fix: approval windows open as wide as the page (closes #518)

The approval window was opened 360 pixels wide while the page is 396, so
it scrolled sideways and cut off the Reject button. It now opens at 396.
Both browsers count the window's frame in that width, so the approval
page also widens its own window by however far it would scroll sideways;
the toolbar popup's window is left alone. The Firefox suite checks that
the sign prompt does not scroll sideways. The Chrome suite cannot: its
approval windows open at 1280x720 whatever size is asked. README's Visual
Style line, which still said 360x600, now gives the page's real width.

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-check` — check formatting (read-only), on the host
+- `script/fmt` — format all files (writes), on the host, with the `prettier`
+  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_sendTransaction` through the real prompts. Every signature is recovered in
-the runner and compared against the active address, the transaction assertions
-run against the raw signed transaction captured at `eth_sendRawTransaction`
-rather than against anything the extension reported, rejecting each prompt is
-required to return a rejection to the page rather than hang or resolve, a prompt
-raised while another approval window has focus is 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
+`eth_requestAccounts`, `personal_sign`, `eth_signTypedData_v4`,
+`eth_sendTransaction` and `wallet_switchEthereumChain` through the real prompts.
+Every signature is recovered in the runner and compared against the active
+address, the transaction assertions run against the raw signed transaction
+captured at `eth_sendRawTransaction` rather than against anything the extension
+reported, rejecting each prompt is required to return a rejection to the page
+rather than hang or resolve, a network switch request is required to leave the
+stored network unchanged and send no `chainChanged` until it is approved, a
+network switch in Settings is required to send the page `chainChanged` with the
+new chain id, a prompt raised while another approval window has focus is
+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
@@ -457,6 +464,9 @@ papered over:
   forced by clicking Reveal and the settings gear in one page task, which a
   person cannot do; the case a person can hit, the first decrypt after the popup
   opens while libsodium is still loading, is not driven.
+- Approval windows open at 1280x720 whatever size the extension asks for, so
+  whether an approval screen fits its window is checked in the Firefox suite
+  only.
 
 Any test that drives a failure path on purpose declares the `console.error` it
 is about to provoke, via `errors.expect()`. That is not a mute: the declaration
@@ -525,10 +535,12 @@ 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
-round trips — `eth_requestAccounts`, `personal_sign`, `eth_sendTransaction`, and
-a closed approval window rejecting with EIP-1193 4001 — driven through the real
-content script, background page and approval windows.
+suite), wallet creation through the UI, the Add Token screen, and the dApp round
+trips — `eth_requestAccounts`, `personal_sign`, `wallet_switchEthereumChain`
+rejected and then approved, `eth_sendTransaction`, and a closed approval window
+rejecting with EIP-1193 4001 — driven through the real content script,
+background page and approval windows. The `personal_sign` prompt is also
+required to fit its window without scrolling sideways.
 
 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
@@ -885,8 +897,11 @@ discoverable.
   enough that vanilla JS with simple view switching is sufficient. A framework
   would add bundle size, build complexity, and attack surface for no benefit at
   this scale.
-- **360x600 popup**: Standard browser extension popup dimensions. The UI is
-  designed for this fixed viewport.
+- **396x600 popup**: The page is 396 pixels wide (`body` in
+  `src/popup/styles/main.css`), and 600 pixels is as tall as the browser lets
+  the toolbar popup grow. The UI is designed for this fixed viewport. The window
+  an approval opens in is given the same size; the browser counts the window's
+  frame in its width, so the page widens the window by whatever the frame takes.
 
 #### No Layout Shift
 
@@ -1782,8 +1797,12 @@ 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
-      resets the RPC and Blockscout endpoints to that network's defaults
+    - Network: network selector (Ethereum Mainnet / Sepolia Testnet). The
+      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
@@ -2063,7 +2082,9 @@ view would leave a wallet one click from deletion.
   artifact can be compared with it field for field. A nonce the site supplies is
   ignored: the nonce is always the account's next nonce from the node, so a site
   cannot replace one of the user's pending transactions or leave this one stuck
-  behind a gap. A request that cannot be populated — unreachable node, reverting
+  behind a gap. A gas limit the site supplies, as `gas` or `gasLimit`, is used
+  in place of the node's estimate; a request giving both with different values
+  is refused. A request that cannot be populated — unreachable node, reverting
   gas estimate — opens no window and is failed back to the site. Only one
   transaction approval exists at a time: populating fixes the nonce, so a second
   `eth_sendTransaction` arriving while one is unanswered is refused with
@@ -2071,7 +2092,10 @@ 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 +2173,13 @@ 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 +2193,40 @@ 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 +2521,8 @@ 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 +2672,8 @@ 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
 

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
-  `TODO.md` update in that same commit.
-- Move Next Step to the top of Completed Steps; move the top item of Future
-  Steps into Next Step.
+- Do the work as one commit whose title ends with ` (closes #N)`.
+- Add no entry to Completed Steps. What landed is recorded on the tracker and in
+  `git log`, where each commit title names the issue it closes.
 - 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
-// page that asks again before the user has answered is refused with the code
-// above instead of opening another window, so it cannot bury the user in
-// prompts. The pending approval itself holds the place, so a caller must test
-// this and raise its approval with nothing awaited in between.
+// One site-connection approval, one sign approval and one network-switch
+// approval per site at a time: a page that asks again before the user has
+// answered is refused with the code above instead of opening another window,
+// so it cannot bury the user in prompts. The pending approval itself holds the
+// 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 connection handler in its own.
+// approval answers the requesting page in EIP-1193 shape; a site-connection or
+// 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 } };
@@ -420,7 +423,10 @@ function releaseApproval(approval) {
 // the result on the floor, so a rejection here would be unhandled.
 async function openApprovalWindow(id) {
     const popupUrl = runtime.getURL("src/popup/index.html?approval=" + id);
-    const popupWidth = 360;
+    // As wide as the page: body in src/popup/styles/main.css. The browser
+    // counts the window's frame in this width; the page itself adds back
+    // whatever the frame takes (src/popup/index.js).
+    const popupWidth = 396;
     const popupHeight = 600;
 
     let currentWin = null;
@@ -440,7 +446,7 @@ async function openApprovalWindow(id) {
     // Centred on a browser window only. The last focused window can be
     // another approval window still open, and centring on one can give a
     // position the browser refuses ("Bounds must be at least 50% within
-    // visible screen space"): headless Chrome reports this 360x600 popup as
+    // visible screen space"): headless Chrome reports this 396x600 popup as
     // 1280x720. The request then failed with no window at all. Over a popup,
     // the browser picks the position.
     if (currentWin && currentWin.type === "normal") {
@@ -588,6 +594,26 @@ 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 +623,8 @@ 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
-// popup closed without one.
+// site-connection or network-switch approval, and its disconnect is how that
+// 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 +636,9 @@ 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
-// windows.onRemoved listener below.
+// disconnect. When their window closes, the 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 +666,9 @@ 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 +835,10 @@ 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 +860,27 @@ 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 +1399,21 @@ 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
-// here. That popup approves and closes in the same breath, and this event
-// races the decision on a channel of its own — the same race the port exists
-// to end. Its port disconnect says the same thing this event does, in an order
-// that is defined, so the disconnect is left to say it. The window closing
-// before any port connected is the one case with nothing else to speak for it,
-// and is rejected here so the dApp is not left waiting on a window that is
-// gone.
+// A site-connection or network-switch approval whose popup connected its port
+// is not decided here. That popup approves and closes in the same breath, and
+// this event races the decision on a channel of its own — the same race the
+// port exists to end. Its port disconnect says the same thing this event does,
+// in an order that is defined, so the disconnect is left to say it. The window
+// closing before any port connected is the one case with nothing else to speak
+// for it, and is rejected here so the dApp is not left waiting on a window that
+// 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";
-            if (isSite && approval.portConnected) continue;
+            const decidedOnPort =
+                approval.type !== "tx" && approval.type !== "sign";
+            if (decidedOnPort && approval.portConnected) continue;
             const rejection = abandonedResult(
                 approval,
                 APPROVAL_REJECTED_CODE,
@@ -1423,6 +1478,7 @@ 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 +1502,11 @@ 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 +1771,8 @@ 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 +1791,20 @@ 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 +1877,13 @@ 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
-         important: hence font-mono! rather than font-mono. -->
-    <body class="bg-bg text-fg font-mono! text-sm">
+         font and its size on body, and a Tailwind class beats it only when
+         marked important: hence font-mono! and text-sm! rather than
+         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">
-                        Enter your 12 or 24 word recovery phrase below, or click
-                        the button to roll the die for a new one.
+                    <!-- The die button shares the instruction's row: on a row
+                         of its own it pushes Import below the fold at
+                         360x600. -->
+                    <div class="mb-2 flex justify-between items-start gap-2">
+                        <p>
+                            Enter your 12 or 24 word recovery phrase below, or
+                            click the button to roll the die for a new one.
                         </p>
-                    <div class="mb-1 flex justify-end">
                         <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

@@ -21,6 +21,7 @@ const {
     goBack,
 } = require("./views/helpers");
 const { applyTheme } = require("./theme");
+const { windowsGetCurrent, windowsUpdate } = require("../shared/browserApi");
 // Renders a view the popup lands on without having navigated to it forward:
 // on restore here, and on Back. Only the views that can be fully re-rendered
 // from persisted state (RESTORABLE_VIEWS, src/shared/restorableViews.js) go
@@ -233,14 +234,30 @@ async function init() {
     const params = new URLSearchParams(window.location.search);
     const approvalId = params.get("approval");
     if (approvalId) {
+        // The background opens this window as wide as the page, but the
+        // browser counts the window's frame in that width, and how wide the
+        // frame is depends on the browser and the system. The window is
+        // widened by however far the page would scroll sideways. The
+        // connection prompt can also show in the toolbar popup, whose window
+        // is the user's browser window; that one is left alone.
+        const sideways =
+            document.documentElement.scrollWidth -
+            document.documentElement.clientWidth;
+        if (sideways > 0) {
+            windowsGetCurrent().then((win) => {
+                if (win.type === "popup") {
+                    windowsUpdate(win.id, { width: win.width + sideways });
+                }
+            });
+        }
         // Deliberately not awaited, and deliberately not .catch()ed. show()
         // is async, so a throw past its first await surfaces as an unhandled
         // 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
-    // active network after this transaction is prepared and back before it is
-    // signed.
+    // Network line names, not the active network's: the active network can
+    // change, in Settings or when the user approves a site's request, after
+    // 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
-// approval port — see approvalPort above for why — and carries no approval id,
-// because the port name already names the approval the background will settle.
-// The post is guarded because a throw must not cost the close: posting on a
-// port whose background worker has been torn down throws, and the approval it
-// would have settled died with that worker, so the only thing left to do is
-// what the user asked for — go away.
-function decideSite(approved) {
+// Answer a site-connection or network-switch approval and close. The decision
+// goes out on the approval port — see approvalPort above for why — and carries
+// no approval id, because the port name already names the approval the
+// background will settle. `remember` means something only for a site
+// connection. The post is guarded because a throw must not cost the close:
+// posting on a port whose background worker has been torn down throws, and the
+// approval it would have settled died with that worker, so the only thing left
+// 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
-            // shows this screen again.
+            // the active network can change, in Settings or when the user
+            // 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
-    // while this screen is open or before a later popup resumes it.
+    // on, not the active network's: the active network can change, in
+    // 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/approvalTx.js

@@ -1,13 +1,14 @@
 // Preparation of the transaction an approval screen displays.
 //
-// A dApp's eth_sendTransaction normally fixes only `to`, `value` and `data`.
-// The nonce, the gas limit and the fees have to be filled in from the network
-// before anything can be signed, and whoever fills them in decides what the
-// user is shown. That work used to happen in the popup, after the user had
-// already approved: the numbers on the approval screen came from the popup and
-// were compared against nothing, so a compromised popup could display one fee
-// and sign another, and the ceilings in approvalVerify.js were all that stood
-// between the user and a fee that hands the validator the balance.
+// A dApp's eth_sendTransaction normally fixes `to`, `value` and `data`, and
+// sometimes the gas limit. The nonce, the fees, and the gas limit when the
+// site gives none have to be filled in from the network before anything can
+// be signed, and whoever fills them in decides what the user is shown. That
+// work used to happen in the popup, after the user had already approved: the
+// numbers on the approval screen came from the popup and were compared against
+// nothing, so a compromised popup could display one fee and sign another, and
+// the ceilings in approvalVerify.js were all that stood between the user and a
+// fee that hands the validator the balance.
 //
 // So it happens here instead, in the background, before the approval window is
 // opened. The background populates the transaction, shows that object, and
@@ -31,6 +32,7 @@ const {
     VoidSigner,
     accessListify,
     getAddress,
+    getBigInt,
     getBytes,
     hexlify,
     toQuantity,
@@ -47,10 +49,11 @@ const {
 // minutes long, which is not a wait anyone will sit through.
 const POPULATE_TIMEOUT_MS = 20000;
 
-// The request fields taken from the page. Anything else is dropped rather than
-// passed to ethers: the object is page-controlled, and a future ethers that
-// learns to carry a new transaction field must not start picking one up out of
-// it without this module knowing.
+// The request fields taken from the page, plus `gas`, which requestFrom()
+// takes as the gas limit. Anything else is dropped rather than passed to
+// ethers: the object is page-controlled, and a future ethers that learns to
+// carry a new transaction field must not start picking one up out of it
+// without this module knowing.
 //
 // The nonce is not taken from the page; it is always the account's next nonce
 // from the network. A page that chose it could replace one of the user's
@@ -84,6 +87,16 @@ function present(v) {
     return v !== null && v !== undefined && v !== "";
 }
 
+// Whether two quantities from the page are the same number. One that is not a
+// number matches nothing.
+function sameQuantity(a, b) {
+    try {
+        return getBigInt(a) === getBigInt(b);
+    } catch {
+        return false;
+    }
+}
+
 // These strings reach the user through the requesting page, so they are full
 // sentences even when the tail of one came from ethers or from the node.
 function sentence(text) {
@@ -111,6 +124,20 @@ function requestFrom(txParams, from) {
     for (const key of REQUEST_FIELDS) {
         if (present(txParams[key])) request[key] = txParams[key];
     }
+    // JSON-RPC calls the gas limit `gas`, and that is the name sites send.
+    // ethers only reads `gasLimit`: left as `gas` it would be dropped and an
+    // estimate signed in its place.
+    if (present(txParams.gas)) {
+        if (
+            present(request.gasLimit) &&
+            !sameQuantity(request.gasLimit, txParams.gas)
+        ) {
+            throw fail(
+                "The site asked for two different gas limits for this transaction.",
+            );
+        }
+        request.gasLimit = txParams.gas;
+    }
     if (
         present(request.type) &&
         !ALLOWED_TX_TYPES.includes(Number(request.type))

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/browserApi.js

@@ -250,6 +250,22 @@ function windowsGetLastFocused() {
     return invoke(windowsApi(), "getLastFocused");
 }
 
+/**
+ * @returns {Promise<Object>} the window the calling page is in.
+ */
+function windowsGetCurrent() {
+    return invoke(windowsApi(), "getCurrent");
+}
+
+/**
+ * @param {number} windowId
+ * @param {Object} updateInfo
+ * @returns {Promise<Object>} the updated window.
+ */
+function windowsUpdate(windowId, updateInfo) {
+    return invoke(windowsApi(), "update", windowId, updateInfo);
+}
+
 /**
  * @param {number} windowId
  * @returns {Promise<void>}
@@ -275,6 +291,8 @@ module.exports = {
     tabsSendMessage,
     windowsApi,
     windowsCreate,
+    windowsGetCurrent,
     windowsGetLastFocused,
     windowsRemove,
+    windowsUpdate,
 };

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/walletDefects.js

@@ -36,11 +36,13 @@ const DEFECTS = {
                 "derivation path beneath that key instead of from a master " +
                 "key, so the addresses listed here are not the ones that key " +
                 "produces under the standard path.",
-            "Signing and sending are disabled for this wallet. The addresses " +
-                "do descend from the extended private key you imported, so " +
-                "anything they hold is still reachable by software that " +
-                "repeats the same non-standard derivation. Check them in a " +
-                "block explorer before deciding what to do.",
+            "Signing, sending and private key export are disabled for this " +
+                "wallet. Anything these addresses hold can be reached outside " +
+                "this wallet with the extended private key you imported, if " +
+                "you kept a copy of it, or with the master extended private " +
+                "key or recovery phrase it came from, in software that " +
+                "repeats the same non-standard derivation. Check the " +
+                "addresses in a block explorer before deciding what to do.",
             "To see the addresses this key produces under the standard path, " +
                 "import the master extended private key, or the recovery " +
                 "phrase it came from, as a new wallet. Nothing here has been " +

tests/approvalOrigin.test.js

@@ -1,5 +1,5 @@
-// The connection, transaction and signature prompts name the site by its full
-// origin, scheme and port included, not by its bare hostname
+// The connection, transaction, signature and network switch prompts name the
+// 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/approvalTx.test.js

@@ -9,7 +9,7 @@
 // requesting page or the RPC node can say turns it into an approval that
 // should never have been raised.
 
-const { Network, Wallet } = require("ethers");
+const { Network, Transaction, Wallet, toQuantity } = require("ethers");
 const {
     prepareApprovalTx,
     serializeApprovedTx,
@@ -138,6 +138,43 @@ describe("prepareApprovalTx", () => {
         expect(approved.maxFeePerGas).toBe("0x12a05f200");
     });
 
+    // `gas` is the JSON-RPC name for the gas limit and the one sites send.
+    // The node would estimate 21000; the site's 200000 is what is shown and
+    // what is signed.
+    test("uses the gas limit a site sends as gas", async () => {
+        const approved = await prepareApprovalTx(
+            providerWith(),
+            signer.address,
+            { ...TX_PARAMS, gas: "0x30d40" },
+        );
+        expect(approved.gasLimit).toBe("0x30d40");
+        const signed = Transaction.from(
+            await signer.signTransaction({ ...approved }),
+        );
+        expect(signed.gasLimit).toBe(200000n);
+    });
+
+    test("accepts gas and gasLimit that name the same number", async () => {
+        const approved = await prepareApprovalTx(
+            providerWith(),
+            signer.address,
+            { ...TX_PARAMS, gas: "0x30d40", gasLimit: 200000 },
+        );
+        expect(approved.gasLimit).toBe("0x30d40");
+    });
+
+    test("refuses gas and gasLimit that disagree", async () => {
+        await expect(
+            prepareApprovalTx(providerWith(), signer.address, {
+                ...TX_PARAMS,
+                gas: "0x30d40",
+                gasLimit: "0x5208",
+            }),
+        ).rejects.toThrow(
+            "The site asked for two different gas limits for this transaction.",
+        );
+    });
+
     test("carries an access list the request asked for", async () => {
         const approved = await prepareApprovalTx(
             providerWith(),
@@ -212,6 +249,15 @@ describe("prepareApprovalTx", () => {
         ).rejects.toThrow(/gas limit no network this wallet supports/);
     });
 
+    test("refuses a gas limit the site sent above the ceiling", async () => {
+        await expect(
+            prepareApprovalTx(providerWith(), signer.address, {
+                ...TX_PARAMS,
+                gas: toQuantity(MAX_GAS_LIMIT + 1n),
+            }),
+        ).rejects.toThrow(/gas limit no network this wallet supports/);
+    });
+
     // The combined bound at population: a gas limit and a fee that are each
     // under their own ceiling but multiply to thousands of ETH is refused
     // before the approval window opens, so the user is never shown a

tests/approvalVerify.test.js

@@ -58,7 +58,6 @@ const TX_PARAMS = {
     to: RECIPIENT,
     value: "0x2386f26fc10000",
     data: "0xdeadbeef",
-    gas: "0x5208",
 };
 
 // The values populateTransaction() fills in when the dApp fixed none of them.

tests/approvalWindow.test.js

@@ -0,0 +1,94 @@
+// 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([]);
+});
+
+// The background opens the approval window as wide as the page, but the
+// browser counts the window's frame in that width
+// (https://git.eeqj.de/sneak/AutistMask/issues/518). The browser suites run
+// without frames, so the widening is checked here.
+function windowsStub(type) {
+    const updates = [];
+    return {
+        updates,
+        getCurrent: (done) => done({ id: 7, type, width: 396 }),
+        update: (id, info, done) => {
+            updates.push({ id, info });
+            done({});
+        },
+    };
+}
+
+const approvalRuntime = {
+    connect: () => ({ postMessage: () => {} }),
+    sendMessage: () => {},
+};
+
+test("the approval window widens itself by whatever its frame takes", async () => {
+    const windows = windowsStub("popup");
+    const env = await bootPopup(unversionedValidProfile(), {
+        search: "?approval=approval-1",
+        runtime: approvalRuntime,
+        windows,
+        documentElement: { scrollWidth: 396, clientWidth: 380 },
+    });
+
+    expect(windows.updates).toEqual([{ id: 7, info: { width: 412 } }]);
+    expect(env.pageErrors).toEqual([]);
+});
+
+test("a connection prompt in the toolbar popup leaves the browser window alone", async () => {
+    const windows = windowsStub("normal");
+    const env = await bootPopup(unversionedValidProfile(), {
+        search: "?approval=approval-1",
+        runtime: approvalRuntime,
+        windows,
+        documentElement: { scrollWidth: 396, clientWidth: 380 },
+    });
+
+    expect(windows.updates).toEqual([]);
+    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);
@@ -2750,7 +2805,7 @@ describe("where an approval window opens", () => {
         await settle();
 
         expect(bg.created).toHaveLength(1);
-        expect(bg.created[0]).toMatchObject({ left: 460, top: 60 });
+        expect(bg.created[0]).toMatchObject({ left: 442, top: 60 });
     });
 
     test("not centred on an approval window the user was last in", async () => {
@@ -2767,7 +2822,7 @@ describe("where an approval window opens", () => {
         bg.requestSign();
         await settle();
 
-        // Centred, it would be at left 900, the position the browser refused.
+        // Centred, it would be at left 882, the position the browser refused.
         expect(bg.created).toHaveLength(1);
         expect(bg.created[0].left).toBeUndefined();
         expect(bg.created[0].top).toBeUndefined();
@@ -2789,7 +2844,7 @@ describe("where an approval window opens", () => {
         await settle();
 
         expect(bg.created).toHaveLength(2);
-        expect(bg.created[0]).toMatchObject({ left: 1520, top: 750 });
+        expect(bg.created[0]).toMatchObject({ left: 1502, top: 750 });
         expect(bg.created[1].left).toBeUndefined();
         expect(bg.created[1].top).toBeUndefined();
 

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
-    // moment, including this one.
+    // sends it to a mainnet node. The user can switch the network in Settings
+    // 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,
-        // and the switch is committed to storage in full before the attempt
-        // goes any further.
+        // The user switches the network in Settings while the attempt is
+        // running: the popup writes the switched record to storage in full
+        // 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;
-        const doSwitch = async () => {
-            switched = bg.rpc("wallet_switchEthereumChain", [
-                { chainId: MAINNET.chainId },
-            ]);
-            await settle();
+        let switched = false;
+        const doSwitch = () => {
+            const record = bg.persisted();
+            applyChainSwitchFields(record, MAINNET.id);
+            global.chrome.storage.write("autistmask", record);
+            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();
-        expect(switched.result()).toEqual({ result: null });
+        if (!switched) doSwitch();
         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
-// is asserted as a refusal to ACT — the state unmoved and no chainChanged
-// broadcast — because an error code alone would not distinguish a gate from
-// a switch that happened and then reported a failure.
+// on Sepolia (https://git.eeqj.de/sneak/AutistMask/issues/308). Gated on the
+// connection, a connected site could still move the wallet between mainnet and
+// Sepolia without asking. Only the user switches the network: a connected
+// 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,
-// which covers the popup's chain switch; this file covers the background's,
-// which goes through storage rather than the shared state singleton.
+// Every refusal is asserted as a refusal to ACT — the stored record unmoved
+// and no chainChanged broadcast — because an error code alone would not
+// 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
-    // here as well as in the state.
+    // is what tells a page the wallet moved, so a switch is visible here as
+    // 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(result.result).toBeUndefined();
+        expect(request.result().error).toEqual({
+            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.
-        expect(bg.walletState().networkId).toBe("mainnet");
-        expect(bg.walletState().rpcUrl).toBe(CUSTOM_RPC);
+        // no page was told the chain moved. Nor was the user asked.
+        expect(bg.walletState()).toEqual(before);
         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);
+    });
 });
 
-    test("a connected origin switches the chain", async () => {
+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("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();
+
+        await choose(select, "mainnet");
+
+        expect(bg.walletState()).toEqual(before);
+        expect(bg.chainChangedEvents()).toEqual([]);
+    });
+
+    test("a page cannot make the background send chainChanged", async () => {
         const bg = loadBackground();
 
-        const result = await bg.switchChain("0x89", CONNECTED_ORIGIN);
+        const reply = bg.send(
+            { type: "AUTISTMASK_NETWORK_CHANGED", chainId: SEPOLIA.chainId },
+            { url: CONNECTED_ORIGIN + "/" },
+        );
+        await settle();
 
-        expect(result.error.code).toBe(4902);
-        expect(bg.walletState().networkId).toBe("mainnet");
-    });
-
-    test("a switch by a connected origin keeps the user's endpoint", async () => {
-        const bg = loadBackground();
-
-        await bg.switchChain(SEPOLIA.chainId, CONNECTED_ORIGIN);
-        expect(bg.walletState().rpcUrl).toBe(SEPOLIA.defaultRpcUrl);
-
-        await bg.switchChain(MAINNET.chainId, CONNECTED_ORIGIN);
-        expect(bg.walletState().rpcUrl).toBe(CUSTOM_RPC);
+        expect(reply).toEqual({ error: "Unauthorized sender" });
+        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
@@ -627,6 +640,19 @@ step(
         await d.switchToWindow(popup);
         await d.waitVisible("#view-approve-sign");
 
+        // The window is opened as wide as the page
+        // (https://git.eeqj.de/sneak/AutistMask/issues/518). This suite is
+        // where that is checked: the Chrome suite's approval windows open at
+        // 1280x720 whatever width the extension asks for.
+        const sideways = await d.execute(
+            "return document.documentElement.scrollWidth -" +
+                " document.documentElement.clientWidth;",
+        );
+        assert(
+            sideways <= 0,
+            "the sign prompt scrolls sideways by " + sideways + "px",
+        );
+
         const screen = await d.execute(
             `return {
              origin: document.getElementById("approve-sign-origin").textContent,
@@ -684,6 +710,159 @@ 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
-//     cannot produce settled === "resolved".
-//   #btn-reject on the site prompt — NOT self-proving. A page that went away
-//     without the click landing disconnects the approval port, the background
-//     settles that as 4001, and 4001 is exactly what assertUserRejection
-//     accepts. Both call sites arm the click trace below and assert it.
+//   #btn-approve, #btn-approve-network — only a decision resolves the promise,
+//     and a swallowed click cannot produce settled === "resolved".
+//   #btn-reject on the site prompt, #btn-reject-network — NOT self-proving. A
+//     page that went away without the click landing disconnects the approval
+//     port, the background settles that as 4001, and 4001 is exactly what
+//     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
-// active network after its transaction is prepared and back before it is
-// signed, and a popup opened after a switch shows a sent or listed transaction
-// again. The wallet's balances follow the active network; these do not.
+// transaction is on, which need not be the active one. The active network can
+// change, in Settings or when the user approves a site's request, after a
+// transaction is prepared and change back before it is signed, and a popup
+// 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 +238,15 @@ 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.
+ * @param {object} [options.windows] chrome.windows, for a test of the approval
+ *     window resizing itself.
+ * @param {object} [options.documentElement] members of document.documentElement
+ *     that replace the stub's own: scrollWidth and clientWidth, which are equal
+ *     unless a test says otherwise, so the page does not scroll sideways.
  * @returns {Promise<object>} handles onto the booted page.
  */
 async function bootPopup(stored, options) {
@@ -273,6 +282,11 @@ async function bootPopup(stored, options) {
         (options && options.storage) ||
         makeStorageStub(stored === undefined ? {} : { autistmask: stored });
     const document = makeDocument(POPUP_HTML);
+    Object.assign(
+        document.documentElement,
+        { scrollWidth: 396, clientWidth: 396 },
+        options && options.documentElement,
+    );
     const reloads = [];
 
     globalThis.chrome = {
@@ -281,12 +295,14 @@ async function bootPopup(stored, options) {
             sendMessage: jest.fn(async () => ({})),
             getURL: (p) => "chrome-extension://autistmask/" + p,
             onMessage: { addListener: () => {} },
+            ...(options && options.runtime),
         },
+        windows: options && options.windows,
     };
     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/walletDefects.test.js

@@ -153,6 +153,18 @@ describe("the explanatory copy", () => {
         expect(all).not.toMatch(/\blost\b|\bstolen\b|\bgone\b/i);
     });
 
+    // The wallet holds the imported key but will not export it, so the copy
+    // must name every key the user may hold that reaches the addresses
+    // outside it.
+    test("it names the keys that reach the addresses outside this wallet", () => {
+        const body = defect.paragraphs.join(" ");
+
+        expect(body).toMatch(/private key export are disabled/);
+        expect(body).toMatch(
+            /with the extended private key you imported, if you kept a copy of it, or with the master extended private key or recovery phrase it came from, in software that repeats the same non-standard derivation/,
+        );
+    });
+
     test("it says the wallet is not deleted and what the user can do", () => {
         const body = defect.paragraphs.join(" ");