fix: a refresh asked for while another runs is no longer dropped (closes #581)

doRefreshAndRender() returned at once when a refresh was already running. An import asks for a refresh after its address scan, and that request was dropped when it came during a refresh, so the addresses the scan found showed 0.0000 until the next ten-second refresh. A request made through ctx while a refresh runs now leads to one more refresh once the running one ends, however many such requests came in. A tick of the ten-second timer during a refresh is still dropped, so the wallet asks the node no more often than before.

Model: opus-5-5

README.md

@@ -1277,22 +1277,18 @@ see Transaction Decoding), do not always read as a number. They can read:
   step pays nothing itself and swaps whatever an earlier step sent to the pair,
   so the calldata states no quantity. A V3 exact-in `amountIn` of zero has no
   such meaning and is shown as a zero.
-- `None (no minimum guaranteed)`: the swap's `Min. received` line, when the
-  minimum it shows is zero, whether a V2, V3 or V4 swap's minimum or a
-  `BALANCE_CHECK_ERC20` step's `minBalance`. Before
-  [#359](https://git.eeqj.de/sneak/AutistMask/issues/359), a zero `minBalance`
-  read `0.0000` when the token's scale was known. The router passes a balance
-  check whenever the balance is at least `minBalance`, so a zero `minBalance`
-  guarantees nothing: it sets `Token Out` and `Min. received` only when the
-  output side holds no minimum, not even a zero one, at the point the check is
-  reached, and otherwise leaves the current token and figure in place. A nonzero
-  `minBalance` sets both lines, as a swap step does. Only a check of the
-  transaction's sender's own balance sets either line; a check of any other
-  address sets neither (see Transaction Decoding). A `BALANCE_CHECK_ERC20` step
-  that the router lets fail without reverting the transaction (see Transaction
-  Decoding) guarantees nothing either, whatever its `minBalance`, and is read as
-  one whose `minBalance` is zero. A minimum stated by a V4 swap step the router
-  lets fail is likewise read as zero.
+- `None (no minimum guaranteed)`: the swap's `Min. received` line, when it shows
+  a V2, V3 or V4 swap's minimum of zero. The router passes a
+  `BALANCE_CHECK_ERC20` step whenever the balance is at least `minBalance`, so a
+  zero `minBalance` guarantees nothing. A check with a zero `minBalance` sets
+  neither `Token Out` nor `Min. received`. A nonzero `minBalance` sets both
+  lines, as a swap step does. Only a check of the transaction's sender's own
+  balance sets either line; a check of any other address sets neither (see
+  Transaction Decoding). A `BALANCE_CHECK_ERC20` step that the router lets fail
+  without reverting the transaction (see Transaction Decoding) guarantees
+  nothing either, whatever its `minBalance`, and is read as one whose
+  `minBalance` is zero. A minimum stated by a V4 swap step the router lets fail
+  is likewise read as zero.
 
 The swap's `Token In` and `Token Out` lines name a currency, not an amount; each
 reads `Unknown (not named in the calldata)` when the decoder found no token for
@@ -2283,6 +2279,9 @@ view would leave a wallet one click from deletion.
           no user data and is made whether or not "Use Blockscout" is ticked.
     - If the network changes before either "Save" stores its URL, the URL is not
       saved and a flash message says so
+    - Either "Save" stores its URL only if the input still shows that URL when
+      the endpoint answers. Otherwise a flash message says that the URL was not
+      saved
     - Etherscan:
         - "Check recipients on Etherscan" checkbox, unticked until the user
           ticks it
@@ -3397,7 +3396,8 @@ Currently supported:
   `Balance Check (of another address)`. A check whose input does not decode,
   such as one whose owner word has a nonzero top byte (the router reads the
   owner from the word's last 20 bytes), likewise sets neither, and it is listed
-  as `Balance Check (could not be decoded)`. When a swap step, `TAKE` or
+  as `Balance Check (could not be decoded)`. A check with a zero `minBalance`
+  sets neither `Token Out` nor the minimum. When a swap step, `TAKE` or
   `TAKE_PORTION` pays the router any token, the swap's output or another, a
   `WRAP_ETH` pays it WETH, or an `UNWRAP_WETH` into the router turns WETH a step
   paid it into ETH, that token stays in the router unless a later step pays out
@@ -3566,10 +3566,14 @@ Currently supported:
   on every router but `UniversalRouterV1`, and otherwise gives the address. A
   move into the router needs none of them, because its `Paid to` line and
   `Token moved into the router` line already give the amount, the token and
-  where it goes, and so its amount is shown once. Every `PERMIT2_PERMIT` whose
-  amount does not stand as the `Amount` figure, before the step that sets the
-  input side or after it, gives three lines, in step order, after those for each
-  `PERMIT2_TRANSFER_FROM`: `Permit2 allowance`, its amount, for example
+  where it goes, and so its amount is shown once. For a move of the zero
+  address, `Moved from the sender` gives the amount in base units and
+  `Token moved` gives the zero address. For such a move into the router, the
+  `Paid to` line gives the amount in base units and
+  `Token moved into the router` gives the zero address. Every `PERMIT2_PERMIT`
+  whose amount does not stand as the `Amount` figure, before the step that sets
+  the input side or after it, gives three lines, in step order, after those for
+  each `PERMIT2_TRANSFER_FROM`: `Permit2 allowance`, its amount, for example
   `5000.0000 DAI`, or `Unlimited` for Permit2's maximum; `Allowance token`,
   giving the token's address as the `Token In` line does; and
   `Allowance spender`, the address it lets take the token. Only a permit whose

src/popup/index.js

@@ -65,7 +65,14 @@ function renderWalletList() {
 const pageClosed = new AbortController();
 window.addEventListener("pagehide", () => pageClosed.abort());
 
+// While a refresh runs, a request through ctx is not dropped. The request sets
+// refreshAgain, and one more refresh runs once the running one ends. Several
+// requests in that time lead to one more refresh, not several. An import asks
+// for a refresh after its address scan. A refresh already running does not
+// have the addresses the scan found
+// (https://git.eeqj.de/sneak/AutistMask/issues/581).
 let refreshInFlight = false;
+let refreshAgain = false;
 
 // The ten-second refresh startRefresh() starts, stopped when the popup moves to
 // the recovery screen: there is no profile left to refresh.
@@ -89,7 +96,10 @@ let refreshTimer = null;
 // user turned "Use Blockscout" off. So the save drops every token the user has
 // not tracked if the stored setting is off by then.
 async function doRefreshAndRender() {
-    if (refreshInFlight) return;
+    if (refreshInFlight) {
+        refreshAgain = true;
+        return;
+    }
     refreshInFlight = true;
     try {
         await followStoredSettings();
@@ -132,28 +142,35 @@ async function doRefreshAndRender() {
         });
         renderWalletList();
     } catch (e) {
-        // Every call site fires this and walks away — the boot below, the ten
-        // second interval, and eight views through ctx — so it must never
-        // reject: an unhandled rejection is not a report of anything. The save
-        // inside it reports its own failure through onSaveFailure() (see
-        // src/shared/state.js); what is left here is a failed network round
-        // trip, which the next tick retries.
+        // No caller waits for this function, so it must never reject. An
+        // unhandled rejection reports nothing. The save inside it reports its
+        // own failure through onSaveFailure() (see src/shared/state.js); what
+        // is left here is a failed network round trip, which the next tick
+        // retries.
         log.errorf("popup: background refresh failed:", e);
     } finally {
         refreshInFlight = false;
     }
+    if (refreshAgain) {
+        refreshAgain = false;
+        doRefreshAndRender();
+    }
 }
 
 // Refreshes now and every ten seconds from then on. Called once a wallet
 // exists: by init() when the popup opens with one, and by AddWallet when it
 // adds one, which in a popup that opened on Welcome is the first
-// (https://git.eeqj.de/sneak/AutistMask/issues/530). With the refresh already
-// running it starts no second one, and on the recovery screen it does nothing.
+// (https://git.eeqj.de/sneak/AutistMask/issues/530). With the ten-second
+// refresh already started, it starts no second one. On the recovery screen it
+// does nothing.
 function startRefresh() {
     if (!$("view-state-recovery").classList.contains("hidden")) return;
     doRefreshAndRender();
     if (refreshTimer === null) {
-        refreshTimer = setInterval(doRefreshAndRender, 10000);
+        // A tick that finds a refresh running is dropped.
+        refreshTimer = setInterval(() => {
+            if (!refreshInFlight) return doRefreshAndRender();
+        }, 10000);
     }
 }
 

src/popup/views/settings.js

@@ -334,16 +334,36 @@ function showNewSettings() {
 // src/popup/index.js) between setting the URL and writing it. If the active
 // network is no longer `networkId`, on this page or in the stored record,
 // nothing is saved. The flash message then says that the network changed.
-async function saveEndpoint(field, url, networkId) {
+//
+// The save writes only the fields that differ from what this page last saved.
+// Another page may have stored a different URL since then. So `url` is set in
+// the stored record too. "Saved." then means that the stored record holds
+// `url`.
+//
+// `input` is the id of the input that the user typed `url` in. When another
+// page changes the network, "Use Blockscout" or "Check recipients on
+// Etherscan", this page draws Settings again. A redraw during the endpoint
+// check puts the URL from `state` back in the input. So if the input no longer
+// shows `url`, nothing is saved. The flash message then says that the URL was
+// changed during the check. The save compares the input and sets `url` in
+// `state` in one step. So a redraw after the comparison shows `url`.
+async function saveEndpoint(field, input, url, networkId) {
     let refused = false;
+    let inputChanged = false;
     await saveState((stored) => {
         refused =
             state.networkId !== networkId || stored.networkId !== networkId;
-        if (refused) return false;
+        inputChanged = $(input).value.trim() !== url;
+        if (refused || inputChanged) return false;
         state[field] = url;
+        stored[field] = url;
     });
     if (refused) {
         showFlash("The URL was not saved because the network changed.");
+    } else if (inputChanged) {
+        showFlash(
+            "The URL was not saved because it was changed during the check.",
+        );
     } else {
         showFlash("Saved.");
     }
@@ -395,7 +415,7 @@ function init(_ctx) {
             showFlash("Could not reach endpoint.");
             return;
         }
-        await saveEndpoint("rpcUrl", url, net.id);
+        await saveEndpoint("rpcUrl", "settings-rpc", url, net.id);
     });
 
     $("btn-save-blockscout").addEventListener("click", async () => {
@@ -419,7 +439,7 @@ function init(_ctx) {
             showFlash("Could not reach endpoint.");
             return;
         }
-        await saveEndpoint("blockscoutUrl", url, net.id);
+        await saveEndpoint("blockscoutUrl", "settings-blockscout", url, net.id);
     });
 
     // Each change is made inside the save, holding the lock. So

src/popup/views/transactionDetail.js

@@ -311,10 +311,21 @@ function populateOnChainDetails(txData, chainId) {
     }
 }
 
+// Whether TransactionDetail still holds the transaction with `txHash` on
+// `chainId`. Opening another transaction replaces the one TransactionDetail
+// holds. A visit to Settings does not.
+function holdsTransaction(txHash, chainId) {
+    const tx = state.viewData.tx;
+    return tx?.hash === txHash && tx?.chainId === chainId;
+}
+
 // Reads the block, network details and calldata from Blockscout, and decodes
 // the calldata. While the stored "Use Blockscout" is off, Blockscout is not
 // asked. An answer that lands after the setting went off is dropped
 // (src/shared/storedSettings.js). Either way none of them is shown.
+//
+// Blockscout can answer after the user has opened another transaction. That
+// answer is dropped.
 async function loadFullTxDetails(txHash, chainId) {
     if (!(await storedSettingIsOn("useBlockscout"))) return;
     const section = $("tx-detail-calldata-section");
@@ -333,6 +344,7 @@ async function loadFullTxDetails(txHash, chainId) {
         if (!resp.ok) return;
         const txData = await resp.json();
         if (!(await storedSettingIsOn("useBlockscout"))) return;
+        if (!holdsTransaction(txHash, chainId)) return;
 
         // Populate on-chain detail fields (block, nonce, gas, fee)
         populateOnChainDetails(txData, chainId);

src/shared/chainSwitch.js

@@ -47,12 +47,43 @@ function clearPopupCaches() {
 // lock, so it is never switched while a follow of a switch saved elsewhere
 // waits for the lock (followStoredSettings() in src/popup/index.js): that
 // follow runs first, and this switch is made after it.
+//
+// The save writes only the fields that differ from what this page last saved.
+// When this page last saved a balance of "0", clearing that balance is no
+// change. So the switch also resets these fields in the stored record:
+//
+// - every address's balance and token balances;
+// - the time of the last balance refresh;
+// - the fraud contracts.
+//
+// A balance or a fraud contract that the background or another page stored
+// since this page's last save is then not kept under the new network
+// (https://git.eeqj.de/sneak/AutistMask/issues/653,
+// https://git.eeqj.de/sneak/AutistMask/issues/692).
+//
+// Before the switch, `state` takes the tracked tokens that another page stored
+// since this page's last save (takeStoredTrackedTokens() in state.js). The
+// switch then puts them away under the previous network, the network they were
+// added on. When the stored record is on another network, a switch saved
+// elsewhere has not reached this page yet. The stored record's tokens are then
+// that network's, and none are taken.
 async function onChainSwitch(newNetworkId) {
-    const { state, saveState } = require("./state");
+    const { state, saveState, takeStoredTrackedTokens } = require("./state");
     let net = null;
-    await saveState(() => {
+    await saveState((stored) => {
         if (state.networkId === newNetworkId) return false;
+        if (stored.networkId === state.networkId) {
+            takeStoredTrackedTokens(stored);
+        }
         net = applyChainSwitchFields(state, newNetworkId);
+        stored.lastBalanceRefresh = 0;
+        stored.fraudContracts = [];
+        for (const wallet of stored.wallets) {
+            for (const addr of wallet.addresses) {
+                addr.balance = "0";
+                addr.tokenBalances = [];
+            }
+        }
         clearPopupCaches();
     });
     return net;

src/shared/state.js

@@ -125,11 +125,12 @@ function currentNetwork() {
     return networkById(state.networkId);
 }
 
-// The persisted fields as this page held them when its last loadState()
-// finished, or when its last successful saveState() began, with any network
-// switch saved elsewhere that this page has taken since (takeStoredNetwork()).
-// saveState() diffs the live state against this to find only the fields THIS
-// page changed since.
+// `baseline` holds the persisted fields as this page held them when its last
+// loadState() finished, or when its last successful saveState() began.
+// takeStoredNetwork() and takeStoredTrackedTokens() also write into it what
+// this page has taken from the stored record since then. saveState() diffs the
+// live state against `baseline` to find only the fields THIS page changed
+// since.
 //
 // Deep-cloned, not a reference: callers mutate persisted objects and arrays
 // in place (state.wallets.push(...)), and a reference baseline would mutate
@@ -442,8 +443,10 @@ function mergeNetworkEndpoints(base, ours, theirs) {
 // milder than the other two.
 //
 // Every other persisted field stays a whole-field diff:
-// `trackedTokens`/`fraudContracts`/`viewStack` are arrays of scalars with no
-// per-element identity to merge by; `networkTrackedTokens` is diffed whole like
+// `fraudContracts`/`viewStack` are arrays of scalars with no per-element
+// identity to merge by; a save diffs `trackedTokens` whole, and a switch in
+// Settings first merges that list by contract address
+// (takeStoredTrackedTokens()); `networkTrackedTokens` is diffed whole like
 // `trackedTokens` and `networkId`, the two fields a network switch moves
 // together with it; `tokenHolderCache` is a map shaped like the ones above,
 // but nothing in src/ ever writes an entry into it — it is only ever reset
@@ -591,8 +594,10 @@ function reportSaveFailure(err) {
 //
 // `beforeWrite`, when given, is called inside the lock with the stored record
 // as just read, before this page's state is compared against it. It may change
-// `state`, and this save writes that change. When it returns false, nothing is
-// written; any other return lets the save go ahead.
+// `state`, and this save writes that change. It may also change the stored
+// record. A field that this page did not change is then written as
+// `beforeWrite` left it. When it returns false, nothing is written; any other
+// return lets the save go ahead.
 function saveState(beforeWrite) {
     const turn = withLock("autistmask", () => saveStateOnce(beforeWrite));
     // Every failed save is reported, whether or not the caller awaited this
@@ -613,6 +618,28 @@ function takeStoredNetwork(stored) {
     copyChainSwitchFields(baseline, structuredClone(stored));
 }
 
+// Give this page the tracked tokens of `stored`, a record on this page's
+// network that a save of this page has just read (onChainSwitch() in
+// src/shared/chainSwitch.js calls this from `beforeWrite`):
+//
+// - A token that another page tracked or removed since this page's last save
+//   is tracked or removed in `state` too.
+// - A token that this page tracked or removed since then stays as this page
+//   has it.
+//
+// `baseline` takes the stored list, so the save stores the list in `state`
+// whenever the two differ.
+function takeStoredTrackedTokens(stored) {
+    rawState.trackedTokens = mergeListByIdentity(
+        baseline.trackedTokens,
+        rawState.trackedTokens,
+        stored.trackedTokens,
+        (token) => token.address.toLowerCase(),
+        (base, ours) => ours,
+    );
+    baseline.trackedTokens = structuredClone(stored.trackedTokens);
+}
+
 // Rejects with StateUnusableError for a stored record this build cannot make
 // sense of. Nothing is assigned and `loaded` stays false in that case, so a
 // caller that ignores the rejection gets StateNotLoadedError on the first
@@ -659,6 +686,7 @@ module.exports = {
     saveState,
     onSaveFailure,
     takeStoredNetwork,
+    takeStoredTrackedTokens,
     loadState,
     currentAddress,
     currentNetwork,

src/shared/uniswap.js

@@ -479,6 +479,17 @@ function tokenInfo(address, sources) {
     };
 }
 
+// The token of a Permit2 allowance or of a PERMIT2_TRANSFER_FROM, in the
+// shape tokenInfo() gives. Permit2 has no allowance of ETH and moves no ETH.
+// The zero address there reads as a token nothing knows: its amount in base
+// units, and the zero address as its token.
+function permit2TokenInfo(address, sources) {
+    if (address === "0x0000000000000000000000000000000000000000") {
+        return { symbol: null, decimals: null, address };
+    }
+    return tokenInfo(address, sources);
+}
+
 // A swap amount line. With a scale it is the token quantity; with none it is
 // the base-unit integer with the unknown scale stated, the same refusal the
 // ERC-20 amount line makes, so the screen has one way of saying it. `display`
@@ -497,16 +508,18 @@ function amountText(raw, info) {
 
 // The line giving a moved token, or the token of a permit, under `label`, in
 // the shape of the Token In line, so the screens show it as they show that
-// one. ETH has no address.
-function tokenMovedLine(label, token, sources) {
-    const info = tokenInfo(token, sources);
+// one. `info` is what tokenInfo() or permit2TokenInfo() gives for the token.
+// ETH has no address.
+function tokenMovedLine(label, info) {
     if (!present(info.address)) {
         return { label, value: info.symbol };
     }
     return {
         label,
-        value: info.symbol ? info.symbol + " (" + token + ")" : token,
-        address: token,
+        value: info.symbol
+            ? info.symbol + " (" + info.address + ")"
+            : info.address,
+        address: info.address,
         isToken: true,
     };
 }
@@ -1616,13 +1629,13 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                     } else {
                         // The router passes this check whenever the owner
                         // holds at least minBalance, so a zero one guarantees
-                        // nothing and does not replace a minimum an earlier
-                        // step stated. A check the router lets fail guarantees
-                        // nothing either, so it is read as a zero one. Any
+                        // nothing. A check the router lets fail guarantees
+                        // nothing either, so it is read as a zero one. A zero
+                        // check sets neither Token Out nor the minimum. Any
                         // other minBalance sets the output side as a swap
-                        // does. It pays nobody.
+                        // does. The check pays nobody.
                         const minBalance = allowedToFail ? 0n : b.minBalance;
-                        if (!(minBalance === 0n && present(minOutput))) {
+                        if (minBalance !== 0n) {
                             setOutput(i, b.token, minBalance, []);
                         }
                         keepsRouterWeth = true;
@@ -2329,7 +2342,9 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                     : UNDECODED_CURRENCY,
             });
             if (present(s.token)) {
-                details.push(tokenMovedLine("Token moved", s.token, sources));
+                details.push(
+                    tokenMovedLine("Token moved", tokenInfo(s.token, sources)),
+                );
                 details.push({
                     label: "Moved to",
                     value: "The swap step that spends it",
@@ -2340,12 +2355,12 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
         // What each PERMIT2_TRANSFER_FROM moves: its amount, its token and
         // where it goes, an address on a line of its own.
         for (const m of movedFromSender) {
+            const info = permit2TokenInfo(m.token, sources);
             details.push({
                 label: "Moved from the sender",
-                value: amountText(m.amount, tokenInfo(m.token, sources))
-                    .display,
+                value: amountText(m.amount, info).display,
             });
-            details.push(tokenMovedLine("Token moved", m.token, sources));
+            details.push(tokenMovedLine("Token moved", info));
             details.push(
                 present(m.to)
                     ? { label: "Moved to", value: m.to }
@@ -2375,36 +2390,15 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                 });
                 continue;
             }
-            // Permit2 has no allowance of ETH. An allowance of the zero
-            // address reads as one of a token nothing knows: its amount in
-            // base units, and the zero address as its token.
-            if (p.token === "0x0000000000000000000000000000000000000000") {
-                details.push({
-                    label: "Permit2 allowance",
-                    value:
-                        p.amount >= MAX_UINT160
-                            ? "Unlimited"
-                            : unknownDecimalsAmount(p.amount),
-                });
-                details.push({
-                    label: "Allowance token",
-                    value: p.token,
-                    address: p.token,
-                    isToken: true,
-                });
-            } else {
-                details.push({
-                    label: "Permit2 allowance",
-                    value:
-                        p.amount >= MAX_UINT160
-                            ? "Unlimited"
-                            : amountText(p.amount, tokenInfo(p.token, sources))
-                                  .display,
-                });
-                details.push(
-                    tokenMovedLine("Allowance token", p.token, sources),
-                );
-            }
+            const info = permit2TokenInfo(p.token, sources);
+            details.push({
+                label: "Permit2 allowance",
+                value:
+                    p.amount >= MAX_UINT160
+                        ? "Unlimited"
+                        : amountText(p.amount, info).display,
+            });
+            details.push(tokenMovedLine("Allowance token", info));
             details.push({
                 label: "Allowance spender",
                 value: p.spender,
@@ -2462,7 +2456,7 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
             paidTo.push({ label: "Paid to", value: PAID_TO_BRIDGE });
         }
         for (const m of movedIntoRouter) {
-            const info = tokenInfo(m.token, sources);
+            const info = permit2TokenInfo(m.token, sources);
             paidTo.push({
                 label: "Paid to",
                 value:
@@ -2470,9 +2464,7 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                     amountText(m.amount, info).display +
                     " from the sender (later steps may not spend all of it)",
             });
-            paidTo.push(
-                tokenMovedLine("Token moved into the router", m.token, sources),
-            );
+            paidTo.push(tokenMovedLine("Token moved into the router", info));
         }
         if (outputHeld) {
             paidTo.push({ label: "Paid to", value: STAYS_IN_ROUTER });
@@ -2489,8 +2481,7 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
             paidTo.push(
                 tokenMovedLine(
                     "Token moved into the router",
-                    getAddress(token),
-                    sources,
+                    tokenInfo(getAddress(token), sources),
                 ),
             );
         }

tests/balanceRefreshNetworkSwitch.test.js

@@ -6,6 +6,10 @@
 // approved a site's request, which changes only the stored record. Driven
 // through the real popup over a stored profile on Ethereum Mainnet. The same
 // refresh in the background is in tests/backgroundStateIsolation.test.js.
+//
+// The last test covers a balance refresh by the background that is saved while
+// a switch in Settings waits for the lock
+// (https://git.eeqj.de/sneak/AutistMask/issues/653).
 
 const {
     bootPopup,
@@ -159,3 +163,50 @@ test("a refresh that returns after the background switched the network writes no
 
     expectNothingStored(page);
 });
+
+// The background's refresh saves Ethereum Mainnet's balances while the switch
+// in Settings waits for the lock. This page last saved a balance of "0" and no
+// token balances, the values that the switch sets.
+test("a background refresh saved while a switch in Settings waits for the lock leaves none of its balances stored", async () => {
+    const profile = unversionedValidProfile();
+    profile.wallets[0].addresses[0].balance = "0";
+    const page = await bootPopup(profile);
+    expect(page.pageErrors).toEqual([]);
+    const background = require("../src/background/state");
+    await page.click("btn-settings");
+
+    // The background takes the lock first and holds it until the test calls
+    // `letGo()`. It then saves balances as backgroundRefresh() in
+    // src/background/index.js does.
+    let letGo;
+    const refreshSave = background.updateState(async (fresh) => {
+        await new Promise((resolve) => {
+            letGo = resolve;
+        });
+        fresh.wallets[0].addresses[0].balance = "7.0";
+        fresh.wallets[0].addresses[0].tokenBalances = [
+            {
+                address: TOKEN_ADDRESS,
+                name: "Test Token",
+                symbol: "TST",
+                decimals: 18,
+                balance: "5.0",
+                holders: null,
+            },
+        ];
+        fresh.lastBalanceRefresh = Date.now();
+    });
+    await page.settle();
+
+    const select = page.node("settings-network");
+    select.value = "sepolia";
+    const switching = Promise.all(select.listeners.change.map((fn) => fn()));
+    await page.settle();
+
+    letGo();
+    await refreshSave;
+    await switching;
+    await page.settle();
+
+    expectNothingStored(page);
+});

tests/refreshDuringRefresh.test.js

@@ -0,0 +1,157 @@
+// While a refresh runs, a request through ctx is not dropped. One more refresh
+// runs once the running one ends, however many were asked for in that time
+// (https://git.eeqj.de/sneak/AutistMask/issues/581). A tick of the ten-second
+// timer that finds a refresh running is dropped. Each test boots the real popup
+// over a stored profile and holds the ten-second refresh open. `readChain()`
+// sets each address's balance from `CHAIN`, as the real `refreshBalances()`
+// sets it from the node.
+
+const {
+    bootPopup,
+    cleanupPopup,
+    unversionedValidProfile,
+    ADDRESS,
+} = require("./support/popupBoot");
+const {
+    hdWalletFromMnemonic,
+    deriveAddressFromXpub,
+} = require("../src/shared/wallet");
+
+const PHRASE =
+    "abandon abandon abandon abandon abandon abandon " +
+    "abandon abandon abandon abandon abandon about";
+const PASSWORD = "correct horse battery staple";
+
+// The first two addresses of PHRASE, both used on the chain.
+const { xpub, firstAddress } = hdWalletFromMnemonic(PHRASE);
+const SECOND_ADDRESS = deriveAddressFromXpub(xpub, 1);
+
+// The ETH balance the chain holds for each address, in ether.
+const CHAIN = {
+    [ADDRESS]: "1.5",
+    [firstAddress]: "2.0",
+    [SECOND_ADDRESS]: "3.0",
+};
+
+afterEach(() => {
+    cleanupPopup();
+});
+
+// The balance stand-in for a refresh that returns.
+async function readChain(wallets) {
+    for (const wallet of wallets) {
+        for (const addr of wallet.addresses) {
+            addr.balance = CHAIN[addr.address];
+        }
+    }
+}
+
+// Boots the popup over a profile with one wallet. From then on,
+// `refreshBalances()` never returns unless the test answers it. So an unwanted
+// refresh is counted once and then waits, instead of starting more.
+async function boot() {
+    const page = await bootPopup(unversionedValidProfile());
+    expect(page.pageErrors).toEqual([]);
+    const { refreshBalances } = require("../src/shared/balances");
+    refreshBalances.mockImplementation(() => new Promise(() => {}));
+    return { page, refreshBalances };
+}
+
+// Starts the ten-second refresh and holds it open until finish() is called.
+// The held refresh then writes the chain's balances. finish() resolves once
+// the held refresh has saved them and drawn Home. The one refresh after the
+// held one also returns.
+async function holdRefresh(page) {
+    const { refreshBalances } = require("../src/shared/balances");
+    let answer;
+    refreshBalances
+        .mockImplementationOnce(async (wallets) => {
+            await new Promise((resolve) => {
+                answer = resolve;
+            });
+            await readChain(wallets);
+        })
+        .mockImplementationOnce(readChain);
+    const ticking = page.tick();
+    await page.settle();
+    return {
+        finish: async () => {
+            answer();
+            await ticking;
+        },
+    };
+}
+
+// Imports PHRASE on AddWallet. Its address scan finds the phrase's first two
+// addresses.
+async function importPhrase(page) {
+    const { scanForAddresses } = require("../src/shared/balances");
+    scanForAddresses.mockImplementationOnce(async () => ({
+        addresses: [
+            { address: firstAddress, index: 0 },
+            { address: SECOND_ADDRESS, index: 1 },
+        ],
+        nextIndex: 2,
+    }));
+    await page.click("btn-add-wallet-bottom");
+    await page.click("tab-mnemonic");
+    page.node("wallet-mnemonic").value = PHRASE;
+    page.node("add-wallet-password").value = PASSWORD;
+    page.node("add-wallet-password-confirm").value = PASSWORD;
+    await page.click("btn-add-wallet-confirm");
+}
+
+// Imports the private key `key` on AddWallet.
+async function importKey(page, key) {
+    await page.click("btn-add-wallet-bottom");
+    await page.click("tab-privkey");
+    page.node("import-private-key").value = key;
+    page.node("add-wallet-password").value = PASSWORD;
+    page.node("add-wallet-password-confirm").value = PASSWORD;
+    await page.click("btn-add-wallet-confirm");
+}
+
+test("addresses that an import finds during a refresh show their balances once one more refresh returns", async () => {
+    const { page } = await boot();
+    const refresh = await holdRefresh(page);
+
+    await importPhrase(page);
+    expect(page.visibleViews()).toEqual(["main"]);
+    expect(page.text("flash-msg")).toBe("Found 2 addresses.");
+
+    await refresh.finish();
+    await page.settle();
+
+    const list = page.node("wallet-list").innerHTML;
+    expect(list).toContain("<span>2.0000</span>");
+    expect(list).toContain("<span>3.0000</span>");
+});
+
+test("several requests during a refresh lead to exactly one more refresh", async () => {
+    const { page, refreshBalances } = await boot();
+    const refresh = await holdRefresh(page);
+    const calls = refreshBalances.mock.calls.length;
+
+    await importKey(page, "0x" + "11".repeat(32));
+    await importKey(page, "0x" + "22".repeat(32));
+    await importPhrase(page);
+    expect(refreshBalances).toHaveBeenCalledTimes(calls);
+
+    await refresh.finish();
+    await page.settle();
+
+    expect(refreshBalances).toHaveBeenCalledTimes(calls + 1);
+});
+
+test("a tick of the ten-second timer during a refresh starts no other refresh", async () => {
+    const { page, refreshBalances } = await boot();
+    const refresh = await holdRefresh(page);
+    const calls = refreshBalances.mock.calls.length;
+
+    await page.tick();
+
+    await refresh.finish();
+    await page.settle();
+
+    expect(refreshBalances).toHaveBeenCalledTimes(calls);
+});

tests/settingsEndpointSave.test.js

@@ -0,0 +1,169 @@
+// Another page stores a different RPC or Blockscout URL for the same network.
+// Then the user taps "Save" in Settings on this page, on the URL that this page
+// loaded. The URL on screen is stored, and the flash message reads "Saved."
+// (https://git.eeqj.de/sneak/AutistMask/issues/688). Driven through the real
+// popup over a stored profile on Ethereum Mainnet.
+
+const {
+    bootPopup,
+    cleanupPopup,
+    unversionedValidProfile,
+} = require("./support/popupBoot");
+const { NETWORKS } = require("../src/shared/networks");
+
+afterEach(() => {
+    cleanupPopup();
+});
+
+test.each([
+    { button: "btn-save-rpc", input: "settings-rpc", field: "rpcUrl" },
+    {
+        button: "btn-save-blockscout",
+        input: "settings-blockscout",
+        field: "blockscoutUrl",
+    },
+])(
+    "$button stores the URL on screen after another page stored a different one",
+    async ({ button, input, field }) => {
+        const page = await bootPopup(unversionedValidProfile());
+        await page.click("btn-settings");
+        const url = page.value(input);
+        // This write sends this page no storage change event.
+        page.storage.write("autistmask", {
+            ...page.storage.read("autistmask"),
+            [field]: "https://other-page.example.invalid",
+        });
+        // This answer passes both endpoint checks on Ethereum Mainnet. The RPC
+        // check reads Ethereum Mainnet's chain id from it. The Blockscout check
+        // reads `ok`.
+        globalThis.fetch.mockResolvedValue({
+            ok: true,
+            json: async () => ({ result: NETWORKS.mainnet.chainId }),
+        });
+
+        await page.click(button);
+
+        expect(page.storage.read("autistmask")[field]).toBe(url);
+        expect(page.text("flash-msg")).toBe("Saved.");
+    },
+);
+
+// The user types a URL in Settings and taps "Save". While the check waits for
+// the endpoint's answer, another page turns "Use Blockscout" on. This page
+// follows that change and draws Settings again, with the stored URL in the
+// input. The check then passes. The typed URL is not stored. The flash message
+// says that the URL was changed during the check
+// (https://git.eeqj.de/sneak/AutistMask/issues/695).
+test.each([
+    { button: "btn-save-rpc", input: "settings-rpc", field: "rpcUrl" },
+    {
+        button: "btn-save-blockscout",
+        input: "settings-blockscout",
+        field: "blockscoutUrl",
+    },
+])(
+    "$button stores nothing when Settings is drawn again during the check",
+    async ({ button, input, field }) => {
+        const page = await bootPopup(unversionedValidProfile());
+        await page.click("btn-settings");
+        const storedUrl = page.value(input);
+        let answer;
+        globalThis.fetch.mockReturnValue(
+            new Promise((resolve) => {
+                answer = resolve;
+            }),
+        );
+
+        page.node(input).value = "https://typed.example.invalid";
+        const saving = page.node(button).listeners.click.map((fn) => fn());
+        await page.settle();
+        // The browser announces this write to this page.
+        await page.storage.local.set({
+            autistmask: {
+                ...page.storage.read("autistmask"),
+                useBlockscout: true,
+            },
+        });
+        await page.settle();
+        expect(page.node("settings-use-blockscout").checked).toBe(true);
+        // This answer passes both endpoint checks on Ethereum Mainnet.
+        answer({
+            ok: true,
+            json: async () => ({ result: NETWORKS.mainnet.chainId }),
+        });
+        await Promise.all(saving);
+        await page.settle();
+
+        expect(page.storage.read("autistmask")[field]).toBe(storedUrl);
+        expect(page.value(input)).toBe(storedUrl);
+        expect(page.text("flash-msg")).toBe(
+            "The URL was not saved because it was changed during the check.",
+        );
+    },
+);
+
+// As above, but another write holds the lock. So this page's follow of the
+// change to "Use Blockscout" waits for the lock. The endpoint answers while the
+// input still shows the typed URL. The save then asks for the lock, after the
+// follow did. So the follow draws Settings again before the save compares the
+// input.
+test.each([
+    { button: "btn-save-rpc", input: "settings-rpc", field: "rpcUrl" },
+    {
+        button: "btn-save-blockscout",
+        input: "settings-blockscout",
+        field: "blockscoutUrl",
+    },
+])(
+    "$button stores nothing when Settings is drawn again while the save waits for the lock",
+    async ({ button, input, field }) => {
+        const page = await bootPopup(unversionedValidProfile());
+        await page.click("btn-settings");
+        const storedUrl = page.value(input);
+        let answer;
+        globalThis.fetch.mockReturnValue(
+            new Promise((resolve) => {
+                answer = resolve;
+            }),
+        );
+        const typedUrl = "https://typed.example.invalid";
+
+        page.node(input).value = typedUrl;
+        const saving = page.node(button).listeners.click.map((fn) => fn());
+        await page.settle();
+        let releaseLock;
+        const lockHeld = navigator.locks.request(
+            "autistmask",
+            () =>
+                new Promise((resolve) => {
+                    releaseLock = resolve;
+                }),
+        );
+        // The browser announces this write to this page.
+        await page.storage.local.set({
+            autistmask: {
+                ...page.storage.read("autistmask"),
+                useBlockscout: true,
+            },
+        });
+        await page.settle();
+        // This answer passes both endpoint checks on Ethereum Mainnet.
+        answer({
+            ok: true,
+            json: async () => ({ result: NETWORKS.mainnet.chainId }),
+        });
+        await page.settle();
+        expect(page.value(input)).toBe(typedUrl);
+        releaseLock();
+        await lockHeld;
+        await Promise.all(saving);
+        await page.settle();
+
+        expect(page.node("settings-use-blockscout").checked).toBe(true);
+        expect(page.storage.read("autistmask")[field]).toBe(storedUrl);
+        expect(page.value(input)).toBe(storedUrl);
+        expect(page.text("flash-msg")).toBe(
+            "The URL was not saved because it was changed during the check.",
+        );
+    },
+);

tests/trackedTokensPerNetwork.test.js

@@ -5,6 +5,9 @@
 // a contract lookup that answers after one. Driven through the real popup over
 // a stored profile; the same switch made by the background is in
 // tests/coldWorkerChainSwitch.test.js.
+//
+// The tests of what another page stored before a switch in Settings cover a
+// fraud contract too (https://git.eeqj.de/sneak/AutistMask/issues/692).
 
 const {
     bootPopup,
@@ -177,6 +180,164 @@ test("a token added by contract address on Sepolia is tracked on Sepolia only",
     expect(onSepolia).not.toContain("DAI");
 });
 
+// Another popup page tracks DAI on Ethereum Mainnet after this page's last
+// save. The switch to Sepolia puts DAI away under Ethereum Mainnet.
+test("a token another page tracked before a switch in Settings stays tracked on Ethereum Mainnet", async () => {
+    const boot = await bootPopup(unversionedValidProfile());
+    expect(boot.pageErrors).toEqual([]);
+    boot.storage.write("autistmask", {
+        ...boot.storage.read("autistmask"),
+        trackedTokens: [MAINNET_TOKEN],
+    });
+
+    await boot.click("btn-settings");
+    await chooseNetwork(boot, "sepolia");
+
+    const stored = boot.storage.read("autistmask");
+    expect(stored.networkId).toBe("sepolia");
+    expect(stored.trackedTokens).toEqual([]);
+    expect(stored.networkTrackedTokens.mainnet).toEqual([MAINNET_TOKEN]);
+});
+
+// Another popup page stops tracking DAI on Ethereum Mainnet after this page's
+// last save. This page still holds DAI. The switch to Sepolia does not store
+// DAI under Ethereum Mainnet again.
+test("a token another page removed before a switch in Settings stays removed", async () => {
+    const boot = await bootPopup(
+        unversionedValidProfile({ trackedTokens: [MAINNET_TOKEN] }),
+    );
+    expect(boot.pageErrors).toEqual([]);
+    boot.storage.write("autistmask", {
+        ...boot.storage.read("autistmask"),
+        trackedTokens: [],
+    });
+
+    await boot.click("btn-settings");
+    await chooseNetwork(boot, "sepolia");
+
+    const stored = boot.storage.read("autistmask");
+    expect(stored.networkId).toBe("sepolia");
+    expect(stored.trackedTokens).toEqual([]);
+    expect(stored.networkTrackedTokens.mainnet).toEqual([]);
+});
+
+// Another popup page removes DAI after this page's last save. That page then
+// adds DAI again, typing the contract address in lower case. The two pages'
+// entries for DAI match, because contract addresses are compared ignoring
+// letter case. The switch to Sepolia keeps this page's entry under Ethereum
+// Mainnet.
+test("a token another page added again with a lower-case address keeps this page's entry", async () => {
+    const boot = await bootPopup(
+        unversionedValidProfile({ trackedTokens: [MAINNET_TOKEN] }),
+    );
+    expect(boot.pageErrors).toEqual([]);
+    boot.storage.write("autistmask", {
+        ...boot.storage.read("autistmask"),
+        trackedTokens: [
+            { ...MAINNET_TOKEN, address: MAINNET_TOKEN.address.toLowerCase() },
+        ],
+    });
+
+    await boot.click("btn-settings");
+    await chooseNetwork(boot, "sepolia");
+
+    const stored = boot.storage.read("autistmask");
+    expect(stored.networkId).toBe("sepolia");
+    expect(stored.networkTrackedTokens.mainnet).toEqual([MAINNET_TOKEN]);
+});
+
+// Another popup page saves a switch to Sepolia after this page's last save.
+// TST is tracked on Sepolia. This page has not taken that switch yet. A switch
+// to Sepolia in this page's Settings keeps TST off Ethereum Mainnet's list.
+test("a token tracked on Sepolia when another page switched there is not tracked on Ethereum Mainnet", async () => {
+    const boot = await bootPopup(unversionedValidProfile());
+    expect(boot.pageErrors).toEqual([]);
+    await boot.click("btn-settings");
+    boot.storage.write("autistmask", {
+        ...boot.storage.read("autistmask"),
+        networkId: "sepolia",
+        trackedTokens: [SEPOLIA_TOKEN],
+    });
+
+    await chooseNetwork(boot, "sepolia");
+
+    const stored = boot.storage.read("autistmask");
+    expect(stored.networkId).toBe("sepolia");
+    expect(stored.trackedTokens).toEqual([SEPOLIA_TOKEN]);
+    expect(stored.networkTrackedTokens.mainnet).toEqual([]);
+});
+
+// Another popup page records a fraud contract on Ethereum Mainnet after this
+// page's last save. The switch to Sepolia drops that fraud contract, as the
+// switch drops this page's own.
+test("a fraud contract another page recorded before a switch in Settings is not kept on Sepolia", async () => {
+    const boot = await bootPopup(unversionedValidProfile());
+    expect(boot.pageErrors).toEqual([]);
+    boot.storage.write("autistmask", {
+        ...boot.storage.read("autistmask"),
+        fraudContracts: [NEW_TOKEN_ADDRESS],
+    });
+
+    await boot.click("btn-settings");
+    await chooseNetwork(boot, "sepolia");
+
+    const stored = boot.storage.read("autistmask");
+    expect(stored.networkId).toBe("sepolia");
+    expect(stored.fraudContracts).toEqual([]);
+});
+
+// The contract lookup on SettingsAddToken answers on Ethereum Mainnet while the
+// switch to Sepolia waits for the lock. The page adds the token to Ethereum
+// Mainnet's list. The switch then keeps that list for Ethereum Mainnet.
+test("a token added while a switch in Settings waits for the lock stays tracked on Ethereum Mainnet", async () => {
+    const boot = await bootOnAddToken("mainnet");
+    expect(boot.pageErrors).toEqual([]);
+    const { lookupTokenInfo } = require("../src/shared/balances");
+    let answer;
+    lookupTokenInfo.mockImplementationOnce(
+        () =>
+            new Promise((resolve) => {
+                answer = resolve;
+            }),
+    );
+    boot.node("settings-addtoken-address").value = NEW_TOKEN_ADDRESS;
+    const adding = boot.click("btn-settings-addtoken-manual");
+    await boot.click("btn-settings");
+
+    // Another write holds the lock, so the switch's save waits for it.
+    let releaseLock;
+    const lockHeld = navigator.locks.request(
+        "autistmask",
+        () =>
+            new Promise((resolve) => {
+                releaseLock = resolve;
+            }),
+    );
+    const select = boot.node("settings-network");
+    select.value = "sepolia";
+    const switching = Promise.all(select.listeners.change.map((fn) => fn()));
+    await boot.settle();
+
+    answer({ symbol: "NEW", decimals: 18, name: "New Token" });
+    await boot.settle();
+    releaseLock();
+    await lockHeld;
+    await switching;
+    await adding;
+
+    const stored = boot.storage.read("autistmask");
+    expect(stored.networkId).toBe("sepolia");
+    expect(stored.trackedTokens).toEqual([]);
+    expect(stored.networkTrackedTokens.mainnet).toEqual([
+        {
+            address: NEW_TOKEN_ADDRESS,
+            symbol: "NEW",
+            decimals: 18,
+            name: "New Token",
+        },
+    ]);
+});
+
 describe("Back after a switch from the Settings gear", () => {
     test("SettingsAddToken no longer offers the common tokens", async () => {
         const boot = await bootOnAddToken("mainnet");

tests/transactionDetailLateAnswer.test.js

@@ -0,0 +1,202 @@
+// TransactionDetail shows only details that Blockscout gave for the
+// transaction on screen (https://git.eeqj.de/sneak/AutistMask/issues/675).
+//
+// The screen asks Blockscout for its transaction and does not wait for the
+// answer. So the user can press Back and open another transaction before
+// Blockscout answers for the first. The first answer must then fill nothing on
+// the second transaction's screen. An answer that lands while Settings is up
+// must still fill TransactionDetail.
+//
+// Driven through the real popup over a stored profile
+// (tests/support/popupBoot.js). Each transaction is opened as a history screen
+// opens it: the current screen is pushed, then transactionDetail.show() draws
+// the transaction.
+
+"use strict";
+
+const {
+    bootPopup,
+    cleanupPopup,
+    unversionedValidProfile,
+    ADDRESS,
+} = require("./support/popupBoot");
+
+const MAINNET_BLOCKSCOUT = "https://eth.blockscout.com/api/v2";
+const SEPOLIA_BLOCKSCOUT = "https://eth-sepolia.blockscout.com/api/v2";
+const RECIPIENT = "0x2222222222222222222222222222222222222222";
+
+// A history entry for a send of 1 `symbol` from ADDRESS to RECIPIENT, on the
+// network with `chainId`.
+function historyEntry(hash, chainId, symbol) {
+    return {
+        hash,
+        from: ADDRESS,
+        to: RECIPIENT,
+        value: "1.0000",
+        exactValue: "1.0",
+        symbol,
+        timestamp: 1790000000,
+        isError: false,
+        direction: "sent",
+        directionLabel: "Sent",
+        contractAddress: null,
+        chainId,
+    };
+}
+
+const FIRST = historyEntry("0x" + "aa".repeat(32), "0x1", "ETH");
+const SECOND = historyEntry("0x" + "bb".repeat(32), "0x1", "ETH");
+// A transaction on Sepolia with the same hash as FIRST.
+const FIRST_ON_SEPOLIA = historyEntry(FIRST.hash, "0xaa36a7", "SepoliaETH");
+
+// The URL that asks Blockscout for `entry`, on the network it was sent on.
+function requestUrl(entry) {
+    const blockscout =
+        entry.chainId === "0x1" ? MAINNET_BLOCKSCOUT : SEPOLIA_BLOCKSCOUT;
+    return blockscout + "/transactions/" + entry.hash;
+}
+
+// What Blockscout reports for each transaction, by the URL that asks for it.
+const ANSWERS = {
+    [requestUrl(FIRST)]: {
+        block_number: 21000001,
+        nonce: 4441,
+        fee: { value: "21000000000000" },
+        raw_input: "0x11111111",
+        method: "firstMethod",
+    },
+    [requestUrl(SECOND)]: {
+        block_number: 21000002,
+        nonce: 4442,
+        fee: { value: "42000000000000" },
+        raw_input: "0x22222222",
+        method: "secondMethod",
+    },
+    [requestUrl(FIRST_ON_SEPOLIA)]: {
+        block_number: 21000003,
+        nonce: 4443,
+        fee: { value: "63000000000000" },
+        raw_input: "0x33333333",
+        method: "sepoliaMethod",
+    },
+};
+
+// The text each answer puts on screen: its block, nonce, fee, method name and
+// raw data. No text from one answer appears in another.
+const FIRST_SHOWN = [
+    "21000001",
+    "4441",
+    "0.000021 ETH",
+    "firstMethod",
+    "0x11111111",
+];
+const SECOND_SHOWN = [
+    "21000002",
+    "4442",
+    "0.000042 ETH",
+    "secondMethod",
+    "0x22222222",
+];
+const FIRST_ON_SEPOLIA_SHOWN = [
+    "21000003",
+    "4443",
+    "0.000063 SepoliaETH",
+    "sepoliaMethod",
+    "0x33333333",
+];
+
+// Everything drawn in the fields that Blockscout's answer fills.
+function drawnDetails(page) {
+    return [
+        "tx-detail-block",
+        "tx-detail-nonce",
+        "tx-detail-fee",
+        "tx-detail-calldata-action",
+        "tx-detail-rawdata",
+    ]
+        .map((id) => page.node(id).innerHTML + page.node(id).textContent)
+        .join("\n");
+}
+
+// Opens `entry` on TransactionDetail, as a history screen does.
+function open(entry) {
+    require("../src/popup/views/helpers").pushCurrentView();
+    require("../src/popup/views/transactionDetail").show(entry);
+}
+
+// The URLs of every request to Blockscout so far, in order.
+function requestedUrls() {
+    return globalThis.fetch.mock.calls.map(([url]) => url);
+}
+
+// Boots the popup on Home with "Use Blockscout" on. Blockscout answers every
+// request at once from ANSWERS, except the request for `held`. Returns the
+// page and answer(), which lets the answer for `held` land.
+async function bootWithHeldRequest(held) {
+    const page = await bootPopup(
+        unversionedValidProfile({ useBlockscout: true }),
+    );
+    let answer;
+    const heldAnswer = new Promise((resolve) => {
+        answer = resolve;
+    });
+    globalThis.fetch = jest.fn(async (url) => {
+        if (url === requestUrl(held)) await heldAnswer;
+        return { ok: true, status: 200, json: async () => ANSWERS[url] };
+    });
+    return { page, answer: () => answer() };
+}
+
+// The user opens `first`, whose request to Blockscout is held. Then the user
+// presses Back and opens `second`. Then the answer for `first` lands. Returns
+// the page.
+async function firstAnswerLandsOnSecond(first, second) {
+    const { page, answer } = await bootWithHeldRequest(first);
+    open(first);
+    await page.settle();
+    await page.click("btn-tx-back");
+    expect(page.visibleViews()).toEqual(["main"]);
+    open(second);
+    await page.settle();
+    expect(requestedUrls()).toEqual([requestUrl(first), requestUrl(second)]);
+    answer();
+    await page.settle();
+    expect(page.visibleViews()).toEqual(["transaction"]);
+    return page;
+}
+
+afterEach(() => {
+    cleanupPopup();
+});
+
+test("an answer for the first transaction that lands on the second one's screen fills nothing", async () => {
+    const page = await firstAnswerLandsOnSecond(FIRST, SECOND);
+
+    const drawn = drawnDetails(page);
+    for (const text of SECOND_SHOWN) expect(drawn).toContain(text);
+    for (const text of FIRST_SHOWN) expect(drawn).not.toContain(text);
+});
+
+test("an answer for a hash on mainnet that lands on the same hash's screen on Sepolia fills nothing", async () => {
+    const page = await firstAnswerLandsOnSecond(FIRST, FIRST_ON_SEPOLIA);
+
+    const drawn = drawnDetails(page);
+    for (const text of FIRST_ON_SEPOLIA_SHOWN) expect(drawn).toContain(text);
+    for (const text of FIRST_SHOWN) expect(drawn).not.toContain(text);
+});
+
+test("an answer that lands while Settings is up still fills TransactionDetail", async () => {
+    const { page, answer } = await bootWithHeldRequest(FIRST);
+    open(FIRST);
+    await page.settle();
+    await page.click("btn-settings");
+    expect(page.visibleViews()).toEqual(["settings"]);
+    answer();
+    await page.settle();
+    await page.click("btn-settings");
+
+    expect(page.visibleViews()).toEqual(["transaction"]);
+    expect(requestedUrls()).toEqual([requestUrl(FIRST)]);
+    const drawn = drawnDetails(page);
+    for (const text of FIRST_SHOWN) expect(drawn).toContain(text);
+});

tests/uniswap.test.js

@@ -3440,6 +3440,82 @@ describe("uniswap decoder", () => {
             });
         });
 
+        // https://git.eeqj.de/sneak/AutistMask/issues/685 — Permit2 moves no
+        // ETH, so a PERMIT2_TRANSFER_FROM of the zero address reads as a move
+        // of a token nothing knows. On next at ec6b6b5 its lines read ETH,
+        // with an ETH figure.
+        describe("a PERMIT2_TRANSFER_FROM of the zero address", () => {
+            const MOVED_AMOUNT =
+                "1000000000000000000 base units (decimals unknown)";
+
+            test("to another address names the address", () => {
+                const result = decodeSteps(
+                    [0x00, 0x02],
+                    [V3_600, transfer(ZERO_ADDR, OTHER_ADDR, ONE_WETH)],
+                );
+                expect(linesBetweenTokens(result)).toEqual([
+                    ["Amount", "600.0000 USDT"],
+                    ["Moved from the sender", MOVED_AMOUNT],
+                    ["Token moved", ZERO_ADDR],
+                    ["Moved to", OTHER_ADDR],
+                ]);
+                expect(detail(result, "Token moved").address).toBe(ZERO_ADDR);
+            });
+
+            test("into the router names the address", () => {
+                const result = decodeSteps(
+                    [0x02, 0x00],
+                    [transfer(ZERO_ADDR, ROUTER_ADDR, ONE_WETH), V3_600],
+                );
+                expect(detail(result, "Paid to").value).toBe(
+                    "The router, " +
+                        MOVED_AMOUNT +
+                        " from the sender (later steps may not spend all of it)",
+                );
+                expect(detail(result, "Token moved into the router")).toEqual({
+                    label: "Token moved into the router",
+                    value: ZERO_ADDR,
+                    address: ZERO_ADDR,
+                    isToken: true,
+                });
+            });
+
+            // The V4 step's SETTLE names the user as payer and states no
+            // amount. The step's lines say that the ETH amount is not known.
+            test("after a V4 exact-out step of ETH, also shows that the ETH amount is not known", () => {
+                const v4EthExactOut = encodeV4Swap(
+                    new Uint8Array([
+                        V4_SWAP_EXACT_OUT_SINGLE_ID,
+                        V4_SETTLE_ID,
+                        V4_TAKE_ALL_ID,
+                    ]),
+                    [
+                        encodeV4ExactOutSingle(
+                            ZERO_ADDR,
+                            USDC_ADDR,
+                            590000000n,
+                            ONE_WETH,
+                        ),
+                        encodeV4Settle(ZERO_ADDR),
+                        encodeV4TakeAll(USDC_ADDR, 0n),
+                    ],
+                );
+                const result = decodeSteps(
+                    [0x10, 0x02],
+                    [v4EthExactOut, transfer(ZERO_ADDR, OTHER_ADDR, ONE_WETH)],
+                );
+                expect(detail(result, "Token In").value).toBe("ETH (native)");
+                expect(linesBetweenTokens(result)).toEqual([
+                    ["Moved from the sender", UNDECODED],
+                    ["Token moved", "ETH"],
+                    ["Moved to", "The swap step that spends it"],
+                    ["Moved from the sender", MOVED_AMOUNT],
+                    ["Token moved", ZERO_ADDR],
+                    ["Moved to", OTHER_ADDR],
+                ]);
+            });
+        });
+
         // https://git.eeqj.de/sneak/AutistMask/issues/682 — V4 pays a SETTLE
         // of ETH from the router's own ETH, whichever payer the SETTLE names,
         // and the router holds the transaction's value. On next at 36b2002 a
@@ -4304,10 +4380,9 @@ describe("uniswap decoder", () => {
         expect(detail(result, "Min. received").value).toBe("2.0000 USDC");
     });
 
-    // With no minimum stated before it, a zero balance check is what sets the
-    // output side, and it guarantees nothing. No step pays anyone, so the
-    // minimum is not said to be received.
-    test("a zero balance check with no earlier minimum states no minimum", () => {
+    // A zero balance check sets neither Token Out nor the minimum. The route
+    // pays only the WRAP_ETH's WETH, to the router, where it stays.
+    test("a zero balance check after a WRAP_ETH into the router names no output token and no minimum", () => {
         const data = buildExecute(
             solidityPacked(["uint8", "uint8"], [0x0b, 0x0e]),
             [
@@ -4320,9 +4395,16 @@ describe("uniswap decoder", () => {
         const result = uniswap.decode(data, ROUTER_ADDR, "0x1", {}, USER_ADDR);
         expect(result).not.toBeNull();
 
-        expect(detail(result, "Token Out").value).toContain("USDT");
-        expect(detail(result, "Min. paid out").value).toBe(
-            "None (no minimum guaranteed)",
+        expect(detail(result, "Token Out").value).toBe(
+            "Unknown (not named in the calldata)",
+        );
+        expect(detail(result, "Min. paid out")).toBeUndefined();
+        expect(detail(result, "Min. received")).toBeUndefined();
+        expect(detail(result, "Paid to").value).toBe(
+            "The router, where it stays (no later step pays it out)",
+        );
+        expect(detail(result, "Token moved into the router").address).toBe(
+            WETH_ADDR,
         );
     });
 

tests/uniswapRecipient.test.js

@@ -688,6 +688,62 @@ describe("an UNWRAP_WETH makes the output ETH only when the router holds it", ()
         ]);
     });
 
+    // The same route, then a balance check of the sender's USDC with a zero
+    // minimum. The check guarantees nothing, so Token Out stays ETH
+    // (https://git.eeqj.de/sneak/AutistMask/issues/649).
+    test("the same route, then a zero balance check of USDC, still reads as ETH with no minimum", () => {
+        const result = decode(
+            execute(
+                v4Swap(
+                    SWAP_USDT_FOR_WETH,
+                    SETTLE_USDT,
+                    take(WETH, MSG_SENDER, (ONE_WETH * 6n) / 10n),
+                    take(WETH, ADDRESS_THIS),
+                ),
+                unwrapWeth(MSG_SENDER),
+                balanceCheck(USDC, 0n),
+            ),
+        );
+        expect(result.name).toBe("Swap USDT → ETH");
+        expect(detail(result, "Token Out").value).toBe("ETH");
+        expect(labels(result)).toEqual([
+            "Protocol",
+            "Token In",
+            "Amount",
+            "Token Out",
+            "Steps",
+            "Deadline",
+        ]);
+    });
+
+    // A PERMIT2_TRANSFER_FROM moves the sender's WETH into the router. An
+    // UNWRAP_WETH pays that WETH to the user as ETH. A zero balance check of
+    // USDC sets neither Token Out nor the minimum, before the UNWRAP_WETH or
+    // after it (https://git.eeqj.de/sneak/AutistMask/issues/649).
+    test.each([
+        {
+            kind: "before the UNWRAP_WETH",
+            steps: [balanceCheck(USDC, 0n), unwrapWeth(MSG_SENDER)],
+        },
+        {
+            kind: "after the UNWRAP_WETH",
+            steps: [unwrapWeth(MSG_SENDER), balanceCheck(USDC, 0n)],
+        },
+    ])(
+        "WETH moved into the router and unwrapped, with a zero balance check of USDC $kind, reads as ETH with no minimum",
+        ({ steps }) => {
+            const result = decode(
+                execute(
+                    permit2TransferFrom(WETH, ADDRESS_THIS, ONE_WETH),
+                    ...steps,
+                ),
+            );
+            expect(detail(result, "Token Out").value).toBe("ETH");
+            expect(detail(result, "Min. received")).toBeUndefined();
+            expect(detail(result, "Min. paid out")).toBeUndefined();
+        },
+    );
+
     // A TAKE the decoder cannot read may pay part of the WETH to the user.
     test("one V4 step paying WETH to the router beside a TAKE that cannot be read, then an UNWRAP_WETH, reads as ETH with no minimum", () => {
         const result = decode(
@@ -2820,17 +2876,16 @@ describe("the allow-revert flag", () => {
         },
     );
 
-    test("a BALANCE_CHECK_ERC20 with the flag, and no minimum before it, states none", () => {
+    test("a BALANCE_CHECK_ERC20 with the flag, and no minimum before it, names no output token and no minimum", () => {
         const check = balanceCheck(WETH, ONE_WETH);
         expect(detail(decode(execute(check)), "Min. paid out").value).toBe(
             "1.0000 WETH",
         );
 
         const withFlag = decode(execute(flagged(check)));
-        expect(detail(withFlag, "Token Out").address).toBe(WETH);
-        expect(detail(withFlag, "Min. paid out").value).toBe(
-            "None (no minimum guaranteed)",
-        );
+        expect(detail(withFlag, "Token Out").value).toBe(UNNAMED);
+        expect(detail(withFlag, "Min. paid out")).toBeUndefined();
+        expect(detail(withFlag, "Min. received")).toBeUndefined();
     });
 
     // Only the routers from UniversalRouterV2 on let a PERMIT2_PERMIT fail.