECTED });
+        expect(bg.walletState()).toEqual(before);
+        expect(bg.chainChangedEvents()).toEqual([]);
+    });
+
+    test("closing the prompt without answering changes nothing and answers 4001", async () => {
+        const bg = loadBackground();
+        const before = bg.walletState();
+
+        const request = await bg.switchChain(SEPOLIA.chainId, CONNECTED_ORIGIN);
+        await bg.closePrompt();
+
+        expect(request.result()).toEqual({ error: USER_REJECTED });
+        expect(bg.walletState()).toEqual(before);
+        expect(bg.chainChangedEvents()).toEqual([]);
+    });
+
+    test("a request for the chain already active opens no prompt", async () => {
+        const bg = loadBackground();
+        const before = bg.walletState();
+
+        const request = await bg.switchChain(MAINNET.chainId, CONNECTED_ORIGIN);
+
+        expect(request.result()).toEqual({ result: null });
+        expect(bg.opened).toEqual([]);
+        expect(bg.walletState()).toEqual(before);
+        expect(bg.chainChangedEvents()).toEqual([]);
+    });
+
+    test("a second request while the prompt is open is refused with -32002", async () => {
+        const bg = loadBackground();
+
+        const first = await bg.switchChain(SEPOLIA.chainId, CONNECTED_ORIGIN);
+        const second = await bg.switchChain(SEPOLIA.chainId, CONNECTED_ORIGIN);
+
+        expect(second.result().error.code).toBe(-32002);
+        expect(bg.opened).toHaveLength(1);
+
+        // The first prompt still decides.
+        await bg.answerPrompt(true);
+        expect(first.result()).toEqual({ result: null });
+        expect(bg.walletState().networkId).toBe("sepolia");
+    });
+
+    test("a request for an unsupported chain still gets 4902 and no prompt", async () => {
+        const bg = loadBackground();
+
+        const request = await bg.switchChain("0x89", CONNECTED_ORIGIN);
+
+        expect(request.result().error.code).toBe(4902);
+        expect(bg.opened).toEqual([]);
+        expect(bg.walletState().networkId).toBe("mainnet");
+    });
+
+    test("an approved switch keeps the user's endpoint", async () => {
+        const bg = loadBackground();
+
+        await bg.switchChain(SEPOLIA.chainId, CONNECTED_ORIGIN);
+        await bg.answerPrompt(true);
+        expect(bg.walletState().rpcUrl).toBe(SEPOLIA.defaultRpcUrl);
+
+        await bg.switchChain(MAINNET.chainId, CONNECTED_ORIGIN);
+        await bg.answerPrompt(true);
+        expect(bg.walletState().rpcUrl).toBe(CUSTOM_RPC);
+    });
+});
+
+// Switching the network in Settings tells open pages, as an approved site
+// request does (https://git.eeqj.de/sneak/AutistMask/issues/500). These drive
+// the real Settings view over the background's storage, with what it sends
+// delivered to the background from the extension's own page.
+describe("switching the network in Settings tells every open tab", () => {
+    const POPUP = { url: EXT_URL + "src/popup/index.html" };
+
+    // A stand-in for one DOM node: enough of an element for init() to set
+    // properties on it and hang listeners off it.
+    function fakeElement() {
+        return {
+            value: "",
+            checked: false,
+            textContent: "",
+            style: {},
+            dataset: {},
+            classList: { add() {}, remove() {} },
+            listeners: {},
+            addEventListener(event, handler) {
+                this.listeners[event] = handler;
+            },
+            querySelectorAll: () => [],
+        };
+    }
+
+    // Settings, opened the way the popup opens it. Returns its network
+    // selector.
+    async function openSettings(bg) {
+        const elements = {};
+        const element = (id) => (elements[id] ||= fakeElement());
+        jest.doMock("../src/popup/views/helpers", () => ({
+            $: element,
+            showView: () => {},
+            updateDebugBanner: () => {},
+            showFlash: () => {},
+            escapeHtml: (s) => s,
+            flashCopyFeedback: () => {},
+            goBack: () => {},
+            pushCurrentView: () => {},
+            onViewLeave: () => {},
+            VIEWS: [],
+        }));
+        global.chrome.runtime.sendMessage = (msg) => {
+            bg.send(msg, POPUP);
+        };
+        await require("../src/shared/state").loadState();
+        require("../src/popup/views/settings").init({
+            pageClosed: new AbortController().signal,
+        });
+        const select = element("settings-network");
+        select.value = "mainnet";
+        return select;
+    }
+
+    // The user picks `networkId` in the selector.
+    async function choose(select, networkId) {
+        select.value = networkId;
+        await select.listeners.change();
+        await settle();
+    }
+
+    afterEach(() => {
+        jest.dontMock("../src/popup/views/helpers");
+    });
+
+    test("switching to the other network sends chainChanged once, with its chain id", async () => {
+        const bg = loadBackground();
+        const select = await openSettings(bg);
+
+        await choose(select, "sepolia");
 
-        expect(result).toEqual({ result: null });
         expect(bg.walletState().networkId).toBe("sepolia");
         expect(bg.chainChangedEvents()).toEqual([
             {
@@ -201,22 +482,27 @@ describe("wallet_switchEthereumChain is gated on the connection", () => {
         ]);
     });
 
-    test("a connected origin asking for an unsupported chain still gets 4902", async () => {
+    test("choosing the network already active changes nothing and sends nothing", async () => {
         const bg = loadBackground();
+        const select = await openSettings(bg);
+        const before = bg.walletState();
 
-        const result = await bg.switchChain("0x89", CONNECTED_ORIGIN);
+        await choose(select, "mainnet");
 
-        expect(result.error.code).toBe(4902);
+        expect(bg.walletState()).toEqual(before);
-        expect(bg.walletState().networkId).toBe("mainnet");
+        expect(bg.chainChangedEvents()).toEqual([]);
     });
 
-    test("a switch by a connected origin keeps the user's endpoint", async () => {
+    test("a page cannot make the background send chainChanged", async () => {
         const bg = loadBackground();
 
-        await bg.switchChain(SEPOLIA.chainId, CONNECTED_ORIGIN);
+        const reply = bg.send(
-        expect(bg.walletState().rpcUrl).toBe(SEPOLIA.defaultRpcUrl);
+            { type: "AUTISTMASK_NETWORK_CHANGED", chainId: SEPOLIA.chainId },
+            { url: CONNECTED_ORIGIN + "/" },
+        );
+        await settle();
 
-        await bg.switchChain(MAINNET.chainId, CONNECTED_ORIGIN);
+        expect(reply).toEqual({ error: "Unauthorized sender" });
-        expect(bg.walletState().rpcUrl).toBe(CUSTOM_RPC);
+        expect(bg.chainChangedEvents()).toEqual([]);
     });
 });

tests/coldWorkerChainSwitch.test.js

@@ -14,6 +14,10 @@
 // itself: the handler has to do it. tests/chainSwitchGate.test.js mocks the
 // state module wholesale and tests/networkEndpoints.test.js always loads
 // first, so neither can see this.
+//
+// A site's switch happens only once the user approves it on a prompt
+// (https://git.eeqj.de/sneak/AutistMask/issues/408), so every switch here is
+// approved the way the popup approves one.
 
 const { networkById } = require("../src/shared/networks");
 const { makeStorageStub } = require("./support/storageStub");
@@ -90,6 +94,9 @@ function loadColdWorker(networkId) {
     const storage = makeStorageStub({ autistmask: storedProfile(networkId) });
 
     let messageListener = null;
+    let connectListener = null;
+    // The URL of every approval window opened; the approval id is in it.
+    const opened = [];
     const toTabs = [];
 
     global.chrome = {
@@ -101,12 +108,19 @@ function loadColdWorker(networkId) {
                     messageListener = fn;
                 },
             },
-            onConnect: { addListener: () => {} },
+            onConnect: {
+                addListener: (fn) => {
+                    connectListener = fn;
+                },
+            },
             lastError: null,
         },
         windows: {
             getLastFocused: (cb) => cb(null),
-            create: (options, cb) => cb({ id: 1 }),
+            create: (options, cb) => {
+                opened.push(options.url);
+                cb({ id: opened.length });
+            },
             remove: (id, cb) => {
                 if (cb) cb();
             },
@@ -124,6 +138,32 @@ function loadColdWorker(networkId) {
 
     require("../src/background/index");
 
+    // The user approves the prompt the request opened, as the popup does: a
+    // decision on the port named for the approval, from the extension's own
+    // page.
+    function approvePrompt() {
+        const id = new URL(opened[opened.length - 1]).searchParams.get(
+            "approval",
+        );
+        let onDecision = null;
+        const port = {
+            name: "approval:" + id,
+            sender: { url: "chrome-extension://autistmask/src/popup/" },
+            onMessage: {
+                addListener: (fn) => {
+                    onDecision = fn;
+                },
+            },
+            onDisconnect: { addListener: () => {} },
+        };
+        connectListener(port);
+        onDecision(
+            { type: "AUTISTMASK_APPROVAL_DECISION", approved: true },
+            port,
+        );
+    }
+
+    // A connected site asks for `chainId`, and the user approves it.
     async function switchChain(chainId) {
         let result = null;
         messageListener(
@@ -138,6 +178,8 @@ function loadColdWorker(networkId) {
             },
         );
         await settle();
+        approvePrompt();
+        await settle();
         return result;
     }
 

tests/e2e/firefox/driver.js

@@ -279,12 +279,18 @@ class Driver {
 
     // Shown means shown: in the popup a view is switched by toggling a
     // "hidden" class, and an element that is present but collapsed is not
-    // the thing a test means by visible.
+    // the thing a test means by visible. Until the page's stylesheet has
+    // applied that class hides nothing and every view lays out, so the page
+    // must also have finished loading, which it does only after its
+    // stylesheet, and neither the element nor anything enclosing it may
+    // carry the class (https://git.eeqj.de/sneak/AutistMask/issues/502).
     async waitVisible(selector, timeout = DEFAULT_WAIT_MS) {
         return this.waitFor(
             "selector " + selector + " to be visible",
             `const el = document.querySelector(arguments[0]);
-             if (!el) return false;
+             if (document.readyState !== "complete" || !el) return false;
+             if (el.closest(".hidden")) return false;
+             if (getComputedStyle(el).visibility !== "visible") return false;
              const r = el.getBoundingClientRect();
              return r.width > 0 && r.height > 0;`,
             [selector],

tests/e2e/firefox/run.js

@@ -63,6 +63,7 @@ const {
 const { ConsoleErrors, EXTENSION_ORIGIN, start, sleep } = require("./driver");
 const { startDappServer } = require("./dapp");
 const { STUB_COUNTERPARTY } = require("../network");
+const { NETWORKS } = require("../../../src/shared/networks");
 const {
     STATE_SCHEMA_VERSION,
     stateProblem,
@@ -127,6 +128,18 @@ step("the popup is drawn in the monospace font it declares", async (env) => {
     );
 });
 
+// The same check as the Chrome suite's (#456), so both browsers are held to
+// the same size.
+step("the popup's text is drawn at the 14px text-sm declares", async (env) => {
+    const size = await env.driver.execute(
+        "return getComputedStyle(document.body).fontSize;",
+    );
+    assert(
+        size === "14px",
+        "the popup's text is drawn at " + size + ", not at the 14px of text-sm",
+    );
+});
+
 // The recovery screen (#361): the Chrome suite's four cases, run before any
 // wallet exists for the same reason. With no wallet nothing saves on a timer,
 // so no save can write a good record over the unreadable one. The last of them
@@ -684,6 +697,159 @@ step(
     },
 );
 
+// The network fields of the stored record, read on the popup page, the one
+// moz-extension:// document the suite has open.
+async function storedNetwork(env) {
+    const d = env.driver;
+    await d.switchToWindow(env.popupWindow);
+    const stored = await d.executeAsync(
+        `const done = arguments[arguments.length - 1];
+         const api = typeof browser !== "undefined" ? browser : chrome;
+         Promise.resolve(api.storage.local.get("autistmask")).then(
+             (r) => done({
+                 networkId: r.autistmask.networkId,
+                 rpcUrl: r.autistmask.rpcUrl,
+                 blockscoutUrl: r.autistmask.blockscoutUrl,
+             }),
+             (e) => done({ error: String((e && e.message) || e) }),
+         );`,
+    );
+    assert(
+        stored && !stored.error,
+        "could not read the stored network: " + (stored && stored.error),
+    );
+    return stored;
+}
+
+// Every chainChanged event the test page has been sent, waiting up to
+// `timeout` for there to be `count` of them: the background sends the event
+// alongside its answer to the request, so it can arrive just after it. Leaves
+// the driver on the page.
+async function chainChangedEvents(env, count = 0, timeout = 5000) {
+    const d = env.driver;
+    await d.switchToWindow(env.dappWindow);
+    const deadline = Date.now() + timeout;
+    for (;;) {
+        const events = (await dappMessages(d, "AUTISTMASK_EVENT")).filter(
+            (m) => m.eventName === "chainChanged",
+        );
+        if (events.length >= count || Date.now() > deadline) return events;
+        await sleep(100);
+    }
+}
+
+// Ask, from the page, to switch from network `from` to network `to`, and
+// return the prompt that opens, checked to name the site and both networks.
+// Leaves the driver on the prompt.
+async function openNetworkPrompt(env, key, from, to) {
+    const d = env.driver;
+    await d.switchToWindow(env.dappWindow);
+    await startRequest(d, key, "wallet_switchEthereumChain", [
+        { chainId: to.chainId },
+    ]);
+    const popup = await waitForApprovalWindow(d);
+    await d.switchToWindow(popup);
+    await d.waitVisible("#view-approve-network");
+    const screen = {
+        origin: await d.text("#approve-network-origin"),
+        current: await d.text("#approve-network-current"),
+        requested: await d.text("#approve-network-requested"),
+    };
+    assert(
+        isDeepStrictEqual(screen, {
+            origin: env.server.origin,
+            current: from.name,
+            requested: to.name,
+        }),
+        "the network switch prompt shows " + JSON.stringify(screen),
+    );
+    return popup;
+}
+
+// Only the user switches the network. A connected site's request opens a
+// prompt, and until the user approves it the stored network does not move and
+// no page is told it did (https://git.eeqj.de/sneak/AutistMask/issues/408).
+// The wallet goes back to mainnet the same way at the end, for the transaction
+// step after this one.
+step(
+    "a site's network switch changes nothing until the user approves it",
+    async (env) => {
+        const d = env.driver;
+        const { mainnet, sepolia } = NETWORKS;
+        const before = await storedNetwork(env);
+        assert(
+            before.networkId === "mainnet",
+            "this step starts on mainnet, not on " + before.networkId,
+        );
+        const eventsBefore = (await chainChangedEvents(env)).length;
+
+        const rejected = await openNetworkPrompt(
+            env,
+            "switch-reject",
+            mainnet,
+            sepolia,
+        );
+        assert(
+            isDeepStrictEqual(await storedNetwork(env), before),
+            "the network moved while its prompt was still open",
+        );
+        // Nothing else closes this window, so a click that did not land
+        // leaves the request unanswered and the assertion below fails.
+        await d.switchToWindow(rejected);
+        await d.click("#btn-reject-network");
+        await d.switchToWindow(env.dappWindow);
+        await assertUserRejection(
+            d,
+            "switch-reject",
+            "the network switch rejection",
+        );
+        assert(
+            isDeepStrictEqual(await storedNetwork(env), before),
+            "a rejected network switch moved the network",
+        );
+        assert(
+            (await chainChangedEvents(env)).length === eventsBefore,
+            "a rejected network switch told the page the chain changed",
+        );
+
+        await openNetworkPrompt(env, "switch-approve", mainnet, sepolia);
+        await d.click("#btn-approve-network");
+        await d.switchToWindow(env.dappWindow);
+        let outcome = await settleRequest(d, "switch-approve");
+        assert(
+            outcome.settled === "resolved" && outcome.result === null,
+            "the approved network switch did not resolve: " +
+                JSON.stringify(outcome),
+        );
+        assert(
+            (await storedNetwork(env)).networkId === "sepolia",
+            "the approved network switch did not move the network",
+        );
+        const events = await chainChangedEvents(env, eventsBefore + 1);
+        assert(
+            events.length === eventsBefore + 1 &&
+                events[events.length - 1].data === sepolia.chainId,
+            "the page was not told of the approved switch: " +
+                JSON.stringify(events),
+        );
+
+        await openNetworkPrompt(env, "switch-restore", sepolia, mainnet);
+        await d.click("#btn-approve-network");
+        await d.switchToWindow(env.dappWindow);
+        outcome = await settleRequest(d, "switch-restore");
+        assert(
+            outcome.settled === "resolved",
+            "switching back to mainnet did not resolve: " +
+                JSON.stringify(outcome),
+        );
+        assert(
+            isDeepStrictEqual(await storedNetwork(env), before),
+            "switching back did not restore the mainnet network and endpoints",
+        );
+        await d.switchToWindow(env.dappWindow);
+    },
+);
+
 step(
     "eth_sendTransaction shows the transaction and returns its hash",
     async (env) => {

tests/e2e/harness.js

@@ -333,8 +333,33 @@ async function launch(routeOpts) {
 
 const PASSWORD = "e2e-harness-password";
 
+// Waits until the page shows `selector`, not only until it lays out. Until the
+// page's stylesheet has applied, the `hidden` class that showView() keeps on
+// every view but the current one hides nothing and every view lays out, so a
+// test could read a screen before the page's script had filled it
+// (https://git.eeqj.de/sneak/AutistMask/issues/502). So the page must also
+// have finished loading, which it does only after its stylesheet, and neither
+// the element nor anything enclosing it may carry `hidden`. Polled on a timer:
+// animation frames are not guaranteed to a window that is not in front.
 async function visible(page, selector, timeout = 15000) {
-    await page.waitForSelector(selector, { state: "visible", timeout });
+    await page
+        .waitForFunction(
+            (sel) => {
+                const el = document.querySelector(sel);
+                if (document.readyState !== "complete" || !el) return false;
+                if (el.closest(".hidden")) return false;
+                if (getComputedStyle(el).visibility !== "visible") return false;
+                const r = el.getBoundingClientRect();
+                return r.width > 0 && r.height > 0;
+            },
+            selector,
+            { polling: 50, timeout },
+        )
+        .catch((e) => {
+            throw new Error(
+                "the page did not show " + selector + ": " + e.message,
+            );
+        });
 }
 
 // An empty WebAssembly module: magic number and version header, no

tests/e2e/run.js

@@ -113,6 +113,18 @@ test("the popup is drawn in the monospace font it declares (#418)", async (env)
     );
 });
 
+// The same stylesheet sets the size on body to 75%, which would draw the
+// popup at 12px.
+test("the popup's text is drawn at the 14px text-sm declares (#456)", async (env) => {
+    const size = await env.page.evaluate(
+        () => getComputedStyle(document.body).fontSize,
+    );
+    assert(
+        size === "14px",
+        "the popup's text is drawn at " + size + ", not at the 14px of text-sm",
+    );
+});
+
 // The empirical half of #182. The manifest change is only a claim about
 // what the CSP permits; this is the observation. Two things have to hold
 // together, and the run covers both: the popup realm compiles WASM (here),
@@ -3499,7 +3511,7 @@ async function closeApprovalPages(ctx) {
 }
 
 // Click a button whose own handler closes the window it lives in — every
-// Reject, and Allow on the site prompt.
+// Reject, Allow on the site prompt, and Switch on the network switch prompt.
 //
 // page.click() dispatches the click and then waits for the renderer to
 // acknowledge it, and a page torn down by the handler never gets to. The
@@ -3514,12 +3526,13 @@ async function closeApprovalPages(ctx) {
 //   #btn-reject-sign, #btn-reject-tx — their disconnect leaves the approval
 //     pending, so a click that never landed leaves the dApp promise unsettled
 //     and the assertion after the call fails on its own.
-//   #btn-approve — only a decision resolves the promise, and a swallowed click
+//   #btn-approve, #btn-approve-network — only a decision resolves the promise,
-//     cannot produce settled === "resolved".
+//     and a swallowed click cannot produce settled === "resolved".
-//   #btn-reject on the site prompt — NOT self-proving. A page that went away
+//   #btn-reject on the site prompt, #btn-reject-network — NOT self-proving. A
-//     without the click landing disconnects the approval port, the background
+//     page that went away without the click landing disconnects the approval
-//     settles that as 4001, and 4001 is exactly what assertUserRejection
+//     port, the background settles that as 4001, and 4001 is exactly what
-//     accepts. Both call sites arm the click trace below and assert it.
+//     assertUserRejection accepts. Every call site arms the click trace below
+//     and asserts it.
 //
 // A button that is missing or unclickable raises a different error, which is
 // rethrown.
@@ -4389,6 +4402,190 @@ test("a prompt raised while another approval window has focus opens its own (#29
     await assertUserRejection(env.dapp, "focus-sign", "the sign prompt");
 });
 
+// The network fields of the stored record.
+async function storedNetwork(page) {
+    const s = await storedRecord(page);
+    return {
+        networkId: s.networkId,
+        rpcUrl: s.rpcUrl,
+        blockscoutUrl: s.blockscoutUrl,
+    };
+}
+
+// Every chainChanged event the test page has been sent, waiting up to
+// `timeout` for there to be `count` of them: the background sends the event
+// alongside its answer to the request, so it can arrive just after it.
+async function chainChangedEvents(page, count = 0, timeout = 5000) {
+    const deadline = Date.now() + timeout;
+    for (;;) {
+        const events = (await dappMessages(page, "AUTISTMASK_EVENT")).filter(
+            (m) => m.eventName === "chainChanged",
+        );
+        if (events.length >= count || Date.now() > deadline) return events;
+        await sleep(50);
+    }
+}
+
+// Ask, from the test page, to switch from network `from` to network `to`, and
+// return the prompt that opens, checked to name the site and both networks.
+async function openNetworkPrompt(env, key, from, to) {
+    await startRequest(env.dapp, key, "wallet_switchEthereumChain", [
+        { chainId: to.chainId },
+    ]);
+    const popup = await waitForApprovalWindow(env.ctx);
+    await visible(popup, "#view-approve-network");
+    const screen = await popup.evaluate(() => ({
+        origin: document.getElementById("approve-network-origin").textContent,
+        current: document.getElementById("approve-network-current").textContent,
+        requested: document.getElementById("approve-network-requested")
+            .textContent,
+    }));
+    assert(
+        isDeepStrictEqual(screen, {
+            origin: DAPP_ORIGIN,
+            current: from.name,
+            requested: to.name,
+        }),
+        "the network switch prompt shows " + JSON.stringify(screen),
+    );
+    return popup;
+}
+
+// Only the user switches the network. A connected site's request opens a
+// prompt, and until the user approves it the stored network does not move and
+// no page is told it did (https://git.eeqj.de/sneak/AutistMask/issues/408).
+// The wallet goes back to mainnet the same way at the end, for the tests after
+// this one.
+test("a site's network switch changes nothing until the user approves it (#408)", async (env) => {
+    const { mainnet, sepolia } = NETWORKS;
+    const before = await storedNetwork(env.page);
+    assert(
+        before.networkId === "mainnet",
+        "this test starts on mainnet, not on " + before.networkId,
+    );
+    const eventsBefore = (await chainChangedEvents(env.dapp)).length;
+
+    const rejected = await openNetworkPrompt(
+        env,
+        "switch-reject",
+        mainnet,
+        sepolia,
+    );
+    try {
+        assert(
+            isDeepStrictEqual(await storedNetwork(env.page), before),
+            "the network moved while its prompt was still open",
+        );
+        // Closing the prompt unanswered is also a rejection, so the click
+        // itself is witnessed.
+        await armClickTrace(env, rejected, "#btn-reject-network");
+        await clickAndClose(rejected, "#btn-reject-network");
+        await assertClickLanded(env, "#btn-reject-network");
+        await assertUserRejection(
+            env.dapp,
+            "switch-reject",
+            "the network switch rejection",
+        );
+    } finally {
+        await closeApprovalPages(env.ctx);
+    }
+    assert(
+        isDeepStrictEqual(await storedNetwork(env.page), before),
+        "a rejected network switch moved the network",
+    );
+    assert(
+        (await chainChangedEvents(env.dapp)).length === eventsBefore,
+        "a rejected network switch told the page the chain changed",
+    );
+
+    const approved = await openNetworkPrompt(
+        env,
+        "switch-approve",
+        mainnet,
+        sepolia,
+    );
+    let outcome;
+    try {
+        await clickAndClose(approved, "#btn-approve-network");
+        outcome = await settleRequest(env.dapp, "switch-approve");
+    } finally {
+        await closeApprovalPages(env.ctx);
+    }
+    assert(
+        outcome.settled === "resolved" && outcome.result === null,
+        "the approved network switch did not resolve: " +
+            JSON.stringify(outcome),
+    );
+    assert(
+        (await storedNetwork(env.page)).networkId === "sepolia",
+        "the approved network switch did not move the network",
+    );
+    const events = await chainChangedEvents(env.dapp, eventsBefore + 1);
+    assert(
+        events.length === eventsBefore + 1 &&
+            events[events.length - 1].data === sepolia.chainId,
+        "the page was not told of the approved switch: " +
+            JSON.stringify(events),
+    );
+
+    const restored = await openNetworkPrompt(
+        env,
+        "switch-restore",
+        sepolia,
+        mainnet,
+    );
+    try {
+        await clickAndClose(restored, "#btn-approve-network");
+        outcome = await settleRequest(env.dapp, "switch-restore");
+    } finally {
+        await closeApprovalPages(env.ctx);
+    }
+    assert(
+        outcome.settled === "resolved",
+        "switching back to mainnet did not resolve: " + JSON.stringify(outcome),
+    );
+    assert(
+        isDeepStrictEqual(await storedNetwork(env.page), before),
+        "switching back did not restore the mainnet network and endpoints",
+    );
+});
+
+// Switching the network in Settings tells the page too, as an approved site
+// request does (https://git.eeqj.de/sneak/AutistMask/issues/500). The wallet
+// goes back to mainnet the same way at the end.
+test("a network switch in Settings tells the page (#500)", async (env) => {
+    const { mainnet, sepolia } = NETWORKS;
+    const before = await storedNetwork(env.page);
+    assert(
+        before.networkId === "mainnet",
+        "this test starts on mainnet, not on " + before.networkId,
+    );
+    const eventsBefore = (await chainChangedEvents(env.dapp)).length;
+    await openSettings(env.page);
+
+    await env.page.selectOption("#settings-network", "sepolia");
+    let events = await chainChangedEvents(env.dapp, eventsBefore + 1);
+    assert(
+        events.length === eventsBefore + 1 &&
+            events[events.length - 1].data === sepolia.chainId,
+        "the page was not told of the switch to Sepolia: " +
+            JSON.stringify(events),
+    );
+
+    await env.page.selectOption("#settings-network", "mainnet");
+    events = await chainChangedEvents(env.dapp, eventsBefore + 2);
+    assert(
+        events.length === eventsBefore + 2 &&
+            events[events.length - 1].data === mainnet.chainId,
+        "the page was not told of the switch back to mainnet: " +
+            JSON.stringify(events),
+    );
+    assert(
+        isDeepStrictEqual(await storedNetwork(env.page), before),
+        "switching back did not restore the mainnet network and endpoints",
+    );
+});
+
 // The closing pass over both boundaries at once. Every message the section
 // put on either channel is re-read here and required to be free of the
 // password — and required to be there at all, method by method, so the

tests/nativeCurrency.test.js

@@ -345,10 +345,10 @@ describe.each([
 });
 
 // A transaction's value and fee are in the native currency of the network the
-// transaction is on, which need not be the active one. A site can switch the
+// transaction is on, which need not be the active one. The active network can
-// active network after its transaction is prepared and back before it is
+// change, in Settings or when the user approves a site's request, after a
-// signed, and a popup opened after a switch shows a sent or listed transaction
+// transaction is prepared and change back before it is signed, and a popup
-// again. The wallet's balances follow the active network; these do not.
+// opened after a switch shows a sent or listed transaction again. The wallet's balances follow the active network; these do not.
 describe.each([
     ["mainnet", "sepolia", "ETH"],
     ["sepolia", "mainnet", "SepoliaETH"],

tests/phishingDomains.test.js

@@ -89,6 +89,12 @@ describe("vendored blocklist", () => {
         expect(isPhishingDomain(LISTED[0].toUpperCase())).toBe(true);
     });
 
+    test("a hostname ending in a dot is the same host", () => {
+        expect(isPhishingDomain(LISTED[1] + ".")).toBe(true);
+        expect(isPhishingDomain("wallet." + LISTED[1] + ".")).toBe(true);
+        expect(isPhishingDomain(CLEAN[0] + ".")).toBe(false);
+    });
+
     test("returns false for an empty or missing hostname", () => {
         expect(isPhishingDomain("")).toBe(false);
         expect(isPhishingDomain(null)).toBe(false);
@@ -133,6 +139,13 @@ describe("hostnameVariants", () => {
     test("lowercases hostnames", () => {
         expect(hostnameVariants("Evil.COM")).toEqual(["evil.com"]);
     });
+
+    test("drops the trailing dot of a fully qualified hostname", () => {
+        expect(hostnameVariants("sub.evil.com.")).toEqual([
+            "sub.evil.com",
+            "evil.com",
+        ]);
+    });
 });
 
 describe("domain hashing", () => {

tests/support/popupBoot.js

@@ -238,6 +238,10 @@ async function settle() {
  * @param {object} [options]
  * @param {object} [options.storage] a storage stub from makeStorageStub(), for
  *     a test that needs to make writes fail or to watch the round trips.
+ * @param {string} [options.search] the page URL's query string, such as
+ *     "?approval=" and an id for the popup opened as an approval window.
+ * @param {object} [options.runtime] members of chrome.runtime that replace the
+ *     stub's own, for a test that has to answer the background's messages.
  * @returns {Promise<object>} handles onto the booted page.
  */
 async function bootPopup(stored, options) {
@@ -281,12 +285,13 @@ async function bootPopup(stored, options) {
             sendMessage: jest.fn(async () => ({})),
             getURL: (p) => "chrome-extension://autistmask/" + p,
             onMessage: { addListener: () => {} },
+            ...(options && options.runtime),
         },
     };
     globalThis.document = document;
     globalThis.window = {
         location: {
-            search: "",
+            search: (options && options.search) || "",
             href: "chrome-extension://autistmask/src/popup/index.html",
             reload: () => reloads.push(Date.now()),
         },

tests/typedDataPermit.test.js

@@ -240,6 +240,7 @@ function request(data) {
 beforeEach(() => {
     state.trackedTokens = [];
     state.wallets = [];
+    state.networkId = "mainnet";
 });
 
 describe("a token permission is warned about, naming spender and amount", () => {
@@ -532,3 +533,66 @@ describe("the sign screen refuses a mismatched primary type", () => {
         expect(node("btn-approve-sign").disabled).toBe(true);
     });
 });
+
+// EIP-712: a wallet refuses typed data whose domain names a chain other than
+// the active one, because the signature is valid on the chain it names
+// (https://git.eeqj.de/sneak/AutistMask/issues/519). The wallet is on Sepolia
+// and the site asks for a mainnet USDC Permit.
+describe("the sign screen refuses typed data for another chain", () => {
+    const REFUSAL =
+        "This typed data is for chain id 1, but the active network is Sepolia Testnet (chain id 11155111), so it cannot be signed.";
+
+    function withChainId(chainId) {
+        return { ...PERMIT, domain: { ...PERMIT.domain, chainId } };
+    }
+
+    beforeEach(() => {
+        decryptWithPassword.mockClear();
+        state.networkId = "sepolia";
+    });
+
+    test("another chain shows the error, with Sign disabled", async () => {
+        await openSignScreen(PERMIT);
+        expect(node("approve-sign-error").textContent).toBe(REFUSAL);
+        expect(node("btn-approve-sign").disabled).toBe(true);
+    });
+
+    test("Sign clicked anyway decrypts and signs nothing", async () => {
+        const sent = await openSignScreen(PERMIT);
+        node("approve-sign-password").value = "any password";
+        await click("btn-approve-sign");
+
+        expect(decryptWithPassword).not.toHaveBeenCalled();
+        expect(sent.map((msg) => msg.type)).not.toContain(
+            "AUTISTMASK_SIGN_RESPONSE",
+        );
+        expect(node("approve-sign-error").textContent).toBe(REFUSAL);
+    });
+
+    // ethers signs 1, "1" and "0x1" as the same chain id.
+    test("the chain id is refused in each form ethers signs", () => {
+        for (const chainId of [1, "1", "0x1"]) {
+            expect(typedDataRefusal(request(withChainId(chainId)))).toBe(
+                REFUSAL,
+            );
+        }
+    });
+
+    test("a chain id that is not a number is refused", () => {
+        expect(typedDataRefusal(request(withChainId("mainnet")))).toBe(
+            "This typed data cannot be read, so it cannot be signed.",
+        );
+    });
+
+    test("the active chain leaves Sign enabled", async () => {
+        await openSignScreen(withChainId("0xaa36a7"));
+        expect(node("approve-sign-error").textContent).toBe("");
+        expect(node("btn-approve-sign").disabled).toBe(false);
+    });
+
+    test("no chain id leaves Sign enabled", async () => {
+        await openSignScreen(withChainId(undefined));
+        expect(node("approve-sign-error").textContent).toBe("");
+        expect(node("btn-approve-sign").disabled).toBe(false);
+    });
+});

tests/uniswap.test.js

@@ -163,6 +163,110 @@ function encodeV4ExactInSingle(currency0, currency1, amountIn, amountOutMin) {
     );
 }
 
+// Each V4 swap action's parameters in two shapes: the struct V4Router has
+// deployed on mainnet and Sepolia, and the one v4-periphery `main` has since
+// moved to, which adds a `minHopPriceX36` field. Each swaps WETH for USDC.
+const POOL_KEY = "tuple(address,address,uint24,int24,address)";
+const PATH_KEY = "tuple(address,uint24,int24,address,bytes)";
+const WETH_USDC_POOL = [WETH_ADDR, USDC_ADDR, 100, 1, ZERO_ADDR];
+const ONE_WETH = 1000000000000000000n;
+const V4_SWAP_ACTION_SHAPES = [
+    {
+        action: "SWAP_EXACT_IN_SINGLE",
+        id: 0x06,
+        deployed: coder.encode(
+            [`tuple(${POOL_KEY},bool,uint128,uint128,bytes)`],
+            [[WETH_USDC_POOL, true, ONE_WETH, 990000n, "0x"]],
+        ),
+        newer: coder.encode(
+            [`tuple(${POOL_KEY},bool,uint128,uint128,uint256,bytes)`],
+            [[WETH_USDC_POOL, true, ONE_WETH, 990000n, 0n, "0x"]],
+        ),
+    },
+    {
+        action: "SWAP_EXACT_IN",
+        id: 0x07,
+        deployed: coder.encode(
+            [`tuple(address,${PATH_KEY}[],uint128,uint128)`],
+            [
+                [
+                    WETH_ADDR,
+                    [[USDC_ADDR, 100, 1, ZERO_ADDR, "0x"]],
+                    ONE_WETH,
+                    990000n,
+                ],
+            ],
+        ),
+        newer: coder.encode(
+            [`tuple(address,${PATH_KEY}[],uint256[],uint128,uint128)`],
+            [
+                [
+                    WETH_ADDR,
+                    [[USDC_ADDR, 100, 1, ZERO_ADDR, "0x"]],
+                    [],
+                    ONE_WETH,
+                    990000n,
+                ],
+            ],
+        ),
+    },
+    {
+        action: "SWAP_EXACT_OUT_SINGLE",
+        id: 0x08,
+        deployed: coder.encode(
+            [`tuple(${POOL_KEY},bool,uint128,uint128,bytes)`],
+            [[WETH_USDC_POOL, true, 990000n, ONE_WETH, "0x"]],
+        ),
+        newer: coder.encode(
+            [`tuple(${POOL_KEY},bool,uint128,uint128,uint256,bytes)`],
+            [[WETH_USDC_POOL, true, 990000n, ONE_WETH, 0n, "0x"]],
+        ),
+    },
+    {
+        action: "SWAP_EXACT_OUT",
+        id: 0x09,
+        deployed: coder.encode(
+            [`tuple(address,${PATH_KEY}[],uint128,uint128)`],
+            [
+                [
+                    USDC_ADDR,
+                    [[WETH_ADDR, 100, 1, ZERO_ADDR, "0x"]],
+                    990000n,
+                    ONE_WETH,
+                ],
+            ],
+        ),
+        newer: coder.encode(
+            [`tuple(address,${PATH_KEY}[],uint256[],uint128,uint128)`],
+            [
+                [
+                    USDC_ADDR,
+                    [[WETH_ADDR, 100, 1, ZERO_ADDR, "0x"]],
+                    [],
+                    990000n,
+                    ONE_WETH,
+                ],
+            ],
+        ),
+    },
+];
+
+// Helper: execute() with one V4_SWAP step holding the swap action, then
+// SETTLE of WETH and TAKE of USDC.
+function v4SwapCalldata(actionId, swapParams) {
+    return buildExecute(
+        "0x10",
+        [
+            encodeV4Swap(new Uint8Array([actionId, V4_SETTLE_ID, V4_TAKE_ID]), [
+                swapParams,
+                encodeV4Settle(WETH_ADDR),
+                encodeV4Take(USDC_ADDR),
+            ]),
+        ],
+        9999999999n,
+    );
+}
+
 function detail(result, label) {
     return result.details.find((d) => d.label === label);
 }
@@ -203,11 +307,83 @@ describe("uniswap decoder", () => {
             result.details.find((d) => d.label === "Min. received").value,
         ).toBe("0.0002 ETH");
 
+        // Real mainnet calldata is in the deployed shape, so its V4 step is
+        // not said to be undecoded.
         const steps = result.details.find((d) => d.label === "Steps");
-        expect(steps.value).toContain("Permit2 Permit");
+        expect(steps.value).toBe("Permit2 Permit → V4 Swap");
-        expect(steps.value).toContain("V4 Swap");
     });
 
+    test.each(V4_SWAP_ACTION_SHAPES)(
+        "a V4 $action in the deployed shape is read",
+        ({ id, deployed }) => {
+            const result = uniswap.decode(
+                v4SwapCalldata(id, deployed),
+                ROUTER_ADDR,
+            );
+            expect(detail(result, "Steps").value).toBe("V4 Swap");
+        },
+    );
+
+    // https://git.eeqj.de/sneak/AutistMask/issues/358 — before it, all four
+    // newer structs decoded as the deployed ones without an error, and the
+    // newer SWAP_EXACT_IN showed the offset of its hop-price array as Amount
+    // ("0.0000000000000004 WETH") and its amountIn as Min. received.
+    test.each(V4_SWAP_ACTION_SHAPES)(
+        "a V4 $action in the newer periphery shape is shown as not decoded",
+        ({ id, newer }) => {
+            const result = uniswap.decode(
+                v4SwapCalldata(id, newer),
+                ROUTER_ADDR,
+            );
+            expect(detail(result, "Amount")).toBeUndefined();
+            expect(detail(result, "Min. received")).toBeUndefined();
+            expect(detail(result, "Steps").value).toBe(
+                "V4 Swap (could not be decoded)",
+            );
+            // SETTLE and TAKE keep their own shape and still name both sides.
+            expect(detail(result, "Token In").address).toBe(WETH_ADDR);
+            expect(detail(result, "Token Out").address).toBe(USDC_ADDR);
+        },
+    );
+
+    // The decoder does not read SETTLE_ALL or TAKE_ALL, so here only the
+    // unread swap action names the currencies. The token lines must not say
+    // the calldata did not name them.
+    test.each(V4_SWAP_ACTION_SHAPES)(
+        "a V4 $action in the newer shape, then SETTLE_ALL and TAKE_ALL, says both tokens could not be decoded",
+        ({ id, newer }) => {
+            const data = buildExecute(
+                "0x10",
+                [
+                    // 0x0c is SETTLE_ALL (currency, maxAmount), 0x0f is
+                    // TAKE_ALL (currency, minAmount).
+                    encodeV4Swap(new Uint8Array([id, 0x0c, 0x0f]), [
+                        newer,
+                        coder.encode(
+                            ["address", "uint256"],
+                            [WETH_ADDR, ONE_WETH],
+                        ),
+                        coder.encode(
+                            ["address", "uint256"],
+                            [USDC_ADDR, 990000n],
+                        ),
+                    ]),
+                ],
+                9999999999n,
+            );
+            const result = uniswap.decode(data, ROUTER_ADDR);
+            expect(detail(result, "Steps").value).toBe(
+                "V4 Swap (could not be decoded)",
+            );
+            expect(detail(result, "Token In").value).toBe(
+                "Unknown (could not be decoded)",
+            );
+            expect(detail(result, "Token Out").value).toBe(
+                "Unknown (could not be decoded)",
+            );
+        },
+    );
+
     test("decodes V2_SWAP_EXACT_IN with known tokens", () => {
         const data = buildExecute(
             "0x08", // V2_SWAP_EXACT_IN
@@ -548,9 +724,11 @@ describe("uniswap decoder", () => {
         const result = uniswap.decode(data, ROUTER_ADDR);
         expect(result).not.toBeNull();
 
+        // The V4 swap action's parameters are empty, so that step is said to
+        // be undecoded.
         const steps = result.details.find((d) => d.label === "Steps");
         expect(steps.value).toBe(
-            "Permit2 Permit \u2192 V4 Swap \u2192 Unwrap WETH",
+            "Permit2 Permit \u2192 V4 Swap (could not be decoded) \u2192 Unwrap WETH",
         );
     });
 

tests/uniswapUndeterminedTokenIn.test.js

@@ -97,7 +97,11 @@ describe("an execute() whose input currency never decoded", () => {
         ]);
 
     test("says the input token is unknown instead of naming ETH", () => {
-        expect(detail(data(), "Token In").value).toBe(REFUSAL);
+        // The swap action that would name it could not be read, so the line
+        // says that rather than REFUSAL's "not named in the calldata".
+        expect(detail(data(), "Token In").value).toBe(
+            "Unknown (could not be decoded)",
+        );
     });
 
     test("keeps a Token In line, so the screen never omits what is paid", () => {