fix: a balance refresh that returns after a network switch writes nothing (closes #577)

The popup's doRefreshAndRender() and the background's backgroundRefresh()
each note the network a refresh starts on and write its balances only if
that network is still the active one when the requests return. Otherwise
nothing is written and lastBalanceRefresh stays as the switch left it. The
background checks inside updateState(). The popup refreshes a copy of its
wallets and copies the results onto `state` from inside its save, under the
lock, only if both its own network and the stored record's still match, so
a switch the background makes is caught too. saveState() takes an optional
function, run there on the stored record before the page's state is
compared, that may change `state` or return false to cancel the write.

Model: opus-5-5

README.md

@@ -1260,17 +1260,29 @@ runs (Transaction Decoding below gives what the router holds). The router
 unwraps only the WETH it holds, so WETH that step paid to the user, or to anyone
 else, stays WETH: a swap that pays the router WETH, then a swap that pays the
 user WETH, then an unwrap, shows WETH with the second swap's minimum. The
-minimum reads in ETH when that step paid all its WETH to the router. When it
-paid only part of it to the router, as a V4 step does that `TAKE`s some of its
-WETH to the user and the rest to the router, or paid the router WETH beside a
-payout the decoder cannot read, the swap shows ETH with no minimum: the decoder
-does not count how much of that step's minimum reaches the router, nor read the
-`UNWRAP_WETH`'s own minimum. A later step that sets the output side sets it
-anew. Otherwise `Token Out` and `Min. received` keep the output side's own token
-and figure, whether the swap was paid in ETH or in a token: a V2 exact-out swap
-that buys USDC and then unwraps the WETH it did not spend shows USDC. The token
-permission warning on the signature screen has its own amount wording, including
-`Unknown`; the SignApproval section below describes it.
+minimum reads in ETH only when that step paid all its WETH to the router and
+every step between it and the `UNWRAP_WETH` is one the decoder read of these: a
+`PERMIT2_PERMIT`, a `BALANCE_CHECK_ERC20`, or a `SWEEP`, `TRANSFER`,
+`PAY_PORTION` or `PAY_PORTION_FULL_PRECISION` of a token other than WETH, but
+not of ETH to a WETH contract, which pays the router WETH. None of these can
+take WETH out of the router or pay anyone WETH; the decoder treats every other
+step as one that may. Otherwise the swap shows ETH with no minimum, as it does
+after a V4 step that `TAKE`s some of its WETH to the user and the rest to the
+router, or that pays the router WETH beside a payout the decoder cannot read,
+and with a WETH interface fee paid by `PAY_PORTION` before the `UNWRAP_WETH`:
+the decoder does not count how much of that step's minimum reaches the
+`UNWRAP_WETH`, nor read the `UNWRAP_WETH`'s own minimum. When an `UNWRAP_WETH`
+of that WETH pays the router, or its recipient cannot be read, the router may
+hold the ETH, and a later step may pay it out as WETH, as a `WRAP_ETH` of it to
+the user does: after any later step but those listed, the swap shows WETH with
+no minimum. Once the swap shows no minimum, or shows WETH this way, no later
+step, a later `UNWRAP_WETH` included, brings back the minimum or ETH; only a
+later step that sets the output side sets it anew. Otherwise `Token Out` and
+`Min. received` keep the output side's own token and figure, whether the swap
+was paid in ETH or in a token: a V2 exact-out swap that buys USDC and then
+unwraps the WETH it did not spend shows USDC. The token permission warning on
+the signature screen has its own amount wording, including `Unknown`; the
+SignApproval section below describes it.
 
 The swap's `Deadline` line is the router's deadline as a UTC date and time, e.g.
 `2026-02-27 08:25:51`. A JavaScript date reaches only to 275760-09-13 00:00:00
@@ -2080,8 +2092,11 @@ view would leave a wallet one click from deletion.
       none, and the tokens tracked on that network, and sends `chainChanged`
       with the new chain id to every open tab. A token is tracked only on the
       network it was added on, because a contract address names a token on one
-      network only. Choosing the network already active changes nothing and
-      sends nothing
+      network only. Switching also clears every address's balances. A balance
+      refresh, by the popup or the background, stores what it fetched only if
+      the stored network is still the one it fetched on when it returns, so the
+      previous network's balances never reach the new one. Choosing the network
+      already active changes nothing and sends nothing
     - Ethereum RPC: endpoint URL input + "Save" button (validated against
       `eth_chainId` before being saved)
     - Blockscout API: endpoint URL input + "Save" button (validated against

src/background/index.js

@@ -1379,6 +1379,13 @@ const RECENT_BALANCE_REFRESH_MS = Math.floor(BALANCE_REFRESH_PERIOD_MS / 2);
 // balances that came back — by address, onto whatever storage holds NOW.
 // Applying by address rather than writing the array back is what keeps a
 // wallet or address added, renamed or deleted during the round trip.
+//
+// Nothing is applied when the network stored NOW is not the one the refresh
+// ran on. A network switch during the round trip cleared every address's
+// balances (applyChainSwitchFields()), and the previous network's must not come
+// back over them (https://git.eeqj.de/sneak/AutistMask/issues/577).
+// lastBalanceRefresh is left as the switch set it, so the next tick refreshes
+// the new network.
 async function backgroundRefresh() {
     const s = await getState();
     const now = Date.now();
@@ -1402,6 +1409,7 @@ async function backgroundRefresh() {
     }
 
     await updateState((fresh) => {
+        if (fresh.networkId !== s.networkId) return;
         for (const wallet of fresh.wallets) {
             for (const addr of wallet.addresses || []) {
                 const got = refreshed.get(String(addr.address).toLowerCase());

src/popup/index.js

@@ -68,23 +68,54 @@ let refreshInFlight = false;
 // the recovery screen: there is no profile left to refresh.
 let refreshTimer = null;
 
+// The refresh writes into a copy of the wallets. Inside the save, under the
+// lock, its results are copied onto the address records in `state` only if the
+// network it ran on is still the active one, on this page and in the stored
+// record; the background's switch, after the user approves a site's request,
+// changes only the stored record. A switch while the refresh ran cleared every
+// address's balances (applyChainSwitchFields() in
+// src/shared/chainSwitchFields.js), and the previous network's must not come
+// back over them (https://git.eeqj.de/sneak/AutistMask/issues/577). A dropped
+// refresh is not recorded as done. Results are copied by address, so an address
+// added or removed meanwhile is left as it is.
 async function doRefreshAndRender() {
     if (refreshInFlight) return;
     refreshInFlight = true;
     try {
+        const networkId = state.networkId;
+        const wallets = structuredClone(state.wallets);
         await Promise.all([
             refreshPrices(),
             refreshBalances(
-                state.wallets,
+                wallets,
                 state.rpcUrl,
                 state.blockscoutUrl,
                 state.trackedTokens,
-                state.networkId,
+                networkId,
                 pageClosed.signal,
             ),
         ]);
-        state.lastBalanceRefresh = Date.now();
-        await saveState();
+        const refreshed = new Map();
+        for (const wallet of wallets) {
+            for (const addr of wallet.addresses) {
+                refreshed.set(addr.address, addr);
+            }
+        }
+        await saveState((stored) => {
+            if (state.networkId !== networkId) return false;
+            if (stored.networkId !== networkId) return false;
+            for (const wallet of state.wallets) {
+                for (const addr of wallet.addresses) {
+                    const got = refreshed.get(addr.address);
+                    if (!got) continue;
+                    for (const key of ["balance", "ensName", "tokenBalances"]) {
+                        if (got[key] !== undefined) addr[key] = got[key];
+                    }
+                }
+            }
+            state.lastBalanceRefresh = Date.now();
+            return true;
+        });
         renderWalletList();
     } catch (e) {
         // Every call site fires this and walks away — the boot below, the ten

src/shared/state.js

@@ -467,11 +467,7 @@ function mergeNetworkEndpoints(base, ours, theirs) {
 // (caught by tests/txStatus.test.js). A page's live picture of a field it
 // does not own goes on being whatever its last loadState() saw, same as
 // before this fix; only the persisted record is guaranteed current.
-async function saveStateOnce() {
-    // A copy, so what this save compares and writes is the page's state as it
-    // stood when the save began. A change made while it waits on storage is
-    // left for the next save, which compares against this copy.
-    const current = structuredClone(snapshotPersisted());
+async function saveStateOnce(beforeWrite) {
     const result = await storageGet("autistmask");
     // The record in storage right now is about to be merged into and written
     // back, so it is validated exactly like a load validates it. Without this,
@@ -485,6 +481,12 @@ async function saveStateOnce() {
     // come from storage in its loaded (self-healed) shape. See
     // normalizePersisted() in persistedState.js.
     const fresh = normalizePersisted(result.autistmask);
+    if (beforeWrite && beforeWrite(fresh) === false) return;
+
+    // A copy, so what this save compares and writes is the page's state as it
+    // stood once the stored record was read. A change made while it waits on
+    // the write is left for the next save, which compares against this copy.
+    const current = structuredClone(snapshotPersisted());
 
     const merged = { ...fresh };
     for (const key of PERSISTED_FIELDS) {
@@ -579,10 +581,15 @@ function reportSaveFailure(err) {
 // The same lock orders this page's own saves. showView() calls saveState() on
 // every navigation without awaiting it, so two saves from one page can be
 // asked for at once; they take the lock in the order they were asked, and each
-// compares the page's state as it stands when its turn begins against the
-// baseline the save before it left.
-function saveState() {
-    const turn = withLock("autistmask", saveStateOnce);
+// compares the page's state, as it stands once the stored record has been read
+// and `beforeWrite` has run, against the baseline the save before it left.
+//
+// `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.
+function saveState(beforeWrite) {
+    const turn = withLock("autistmask", () => saveStateOnce(beforeWrite));
     // Every failed save is reported, whether or not the caller awaited this
     // one. The returned promise still rejects, so a caller that DOES await
     // keeps its own error handling.

src/shared/uniswap.js

@@ -1221,8 +1221,23 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
         let hasUnwrapWeth = false;
         // Set when an UNWRAP_WETH pays out, as ETH, the output side's WETH,
         // which the router holds; cleared whenever the output side is set
-        // again.
+        // again, or a later step may pay that ETH out as WETH (see after the
+        // loop). `unwrapIntoRouterStep` is the index of the first such
+        // UNWRAP_WETH that may have paid the ETH to the router, which then
+        // holds it: its recipient is the router or cannot be read. A later
+        // UNWRAP_WETH does not replace it. It is null when there is none, and
+        // is cleared with `outputUnwrapped` when the output side is set again.
         let outputUnwrapped = false;
+        let unwrapIntoRouterStep = null;
+        // The index of the step that set the output side.
+        let outputStep = -1;
+        // The index of the last step this decoder treats as one that may take
+        // WETH out of the router or pay anyone WETH: any step but one it read
+        // that is a PERMIT2_PERMIT, a BALANCE_CHECK_ERC20, or a SWEEP,
+        // TRANSFER, PAY_PORTION or PAY_PORTION_FULL_PRECISION of a token
+        // other than WETH, and not of ETH to a WETH contract, which pays the
+        // router WETH (see keepsRouterWeth in the loop). None of those can.
+        let lastWethStep = -1;
         // Where the step that set the output side paid its output: the
         // recipient of a swap step, as written, or of each TAKE, TAKE_ALL and
         // TAKE_PORTION of it in a V4 step, a TAKE_ALL as paid to the sender,
@@ -1265,13 +1280,15 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
             if (!present(token) && !present(amount)) return;
             setInput(token, amount);
         };
-        const setOutput = (token, amount, recipients) => {
+        const setOutput = (step, token, amount, recipients) => {
             if (!present(token) && !present(amount)) return;
             outputToken = present(token) ? token : null;
             minOutput = present(amount) ? amount : null;
             outputEstablished = true;
             outputUnwrapped = false;
+            unwrapIntoRouterStep = null;
             outputRecipients = recipients;
+            outputStep = step;
         };
 
         // What the steps take from the sender beyond the amount of the step
@@ -1405,6 +1422,14 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                     v2PairFor(chainId, next.path[0], next.path[1]).toLowerCase()
             );
         };
+        // Whether a SWEEP, TRANSFER, PAY_PORTION or PAY_PORTION_FULL_PRECISION
+        // of `token` to `recipient` pays anyone WETH (see lastWethStep): it
+        // does when `token` is WETH, and when it pays ETH to a WETH contract,
+        // which pays the router WETH for it.
+        const paysWeth = (token, recipient) =>
+            WETH_ADDRESSES.includes(token.toLowerCase()) ||
+            (token === "0x0000000000000000000000000000000000000000" &&
+                WETH_ADDRESSES.includes(recipient.toLowerCase()));
 
         for (let i = 0; i < commandsBytes.length; i++) {
             const cmdId = commandsBytes[i] & commandTypeMask;
@@ -1421,6 +1446,9 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                     ? COMMAND_NAMES[command]
                     : "Command 0x" + cmdId.toString(16).padStart(2, "0"),
             );
+            // Set by a branch below that reads a step that cannot take WETH
+            // out of the router or pay anyone WETH (see lastWethStep).
+            let keepsRouterWeth = false;
 
             try {
                 if (command === "EXECUTE_SUB_PLAN") {
@@ -1452,6 +1480,7 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                             allowedToFail,
                             beforeEveryTake: !tookBefore,
                         };
+                        keepsRouterWeth = true;
                     } else {
                         stepsUnread.push(i);
                     }
@@ -1507,6 +1536,7 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                         // what the user receives: it sets no side, and the
                         // step says so.
                         commandNames[i] += " (of another address)";
+                        keepsRouterWeth = true;
                     } else {
                         // The router passes this check whenever the owner
                         // holds at least minBalance, so a zero one guarantees
@@ -1517,8 +1547,9 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                         // does. It pays nobody.
                         const minBalance = allowedToFail ? 0n : b.minBalance;
                         if (!(minBalance === 0n && present(minOutput))) {
-                            setOutput(b.token, minBalance, []);
+                            setOutput(i, b.token, minBalance, []);
                         }
+                        keepsRouterWeth = true;
                     }
                 } else if (command === "V3_SWAP_EXACT_IN") {
                     const s = decodeV3SwapExactIn(inputs[i]);
@@ -1531,7 +1562,7 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                         // Always update output: in multi-step swaps (V3 → V4),
                         // the last swap step determines the final output token
                         // and minimum received amount.
-                        setOutput(s.tokenOut, s.amountOutMin, [s.recipient]);
+                        setOutput(i, s.tokenOut, s.amountOutMin, [s.recipient]);
                         if (!s.payerIsUser) {
                             spendFromRouter(s.tokenIn, s.amountIn);
                         }
@@ -1551,7 +1582,7 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                         } else if (s.payerIsUser) {
                             addUserPaid(s.tokenIn, s.amountIn);
                         }
-                        setOutput(s.tokenOut, s.amountOutMin, [s.recipient]);
+                        setOutput(i, s.tokenOut, s.amountOutMin, [s.recipient]);
                         if (!s.payerIsUser) {
                             spendFromRouter(s.tokenIn, s.amountIn);
                         }
@@ -1582,7 +1613,7 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                         } else if (s.payerIsUser) {
                             addUserPaid(s.tokenIn, s.amountInMax);
                         }
-                        setOutput(s.tokenOut, s.amountOut, [s.recipient]);
+                        setOutput(i, s.tokenOut, s.amountOut, [s.recipient]);
                         if (!isHop(i, s.tokenOut, s.recipient)) {
                             addPayee(s.recipient, s.tokenOut);
                         }
@@ -1604,6 +1635,7 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                         if (!isRouter(s.recipient)) {
                             heldByRouter.delete(s.token.toLowerCase());
                         }
+                        keepsRouterWeth = !paysWeth(s.token, s.recipient);
                     } else {
                         payeeUnread = true;
                         stepsUnread.push(i);
@@ -1641,6 +1673,7 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                         ) {
                             heldByRouter.delete(t.token.toLowerCase());
                         }
+                        keepsRouterWeth = !paysWeth(t.token, t.recipient);
                     } else {
                         payeeUnread = true;
                         stepsUnread.push(i);
@@ -1765,14 +1798,21 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                         minOutput = v4.amountOutMin;
                         outputEstablished = true;
                         outputUnwrapped = false;
+                        unwrapIntoRouterStep = null;
                         outputRecipients = takeRecipients;
+                        outputStep = i;
                     } else if (v4) {
                         // A step with no swap action sets only the sides its
                         // SETTLE, SETTLE_ALL, TAKE or TAKE_ALL names:
                         // setInputOnce() and setOutput() leave alone a side
                         // whose two halves are both unstated.
                         setInputOnce(v4.tokenIn, amountIn);
-                        setOutput(v4.tokenOut, v4.amountOutMin, takeRecipients);
+                        setOutput(
+                            i,
+                            v4.tokenOut,
+                            v4.amountOutMin,
+                            takeRecipients,
+                        );
                     }
                     // Every V4 step, with a swap action or without, takes
                     // from the sender what the user pays it (an amount an
@@ -1799,12 +1839,17 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                     // among it when the step that set the output side paid it
                     // to the router and the router still holds WETH. WETH
                     // that step paid to the user, or to anyone else, stays
-                    // WETH, so when that step also paid some of its output
-                    // elsewhere, or made a payout this decoder did not read,
-                    // only part of it may be unwrapped. This decoder does not
-                    // count how much of that step's minimum then reaches the
-                    // router, nor read the UNWRAP_WETH's own minimum, so the
-                    // output side keeps no figure.
+                    // WETH. When that step also paid some of its output
+                    // elsewhere or made a payout this decoder did not read,
+                    // or this decoder treats a step between the two as one
+                    // that may take WETH out of the router or pay anyone WETH
+                    // (see lastWethStep), the WETH unwrapped may be only part
+                    // of the output side's, or none of it.
+                    // This decoder does not count how much of that step's
+                    // minimum then reaches the UNWRAP_WETH, nor read the
+                    // UNWRAP_WETH's own minimum, so the output side keeps no
+                    // figure.
+                    const u = decodeUnwrapWeth(inputs[i]);
                     const toRouter = (r) => present(r) && isRouter(r);
                     if (
                         present(outputToken) &&
@@ -1813,11 +1858,19 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                         outputRecipients.some(toRouter)
                     ) {
                         outputUnwrapped = true;
-                        if (!outputRecipients.every(toRouter)) {
+                        if (
+                            unwrapIntoRouterStep === null &&
+                            (u === null || isRouter(u.recipient))
+                        ) {
+                            unwrapIntoRouterStep = i;
+                        }
+                        if (
+                            !outputRecipients.every(toRouter) ||
+                            lastWethStep > outputStep
+                        ) {
                             minOutput = null;
                         }
                     }
-                    const u = decodeUnwrapWeth(inputs[i]);
                     if (u) {
                         addPayee(u.recipient);
                         // It pays out all the router's WETH, as ETH. Into the
@@ -1854,6 +1907,26 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
             if (allowedToFail) {
                 commandNames[i] += " (allowed to fail)";
             }
+            if (!keepsRouterWeth) {
+                lastWethStep = i;
+            }
+        }
+
+        // After an UNWRAP_WETH that may have paid the output side's WETH to
+        // the router as ETH, a later step may pay that ETH out as WETH, as a
+        // WRAP_ETH of it to the user does. This decoder treats every later
+        // step but those lastWethStep names as one that may, and does not
+        // count how much of that ETH each pays out: after one, the output
+        // side reads as WETH with no figure. Neither this nor the loss of the
+        // figure in the UNWRAP_WETH branch is undone by any later step, a
+        // later UNWRAP_WETH included, but one that sets the output side again.
+        if (
+            outputUnwrapped &&
+            unwrapIntoRouterStep !== null &&
+            lastWethStep > unwrapIntoRouterStep
+        ) {
+            outputUnwrapped = false;
+            minOutput = null;
         }
 
         // The Amount line, and the lines for what the steps take beyond it.

tests/backgroundStateIsolation.test.js

@@ -19,7 +19,10 @@
 //     that followed persisted the pre-refresh values — while still stamping
 //     lastBalanceRefresh, suppressing the redo.
 //
-// Both use the real persistence path over a cloning storage stub. Nothing here
+// A network switch landing inside a balance refresh's round trip is covered at
+// the end (https://git.eeqj.de/sneak/AutistMask/issues/577).
+//
+// All use the real persistence path over a cloning storage stub. Nothing here
 // asserts the absence of a loadState() call; each asserts the OUTCOME, so it
 // holds against any implementation that gets the outcome right.
 
@@ -395,3 +398,48 @@ describe("a balance refresh under another handler's state read", () => {
         expect(after.wallets[0].addresses[0].balance).toBe(REFRESHED_BALANCE);
     });
 });
+
+describe("a balance refresh under a network switch", () => {
+    // https://git.eeqj.de/sneak/AutistMask/issues/577. The switch clears every
+    // address's balances, and a refresh that started on the previous network
+    // must not write that network's back over them when it returns. The same
+    // refresh in the popup is in tests/balanceRefreshNetworkSwitch.test.js.
+    test("a refresh that returns after a switch writes nothing, and the next one runs on the new network", async () => {
+        const roundTrip = deferred();
+        const reachedNetwork = deferred();
+        const ranOn = [];
+
+        const bg = loadWorker("sepolia", {
+            refreshBalances: async (wallets, rpcUrl, explorer, tokens, id) => {
+                ranOn.push(id);
+                reachedNetwork.resolve();
+                await roundTrip.promise;
+                wallets[0].addresses[0].balance = REFRESHED_BALANCE;
+            },
+        });
+
+        const refresh = bg.fireBalanceAlarm();
+        await reachedNetwork.promise;
+
+        // The user switches to Ethereum Mainnet in Settings while the round
+        // trip is out.
+        const during = bg.persisted();
+        applyChainSwitchFields(during, MAINNET.id);
+        global.chrome.storage.write("autistmask", during);
+
+        roundTrip.resolve();
+        await refresh;
+
+        const after = bg.persisted();
+        expect(after.networkId).toBe("mainnet");
+        expect(after.wallets[0].addresses[0].balance).toBe("0");
+        expect(after.lastBalanceRefresh).toBe(0);
+
+        await bg.fireBalanceAlarm();
+
+        expect(ranOn).toEqual(["sepolia", "mainnet"]);
+        expect(bg.persisted().wallets[0].addresses[0].balance).toBe(
+            REFRESHED_BALANCE,
+        );
+    });
+});

tests/balanceRefreshNetworkSwitch.test.js

@@ -0,0 +1,160 @@
+// A balance refresh the popup started on one network, and that returns after
+// the network was switched to another, writes nothing: the switch cleared every
+// address's balances, and the previous network's must not come back over them
+// (https://git.eeqj.de/sneak/AutistMask/issues/577). The switch is made either
+// by the user in this popup's Settings, or by the background after the user
+// 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.
+
+const {
+    bootPopup,
+    cleanupPopup,
+    unversionedValidProfile,
+    TOKEN_ADDRESS,
+} = require("./support/popupBoot");
+const { applyChainSwitchFields } = require("../src/shared/chainSwitchFields");
+
+afterEach(() => {
+    cleanupPopup();
+});
+
+// Starts the ten-second refresh and holds it open. The balance stand-in writes
+// Ethereum Mainnet's balances in place, on the records handed in, as the real
+// refreshBalances() does, once the returned function is called. Resolves with
+// that function and the refresh still running.
+async function holdRefresh(page) {
+    const { refreshBalances } = require("../src/shared/balances");
+    let answer;
+    refreshBalances.mockImplementationOnce(async (wallets) => {
+        await new Promise((resolve) => {
+            answer = resolve;
+        });
+        wallets[0].addresses[0].balance = "7.0";
+        wallets[0].addresses[0].tokenBalances = [
+            {
+                address: TOKEN_ADDRESS,
+                name: "Test Token",
+                symbol: "TST",
+                decimals: 18,
+                balance: "5.0",
+                holders: null,
+            },
+        ];
+    });
+    const ticking = page.tick();
+    await page.settle();
+    return {
+        finish: async () => {
+            answer();
+            await ticking;
+        },
+    };
+}
+
+// Picks `networkId` in the Settings network selector, as the user does.
+async function chooseNetwork(page, networkId) {
+    const select = page.node("settings-network");
+    select.value = networkId;
+    for (const fn of select.listeners.change) await fn();
+    await page.settle();
+}
+
+// The stored record holds none of Ethereum Mainnet's balances, and no refresh
+// recorded as done.
+function expectNothingStored(page) {
+    const stored = page.storage.read("autistmask");
+    expect(stored.networkId).toBe("sepolia");
+    expect(stored.wallets[0].addresses[0].balance).toBe("0");
+    expect(stored.wallets[0].addresses[0].tokenBalances).toEqual([]);
+    expect(stored.lastBalanceRefresh).toBe(0);
+}
+
+test("a refresh that returns after a switch in Settings writes nothing, and the next one runs on the new network", async () => {
+    const page = await bootPopup(unversionedValidProfile());
+    expect(page.pageErrors).toEqual([]);
+    const { refreshBalances } = require("../src/shared/balances");
+    const { state } = require("../src/shared/state");
+
+    const refresh = await holdRefresh(page);
+    await page.click("btn-settings");
+    await chooseNetwork(page, "sepolia");
+    await refresh.finish();
+
+    expect(state.wallets[0].addresses[0].balance).toBe("0");
+    expect(state.wallets[0].addresses[0].tokenBalances).toEqual([]);
+    expectNothingStored(page);
+
+    await page.click("btn-settings-back");
+    expect(page.visibleViews()).toEqual(["main"]);
+    expect(page.text("total-value")).toBe("0.0000 SepoliaETH");
+
+    await page.tick();
+
+    expect(refreshBalances.mock.lastCall[4]).toBe("sepolia");
+    expect(page.storage.read("autistmask").lastBalanceRefresh).toBeGreaterThan(
+        0,
+    );
+});
+
+// The stored record still holds Ethereum Mainnet while the refresh's save reads
+// it, so only this page's own network shows the switch.
+test("a refresh whose save is reading the stored record when the user switches in Settings writes nothing", async () => {
+    const page = await bootPopup(unversionedValidProfile());
+    expect(page.pageErrors).toEqual([]);
+    const { state } = require("../src/shared/state");
+
+    const refresh = await holdRefresh(page);
+    await page.click("btn-settings");
+
+    // The next read of the stored record, the refresh's save's, is held.
+    const get = page.storage.local.get;
+    const read = get.getMockImplementation();
+    let releaseRead;
+    get.mockImplementationOnce(async (key) => {
+        await new Promise((resolve) => {
+            releaseRead = resolve;
+        });
+        return read(key);
+    });
+    const finishing = refresh.finish();
+    await page.settle();
+
+    // The user picks Sepolia meanwhile; the switch's own save waits for the
+    // refresh's save to let the lock go.
+    const select = page.node("settings-network");
+    select.value = "sepolia";
+    const switching = Promise.all(select.listeners.change.map((fn) => fn()));
+    await page.settle();
+
+    releaseRead();
+    await finishing;
+    await switching;
+    await page.settle();
+
+    expect(state.networkId).toBe("sepolia");
+    expect(state.wallets[0].addresses[0].balance).toBe("0");
+    expect(state.wallets[0].addresses[0].tokenBalances).toEqual([]);
+    expectNothingStored(page);
+});
+
+test("a refresh that returns after the background switched the network writes nothing", async () => {
+    const page = await bootPopup(unversionedValidProfile());
+    expect(page.pageErrors).toEqual([]);
+    const { saveState } = require("../src/shared/state");
+
+    const refresh = await holdRefresh(page);
+    // The background writes the switch to Sepolia, as its updateState() does
+    // once the user approves a site's request. This page is not told.
+    const record = page.storage.read("autistmask");
+    applyChainSwitchFields(record, "sepolia");
+    page.storage.write("autistmask", record);
+    await refresh.finish();
+
+    expectNothingStored(page);
+
+    // Nor does a later save by this page, such as every navigation makes.
+    await saveState();
+
+    expectNothingStored(page);
+});

tests/uniswapRecipient.test.js

@@ -11,7 +11,8 @@
 // what each PERMIT2_TRANSFER_FROM moves
 // (https://git.eeqj.de/sneak/AutistMask/issues/611), and when an
 // UNWRAP_WETH makes the output ETH
-// (https://git.eeqj.de/sneak/AutistMask/issues/607).
+// (https://git.eeqj.de/sneak/AutistMask/issues/607 and
+// https://git.eeqj.de/sneak/AutistMask/issues/642).
 //
 // Every swap command, SWEEP, WRAP_ETH, UNWRAP_WETH, TRANSFER, PAY_PORTION,
 // PAY_PORTION_FULL_PRECISION, PERMIT2_TRANSFER_FROM, ACROSS_V4_DEPOSIT_V3 and
@@ -745,6 +746,365 @@ describe("an UNWRAP_WETH makes the output ETH only when the router holds it", ()
     });
 });
 
+// https://git.eeqj.de/sneak/AutistMask/issues/642: a step between the swap and
+// the UNWRAP_WETH may take WETH out of the router or pay it WETH, and a step
+// after an UNWRAP_WETH into the router may pay its ETH out as WETH, yet each
+// route read as ETH with the swap's minimum. A step the decoder read that is a
+// PERMIT2_PERMIT, a BALANCE_CHECK_ERC20, or a SWEEP, TRANSFER, PAY_PORTION or
+// PAY_PORTION_FULL_PRECISION of a token other than WETH, and not of ETH to a
+// WETH contract, cannot take WETH out of the router or pay anyone WETH; the
+// decoder treats every other step as one that may.
+describe("what reaches the UNWRAP_WETH of the swap's WETH", () => {
+    const NO_MINIMUM_TO_USER = PAID_TO_USER.filter(
+        (l) => l !== "Min. received",
+    );
+    const NO_MINIMUM_ELSEWHERE = PAID_ELSEWHERE.filter(
+        (l) => l !== "Min. paid out",
+    );
+
+    test.each([
+        {
+            kind: "a TRANSFER of 0.0025 WETH",
+            step: transfer(0x05, WETH, OTHER, ONE_WETH / 400n),
+        },
+        {
+            kind: "a PAY_PORTION of 25 bips",
+            step: transfer(0x06, WETH, OTHER, 25n),
+        },
+        {
+            kind: "a PAY_PORTION_FULL_PRECISION of 1e15",
+            step: transfer(0x07, WETH, OTHER, 10n ** 15n),
+        },
+    ])(
+        "$kind to another address between them reads as ETH with no minimum",
+        ({ step }) => {
+            const result = decode(
+                execute(swapToWeth(ADDRESS_THIS), step, unwrapWeth(MSG_SENDER)),
+                USER,
+                ROUTER_V2_1_2,
+            );
+            expect(result.name).toBe("Swap USDT → ETH");
+            expect(labels(result)).toEqual(NO_MINIMUM_ELSEWHERE);
+            expect(paidTo(result)).toEqual([OTHER]);
+        },
+    );
+
+    test.each([
+        {
+            kind: "a SWEEP whose recipient cannot be read",
+            step: withDirtyWord(sweep(WETH, OTHER), 1),
+        },
+        {
+            kind: "a V4 SETTLE of 0.5 WETH from the router",
+            step: v4Swap([
+                0x0b,
+                coder.encode(
+                    ["address", "uint256", "bool"],
+                    [WETH, ONE_WETH / 2n, false],
+                ),
+            ]),
+        },
+        {
+            kind: "a bridge deposit of 0.5 WETH",
+            step: acrossDeposit(USER, USER, WETH, ONE_WETH / 2n),
+        },
+        {
+            kind: "a PERMIT2_TRANSFER_FROM of 0.5 WETH into the router",
+            step: permit2TransferFrom(WETH, ADDRESS_THIS, ONE_WETH / 2n),
+        },
+    ])("$kind between them reads as ETH with no minimum", ({ step }) => {
+        const result = decode(
+            execute(swapToWeth(ADDRESS_THIS), step, unwrapWeth(MSG_SENDER)),
+        );
+        expect(result.name).toBe("Swap USDT → ETH");
+        expect(detail(result, "Min. received")).toBeUndefined();
+        expect(detail(result, "Min. paid out")).toBeUndefined();
+    });
+
+    test.each([
+        {
+            kind: "a PERMIT2_PERMIT between them",
+            steps: [permit2Permit(USDT, USDT_2000), unwrapWeth(MSG_SENDER)],
+        },
+        {
+            kind: "a BALANCE_CHECK_ERC20 of another address between them",
+            steps: [balanceCheck(USDC, 1n, OTHER), unwrapWeth(MSG_SENDER)],
+        },
+        {
+            kind: "a BALANCE_CHECK_ERC20 of the sender with a zero minimum between them",
+            steps: [balanceCheck(USDC, 0n), unwrapWeth(MSG_SENDER)],
+        },
+        {
+            kind: "a SWEEP of USDC between them",
+            steps: [sweep(USDC, MSG_SENDER), unwrapWeth(MSG_SENDER)],
+        },
+        {
+            kind: "an UNWRAP_WETH into the router, then a SWEEP of its ETH,",
+            steps: [unwrapWeth(ADDRESS_THIS), sweep(ZERO, MSG_SENDER)],
+        },
+    ])("$kind reads as ETH with the swap's minimum", ({ steps }) => {
+        const result = decode(execute(swapToWeth(ADDRESS_THIS), ...steps));
+        expect(result.name).toBe("Swap USDT → ETH");
+        expect(detail(result, "Min. received").value).toBe("1.0000 ETH");
+    });
+
+    test("a V4 step that TAKEs its WETH to the router, then an UNWRAP_WETH to the user, reads as ETH with the swap's minimum", () => {
+        const result = decode(
+            execute(
+                v4Swap(
+                    SWAP_USDT_FOR_WETH,
+                    SETTLE_USDT,
+                    take(WETH, ADDRESS_THIS),
+                ),
+                unwrapWeth(MSG_SENDER),
+            ),
+        );
+        expect(result.name).toBe("Swap USDT → ETH");
+        expect(detail(result, "Min. received").value).toBe("1.0000 ETH");
+    });
+
+    test.each([
+        {
+            kind: "a TRANSFER of 100 USDC",
+            step: transfer(0x05, USDC, OTHER, 100000000n),
+        },
+        {
+            kind: "a PAY_PORTION of 25 bips of USDC",
+            step: transfer(0x06, USDC, OTHER, 25n),
+        },
+        {
+            kind: "a PAY_PORTION_FULL_PRECISION of 1e15 of USDC",
+            step: transfer(0x07, USDC, OTHER, 10n ** 15n),
+        },
+    ])(
+        "$kind to another address between them reads as ETH with the swap's minimum",
+        ({ step }) => {
+            const result = decode(
+                execute(swapToWeth(ADDRESS_THIS), step, unwrapWeth(MSG_SENDER)),
+                USER,
+                ROUTER_V2_1_2,
+            );
+            expect(result.name).toBe("Swap USDT → ETH");
+            expect(paidTo(result)).toEqual([OTHER]);
+            expect(detail(result, "Min. paid out").value).toBe("1.0000 ETH");
+        },
+    );
+
+    test.each([
+        {
+            kind: "a TRANSFER of 0.0025 ETH",
+            step: transfer(0x05, ZERO, OTHER, ONE_WETH / 400n),
+        },
+        {
+            kind: "a PAY_PORTION of 25 bips of its ETH",
+            step: transfer(0x06, ZERO, OTHER, 25n),
+        },
+        {
+            kind: "a PAY_PORTION_FULL_PRECISION of 1e15 of its ETH",
+            step: transfer(0x07, ZERO, OTHER, 10n ** 15n),
+        },
+    ])(
+        "an UNWRAP_WETH into the router, then $kind to another address, then a SWEEP of its ETH to the user, reads as ETH with the swap's minimum",
+        ({ step }) => {
+            const result = decode(
+                execute(
+                    swapToWeth(ADDRESS_THIS),
+                    unwrapWeth(ADDRESS_THIS),
+                    step,
+                    sweep(ZERO, MSG_SENDER),
+                ),
+                USER,
+                ROUTER_V2_1_2,
+            );
+            expect(result.name).toBe("Swap USDT → ETH");
+            expect(paidTo(result)).toEqual([OTHER]);
+            expect(detail(result, "Min. paid out").value).toBe("1.0000 ETH");
+        },
+    );
+
+    // The SWEEP pays the user the swap's WETH, so the UNWRAP_WETH unwraps the
+    // WRAP_ETH's.
+    test("a SWEEP of the swap's WETH to the user, then a WRAP_ETH into the router, reads as ETH with no minimum", () => {
+        const result = decode(
+            execute(
+                swapToWeth(ADDRESS_THIS),
+                sweep(WETH, MSG_SENDER),
+                wrapEth(ADDRESS_THIS, ONE_WETH),
+                unwrapWeth(MSG_SENDER),
+            ),
+        );
+        expect(result.name).toBe("Swap USDT → ETH");
+        expect(labels(result)).toEqual(NO_MINIMUM_TO_USER);
+    });
+
+    test("an UNWRAP_WETH into the router, then a WRAP_ETH of all its ETH to the user, reads as WETH with no minimum", () => {
+        const result = decode(
+            execute(
+                swapToWeth(ADDRESS_THIS),
+                unwrapWeth(ADDRESS_THIS),
+                wrapEth(MSG_SENDER, CONTRACT_BALANCE),
+            ),
+        );
+        expect(result.name).toBe("Swap USDT → WETH");
+        expect(labels(result)).toEqual(NO_MINIMUM_TO_USER);
+    });
+
+    // The router reads the recipient from the last 20 bytes of its word,
+    // here address(2), the router itself.
+    test("an UNWRAP_WETH whose recipient cannot be read, then a WRAP_ETH of all the router's ETH to the user, reads as WETH with no minimum", () => {
+        const result = decode(
+            execute(
+                swapToWeth(ADDRESS_THIS),
+                withDirtyWord(unwrapWeth(ADDRESS_THIS), 0),
+                wrapEth(MSG_SENDER, CONTRACT_BALANCE),
+            ),
+        );
+        expect(result.name).toBe("Swap USDT → WETH");
+        expect(detail(result, "Min. received")).toBeUndefined();
+        expect(detail(result, "Min. paid out")).toBeUndefined();
+    });
+
+    // The first UNWRAP_WETH may pay the router the swap's output as ETH, and
+    // the WRAP_ETH to the user pays all of it out as WETH, so the last
+    // UNWRAP_WETH finds none of it.
+    test.each([
+        {
+            kind: "an UNWRAP_WETH whose recipient cannot be read, then a WRAP_ETH of all the router's ETH to the user",
+            steps: [
+                withDirtyWord(unwrapWeth(ADDRESS_THIS), 0),
+                wrapEth(MSG_SENDER, CONTRACT_BALANCE),
+            ],
+        },
+        {
+            kind: "an UNWRAP_WETH into the router, a WRAP_ETH of all its ETH to the user, then a WRAP_ETH of all its ETH into the router",
+            steps: [
+                unwrapWeth(ADDRESS_THIS),
+                wrapEth(MSG_SENDER, CONTRACT_BALANCE),
+                wrapEth(ADDRESS_THIS, CONTRACT_BALANCE),
+            ],
+        },
+    ])(
+        "$kind, then an UNWRAP_WETH to the user, reads as WETH with no minimum",
+        ({ steps }) => {
+            const result = decode(
+                execute(
+                    swapToWeth(ADDRESS_THIS),
+                    ...steps,
+                    unwrapWeth(MSG_SENDER),
+                ),
+            );
+            expect(result.name).toBe("Swap USDT → WETH");
+            expect(detail(result, "Min. received")).toBeUndefined();
+            expect(detail(result, "Min. paid out")).toBeUndefined();
+        },
+    );
+
+    // A SWEEP of WETH pays out WETH, and ETH paid to a WETH contract pays the
+    // router WETH for it. The decoder treats each as a step that may pay out
+    // as WETH the swap's output, which the router holds as ETH.
+    test.each([
+        {
+            kind: "a SWEEP of WETH to the user",
+            step: sweep(WETH, MSG_SENDER),
+        },
+        {
+            kind: "a SWEEP of its ETH to the WETH contract",
+            step: sweep(ZERO, WETH),
+        },
+        {
+            kind: "a TRANSFER of 0.5 ETH to the WETH contract",
+            step: transfer(0x05, ZERO, WETH, ONE_WETH / 2n),
+        },
+        {
+            kind: "a PAY_PORTION of all its ETH to the WETH contract",
+            step: transfer(0x06, ZERO, WETH, 10000n),
+        },
+    ])(
+        "an UNWRAP_WETH into the router, then $kind, reads as WETH with no minimum",
+        ({ step }) => {
+            const result = decode(
+                execute(
+                    swapToWeth(ADDRESS_THIS),
+                    unwrapWeth(ADDRESS_THIS),
+                    step,
+                ),
+            );
+            expect(result.name).toBe("Swap USDT → WETH");
+            expect(detail(result, "Min. received")).toBeUndefined();
+            expect(detail(result, "Min. paid out")).toBeUndefined();
+        },
+    );
+
+    // The user receives 0.5 WETH and the rest of the swap's output as ETH.
+    test("an UNWRAP_WETH into the router, then a WRAP_ETH of 0.5 ETH to the user, reads as WETH with no minimum", () => {
+        const result = decode(
+            execute(
+                swapToWeth(ADDRESS_THIS),
+                unwrapWeth(ADDRESS_THIS),
+                wrapEth(MSG_SENDER, ONE_WETH / 2n),
+                sweep(ZERO, MSG_SENDER),
+            ),
+        );
+        expect(result.name).toBe("Swap USDT → WETH");
+        expect(labels(result)).toEqual(NO_MINIMUM_TO_USER);
+    });
+
+    // The UNWRAP_WETH pays the user the swap's WETH as ETH; the WRAP_ETH wraps
+    // the ETH an earlier V4 step paid the router.
+    test("an UNWRAP_WETH to the user, then a WRAP_ETH of all the router's ETH to the user, reads as ETH", () => {
+        const result = decode(
+            execute(
+                v4Swap(
+                    SWAP_USDT_FOR_ETH,
+                    SETTLE_USDT,
+                    take(ZERO, ADDRESS_THIS),
+                ),
+                swapToWeth(ADDRESS_THIS),
+                unwrapWeth(MSG_SENDER),
+                wrapEth(MSG_SENDER, CONTRACT_BALANCE),
+            ),
+        );
+        expect(detail(result, "Token Out").value).toBe("ETH");
+        expect(detail(result, "Min. received").value).toBe("1.0000 ETH");
+    });
+
+    // The first swap is for at least 0.5 WETH and the second for at least
+    // 1 WETH. The second sets the output side again, so the first
+    // UNWRAP_WETH into the router no longer bears on it.
+    test.each([
+        { kind: "a V3 swap step", step: swapToWeth(ADDRESS_THIS) },
+        {
+            kind: "a V4 step that TAKEs its WETH to the router",
+            step: v4Swap(
+                SWAP_USDT_FOR_WETH,
+                SETTLE_USDT,
+                take(WETH, ADDRESS_THIS),
+            ),
+        },
+    ])(
+        "a swap paying WETH to the router, an UNWRAP_WETH into the router, a SWEEP of its ETH to the user, then $kind and an UNWRAP_WETH to the user, reads as ETH with the second swap's minimum",
+        ({ step }) => {
+            const result = decode(
+                execute(
+                    v3SwapExactIn(
+                        ADDRESS_THIS,
+                        USDT_2000,
+                        ONE_WETH / 2n,
+                        USDT,
+                        WETH,
+                    ),
+                    unwrapWeth(ADDRESS_THIS),
+                    sweep(ZERO, MSG_SENDER),
+                    step,
+                    unwrapWeth(MSG_SENDER),
+                ),
+            );
+            expect(result.name).toBe("Swap USDT → ETH");
+            expect(detail(result, "Min. received").value).toBe("1.0000 ETH");
+        },
+    );
+});
+
 // https://git.eeqj.de/sneak/AutistMask/issues/606: any token a step pays the
 // router stays there unless a later step pays out or spends all of it, not
 // only the swap's output. A V4 SETTLE can take more of the user's tokens than
@@ -1711,15 +2071,6 @@ describe("a payout of part of the router's output", () => {
             ),
             min: "1.0000 WETH",
         },
-        {
-            kind: "PAY_PORTION of 25 bips, then UNWRAP_WETH",
-            data: execute(
-                swapToWeth(ADDRESS_THIS),
-                transfer(0x06, WETH, OTHER, 25n),
-                unwrapWeth(MSG_SENDER),
-            ),
-            min: "1.0000 ETH",
-        },
         {
             kind: "V4 TAKE_PORTION of 25 bips, then TAKE_ALL",
             data: execute(