fix: one transaction approval at a time, and honest copy for a nonce collision (closes #271)

Populating the transaction in the background before the approval window
opens is what makes the displayed object the verified object. It also
fixes the nonce before the user has answered anything, so two
eth_sendTransaction calls populated concurrently took the same nonce
from a node that had seen neither of them broadcast, and the second
could never be sent: its approved nonce is spent, and the only way to
give it a fresh one is to populate it again after the user has read the
old one off the screen.

A second transaction approval is now refused while one is unanswered,
with EIP-1193 code -32002. The refusal happens before anything is
populated — no second nonce is allocated, no window opens — and the slot
is released when the requesting page has its answer. Signature approvals
are not gated; a signature consumes no nonce.

A collision that does happen is now reported for what it is. A broadcast
the node refused for the nonce, and an approval carrying a nonce this
worker has already broadcast (caught before the node is asked at all),
both report that the transaction did not reach the network and to send
it again, instead of the standing broadcast wording that warns it may
have sent. "already known" keeps that ambiguous wording deliberately: a
node that says it has the transaction has it.

Nothing about verification is weakened. The approval still carries the
transaction the screen displayed, and the artifact is still compared
against that object field for field.

README.md

@@ -185,17 +185,14 @@ to the background — with the message that would carry it required to be presen
 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).
 
-Three limits of that coverage, none of them papered over. The RPC is stubbed
+Two limits of that coverage, neither of them papered over. The RPC is stubbed
 throughout, so this is **not** a real dApp against a real network with real
 funds; that remains a human pass before 1.0.0. The site-connection prompt is
 raised through `chrome.action.openPopup()`, and headless Chromium's
 browser-action popup is not a page Playwright can see or click, so that one
 prompt is driven at the URL the extension itself puts on the action — the same
 page and the same approval id, but whether a real toolbar click shows it is not
-observable here. And the EIP-1193 error code does not survive the last hop: the
-rejection that crosses the boundary carries code 4001 and is asserted to, but
-`src/content/inpage.js` rebuilds it as `new Error(message)`, so the calling page
-catches an error with no `code` property.
+observable here.
 
 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
@@ -638,6 +635,21 @@ ExportPrivKey and ShowRecoveryPhrase — are deliberately absent from that list,
 so the popup can never reopen onto one of them with no password prompt in front
 of it.
 
+A reopened popup renders the wallet list and the one screen it restores onto,
+and nothing else, so every screen on the stack behind that one is still the
+blank template from `index.html`. "Back" therefore renders its target rather
+than only unhiding it, through the same dispatch and data guards as the restore
+(`src/popup/viewRouter.js`), and falls back to Home when the state the target
+would render is gone.
+
+It renders only a screen this page load has not rendered yet. Forward navigation
+renders as it goes, and `viewRouter.js` records every screen that reaches
+`showView()`, so "Back" onto a screen already on the page unhides it and nothing
+more — rendering it a second time would re-fetch and overwrite what it holds,
+such as an edit typed into Settings and not yet saved. Home is the one screen
+"Back" always re-renders, so the wallet list reflects anything that changed
+while the user was away from it.
+
 Every screen that holds secret material in the page registers a cleanup with
 `onViewLeave()` (`src/popup/views/helpers.js`), which `showView()` runs on every
 exit from that screen rather than only on its "Back" button, so nothing secret
@@ -1163,7 +1175,11 @@ on ConfirmTx, DeleteWallet, ApproveTx and ApproveSign.
   opening the window, so the screen shows a complete transaction and the signed
   artifact can be compared with it field for field. A request that cannot be
   populated — unreachable node, reverting gas estimate — opens no window and is
-  failed back to the site.
+  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 EIP-1193 code `-32002` rather than being
+  populated at the same nonce. It opens no window and takes no nonce, and the
+  site can send it again once the pending one is answered.
 - **Elements**:
     - "Transaction Request" heading
     - Phishing warning banner (shown when the hostname is on the phishing

TODO.md

@@ -45,6 +45,40 @@ undefined identifiers, which is how
 
 # Completed Steps
 
+- 2026-08-17: `README.md` no longer advertises a defect the wallet does not
+  have. The End-to-End Tests section listed the EIP-1193 code being dropped in
+  the last hop into the page as a standing limit of the dApp coverage; that
+  stopped being true when
+  [#274](https://git.eeqj.de/sneak/AutistMask/issues/274) landed and did not
+  touch the README. The paragraph is deleted and the two remaining limits — the
+  stubbed RPC and the unobservable toolbar popup — were checked against the
+  current `src/content/inpage.js` and `tests/e2e/` and left as they are
+  ([#285](https://git.eeqj.de/sneak/AutistMask/issues/285)).
+- 2026-08-17: One transaction approval at a time. Populating in the background
+  before the window opens is what makes the displayed object the verified
+  object, and it also fixes the nonce: two `eth_sendTransaction` calls populated
+  concurrently took the same nonce from a node that had seen neither broadcast,
+  and the second could then never be sent, because the only way to give it a
+  fresh nonce is to populate it again after the user has read the old one off
+  the screen. A second request is now refused with EIP-1193 `-32002` while one
+  is unanswered — the slot is taken immediately before population, after the
+  authorization checks, so no second nonce is allocated, no second window opens,
+  and a page the wallet refuses anyway cannot hold the slot against the
+  connected site. The slot is freed at `settleApproval()`, the single point an
+  approval is retired, so every path that ends an approval ends the hold with
+  it; an approval whose window is gone and whose attempt has failed is settled
+  there rather than left waiting on a window that no longer exists, and an
+  approval window that could not be opened at all is answered with `-32603`
+  instead of holding the page's promise open. Signature approvals are not gated,
+  consuming no nonce. A collision that does happen is also reported accurately
+  now: a broadcast the node refused for the nonce, and an approval carrying a
+  nonce this worker has already broadcast for that address on that chain (caught
+  before the node is asked at all), both say the transaction did not reach the
+  network and to send it again, instead of warning that it may have sent. The
+  record is keyed by chain as well as address, because nonce spaces are per
+  chain and low nonces overlap across them. `already known` deliberately keeps
+  the ambiguous wording, because a node that says it has the transaction has it
+  ([#271](https://git.eeqj.de/sneak/AutistMask/issues/271)).
 - 2026-08-12: EIP-1193 error codes now reach the page. `src/content/inpage.js`
   rebuilt every failure as `new Error(error.message)`, so the code the
   background produced and the content script relayed intact was dropped in the
@@ -59,6 +93,23 @@ undefined identifiers, which is how
   `tests/inpageErrors.test.js`, and the e2e probe that printed the missing code
   now requires it on the page's Error as well as on the wire, for all four
   rejected flows ([#274](https://git.eeqj.de/sneak/AutistMask/issues/274)).
+- 2026-08-12: "Back" now renders the screen it lands on instead of only unhiding
+  it. A reopened popup renders the wallet list and the one screen it restores
+  onto, so every screen further down the stack was still the blank template from
+  `index.html`, and Back walked straight onto it — an empty address, no
+  balances, no QR code. The Back path now goes through the same per-view
+  dispatch and data guards as the restore (`src/popup/viewRouter.js`, shared
+  with `restoreView()`), falling back to Home when the state the target would
+  render is gone. It renders only a view this page load has not rendered yet:
+  `viewRouter.js` records every view that reaches `showView()`, which is where
+  forward navigation and the restore both end, so Back onto a view already on
+  the page unhides it and nothing more. That is what keeps a second render from
+  re-fetching and overwriting what the view holds — an unsaved edit in Settings,
+  a transaction list already loaded. Home is the exception and is always
+  re-rendered, as it was before. Covered by unit tests on the real `goBack()`
+  and by three end-to-end cases against the real popup, each demonstrated
+  failing on the unfixed build
+  ([#268](https://git.eeqj.de/sneak/AutistMask/issues/268)).
 - 2026-08-12: `KNOWN_SYMBOLS` now maps a symbol to the set of contract addresses
   that bear it, not to one of them. A ticker is not unique: seven of the 512
   bundled tokens — `FRAX`, `REUSD`, `TON`, `EURE`, `MSUSD`, `MUSD` and `JPYC` —

src/background/index.js

@@ -24,6 +24,7 @@ const {
     TX_STAGE_VERIFY,
     TX_STAGE_BROADCAST,
     TX_STAGE_INFLIGHT,
+    TX_STAGE_NONCE,
 } = require("../shared/approvalVerify");
 const { prepareApprovalTx } = require("../shared/approvalTx");
 const {
@@ -57,6 +58,114 @@ const connectedSites = {};
 // Pending approval requests: { id: { origin, hostname, resolve } }
 const pendingApprovals = {};
 
+// One transaction approval at a time, wallet-wide.
+//
+// The transaction a site asks for is populated before its approval window
+// opens, so that the object the user is shown is the object the signed
+// artifact is verified against. Populating fixes the nonce. Two requests
+// populated concurrently therefore take the SAME nonce — the node reports the
+// same pending count to both, neither having been broadcast — and whichever is
+// broadcast second is refused by the network for a nonce it can never be
+// re-signed at, because re-signing it would mean signing something other than
+// what was displayed.
+//
+// So the second request is refused while the first is unanswered. It is
+// refused before anything is populated, so no second nonce is allocated at
+// all, and while the page is still waiting with nothing on screen. The
+// alternatives were considered and rejected in
+// https://git.eeqj.de/sneak/AutistMask/issues/271: populating again at Confirm
+// puts a nonce on screen that is not the nonce that gets signed, and
+// allocating around in-flight approvals makes the wallet's own bookkeeping the
+// authority on a nonce the network has not accepted, which an abandoned
+// approval then leaves a hole in.
+//
+// Sign approvals are not gated: a signature consumes no nonce.
+//
+// The slot is null when free, and otherwise the handle of the request holding
+// it. Once that request has raised its approval the handle carries the
+// approval's id, so that retiring the approval frees the slot: every exit from
+// pendingApprovals goes through settleApproval(), which makes that one hook
+// complete. The holder's own finally is the backstop for the interval before
+// the approval exists.
+let txApprovalSlot = null;
+
+// EIP-1474 "resource unavailable": the standard code for a request that is
+// refused because another one is already pending.
+const TX_APPROVAL_PENDING_CODE = -32002;
+
+// True at every moment this can be sent: the slot is taken immediately before
+// the transaction is populated, so the other request is either being prepared
+// or on screen. It does not claim the other one is displayed yet, because for
+// the length of one network round trip it is not.
+const TX_APPROVAL_PENDING_MESSAGE =
+    "AutistMask handles one transaction at a time, and another one is" +
+    " already in progress, so this one was not sent. Please finish that" +
+    " transaction, then send this one again.";
+
+// Take the slot, or refuse. Nothing awaits between the test and the set, so
+// two requests that reach this in the same tick cannot both pass it — the
+// position of the call in the handler is irrelevant to that, which is why it
+// sits after the authorization checks. A page the wallet is going to refuse
+// anyway must not be able to take the slot away from the connected site.
+function reserveTxApprovalSlot() {
+    if (txApprovalSlot) return null;
+    txApprovalSlot = { approvalId: null };
+    return txApprovalSlot;
+}
+
+// Free the slot, if this handle is still the one holding it.
+function releaseTxApprovalSlot(handle) {
+    if (handle && txApprovalSlot !== handle) return;
+    txApprovalSlot = null;
+}
+
+// Free the slot held on behalf of a retired approval. Called from
+// settleApproval() for every approval, and a no-op for the ones the slot was
+// not taken for.
+function releaseTxApprovalSlotFor(approvalId) {
+    if (txApprovalSlot && txApprovalSlot.approvalId === approvalId) {
+        txApprovalSlot = null;
+    }
+}
+
+// Nonces this worker has already handed to the node, per chain and address.
+// This is the wallet's own knowledge that a nonce is spent, and it is checked
+// before a broadcast rather than after: a node's pending count can lag a
+// transaction it has itself just accepted, and a request populated inside that
+// window would otherwise be signed and sent at a nonce this wallet has already
+// used.
+//
+// The chain is part of the key because nonce spaces are per chain and the
+// wallet switches networks. Without it a nonce spent on one chain would refuse
+// that nonce on every other chain — and low nonces overlap across chains as a
+// matter of course, so the refusal would be both routine and false.
+//
+// The record dies with the worker, which is correct rather than merely
+// convenient: after a restart the node's count is the only answer available,
+// and a transaction of this wallet's that the node has forgotten is one the
+// user does want to be able to send again.
+const broadcastNonces = {};
+
+function broadcastNoncesFor(chainId, address) {
+    const key =
+        String(chainId).toLowerCase() +
+        ":" +
+        String(address || "").toLowerCase();
+    if (!broadcastNonces[key]) broadcastNonces[key] = new Set();
+    return broadcastNonces[key];
+}
+
+// An approved transaction's nonce as a decimal string, or null if it cannot be
+// read as a number. Verification refuses an unreadable nonce before this is
+// ever reached; null here only keeps the record from holding junk.
+function approvedNonce(approvedTx) {
+    try {
+        return BigInt(approvedTx.nonce).toString();
+    } catch {
+        return null;
+    }
+}
+
 async function getState() {
     const result = await storageApi.get("autistmask");
     return (
@@ -148,11 +257,41 @@ function settleApproval(id, result, options) {
     const holdsClaim = !!(options && options.holdsClaim);
     if (approval.attemptInFlight && !holdsClaim) return false;
     delete pendingApprovals[id];
+    // The transaction-approval slot is held for exactly as long as the
+    // approval it was taken for is alive, and this is the one place an
+    // approval stops being alive.
+    releaseTxApprovalSlotFor(id);
     approval.resolve(result);
     resetPopupUrl();
     return true;
 }
 
+// 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.
+function abandonedResult(approval, code, message) {
+    if (approval.type === "tx" || approval.type === "sign") {
+        return { error: { code, message } };
+    }
+    return { approved: false, remember: false };
+}
+
+// A window the user closed without answering is a refusal by the user, which
+// is 4001 and the wording every other rejection path already uses.
+const APPROVAL_REJECTED_CODE = 4001;
+const APPROVAL_REJECTED_MESSAGE = "User rejected the request.";
+
+// The window could not be opened, so the user was never asked. This is the
+// wallet failing, not the user refusing, so it does not claim to be a
+// rejection: -32603 is the JSON-RPC code for the wallet's own internal
+// failure, and the page is told plainly that nothing was shown.
+const APPROVAL_WINDOW_FAILED_CODE = -32603;
+
+const APPROVAL_WINDOW_FAILED_MESSAGE =
+    "AutistMask could not open its approval window, so this request was not" +
+    " shown to you and nothing was sent.";
+
 // Take exclusive hold of a pending approval for one attempt, or refuse.
 //
 // An approval that failed retryably has to stay in pendingApprovals, so its
@@ -172,8 +311,26 @@ function claimApproval(approval) {
 
 // Release an approval whose attempt failed in a way the user can retry.
 // Nothing was broadcast, so the next attempt may claim it.
+//
+// Unless the window it would be retried in is already gone. The user closed it
+// while the attempt was running and settleApproval() declined then, correctly,
+// because the attempt still owned the approval; the attempt has now failed, so
+// nothing owns it and nothing can reach it. Left standing it would hold the
+// requesting page's promise open forever and, with it, the transaction
+// approval slot. It is settled here as the rejection the closed window
+// already meant.
 function releaseApproval(approval) {
     approval.attemptInFlight = false;
+    if (approval.windowClosed) {
+        settleApproval(
+            approval.id,
+            abandonedResult(
+                approval,
+                APPROVAL_REJECTED_CODE,
+                APPROVAL_REJECTED_MESSAGE,
+            ),
+        );
+    }
 }
 
 // Open approval in a separate popup window.
@@ -200,10 +357,36 @@ function openApprovalWindow(id) {
             );
         }
         windowsApi.create(opts, (win) => {
+            const approval = pendingApprovals[id];
+            if (!approval) {
+                // Settled while the window was opening — an address switch,
+                // say. Nothing is waiting on it, and a window showing an
+                // approval that no longer exists is not left on screen.
                 if (win) {
-                pendingApprovals[id].windowId = win.id;
+                    windowsApi.remove(win.id, () => {
+                        if (runtime.lastError) {
+                            // window already closed
                         }
                     });
+                }
+                return;
+            }
+            if (!win) {
+                // No window means no way to ever answer this approval, and an
+                // approval nothing can answer holds the requesting page's
+                // promise open forever. Settle it now instead.
+                settleApproval(
+                    id,
+                    abandonedResult(
+                        approval,
+                        APPROVAL_WINDOW_FAILED_CODE,
+                        APPROVAL_WINDOW_FAILED_MESSAGE,
+                    ),
+                );
+                return;
+            }
+            approval.windowId = win.id;
+        });
     });
 }
 
@@ -212,7 +395,7 @@ function openApprovalWindow(id) {
 function requestApproval(origin, hostname) {
     return new Promise((resolve) => {
         const id = crypto.randomUUID();
-        pendingApprovals[id] = { origin, hostname, resolve };
+        pendingApprovals[id] = { id, origin, hostname, resolve };
 
         if (actionApi && typeof actionApi.openPopup === "function") {
             actionApi.setPopup({
@@ -243,10 +426,13 @@ function requestApproval(origin, hostname) {
 // it is pinned here rather than read again at signing time — an address switch
 // between approval and signing must refuse, not sign from an account this
 // screen never named.
-function requestTxApproval(origin, hostname, approvedTx, approvedFrom) {
+// `slot` is the transaction-approval slot its caller holds. Handing the
+// approval's id to it is what makes retiring the approval free the slot.
+function requestTxApproval(origin, hostname, approvedTx, approvedFrom, slot) {
     return new Promise((resolve) => {
         const id = crypto.randomUUID();
         pendingApprovals[id] = {
+            id,
             origin,
             hostname,
             approvedTx,
@@ -254,6 +440,7 @@ function requestTxApproval(origin, hostname, approvedTx, approvedFrom) {
             resolve,
             type: "tx",
         };
+        if (slot) slot.approvalId = id;
 
         openApprovalWindow(id);
     });
@@ -267,6 +454,7 @@ function requestSignApproval(origin, hostname, signParams, approvedFrom) {
     return new Promise((resolve) => {
         const id = crypto.randomUUID();
         pendingApprovals[id] = {
+            id,
             origin,
             hostname,
             signParams,
@@ -585,10 +773,30 @@ async function handleRpc(method, params, origin) {
     }
 
     if (method === "eth_sendTransaction") {
+        return await handleSendTransaction(params, origin);
+    }
+
+    // Proxy safe read-only methods to the RPC node
+    if (PROXY_METHODS.includes(method)) {
+        try {
+            const result = await proxyRpc(method, params);
+            return { result };
+        } catch (e) {
+            return { error: { message: e.message } };
+        }
+    }
+
+    return { error: { message: "Unsupported method: " + method } };
+}
+
+// The body of eth_sendTransaction, from the connection check through to the
+// user's decision. It takes the single transaction-approval slot once it knows
+// it is going to populate a transaction, and holds it until the requesting
+// page has its answer.
+async function handleSendTransaction(params, origin) {
     const s = await getState();
     const activeAddress = await getActiveAddress();
-        if (!activeAddress)
-            return { error: { message: "No accounts available" } };
+    if (!activeAddress) return { error: { message: "No accounts available" } };
 
     const hostname = extractHostname(origin);
     const allowed = s.allowedSites[activeAddress] || [];
@@ -610,6 +818,23 @@ async function handleRpc(method, params, origin) {
         };
     }
 
+    // Everything above refuses without populating anything, so the slot is
+    // taken here rather than at the top of the handler: a page the wallet was
+    // never going to serve must not be able to hold the slot and make the
+    // connected site's own transaction fail as "already in progress". The
+    // reservation is atomic because nothing awaits between its test and its
+    // set, not because of where it sits.
+    const slot = reserveTxApprovalSlot();
+    if (!slot) {
+        return {
+            error: {
+                code: TX_APPROVAL_PENDING_CODE,
+                message: TX_APPROVAL_PENDING_MESSAGE,
+            },
+        };
+    }
+
+    try {
         // Populate here, before any window opens, so that the transaction the
         // user is shown is a complete one and is the same object the signed
         // artifact is checked against. A failure raises no approval at all and
@@ -644,22 +869,17 @@ async function handleRpc(method, params, origin) {
             hostname,
             approvedTx,
             activeAddress,
+            slot,
         );
         if (decision.error) return { error: decision.error };
         return { result: decision.txHash };
+    } finally {
+        // Retiring the approval has normally freed the slot already, through
+        // settleApproval(); this covers the paths that return before an
+        // approval exists at all, and frees nothing if another request has
+        // since taken the slot.
+        releaseTxApprovalSlot(slot);
     }
-
-    // Proxy safe read-only methods to the RPC node
-    if (PROXY_METHODS.includes(method)) {
-        try {
-            const result = await proxyRpc(method, params);
-            return { result };
-        } catch (e) {
-            return { error: { message: e.message } };
-        }
-    }
-
-    return { error: { message: "Unsupported method: " + method } };
 }
 
 // Broadcast chainChanged to all tabs when the network is switched.
@@ -694,15 +914,11 @@ async function broadcastAccountsChanged() {
     // being signed and broadcast right now, and neither rejecting it to the
     // page nor closing the window it is reporting into is survivable.
     for (const [id, approval] of Object.entries(pendingApprovals)) {
-        const rejection =
-            approval.type === "tx" || approval.type === "sign"
-                ? {
-                      error: {
-                          code: 4001,
-                          message: "User rejected the request.",
-                      },
-                  }
-                : { approved: false, remember: false };
+        const rejection = abandonedResult(
+            approval,
+            APPROVAL_REJECTED_CODE,
+            APPROVAL_REJECTED_MESSAGE,
+        );
         if (!settleApproval(id, rejection)) continue;
         if (approval.windowId) {
             windowsApi.remove(approval.windowId, () => {
@@ -831,21 +1047,19 @@ startBackgroundJobs();
 // verify and broadcast it is waiting on, so a user closing an apparently-hung
 // window is an ordinary event with an attempt already in flight behind it.
 // settleApproval() refuses those, which leaves the attempt to report its real
-// outcome to the page.
+// outcome to the page — and the window is recorded as gone, so that an attempt
+// which then fails retryably settles instead of waiting in a window that no
+// longer exists.
 if (windowsApi && windowsApi.onRemoved) {
     windowsApi.onRemoved.addListener((windowId) => {
         for (const [id, approval] of Object.entries(pendingApprovals)) {
             if (approval.windowId !== windowId) continue;
-            const rejection =
-                approval.type === "tx" || approval.type === "sign"
-                    ? {
-                          error: {
-                              code: 4001,
-                              message: "User rejected the request.",
-                          },
-                      }
-                    : { approved: false, remember: false };
-            settleApproval(id, rejection);
+            const rejection = abandonedResult(
+                approval,
+                APPROVAL_REJECTED_CODE,
+                APPROVAL_REJECTED_MESSAGE,
+            );
+            if (!settleApproval(id, rejection)) approval.windowClosed = true;
         }
     });
 }
@@ -959,7 +1173,7 @@ runtime.onMessage.addListener((msg, sender, sendResponse) => {
             sendResponse({
                 error: outcome.error,
                 retryable: outcome.retryable,
-                stage: TX_STAGE_SIGN,
+                stage: outcome.stage,
             });
             return false;
         }
@@ -975,8 +1189,15 @@ runtime.onMessage.addListener((msg, sender, sendResponse) => {
         }
 
         (async () => {
+            // The chain this attempt is on, read once. Verification below
+            // refuses an artifact signed for any other chain, and the nonce
+            // record is both consulted and written under this one, so a
+            // network switch part-way through cannot make the check and the
+            // record disagree about which chain the nonce was spent on.
+            let chainId;
             try {
                 await loadState();
+                chainId = currentNetwork().chainId;
                 const activeAddress = await getActiveAddress();
                 // An address switch between approval and signing refuses. The
                 // approval named one account; signing from whichever account
@@ -999,7 +1220,7 @@ runtime.onMessage.addListener((msg, sender, sendResponse) => {
                     msg.rawSignedTx,
                     approval.approvedTx,
                     approval.approvedFrom,
-                    currentNetwork().chainId,
+                    chainId,
                 );
             } catch (e) {
                 // A signed transaction that is not the approved one is not
@@ -1019,7 +1240,31 @@ runtime.onMessage.addListener((msg, sender, sendResponse) => {
                 sendResponse({
                     error: outcome.error,
                     retryable: outcome.retryable,
-                    stage: TX_STAGE_VERIFY,
+                    stage: outcome.stage,
+                });
+                return;
+            }
+
+            // A nonce this worker has already broadcast for this address on
+            // this chain. The node is not asked: it has answered once already,
+            // and the wallet holding the receipt of that answer is what makes
+            // this failure one the user can be told did not reach the network.
+            // A nonce spent on another chain is not spent here — the chains
+            // count separately, and refusing across them would block ordinary
+            // use with a message that is not true.
+            const nonce = approvedNonce(approval.approvedTx);
+            const spent = broadcastNoncesFor(chainId, approval.approvedFrom);
+            if (nonce !== null && spent.has(nonce)) {
+                const outcome = describeTxFailure(TX_STAGE_NONCE, null);
+                settleApproval(
+                    msg.id,
+                    { error: { message: outcome.error } },
+                    { holdsClaim: true },
+                );
+                sendResponse({
+                    error: outcome.error,
+                    retryable: outcome.retryable,
+                    stage: outcome.stage,
                 });
                 return;
             }
@@ -1027,6 +1272,7 @@ runtime.onMessage.addListener((msg, sender, sendResponse) => {
             try {
                 const provider = getProvider(state.rpcUrl);
                 const tx = await provider.broadcastTransaction(msg.rawSignedTx);
+                if (nonce !== null) spent.add(nonce);
                 settleApproval(
                     msg.id,
                     { txHash: tx.hash },
@@ -1039,6 +1285,11 @@ runtime.onMessage.addListener((msg, sender, sendResponse) => {
                 // tell a transaction that never left from one already in the
                 // mempool. The page has been given its outcome for this
                 // request; a second attempt would report a second one.
+                //
+                // Unless the node blamed the nonce, which is the one answer
+                // that says plainly it did not take the transaction:
+                // describeTxFailure() reclassifies that, and the stage it
+                // returns is the one reported.
                 const outcome = describeTxFailure(TX_STAGE_BROADCAST, e);
                 settleApproval(
                     msg.id,
@@ -1048,7 +1299,7 @@ runtime.onMessage.addListener((msg, sender, sendResponse) => {
                 sendResponse({
                     error: outcome.error,
                     retryable: outcome.retryable,
-                    stage: TX_STAGE_BROADCAST,
+                    stage: outcome.stage,
                 });
             }
         })();

src/popup/index.js

@@ -9,16 +9,17 @@ const {
     $,
     showView,
     updateDebugBanner,
-    setRenderMain,
+    setBackRenderer,
     pushCurrentView,
     goBack,
     clearViewStack,
 } = require("./views/helpers");
 const { applyTheme } = require("./theme");
-// Views that can be fully re-rendered from persisted state. All others fall
-// back to the nearest restorable parent; see the module for why the
-// secret-bearing views are absent.
-const { RESTORABLE_VIEWS } = require("./restorableViews");
+// 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/popup/restorableViews.js) go
+// through it; anything else falls back to the nearest restorable parent.
+const { renderView, makeBackRenderer } = require("./viewRouter");
 
 const home = require("./views/home");
 const welcome = require("./views/welcome");
@@ -108,92 +109,23 @@ const ctx = {
     },
 };
 
-function needsAddress(view) {
-    return (
-        view === "address" ||
-        view === "address-token" ||
-        view === "receive" ||
-        view === "transaction"
-    );
-}
-
-function hasValidAddress() {
-    return (
-        state.selectedWallet !== null &&
-        state.selectedAddress !== null &&
-        state.wallets[state.selectedWallet] &&
-        state.wallets[state.selectedWallet].addresses[state.selectedAddress]
-    );
-}
+// The view modules the router renders through, keyed as it expects them.
+const viewModules = {
+    main: { show: () => fallbackView() },
+    addressDetail,
+    addressToken,
+    receive,
+    settings,
+    settingsAddToken,
+    confirmTx,
+    transactionDetail,
+    txStatus,
+};
 
 function restoreView() {
-    const view = state.currentView;
-    if (!view || !RESTORABLE_VIEWS.has(view)) {
-        return fallbackView();
-    }
-
-    if (needsAddress(view) && !hasValidAddress()) {
-        return fallbackView();
-    }
-
-    if (view === "address-token" && !state.selectedToken) {
-        return fallbackView();
-    }
-
-    switch (view) {
-        case "address":
-            addressDetail.show();
-            break;
-        case "address-token":
-            addressToken.show();
-            break;
-        case "receive":
-            receive.show();
-            break;
-        case "settings":
-            settings.show();
-            break;
-        case "settings-addtoken":
-            settingsAddToken.show();
-            break;
-        case "confirm-tx":
-            if (state.viewData && state.viewData.pendingTx) {
-                confirmTx.restore();
-            } else {
+    if (!renderView(state.currentView, state, viewModules)) {
         fallbackView();
     }
-            break;
-        case "transaction":
-            if (state.viewData && state.viewData.tx) {
-                transactionDetail.render();
-            } else {
-                fallbackView();
-            }
-            break;
-        case "wait-tx":
-            // Resumes the receipt poll from the persisted broadcast time.
-            if (!txStatus.restoreWait()) {
-                fallbackView();
-            }
-            break;
-        case "success-tx":
-            if (state.viewData && state.viewData.hash) {
-                txStatus.renderSuccess();
-            } else {
-                fallbackView();
-            }
-            break;
-        case "error-tx":
-            if (state.viewData && state.viewData.message) {
-                txStatus.renderError();
-            } else {
-                fallbackView();
-            }
-            break;
-        default:
-            fallbackView();
-            break;
-    }
 }
 
 function fallbackView() {
@@ -247,7 +179,7 @@ async function init() {
         settings.show();
     });
 
-    setRenderMain(renderWalletList);
+    setBackRenderer(makeBackRenderer(state, viewModules));
 
     welcome.init(ctx);
     addWallet.init(ctx);

src/popup/viewRouter.js

@@ -0,0 +1,167 @@
+// Rendering a view the popup lands on without having navigated to it
+// forward: on restore, and on Back. In both cases the view may never have
+// been rendered in this page load — a reopened popup renders only the
+// wallet list and the view it restores onto, so every other view is still
+// the blank static template from index.html — so unhiding it is not enough.
+//
+// Forward navigation renders as it goes and must NOT come through here:
+// rendering a second time would re-fetch and clobber whatever the view has
+// in flight.
+//
+// The view modules are injected and nothing here touches the DOM, so the
+// dispatch and its data guards can be tested directly; src/popup/index.js
+// cannot be required outside a browser.
+
+const { RESTORABLE_VIEWS } = require("./restorableViews");
+
+// The views this page load has rendered.
+//
+// The Back path cannot otherwise tell its two cases apart. A view the popup
+// never rendered is still the blank template from index.html and has to be
+// rendered; a view already on the page must NOT be rendered again, because
+// a second render re-fetches and overwrites whatever the user has typed
+// into it and not yet saved.
+//
+// Registration is showView() in views/helpers.js, which is the last thing
+// every render path runs — restoreView()'s, the Back path's, and every
+// forward show(). That is the point of putting it there rather than in the
+// individual views: a view added later registers itself with no one having
+// to remember it, so this cannot decay.
+//
+// Module scope is page-load scope: the popup loads this module once per
+// page load, and a reopened popup gets a fresh, empty set — which is
+// exactly the state that makes the Back path render.
+const renderedViews = new Set();
+
+function markViewRendered(view) {
+    if (view) renderedViews.add(view);
+}
+
+// Begin a fresh page-load scope. The popup gets one by being loaded; the
+// unit tests, which simulate several page loads against one module
+// instance, ask for one.
+function resetRenderedViews() {
+    renderedViews.clear();
+}
+
+// Home is the exception: Back re-renders it every time, which is what the
+// popup did before this router existed (index.js registered
+// renderWalletList() as setRenderMain(), and goBack() called it on every
+// Back onto "main"). It must stay that way — the wallet list has to reflect
+// what changed while the user was away from it, such as a wallet renamed or
+// an address removed in Settings — and Home holds no unsaved input to lose.
+const ALWAYS_RENDER_ON_BACK = new Set(["main"]);
+
+// Views that render an address the user picked and cannot be rendered
+// without one.
+const ADDRESS_VIEWS = new Set([
+    "address",
+    "address-token",
+    "receive",
+    "transaction",
+]);
+
+function needsAddress(view) {
+    return ADDRESS_VIEWS.has(view);
+}
+
+function hasValidAddress(state) {
+    return Boolean(
+        state.selectedWallet !== null &&
+        state.selectedAddress !== null &&
+        state.wallets[state.selectedWallet] &&
+        state.wallets[state.selectedWallet].addresses[state.selectedAddress],
+    );
+}
+
+// Render `view` from persisted state. Each view module shows itself, so a
+// true return means the view is both rendered and on screen.
+//
+// Returns false when the view is not one the popup renders from state, or
+// when the state it would render is gone — a token no longer selected, a
+// transaction no longer persisted. The caller falls back rather than
+// putting an empty template on screen.
+function renderView(view, state, views) {
+    if (!view || !RESTORABLE_VIEWS.has(view)) return false;
+    if (needsAddress(view) && !hasValidAddress(state)) return false;
+    if (view === "address-token" && !state.selectedToken) return false;
+
+    const data = state.viewData || {};
+    switch (view) {
+        case "main":
+            views.main.show();
+            return true;
+        case "address":
+            views.addressDetail.show();
+            return true;
+        case "address-token":
+            views.addressToken.show();
+            return true;
+        case "receive":
+            views.receive.show();
+            return true;
+        case "settings":
+            views.settings.show();
+            return true;
+        case "settings-addtoken":
+            views.settingsAddToken.show();
+            return true;
+        case "confirm-tx":
+            if (!data.pendingTx) return false;
+            views.confirmTx.restore();
+            return true;
+        case "transaction":
+            if (!data.tx) return false;
+            views.transactionDetail.render();
+            return true;
+        case "wait-tx":
+            // Resumes the receipt poll from the persisted broadcast time,
+            // and answers false when there is nothing resumable left.
+            return Boolean(views.txStatus.restoreWait());
+        case "success-tx":
+            if (!data.hash) return false;
+            views.txStatus.renderSuccess();
+            return true;
+        case "error-tx":
+            if (!data.message) return false;
+            views.txStatus.renderError();
+            return true;
+        default:
+            return false;
+    }
+}
+
+// The Back-path renderer, registered with setBackRenderer() in
+// views/helpers.js.
+//
+// Returns false — leaving goBack() to unhide the view, as it always did —
+// in the two cases where the view is known to be on the page already:
+//
+//   - It is not one the popup renders from persisted state. The restored
+//     stack is filtered against RESTORABLE_VIEWS, so such a view can only
+//     be on the stack from this page load, where forward navigation
+//     rendered it on the way in.
+//   - This page load has rendered it. Re-rendering would re-fetch and
+//     clobber what it holds; Home is rendered anyway, see above.
+//
+// What is left is the case the router exists for: a view on the stack that
+// this page load has never rendered, whose template is still blank.
+function makeBackRenderer(state, views) {
+    return function renderBack(view) {
+        if (!RESTORABLE_VIEWS.has(view)) return false;
+        if (renderedViews.has(view) && !ALWAYS_RENDER_ON_BACK.has(view)) {
+            return false;
+        }
+        if (!renderView(view, state, views)) {
+            views.main.show();
+        }
+        return true;
+    };
+}
+
+module.exports = {
+    renderView,
+    makeBackRenderer,
+    markViewRendered,
+    resetRenderedViews,
+};

src/popup/views/helpers.js

@@ -7,6 +7,7 @@ const {
     getAddressValueUsd,
 } = require("../../shared/prices");
 const { state, saveState, currentNetwork } = require("../../shared/state");
+const { markViewRendered } = require("../viewRouter");
 
 // When views are added, removed, or transitions between them change,
 // update the view-navigation documentation in README.md to match.
@@ -76,6 +77,10 @@ function showView(name) {
     }
     clearFlash();
     state.currentView = name;
+    // A view's show() ends here, so this is where the Back path learns the
+    // view is no longer the blank template from index.html and must not be
+    // rendered a second time. See viewRouter.js.
+    markViewRendered(name);
     saveState();
     updateDebugBanner(name);
 }
@@ -111,12 +116,19 @@ function updateDebugBanner(viewName) {
     }
 }
 
-// Callback to re-render the main/home view when navigating back to it.
-// Set once by index.js via setRenderMain().
-let _renderMain = null;
+// Callback that renders a view being navigated BACK onto. Set once by
+// index.js via setBackRenderer(), which routes the view through the same
+// per-view render and data guards restoreView() uses.
+//
+// It answers true when it took the navigation — the view is rendered and
+// shown, or its backing data was gone and it fell back — and false for a
+// view the popup does not render from persisted state. Those can only be
+// on the stack from this page load, because the stack is filtered on load,
+// so they have already been rendered and only need unhiding.
+let _renderBack = null;
 
-function setRenderMain(fn) {
-    _renderMain = fn;
+function setBackRenderer(fn) {
+    _renderBack = fn;
 }
 
 // Push the current view onto the navigation stack so goBack() can
@@ -136,9 +148,11 @@ function goBack() {
     } else {
         target = "main";
     }
-    if (target === "main" && _renderMain) {
-        _renderMain();
-    }
+    // A popped view is landed on, not navigated to. If the popup has been
+    // closed and reopened since the view was pushed, nothing has ever
+    // rendered it in this page load and its template is still blank, so it
+    // has to be rendered here rather than merely unhidden.
+    if (_renderBack && _renderBack(target)) return;
     showView(target);
 }
 
@@ -470,7 +484,7 @@ module.exports = {
     showView,
     onViewLeave,
     updateDebugBanner,
-    setRenderMain,
+    setBackRenderer,
     pushCurrentView,
     goBack,
     clearViewStack,

src/shared/approvalVerify.js

@@ -602,6 +602,12 @@ const TX_STAGE_BROADCAST = "broadcast";
 // may yet succeed, so the one thing the popup must not say is "start again
 // from the site".
 const TX_STAGE_INFLIGHT = "inflight";
+// A transaction refused for a nonce that is already spoken for, either by the
+// node's own answer or by this wallet's record of what it has broadcast. It is
+// the one broadcast-stage failure that is not ambiguous: the transaction was
+// not taken, so the user is told it did not reach the network and to send it
+// again, rather than being warned that it might already be out there.
+const TX_STAGE_NONCE = "nonce";
 
 function errorText(err) {
     if (typeof err === "string" && err !== "") return err;
@@ -611,6 +617,59 @@ function errorText(err) {
     return "The transaction could not be sent.";
 }
 
+// Every string a failure might carry its reason in. ethers reports the node's
+// own words in `shortMessage`, but a JSON-RPC error it could not classify is
+// nested under `error` or `info.error` with the node's message intact, and the
+// classification below has to see that too.
+function failureTexts(err) {
+    if (typeof err === "string") return [err];
+    if (!err || typeof err !== "object") return [];
+    const texts = [];
+    for (const text of [err.shortMessage, err.message, err.reason]) {
+        if (text) texts.push(String(text));
+    }
+    const nested = err.error || (err.info && err.info.error);
+    if (nested && nested.message) texts.push(String(nested.message));
+    return texts;
+}
+
+// What the Ethereum clients say when a transaction's nonce is already spoken
+// for: either it is below the account's next nonce, or another transaction is
+// sitting in the pool at that nonce and this one did not outbid it. Either way
+// the node answered, and its answer was that it did not take this transaction.
+//
+// "already known" is deliberately absent. A node that says it knows the
+// transaction has it, so that transaction did reach the network and the
+// ambiguous broadcast wording is the correct one for it.
+const NONCE_COLLISION_PATTERNS = [
+    /nonce too low/i,
+    /nonce has already been used/i,
+    /invalid nonce/i,
+    /oldnonce/i,
+    /replacement transaction underpriced/i,
+    /replacement fee too low/i,
+];
+
+// ethers' own classification of the same two conditions.
+const NONCE_COLLISION_CODES = ["NONCE_EXPIRED", "REPLACEMENT_UNDERPRICED"];
+
+// Whether a failed send is a nonce collision.
+function isNonceCollision(err) {
+    if (!err) return false;
+    if (err.code && NONCE_COLLISION_CODES.includes(err.code)) return true;
+    return failureTexts(err).some((text) =>
+        NONCE_COLLISION_PATTERNS.some((pattern) => pattern.test(text)),
+    );
+}
+
+// What both the requesting page and the popup are told about a nonce
+// collision. The node's own words ("nonce too low") are a fragment and are
+// replaced rather than passed through: they are not a sentence, and they say
+// less than the wallet knows.
+const NONCE_COLLISION_MESSAGE =
+    "The transaction was not sent, because its nonce had already been used" +
+    " by another transaction.";
+
 // What the background does with a pending transaction approval after a failed
 // attempt: what it tells the popup, and whether the approval is spent
 // (resolved to the requesting page as an error and deleted) or left standing
@@ -627,12 +686,31 @@ function errorText(err) {
 //    that never left from one that is already in the mempool. The approval is
 //    spent and the requesting page has been given its outcome; a second
 //    attempt against it would report a second outcome for one request.
+//  - nonce: terminal too, and the one case where the wallet does know the
+//    transaction never left. The approval carries a nonce that is spent, so
+//    the artifact signed against it can never be accepted and the user is told
+//    to send it again from the site.
+//
+// The stage comes back out because a broadcast failure the node blamed on the
+// nonce is reclassified here; the caller reports the stage this returns rather
+// than the one it passed in.
 function describeTxFailure(stage, err) {
+    if (
+        stage === TX_STAGE_NONCE ||
+        (stage === TX_STAGE_BROADCAST && isNonceCollision(err))
+    ) {
+        return {
+            error: NONCE_COLLISION_MESSAGE,
+            retryable: false,
+            spendApproval: true,
+            stage: TX_STAGE_NONCE,
+        };
+    }
     const error = errorText(err);
     const retryable =
         stage === TX_STAGE_SIGN ||
         (stage === TX_STAGE_VERIFY && failureIsRetryable(err));
-    return { error, retryable, spendApproval: !retryable };
+    return { error, retryable, spendApproval: !retryable, stage };
 }
 
 // What the popup shows and does after the background reports a failed signing
@@ -642,14 +720,20 @@ function describeTxFailure(stage, err) {
 //
 // A failed broadcast gets its own wording: the transaction may already be on
 // the network, so telling the user to start again from the site is exactly the
-// wrong instruction.
+// wrong instruction. A nonce collision is the exception to that exception —
+// the transaction demonstrably did not go out, and saying it might have would
+// send the user hunting for a transaction that does not exist.
 function describeSigningFailure(response, fallbackMessage) {
     let message = (response && response.error) || fallbackMessage;
     if (!/[.!?]$/.test(message)) message += ".";
     const retryable = !!(response && response.retryable);
     const stage = response && response.stage;
     if (!retryable) {
-        if (stage === TX_STAGE_BROADCAST) {
+        if (stage === TX_STAGE_NONCE) {
+            message +=
+                " The transaction did not reach the network." +
+                " Please send it again from the site.";
+        } else if (stage === TX_STAGE_BROADCAST) {
             message +=
                 " The transaction may still have reached the network." +
                 " Check the account before sending it again.";
@@ -675,9 +759,11 @@ module.exports = {
     assertWithinCeilings,
     sameAddress,
     failureIsRetryable,
+    isNonceCollision,
     describeTxFailure,
     describeSigningFailure,
     ApprovalMismatchError,
+    NONCE_COLLISION_MESSAGE,
     ALLOWED_TX_TYPES,
     SERIALIZED_FIELDS,
     FORBIDDEN_FIELDS,
@@ -686,6 +772,7 @@ module.exports = {
     TX_STAGE_VERIFY,
     TX_STAGE_BROADCAST,
     TX_STAGE_INFLIGHT,
+    TX_STAGE_NONCE,
     MAX_GAS_LIMIT,
     MAX_FEE_PER_GAS,
 };

tests/approvalVerify.test.js

@@ -14,8 +14,10 @@ const {
     assertWithinCeilings,
     sameAddress,
     failureIsRetryable,
+    isNonceCollision,
     describeTxFailure,
     describeSigningFailure,
+    NONCE_COLLISION_MESSAGE,
     ALLOWED_TX_TYPES,
     SERIALIZED_FIELDS,
     FORBIDDEN_FIELDS,
@@ -23,6 +25,7 @@ const {
     TX_STAGE_SIGN,
     TX_STAGE_VERIFY,
     TX_STAGE_BROADCAST,
+    TX_STAGE_NONCE,
     MAX_GAS_LIMIT,
     MAX_FEE_PER_GAS,
 } = require("../src/shared/approvalVerify");
@@ -1191,7 +1194,6 @@ describe("signing failure and retry", () => {
             "already known",
             "timeout of 30000ms exceeded",
             "could not coalesce error",
-            "replacement transaction underpriced",
         ]) {
             const outcome = describeTxFailure(
                 TX_STAGE_BROADCAST,
@@ -1199,10 +1201,76 @@ describe("signing failure and retry", () => {
             );
             expect(outcome.retryable).toBe(false);
             expect(outcome.spendApproval).toBe(true);
+            expect(outcome.stage).toBe(TX_STAGE_BROADCAST);
             expect(outcome.error).toBe(message);
         }
     });
 
+    // The one broadcast failure that is not ambiguous. The node answered, and
+    // its answer was that the nonce was already spoken for, so this
+    // transaction is not in a mempool anywhere.
+    test("a nonce the node refused is classified however it was worded", () => {
+        for (const err of [
+            new Error("nonce too low"),
+            new Error("replacement transaction underpriced"),
+            Object.assign(new Error("could not coalesce error"), {
+                code: "NONCE_EXPIRED",
+            }),
+            Object.assign(new Error("could not coalesce error"), {
+                code: "REPLACEMENT_UNDERPRICED",
+            }),
+            // The shape ethers hands up when it could not classify the node's
+            // error itself: the node's own words are nested underneath.
+            Object.assign(new Error("could not coalesce error"), {
+                info: { error: { code: -32000, message: "OldNonce" } },
+            }),
+        ]) {
+            const outcome = describeTxFailure(TX_STAGE_BROADCAST, err);
+            expect(
+                describeSigningFailure(
+                    outcome,
+                    "The transaction could not be sent.",
+                ).message,
+            ).toMatch(/did not reach the network/);
+            expect(outcome.retryable).toBe(false);
+            expect(outcome.spendApproval).toBe(true);
+            expect(outcome.error).toBe(NONCE_COLLISION_MESSAGE);
+            expect(outcome.stage).toBe(TX_STAGE_NONCE);
+            expect(isNonceCollision(err)).toBe(true);
+        }
+    });
+
+    // A node that says it knows the transaction has it, so it did reach the
+    // network and the ambiguous wording is the correct one.
+    test("already known is not a nonce collision", () => {
+        const err = new Error("already known");
+        const outcome = describeTxFailure(TX_STAGE_BROADCAST, err);
+        expect(
+            describeSigningFailure(
+                outcome,
+                "The transaction could not be sent.",
+            ).message,
+        ).toMatch(/may still have reached the network/);
+        expect(outcome.stage).toBe(TX_STAGE_BROADCAST);
+        expect(isNonceCollision(err)).toBe(false);
+    });
+
+    test("a nonce collision says the transaction did not reach the network", () => {
+        const outcome = describeTxFailure(
+            TX_STAGE_BROADCAST,
+            new Error("nonce too low"),
+        );
+        const copy = describeSigningFailure(
+            outcome,
+            "The transaction could not be sent.",
+        );
+        expect(copy.retryable).toBe(false);
+        expect(copy.message).toMatch(/did not reach the network/);
+        expect(copy.message).not.toMatch(/may still have reached the network/);
+        expect(copy.message).toMatch(/Please send it again from the site\.$/);
+        expect(copy.message).toMatch(/^[A-Z].*\.$/);
+    });
+
     test("a failed broadcast does not tell the user to send it again", () => {
         const outcome = describeSigningFailure(
             {

tests/backNavigation.test.js

@@ -0,0 +1,329 @@
+// Back after reopening the popup (#268).
+//
+// A reopened popup renders the wallet list and the one view it restores
+// onto; every other view is still the blank static template from
+// index.html. goBack() used to only unhide its target, so Back landed on
+// that blank template for any view the popup had not rendered in this page
+// load. These tests drive the real goBack() with the real router wired to
+// recording view modules, so what is asserted is which view render ran —
+// the thing that was missing.
+//
+// The rendering itself is asserted against the real popup in a real
+// browser by tests/e2e/run.js; here the DOM is a stub, because goBack()
+// only needs showView() to work.
+
+const els = new Map();
+
+function fakeEl() {
+    return {
+        textContent: "",
+        innerHTML: "",
+        classList: {
+            toggle() {},
+            add() {},
+            remove() {},
+            contains: () => false,
+        },
+        remove() {},
+    };
+}
+
+globalThis.document = {
+    getElementById(id) {
+        if (!els.has(id)) els.set(id, fakeEl());
+        return els.get(id);
+    },
+};
+
+// helpers.js pulls in state.js, which reads chrome.storage.local at load.
+globalThis.chrome = {
+    storage: { local: { get: async () => ({}), set: async () => {} } },
+};
+
+const {
+    showView,
+    goBack,
+    setBackRenderer,
+    pushCurrentView,
+} = require("../src/popup/views/helpers");
+const {
+    makeBackRenderer,
+    markViewRendered,
+    resetRenderedViews,
+} = require("../src/popup/viewRouter");
+const { state } = require("../src/shared/state");
+
+const ADDRESS = "0x1111111111111111111111111111111111111111";
+const TOKEN = "0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48";
+
+let calls;
+
+// Stand-ins for the view modules. Each records itself and then shows its
+// view, which is what every real view render ends with — so the assertions
+// can tell "rendered and shown" apart from "merely unhidden".
+function recorder(name, view) {
+    return () => {
+        calls.push(name);
+        showView(view);
+    };
+}
+
+function makeViews() {
+    return {
+        main: { show: recorder("main", "main") },
+        addressDetail: { show: recorder("addressDetail", "address") },
+        addressToken: { show: recorder("addressToken", "address-token") },
+        receive: { show: recorder("receive", "receive") },
+        settings: { show: recorder("settings", "settings") },
+        settingsAddToken: {
+            show: recorder("settingsAddToken", "settings-addtoken"),
+        },
+        confirmTx: { restore: recorder("confirmTx", "confirm-tx") },
+        transactionDetail: {
+            render: recorder("transactionDetail", "transaction"),
+        },
+        txStatus: {
+            restoreWait: () => {
+                calls.push("waitTx");
+                showView("wait-tx");
+                return true;
+            },
+            renderSuccess: recorder("successTx", "success-tx"),
+            renderError: recorder("errorTx", "error-tx"),
+        },
+    };
+}
+
+// The popup as it stands just after a reopen: one wallet with one address,
+// the view the popup restored onto, and the stack behind it.
+//
+// A reopen is a fresh page load, so the record of what has been rendered
+// starts empty — that emptiness is what makes the Back path render at all.
+// Returns the view modules so a test can drive forward navigation through
+// the same recorders the router renders through.
+function reopenedOn(view, stack, extra) {
+    calls = [];
+    resetRenderedViews();
+    state.wallets = [
+        {
+            name: "Wallet 1",
+            addresses: [{ address: ADDRESS, balance: "0", tokenBalances: [] }],
+        },
+    ];
+    state.selectedWallet = 0;
+    state.selectedAddress = 0;
+    state.selectedToken = null;
+    state.viewData = null;
+    state.currentView = view;
+    state.viewStack = stack.slice();
+    Object.assign(state, extra || {});
+    // Restoring onto a view renders it, so the reopened popup has that one
+    // view on the page and nothing else.
+    markViewRendered(view);
+    const views = makeViews();
+    setBackRenderer(makeBackRenderer(state, views));
+    return views;
+}
+
+// The reproduction from the issue, step for step.
+describe("Back onto a view the reopened popup never rendered", () => {
+    test("Back from settings renders the address detail underneath", () => {
+        reopenedOn("settings", ["main", "address"]);
+        goBack();
+        expect(calls).toEqual(["addressDetail"]);
+        expect(state.currentView).toBe("address");
+        expect(state.viewStack).toEqual(["main"]);
+    });
+
+    test("Back onto the token detail renders it", () => {
+        reopenedOn("settings", ["main", "address", "address-token"], {
+            selectedToken: TOKEN,
+        });
+        goBack();
+        expect(calls).toEqual(["addressToken"]);
+        expect(state.currentView).toBe("address-token");
+    });
+
+    test("Back onto Receive renders it", () => {
+        reopenedOn("settings", ["main", "address", "receive"]);
+        goBack();
+        expect(calls).toEqual(["receive"]);
+        expect(state.currentView).toBe("receive");
+    });
+
+    test("Back onto the transaction detail renders it", () => {
+        reopenedOn("settings", ["main", "transaction"], {
+            viewData: { tx: { hash: "0xdead" } },
+        });
+        goBack();
+        expect(calls).toEqual(["transactionDetail"]);
+        expect(state.currentView).toBe("transaction");
+    });
+
+    test("Back onto the transaction confirmation restores it", () => {
+        reopenedOn("settings", ["main", "confirm-tx"], {
+            viewData: { pendingTx: { to: ADDRESS, amount: "1" } },
+        });
+        goBack();
+        expect(calls).toEqual(["confirmTx"]);
+        expect(state.currentView).toBe("confirm-tx");
+    });
+
+    test("Back onto the success screen renders it", () => {
+        reopenedOn("settings", ["main", "success-tx"], {
+            viewData: { hash: "0xdead" },
+        });
+        goBack();
+        expect(calls).toEqual(["successTx"]);
+        expect(state.currentView).toBe("success-tx");
+    });
+
+    test("Back onto the failure screen renders it", () => {
+        reopenedOn("settings", ["main", "error-tx"], {
+            viewData: { message: "execution reverted" },
+        });
+        goBack();
+        expect(calls).toEqual(["errorTx"]);
+        expect(state.currentView).toBe("error-tx");
+    });
+
+    test("Back onto Home renders the wallet list", () => {
+        reopenedOn("settings", ["main"]);
+        goBack();
+        expect(calls).toEqual(["main"]);
+        expect(state.currentView).toBe("main");
+    });
+
+    test("Back with an empty stack renders Home", () => {
+        reopenedOn("settings", []);
+        goBack();
+        expect(calls).toEqual(["main"]);
+        expect(state.currentView).toBe("main");
+    });
+});
+
+// The guards are restoreView()'s, so a popped view whose backing data is
+// gone lands on Home rather than on an empty template.
+describe("Back onto a view whose backing data is gone", () => {
+    test("the token detail with no token selected falls back to Home", () => {
+        reopenedOn("settings", ["main", "address-token"]);
+        goBack();
+        expect(calls).toEqual(["main"]);
+        expect(state.currentView).toBe("main");
+    });
+
+    test("the transaction detail with no transaction falls back to Home", () => {
+        reopenedOn("settings", ["main", "transaction"]);
+        goBack();
+        expect(calls).toEqual(["main"]);
+        expect(state.currentView).toBe("main");
+    });
+
+    test("the confirmation with no pending transaction falls back to Home", () => {
+        reopenedOn("settings", ["main", "confirm-tx"]);
+        goBack();
+        expect(calls).toEqual(["main"]);
+        expect(state.currentView).toBe("main");
+    });
+
+    test("an address view with no address selected falls back to Home", () => {
+        reopenedOn("settings", ["main", "receive"], {
+            selectedAddress: null,
+        });
+        goBack();
+        expect(calls).toEqual(["main"]);
+        expect(state.currentView).toBe("main");
+    });
+
+    test("the success screen with no transaction hash falls back to Home", () => {
+        reopenedOn("settings", ["main", "success-tx"]);
+        goBack();
+        expect(calls).toEqual(["main"]);
+        expect(state.currentView).toBe("main");
+    });
+
+    test("the failure screen with no message falls back to Home", () => {
+        reopenedOn("settings", ["main", "error-tx"]);
+        goBack();
+        expect(calls).toEqual(["main"]);
+        expect(state.currentView).toBe("main");
+    });
+
+    test("a wait that can no longer be resumed falls back to Home", () => {
+        reopenedOn("settings", ["main", "wait-tx"]);
+        const views = makeViews();
+        views.txStatus.restoreWait = () => false;
+        setBackRenderer(makeBackRenderer(state, views));
+        goBack();
+        expect(calls).toEqual(["main"]);
+        expect(state.currentView).toBe("main");
+    });
+});
+
+// Forward navigation renders as it goes, and a second render would re-fetch
+// and clobber whatever the view holds — an unsaved edit, a request in
+// flight. So the Back path renders only a view this page load has never
+// rendered, and merely unhides every other one: the views it does not
+// render from persisted state, and the views already on the page.
+describe("what the Back path leaves alone", () => {
+    test("forward navigation renders nothing by itself", () => {
+        reopenedOn("address", ["main"]);
+        pushCurrentView();
+        showView("send");
+        expect(calls).toEqual([]);
+        expect(state.viewStack).toEqual(["main", "address"]);
+    });
+
+    test("Back onto a live-session view only unhides it", () => {
+        reopenedOn("confirm-tx", ["main", "address", "send"]);
+        goBack();
+        expect(calls).toEqual([]);
+        expect(state.currentView).toBe("send");
+    });
+
+    test("Back renders its target exactly once", () => {
+        reopenedOn("settings", ["main", "address"]);
+        goBack();
+        expect(calls.filter((c) => c === "addressDetail")).toHaveLength(1);
+    });
+
+    test("Back onto a view this page load already rendered only unhides it", () => {
+        const views = reopenedOn("main", []);
+        pushCurrentView();
+        views.addressDetail.show();
+        pushCurrentView();
+        views.settings.show();
+        calls = [];
+        goBack();
+        expect(calls).toEqual([]);
+        expect(state.currentView).toBe("address");
+    });
+
+    // The unit mirror of the regression the browser suite pins: Settings
+    // reassigns its fields from persisted state on every render, so a
+    // re-render on the way back discards an edit the user has not saved.
+    test("Back onto Settings visited earlier in this page load does not re-render it", () => {
+        const views = reopenedOn("main", []);
+        pushCurrentView();
+        views.settings.show();
+        pushCurrentView();
+        views.settingsAddToken.show();
+        calls = [];
+        goBack();
+        expect(calls).toEqual([]);
+        expect(state.currentView).toBe("settings");
+    });
+
+    // Home is the deliberate exception, unchanged from the popup's
+    // behaviour before the router existed: it re-renders on every Back so
+    // the wallet list reflects what changed while the user was away.
+    test("Back onto Home renders it again even when it is already on the page", () => {
+        const views = reopenedOn("main", []);
+        pushCurrentView();
+        views.addressDetail.show();
+        calls = [];
+        goBack();
+        expect(calls).toEqual(["main"]);
+        expect(state.currentView).toBe("main");
+    });
+});

tests/backgroundApproval.test.js

@@ -30,6 +30,8 @@ const RECIPIENT = "0x66133E8ea0f5D1d612D2502a968757D1048c214a";
 
 const ORIGIN = "https://dapp.example";
 const HOSTNAME = "dapp.example";
+// A page the wallet has never been connected to, whose requests are refused.
+const UNCONNECTED_ORIGIN = "https://stranger.example";
 const EXT_URL = "chrome-extension://autistmask/";
 
 // What the dApp asks for: no nonce, no gas, no fees. This is the shape that
@@ -51,10 +53,16 @@ const MESSAGE = "0x48656c6c6f204175746973744d61736b";
 // The transaction the background populates and the approval screen displays.
 // The nonce is a parameter because the duplicate case turns on two artifacts
 // differing in a field the dApp fixed nothing for.
-function populated(nonce) {
+// The two chains the tests switch between, as both forms the code uses: the
+// hex chain id the wallet's network record carries, and the number the node
+// and the signed artifact carry.
+const MAINNET = { hex: "0x1", num: 1 };
+const SEPOLIA = { hex: "0xaa36a7", num: 11155111 };
+
+function populated(nonce, chainId) {
     return {
         type: 2,
-        chainId: 1,
+        chainId: chainId || MAINNET.num,
         nonce,
         gasLimit: 100000n,
         maxFeePerGas: 2000000000n,
@@ -65,17 +73,17 @@ function populated(nonce) {
     };
 }
 
-function signedAtNonce(nonce, withWallet) {
-    return (withWallet || signer).signTransaction(populated(nonce));
+function signedAtNonce(nonce, withWallet, chainId) {
+    return (withWallet || signer).signTransaction(populated(nonce, chainId));
 }
 
 // The node the background populates against. Its answers are the numbers the
 // approval screen shows, so they are also the numbers every artifact below is
 // signed at.
-function fakeProvider(broadcastTransaction, overrides) {
+function fakeProvider(broadcastTransaction, overrides, chainId) {
     return {
         broadcastTransaction,
-        getNetwork: async () => Network.from(1),
+        getNetwork: async () => Network.from(chainId || MAINNET.num),
         getTransactionCount: async () => NONCE,
         estimateGas: async () => 100000n,
         getFeeData: async () => ({
@@ -111,14 +119,20 @@ function loadBackground(options) {
     const broadcastTransaction = jest.fn();
     const loadState = jest.fn(opts.loadState || (async () => {}));
 
+    // The network the wallet is on, which the tests switch under a pending
+    // approval. The node the transaction is populated against is on the same
+    // one, as it would be: switching networks switches the RPC endpoint too.
+    let chain = MAINNET;
+
     jest.doMock("../src/shared/state", () => ({
         state: { rpcUrl: "https://rpc.invalid", wallets: [] },
         loadState,
         saveState: jest.fn(async () => {}),
-        currentNetwork: () => ({ chainId: "0x1" }),
+        currentNetwork: () => ({ chainId: chain.hex }),
     }));
     jest.doMock("../src/shared/balances", () => ({
-        getProvider: () => fakeProvider(broadcastTransaction, opts.provider),
+        getProvider: () =>
+            fakeProvider(broadcastTransaction, opts.provider, chain.num),
         refreshBalances: jest.fn(async () => {}),
     }));
     jest.doMock("../src/shared/phishingDomains", () => ({
@@ -170,7 +184,9 @@ function loadBackground(options) {
             getLastFocused: (cb) => cb(null),
             create: (options2, cb) => {
                 created.push(options2);
-                cb({ id: created.length });
+                // A browser that answers with no window at all. The approval
+                // then has no window it can ever be answered in.
+                cb(opts.noWindow ? undefined : { id: created.length });
             },
             remove: (id, cb) => {
                 removed.push(id);
@@ -204,8 +220,12 @@ function loadBackground(options) {
 
     // Raise a pending transaction approval the way a dApp does, and dig the
     // approval id back out of the popup URL the background opened.
-    function requestTx(txParams) {
+    function requestTx(txParams, origin) {
         let rpcResult = null;
+        // The window this request opens, if it opens one. A request refused
+        // before an approval is raised opens none, and the window belonging to
+        // some other request must not be handed back as this one's.
+        const windowIndex = created.length;
         const sendResponse = jest.fn((r) => {
             rpcResult = r;
         });
@@ -215,11 +235,16 @@ function loadBackground(options) {
                 method: "eth_sendTransaction",
                 params: [txParams || TX_PARAMS],
             },
-            { origin: ORIGIN },
+            { origin: origin || ORIGIN },
             sendResponse,
         );
         return {
-            id: () => new URL(created[0].url).searchParams.get("approval"),
+            id: () =>
+                created.length > windowIndex
+                    ? new URL(created[windowIndex].url).searchParams.get(
+                          "approval",
+                      )
+                    : null,
             result: () => rpcResult,
         };
     }
@@ -269,6 +294,10 @@ function loadBackground(options) {
         setActiveAddress: (address) => {
             persisted.activeAddress = address;
         },
+        // The user switching network in the toolbar popup.
+        setNetwork: (network) => {
+            chain = network;
+        },
         fromPopup: { url: EXT_URL + "src/popup/index.html" },
     };
 }
@@ -444,6 +473,318 @@ describe("one approval, one broadcast", () => {
     });
 });
 
+// Populating the transaction before the approval window opens is what makes
+// the displayed object the verified object. It also fixes the nonce before the
+// user has answered anything: two requests populated concurrently take the
+// same nonce from a node that has seen neither of them broadcast, and the
+// second can then never be sent, because the only way to give it a fresh nonce
+// is to populate it again after the user has read the old one off the screen.
+// So the second request is refused while the first is unanswered.
+describe("one transaction approval at a time", () => {
+    test("a second eth_sendTransaction while one is pending is refused before it takes a nonce", async () => {
+        const getTransactionCount = jest.fn(async () => NONCE);
+        const bg = loadBackground({ provider: { getTransactionCount } });
+
+        const first = bg.requestTx();
+        await settle();
+        expect(first.id()).toBeTruthy();
+        expect(getTransactionCount).toHaveBeenCalledTimes(1);
+
+        const second = bg.requestTx();
+        await settle();
+
+        expect(second.result()).toEqual({
+            error: {
+                code: -32002,
+                message: expect.stringMatching(
+                    /one transaction at a time.+already in progress/,
+                ),
+            },
+        });
+        // Where the refusal happened matters as much as that it happened: no
+        // second window, and the node was never asked for a second nonce.
+        expect(bg.created).toHaveLength(1);
+        expect(getTransactionCount).toHaveBeenCalledTimes(1);
+
+        // The refusal leaves the pending approval untouched, and it still
+        // sends.
+        bg.broadcastTransaction.mockResolvedValue({ hash: "0xfeed" });
+        bg.send(
+            {
+                type: "AUTISTMASK_TX_RESPONSE",
+                id: first.id(),
+                approved: true,
+                rawSignedTx: await signedAtNonce(NONCE),
+            },
+            { url: bg.fromPopup.url },
+        );
+        await settle();
+        expect(first.result()).toEqual({ result: "0xfeed" });
+    });
+
+    // The slot is only defensible if the wallet was going to raise an approval
+    // anyway. Taken any earlier, a request the wallet refuses outright still
+    // holds it, and any page at all — connected or not — can deny the user's
+    // own transactions for as long as it keeps asking.
+    test("a request the wallet refuses does not take the slot from the connected site", async () => {
+        const bg = loadBackground();
+
+        // Both delivered before either reaches its first suspension point,
+        // which is the interleaving the slot exists for.
+        const stranger = bg.requestTx(TX_PARAMS, UNCONNECTED_ORIGIN);
+        const connected = bg.requestTx();
+        await settle();
+
+        expect(stranger.result()).toEqual({
+            error: { code: 4100, message: "Unauthorized" },
+        });
+        // The connected site's transaction was raised, not refused as one the
+        // user already has in progress.
+        expect(connected.result()).toBeNull();
+        expect(connected.id()).toBeTruthy();
+        expect(bg.created).toHaveLength(1);
+    });
+
+    // The user closes an approval window that looks hung while the attempt
+    // behind it is still running, and that attempt then fails in a way that
+    // would normally leave the approval standing for a retry. There is no
+    // window left to retry in, so leaving it standing answers the requesting
+    // page never — and holds the slot for the life of the worker with it.
+    test("an approval whose window closed under a failed attempt is answered, and frees the next request", async () => {
+        const stalled = deferred();
+        const bg = loadBackground({
+            loadState: async () => {
+                await stalled.promise;
+                throw new Error("The wallet data could not be read.");
+            },
+        });
+
+        const first = bg.requestTx();
+        await settle();
+        bg.send(
+            {
+                type: "AUTISTMASK_TX_RESPONSE",
+                id: first.id(),
+                approved: true,
+                rawSignedTx: await signedAtNonce(NONCE),
+            },
+            { url: bg.fromPopup.url },
+        );
+        await settle();
+
+        // The attempt owns the approval, so closing the window does not settle
+        // it: the attempt may yet broadcast, and it is the one that reports.
+        bg.closeWindow(1);
+        await settle();
+        expect(first.result()).toBeNull();
+
+        stalled.resolve();
+        await settle();
+        expect(first.result()).toEqual({
+            error: { code: 4001, message: "User rejected the request." },
+        });
+
+        const second = bg.requestTx();
+        await settle();
+        expect(second.result()).toBeNull();
+        expect(second.id()).toBeTruthy();
+        expect(bg.created).toHaveLength(2);
+    });
+
+    // An approval with no window is one nothing can ever answer.
+    test("a request whose approval window cannot be opened is answered rather than left waiting", async () => {
+        const bg = loadBackground({ noWindow: true });
+
+        const first = bg.requestTx();
+        await settle();
+        expect(first.result()).toEqual({
+            error: {
+                code: -32603,
+                message: expect.stringMatching(
+                    /could not open its approval window/,
+                ),
+            },
+        });
+
+        // And it did not take the slot with it.
+        const second = bg.requestTx();
+        await settle();
+        expect(second.result()).toEqual({
+            error: {
+                code: -32603,
+                message: expect.stringMatching(
+                    /could not open its approval window/,
+                ),
+            },
+        });
+    });
+
+    test("an answered approval frees the next request", async () => {
+        const bg = loadBackground();
+        const first = bg.requestTx();
+        await settle();
+
+        // The user closes the approval window, which rejects it.
+        bg.closeWindow(1);
+        await settle();
+        expect(first.result()).toEqual({
+            error: { code: 4001, message: "User rejected the request." },
+        });
+
+        const second = bg.requestTx();
+        await settle();
+        expect(second.id()).toBeTruthy();
+        expect(bg.created).toHaveLength(2);
+    });
+
+    test("a signature request is not held up by a pending transaction", async () => {
+        const bg = loadBackground();
+        bg.requestTx();
+        await settle();
+
+        // A signature consumes no nonce, so it has nothing to collide with.
+        const signing = bg.requestSign();
+        await settle();
+        expect(signing.id()).toBeTruthy();
+        expect(signing.result()).toBeNull();
+        expect(bg.created).toHaveLength(2);
+    });
+});
+
+// A nonce collision found before the transaction reaches the network is the
+// one send failure the wallet can speak about with certainty. The user is told
+// it did not go out and to send it again, rather than being warned it might
+// already be on the chain — which would send them looking for a transaction
+// that does not exist, and stop them retrying the one that never went.
+describe("a nonce collision is reported as a transaction that did not go out", () => {
+    test("a broadcast the node refused for the nonce is not reported as possibly sent", async () => {
+        const bg = loadBackground();
+        const pending = bg.requestTx();
+        await settle();
+
+        bg.broadcastTransaction.mockRejectedValue(
+            Object.assign(new Error("nonce too low"), {
+                code: "NONCE_EXPIRED",
+            }),
+        );
+        const answer = bg.send(
+            {
+                type: "AUTISTMASK_TX_RESPONSE",
+                id: pending.id(),
+                approved: true,
+                rawSignedTx: await signedAtNonce(NONCE),
+            },
+            { url: bg.fromPopup.url },
+        );
+        await settle();
+
+        expect(answer.sendResponse).toHaveBeenCalledWith({
+            error: expect.stringMatching(/nonce had already been used/),
+            retryable: false,
+            stage: "nonce",
+        });
+        expect(pending.result()).toEqual({
+            error: {
+                message: expect.stringMatching(
+                    /transaction was not sent, because its nonce/,
+                ),
+            },
+        });
+    });
+
+    test("a nonce this wallet already broadcast is refused without asking the node again", async () => {
+        const bg = loadBackground();
+        const first = bg.requestTx();
+        await settle();
+
+        bg.broadcastTransaction.mockResolvedValue({ hash: "0xfeed" });
+        bg.send(
+            {
+                type: "AUTISTMASK_TX_RESPONSE",
+                id: first.id(),
+                approved: true,
+                rawSignedTx: await signedAtNonce(NONCE),
+            },
+            { url: bg.fromPopup.url },
+        );
+        await settle();
+        expect(first.result()).toEqual({ result: "0xfeed" });
+
+        // The stubbed node still reports NONCE as the next nonce — a pending
+        // count that lags a broadcast the node has already taken — so this
+        // second approval is populated at a nonce this worker has spent.
+        const second = bg.requestTx();
+        await settle();
+        const answer = bg.send(
+            {
+                type: "AUTISTMASK_TX_RESPONSE",
+                id: second.id(),
+                approved: true,
+                rawSignedTx: await signedAtNonce(NONCE),
+            },
+            { url: bg.fromPopup.url },
+        );
+        await settle();
+
+        expect(bg.broadcastTransaction).toHaveBeenCalledTimes(1);
+        expect(answer.sendResponse).toHaveBeenCalledWith({
+            error: expect.stringMatching(/nonce had already been used/),
+            retryable: false,
+            stage: "nonce",
+        });
+        expect(second.result()).toEqual({
+            error: {
+                message: expect.stringMatching(/nonce had already been used/),
+            },
+        });
+    });
+
+    // Nonce spaces are per chain, and the wallet switches networks. A nonce
+    // this wallet spent on one chain says nothing about the same nonce on
+    // another — and low nonces overlap across chains as a matter of course, so
+    // a record that ignored the chain would refuse ordinary transactions,
+    // permanently and with a message that is not true of them.
+    test("a nonce spent on one chain is not refused on another", async () => {
+        const bg = loadBackground();
+
+        const first = bg.requestTx();
+        await settle();
+        bg.broadcastTransaction.mockResolvedValue({ hash: "0xfeed" });
+        bg.send(
+            {
+                type: "AUTISTMASK_TX_RESPONSE",
+                id: first.id(),
+                approved: true,
+                rawSignedTx: await signedAtNonce(NONCE),
+            },
+            { url: bg.fromPopup.url },
+        );
+        await settle();
+        expect(first.result()).toEqual({ result: "0xfeed" });
+
+        // The user switches network. On this chain the address has sent
+        // nothing, so the node populates the next transaction at the same
+        // nonce — correctly.
+        bg.setNetwork(SEPOLIA);
+        const second = bg.requestTx();
+        await settle();
+        bg.broadcastTransaction.mockResolvedValue({ hash: "0xbeef" });
+        bg.send(
+            {
+                type: "AUTISTMASK_TX_RESPONSE",
+                id: second.id(),
+                approved: true,
+                rawSignedTx: await signedAtNonce(NONCE, undefined, SEPOLIA.num),
+            },
+            { url: bg.fromPopup.url },
+        );
+        await settle();
+
+        expect(bg.broadcastTransaction).toHaveBeenCalledTimes(2);
+        expect(second.result()).toEqual({ result: "0xbeef" });
+    });
+});
+
 // The approval carries the transaction the user was shown and the address it
 // was raised for, and the artifact is checked against both. Every case here is
 // one the old comparison — against the dApp's request, for the address that is

tests/e2e/run.js

@@ -419,6 +419,172 @@ test("reopening the popup never lands on the phrase screen (#161)", async (env)
     assertWiped(st, env.phrase, "after reopening the popup");
 });
 
+// ------------------------------- Back after reopening the popup (#268)
+
+// A reopened popup renders the wallet list and the view it restores onto,
+// and nothing else: every other screen is still the blank static template
+// from index.html. Back used to only unhide its target, which is why these
+// have to run against the real popup — the template is present and
+// well-formed, so only its emptiness distinguishes the defect, and only a
+// real reopen produces it.
+
+// Everything the address screen must have on it, read out of the DOM.
+function addressScreenState(page) {
+    return page.evaluate(() => {
+        const line = document.getElementById("address-line");
+        const balances = document.getElementById("address-balances");
+        return {
+            hidden: document
+                .getElementById("view-address")
+                .classList.contains("hidden"),
+            line: line ? line.innerText.trim() : "",
+            balances: balances ? balances.innerText.trim() : "",
+        };
+    });
+}
+
+// Close and reopen the page rather than reload it: that is what the toolbar
+// popup does, and it is the only thing that produces the unrendered views.
+async function reopenPopup(env, restoredView) {
+    await env.page.close();
+    env.page = await openPopup(env.ctx, env.popupUrl);
+    await visible(env.page, restoredView);
+}
+
+// The reproduction from the issue, step for step.
+test("Back after reopening the popup renders the address screen (#268)", async (env) => {
+    await openAddressDetail(env.page);
+    const before = await addressScreenState(env.page);
+    assert(
+        before.line.length > 0,
+        "the address screen was blank to begin with",
+    );
+
+    await env.page.click("#btn-settings");
+    await visible(env.page, "#view-settings");
+
+    await reopenPopup(env, "#view-settings");
+
+    await env.page.click("#btn-settings-back");
+    await visible(env.page, "#view-address");
+
+    const after = await addressScreenState(env.page);
+    assert(
+        after.line === before.line,
+        "the address line reads " +
+            JSON.stringify(after.line) +
+            ", expected " +
+            JSON.stringify(before.line),
+    );
+    assert(
+        after.balances.includes("ETH"),
+        "the balances read " + JSON.stringify(after.balances),
+    );
+});
+
+// The same defect one screen further in. Receive holds the address twice
+// over — as text and as the QR code the sender scans — and a blank one is
+// worse than a missing screen.
+// Everything the Receive screen must have on it. The QR code is read as
+// pixels, not as an element: the blank template carries the canvas too, a
+// default 300x150 one with nothing drawn on it and every pixel fully
+// transparent. A drawn QR paints an opaque background across the whole
+// canvas, so a single opaque pixel is the whole question.
+function receiveScreenState(page) {
+    return page.evaluate(() => {
+        const block = document.getElementById("receive-address-block");
+        const canvas = document.getElementById("receive-qr");
+        const px = canvas
+            .getContext("2d")
+            .getImageData(0, 0, canvas.width, canvas.height).data;
+        let opaque = 0;
+        for (let i = 3; i < px.length; i += 4) {
+            if (px[i] > 0) opaque += 1;
+        }
+        return {
+            address: block.dataset.full || "",
+            text: block.innerText.trim(),
+            qrOpaquePixels: opaque,
+        };
+    });
+}
+
+test("Back after reopening the popup renders the Receive screen (#268)", async (env) => {
+    await openAddressDetail(env.page);
+    await env.page.click("#btn-receive");
+    await visible(env.page, "#view-receive");
+    const before = await receiveScreenState(env.page);
+    assert(
+        /^0x[0-9a-fA-F]{40}$/.test(before.address),
+        "Receive showed no address to begin with: " +
+            JSON.stringify(before.address),
+    );
+
+    await env.page.click("#btn-settings");
+    await visible(env.page, "#view-settings");
+
+    await reopenPopup(env, "#view-settings");
+
+    await env.page.click("#btn-settings-back");
+    await visible(env.page, "#view-receive");
+
+    const shown = await receiveScreenState(env.page);
+    assert(
+        shown.address === before.address,
+        "Receive shows " +
+            JSON.stringify(shown.address) +
+            ", expected " +
+            JSON.stringify(before.address),
+    );
+    assert(
+        shown.text.includes(before.address),
+        "the Receive address is not on screen: " + JSON.stringify(shown.text),
+    );
+    assert(shown.qrOpaquePixels > 0, "Receive shows an unpainted QR code");
+
+    // Leave the suite where it found it.
+    await env.page.click("#btn-receive-back");
+    await visible(env.page, "#view-address");
+    await env.page.click("#btn-address-back");
+    await visible(env.page, "#view-main");
+});
+
+// The other half of the requirement: Back renders a screen this page load
+// never rendered, and must NOT re-render one it already has on screen.
+// settings.show() reassigns #settings-rpc from persisted state, so
+// re-rendering Settings on the way back would silently revert whatever the
+// user typed and had not saved yet — and they could then press Save and
+// store the value they believed they had replaced. No reopen here: this is
+// an ordinary in-session forward-and-back, which is exactly why the render
+// must not happen.
+test("Back onto Settings keeps unsaved input (#268)", async (env) => {
+    await visible(env.page, "#view-main");
+    await env.page.click("#btn-settings");
+    await visible(env.page, "#view-settings");
+
+    const typed = "https://rpc.example.invalid/unsaved";
+    await env.page.fill("#settings-rpc", typed);
+
+    await env.page.click("#btn-settings-add-token");
+    await visible(env.page, "#view-settings-addtoken");
+    await env.page.click("#btn-settings-addtoken-back");
+    await visible(env.page, "#view-settings");
+
+    const kept = await env.page.inputValue("#settings-rpc");
+    assert(
+        kept === typed,
+        "the unsaved RPC URL reads " +
+            JSON.stringify(kept) +
+            ", expected " +
+            JSON.stringify(typed),
+    );
+
+    // Leave the suite where it found it. The typed value was never saved,
+    // and Settings reloads the field from state next time it renders.
+    await env.page.click("#btn-settings-back");
+    await visible(env.page, "#view-main");
+});
+
 // -------------------------------------------- address removal (#162)
 
 // Number of address rows across every wallet in the list, counted in the DOM