fix: a V4 SETTLE of ETH paid from the router reads as moved from the sender (closes #682)

V4Router pays a SETTLE of ETH from the router's own ETH, whichever payer
it names. The router holds the transaction's value. So a SETTLE of ETH
that names the router as payer now counts as paid by the user.

When an earlier step left ETH in the router, such a SETTLE gets lines of
its own. Its line reads "Up to" and its amount, and that amount never
joins the Amount total. When the decoder does not know the SETTLE's
amount, as for CONTRACT_BALANCE, its line reads "Unknown (could not be
decoded)", also on the step that sets the input side.

One existing row in tests/uniswapRecipient.test.js now expects the ETH
lines. Its SETTLE spends all the router's ETH, the transaction's value
included.

Model: opus-5-5

README.md

@@ -3477,83 +3477,89 @@ Currently supported:
   of any amount but `OPEN_DELTA` pays that amount, and a `SETTLE` of
   `OPEN_DELTA` or a `SETTLE_ALL` pays what the step owes, as above. So a V4 step
   that swaps 400 USDT, with a `SETTLE` of 5,000 USDT paid by the user and the
-  rest taken to another address, reads `5000.0000 USDT`. A later step paid from
+  rest taken to another address, reads `5000.0000 USDT`. A later step that pays
-  the router spends what the router holds and takes nothing, and so does a V2
+  an ERC-20 token from the router takes none of that token from the user's
-  exact-in whose `amountIn` is `ALREADY_PAID`. A later take of `Token In` is
+  wallet. A V2 exact-in whose `amountIn` is `ALREADY_PAID` takes nothing either.
-  added to the total while both are quantities: a V3 exact-in of 600 USDT and a
+  A V4 `SETTLE` of ETH paid from the router still takes from the user's wallet,
-  V2 exact-in of 400 USDT, both paid by the user, read `1000.0000 USDT`. When
+  since the router holds the transaction's value. When the decoder does not know
-  the decoder does not know a take's amount, the total is not known and there is
+  the amount of such a `SETTLE`, as for `CONTRACT_BALANCE`, that `SETTLE` counts
-  no `Amount` line. A `PERMIT2_PERMIT` names `Token In` only when its amount,
+  as a later step's take. When an earlier step left ETH in the router, that ETH
-  `Unlimited` included, stands as the `Amount` figure in place of the total,
+  may pay part of a `SETTLE` of ETH paid from the router. That `SETTLE` then
-  which it does only in the plain shape of Uniswap's own routes: it comes before
+  gets lines of its own, with `Up to` before its amount. A later take of
-  the step that sets the input side, it is the only `PERMIT2_PERMIT` in the
+  `Token In` that only the user's wallet pays is added to the total while both
-  transaction and there is no `PERMIT2_PERMIT_BATCH`, its spender is the router,
+  are quantities: a V3 exact-in of 600 USDT and a V2 exact-in of 400 USDT, both
-  the router may not let it fail, no step before it takes its token, a
+  paid by the user, read `1000.0000 USDT`. When the decoder does not know a
-  `PERMIT2_TRANSFER_FROM` of it included, or a token the decoder does not know,
+  take's amount, the total is not known and there is no `Amount` line. A
-  and the decoder reads every step after it in full. Permit2 then lets the
+  `PERMIT2_PERMIT` names `Token In` only when its amount, `Unlimited` included,
-  router take no more of the token than that amount, so the permit covers every
+  stands as the `Amount` figure in place of the total, which it does only in the
-  take of it. A step before the permit takes under whatever allowance the router
+  plain shape of Uniswap's own routes: it comes before the step that sets the
-  already had, so it may take more than the permit's amount, which would then
+  input side, it is the only `PERMIT2_PERMIT` in the transaction and there is no
-  read lower than what leaves the user's wallet: a `PERMIT2_TRANSFER_FROM` of
+  `PERMIT2_PERMIT_BATCH`, its spender is the router, the router may not let it
-  2,000 USDT into the router, then a permit of 600 USDT to the router and a V3
+  fail, no step before it takes its token, a `PERMIT2_TRANSFER_FROM` of it
-  exact-in of 2,000 USDT paid from the router, read `Amount 2000.0000 USDT`. A
+  included, or a token the decoder does not know, and the decoder reads every
-  later permit or batch may raise what Permit2 lets the router take, and so may
+  step after it in full. Permit2 then lets the router take no more of the token
-  a step the decoder does not read in full: a command the decoder does not read
+  than that amount, so the permit covers every take of it. A step before the
-  (listed at the end of this section), a step whose input it cannot read, in
+  permit takes under whatever allowance the router already had, so it may take
-  whole or in part, and a step it fails on. Every other `PERMIT2_PERMIT`, before
+  more than the permit's amount, which would then read lower than what leaves
-  the step that sets the input side or after it, leaves `Token In` and the
+  the user's wallet: a `PERMIT2_TRANSFER_FROM` of 2,000 USDT into the router,
-  `Amount` line as they read with no permit, unless it lets a spender other than
+  then a permit of 600 USDT to the router and a V3 exact-in of 2,000 USDT paid
-  the router take `Token In` (see below): a permit of 5,000 DAI to another
+  from the router, read `Amount 2000.0000 USDT`. A later permit or batch may
-  address and then a V3 exact-in of 600 USDT read `Swap USDT → USDC` with
+  raise what Permit2 lets the router take, and so may a step the decoder does
-  `Amount 600.0000 USDT`, and so do that exact-in and then a permit of 5,000 DAI
+  not read in full: a command the decoder does not read (listed at the end of
-  to the router. A permit on the zero address never stands as the `Amount`
+  this section), a step whose input it cannot read, in whole or in part, and a
-  figure, because Permit2 has no allowance of ETH. When a permit's amount stands
+  step it fails on. Every other `PERMIT2_PERMIT`, before the step that sets the
-  and the step that sets the input side spends a token other than the permit's,
+  input side or after it, leaves `Token In` and the `Amount` line as they read
-  or one the decoder does not know, that step's amount gets lines of its own,
+  with no permit, unless it lets a spender other than the router take `Token In`
-  unless it states no amount and the user pays it none of its input token. Each
+  (see below): a permit of 5,000 DAI to another address and then a V3 exact-in
-  take the total does not count gives three lines after the `Amount` line (after
+  of 600 USDT read `Swap USDT → USDC` with `Amount 600.0000 USDT`, and so do
-  `Token In` when there is none): one of a token other than `Token In`; one of
+  that exact-in and then a permit of 5,000 DAI to the router. A permit on the
-  `Token In` after an amount that is not a quantity (a V4 open delta,
+  zero address never stands as the `Amount` figure, because Permit2 has no
-  `ALREADY_PAID`, which keep their wording on the `Amount` line, or no stated
+  allowance of ETH. When a permit's amount stands and the step that sets the
-  amount, as of a V4 exact-out step); and one whose amount the decoder does not
+  input side spends a token other than the permit's, or one the decoder does not
-  know. When there is no `Amount` line, each take the total counts gets them
+  know, that step's amount gets lines of its own, unless it states no amount and
-  too, so that every amount the decoder reads is shown: the amount the step that
+  the user pays it none of its input token. Each take the total does not count
-  sets the input side states, when it is a quantity and the user pays that step
+  gives three lines after the `Amount` line (after `Token In` when there is
-  (a V2 or V3 step whose `payerIsUser` is true, a V4 step the user pays some of
+  none): one of a token other than `Token In`; one of `Token In` after an amount
-  its input token, or a `WRAP_ETH`, whose ETH comes from the transaction's
+  that is not a quantity (a V4 open delta, `ALREADY_PAID`, which keep their
-  value), and each later take of `Token In` added to it. A step that sets the
+  wording on the `Amount` line, or no stated amount, as of a V4 exact-out step);
-  input side and is paid from the router takes nothing from the user's wallet
+  an ETH take whose line reads `Up to` (see above); and one whose amount the
-  and gets none. A `PERMIT2_PERMIT` the decoder cannot read, then V3 exact-ins
+  decoder does not know. When there is no `Amount` line, each take the total
-  of 600 USDT and 400 DAI paid by the user, give lines for both amounts. When
+  counts gets them too, so that every amount the decoder reads is shown: the
-  the step that sets the input side states no amount, the user pays it some of
+  amount the step that sets the input side states, when it is a quantity and the
-  its input token, and there is no `Amount` line, that step gets them too
+  user pays that step (a V2 or V3 step whose `payerIsUser` is true, a V4 step
-  whenever another take's lines give a figure, or a `PERMIT2_TRANSFER_FROM` of
+  the user pays some of its input token, or a `WRAP_ETH`, whose ETH comes from
-  its token gives one, on the lines below or, into the router, on its `Paid to`
+  the transaction's value), and each later take of `Token In` added to it. A
-  line, so that figure cannot read as all that leaves. When it states no amount
+  step that sets the input side gets none when the user pays it none of its
-  and the user pays it none of its input token, as when the router pays it, that
+  input token. A `PERMIT2_PERMIT` the decoder cannot read, then V3 exact-ins of
-  step takes none of that token from the user's wallet and never gets them, with
+  600 USDT and 400 DAI paid by the user, give lines for both amounts. When the
-  a permit or without. They come in step order, except that the step that sets
+  step that sets the input side states no amount, the user pays it some of its
-  the input side comes first when it has them, followed, when there is no
+  input token, and there is no `Amount` line, that step gets them too whenever
-  `Amount` line, by the other takes the total counts: `Moved from the sender`,
+  another take's lines give a figure, or a `PERMIT2_TRANSFER_FROM` of its token
-  its amount, worded as the `Amount` line words one, or
+  gives one, on the lines below or, into the router, on its `Paid to` line, so
-  `Unknown (could not be decoded)` when the decoder does not know it;
+  that figure cannot read as all that leaves. When it states no amount and the
-  `Token moved`, giving the token's address as the `Token In` line does; and
+  user pays it none of its input token, that step never gets them, with a permit
-  `Moved to`, which reads `The swap step that spends it`. A token the decoder
+  or without. They come in step order, except that the step that sets the input
-  does not know gives the `Moved from the sender` line alone. A step may also
+  side comes first when it has them, followed, when there is no `Amount` line,
-  take from the user's wallet what the decoder did not read: a V4 step whose
+  by the other takes the total counts: `Moved from the sender`, its amount,
-  input or one of whose `SETTLE`s or `SETTLE_ALL`s it cannot read, which the
+  worded as the `Amount` line words one, or `Unknown (could not be decoded)`
-  router still runs; a V2 or V3 exact-in or exact-out step or a
+  when the decoder does not know it; `Token moved`, giving the token's address
-  `PERMIT2_TRANSFER_FROM` whose input it cannot read, such as a V3 step whose
+  as the `Token In` line does; and `Moved to`, which reads
-  path is shorter than one token address or has bytes after its last hop; every
+  `The swap step that spends it`. A token the decoder does not know gives the
-  `PERMIT2_TRANSFER_FROM_BATCH`; every `EXECUTE_SUB_PLAN`, wherever it stands;
+  `Moved from the sender` line alone. A step may also take from the user's
-  and every step it fails on. Each such step gives one `Moved from the sender`
+  wallet what the decoder did not read: a V4 step whose input or one of whose
-  line among those, reading `Unknown (could not be decoded)`. That line, or any
+  `SETTLE`s or `SETTLE_ALL`s it cannot read, which the router still runs; a V2
-  line for a token the decoder does not know, leaves no `Amount` line, whose
+  or V3 exact-in or exact-out step or a `PERMIT2_TRANSFER_FROM` whose input it
-  figure might be too low, and such a step before a `PERMIT2_PERMIT` keeps the
+  cannot read, such as a V3 step whose path is shorter than one token address or
-  permit's amount from standing. Then each `PERMIT2_TRANSFER_FROM` but one into
+  has bytes after its last hop; every `PERMIT2_TRANSFER_FROM_BATCH`; every
-  the router, in step order, gives three lines: `Moved from the sender`, the
+  `EXECUTE_SUB_PLAN`, wherever it stands; and every step it fails on. Each such
-  amount it moves, for example `1000000.0000 USDT`; `Token moved`, giving the
+  step gives one `Moved from the sender` line among those, reading
-  token's address as the `Token In` line does; and `Moved to`, which reads
+  `Unknown (could not be decoded)`. That line, or any line for a token the
+  decoder does not know, leaves no `Amount` line, whose figure might be too low,
+  and such a step before a `PERMIT2_PERMIT` keeps the permit's amount from
+  standing. Then each `PERMIT2_TRANSFER_FROM` but one into the router, in step
+  order, gives three lines: `Moved from the sender`, the amount it moves, for
+  example `1000000.0000 USDT`; `Token moved`, giving the token's address as the
+  `Token In` line does; and `Moved to`, which reads
   `The V2 pair the next swap spends` for a hop and `The sender` for `address(1)`
   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

src/shared/uniswap.js

@@ -1240,9 +1240,10 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
         let inputEstablished = false;
         // Whether the user pays the step that set the input side: a V2 or V3
         // swap step with `payerIsUser` true, a V4 step the user pays some of
-        // its input currency (see decodeV4Swap()), or a WRAP_ETH, whose ETH
+        // its input currency (see paidByUser in the loop), or a WRAP_ETH,
-        // comes from the transaction's value. A step paid from the router
+        // whose ETH comes from the transaction's value. A step that pays an
-        // takes nothing from the sender.
+        // ERC-20 token from the router takes none of that token from the
+        // sender.
         let inputPaidByUser = false;
         // The last PERMIT2_PERMIT this decoder read before a step set the
         // input side, or null (see permitStands after the loop).
@@ -1338,7 +1339,9 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
         // What the steps take from the sender beyond the amount of the step
         // that sets the input side, as { token, amount }, in step order.
         // After the loop each joins the Amount line or gets lines of its own
-        // (see permitStands).
+        // (see permitStands). A take with `atMost` set may take less than
+        // `amount`: it never joins the Amount line, and its line reads
+        // "Up to" and the amount.
         const userPaid = [];
         // A swap step the user pays for (`payerIsUser` true) takes `amount`
         // of `token` from the sender. A V2 exact-in of ALREADY_PAID takes
@@ -1815,6 +1818,41 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                 } else if (command === "V4_SWAP") {
                     const v4 = decodeV4Swap(inputs[i]);
                     const inputSetBefore = inputEstablished;
+                    // V4Router pays a SETTLE of ETH from the router's own
+                    // ETH, whichever payer the SETTLE names. The router holds
+                    // the transaction's value, and any ETH an earlier step
+                    // left it (see heldByRouter). So the user also pays a
+                    // SETTLE of ETH that names the router as payer. The user
+                    // pays all of its amount when the router holds no other
+                    // ETH, and up to its amount otherwise. CONTRACT_BALANCE
+                    // pays all the router holds, an amount the calldata does
+                    // not state.
+                    const routerHeldEth = heldByRouter.has(
+                        "0x0000000000000000000000000000000000000000",
+                    );
+                    const ethFromRouter = (v4?.settledFromRouter ?? [])
+                        .filter(
+                            (s) =>
+                                s.currency ===
+                                "0x0000000000000000000000000000000000000000",
+                        )
+                        .map((s) => ({
+                            currency: s.currency,
+                            amount:
+                                s.amount === CONTRACT_BALANCE ? null : s.amount,
+                        }));
+                    // What the user pays the step: what decodeV4Swap() says,
+                    // and the ETH of each SETTLE from the router of a known
+                    // amount when the router holds no other ETH.
+                    const paidByUser = v4
+                        ? v4.paidByUser.concat(
+                              routerHeldEth
+                                  ? []
+                                  : ethFromRouter.filter((s) =>
+                                        present(s.amount),
+                                    ),
+                          )
+                        : [];
                     if (v4) {
                         // Each SETTLE paid from the router spends the amount
                         // decodeV4Swap() says it pays.
@@ -1845,10 +1883,10 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                         commandNames[i] += " (could not be decoded)";
                     }
                     // The step's amount, if it sets the input side: what the
-                    // user pays it of its input currency (see
+                    // user pays it of its input currency, or, when the user
-                    // decodeV4Swap()), or, when the user pays none of it,
+                    // pays none of it, what its swap actions spend of it,
-                    // what its swap actions spend of it, whoever pays that.
+                    // whoever pays that.
-                    const paidIn = v4?.paidByUser.find(
+                    const paidIn = paidByUser.find(
                         (p) => p.currency === v4.tokenIn,
                     );
                     const amountIn = paidIn ? paidIn.amount : v4?.amountIn;
@@ -1902,11 +1940,25 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
                     // router still runs it.
                     const setInputHere = inputEstablished && !inputSetBefore;
                     if (setInputHere) inputPaidByUser = paidIn !== undefined;
-                    if (v4) {
+                    for (const p of paidByUser) {
-                        for (const p of v4.paidByUser) {
                         if (setInputHere && p === paidIn) continue;
                         addUserPaid(p.currency, p.amount);
                     }
+                    // A SETTLE of ETH from the router that `paidByUser` leaves
+                    // out is a take of its own, even on the step that sets
+                    // the input side. Either this decoder does not know its
+                    // amount, or ETH an earlier step left in the router may
+                    // pay part of that amount (see userPaid).
+                    for (const p of ethFromRouter) {
+                        if (!present(p.amount)) {
+                            addUserPaid(p.currency, null);
+                        } else if (routerHeldEth) {
+                            userPaid.push({
+                                token: p.currency,
+                                amount: p.amount,
+                                atMost: true,
+                            });
+                        }
                     }
                     if (!v4 || v4.settleUnread) {
                         spentUnread();
@@ -2013,10 +2065,10 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
         // The total is what the steps take of Token In: the amount of the
         // step that set the input side, with each later take of that token
         // added to it while both are quantities. A take that cannot be added,
-        // being of another token or coming after an amount that is not a
+        // being of another token, coming after an amount that is not a
-        // quantity (a V4 open delta, ALREADY_PAID, or none stated), gets
+        // quantity (a V4 open delta, ALREADY_PAID, or none stated), or having
-        // lines of its own. One whose amount is not known also leaves the
+        // `atMost` set, gets lines of its own. One whose amount is not known
-        // total unknown, with no figure.
+        // also leaves the total unknown, with no figure.
         //
         // A PERMIT2_PERMIT names Token In only when its amount stands as the
         // Amount figure in place of the total, which it does only in the
@@ -2060,14 +2112,14 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
         let total = null;
         // The takes from the sender that `total` adds up, each a quantity, as
         // { token, amount }. When there is no Amount line, each gets lines of
-        // its own (see below). The amount of a step that set the input side
+        // its own (see below). The amount of the step that set the input side
-        // and is paid from the router counts in `total` but is not among them.
+        // counts in `total` whoever pays that step. That amount is among them
+        // only when the user pays the step (see inputPaidByUser).
         const inTotal = [];
         // Whether the step that set the input side counts as a take from the
         // sender, which may get lines of its own. The amount it stated counts
         // whoever pays it. Stating none, it counts only when the user pays it
-        // some of its input token: paid from the router, it takes nothing
+        // some of its input token.
-        // from the sender.
         const hasFirstTake =
             inputEstablished && (present(inputAmount) || inputPaidByUser);
         // The take of the step that set the input side, when the total
@@ -2093,7 +2145,8 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
             if (
                 ofTokenIn &&
                 typeof total === "bigint" &&
-                typeof t.amount === "bigint"
+                typeof t.amount === "bigint" &&
+                !t.atMost
             ) {
                 total += t.amount;
                 inTotal.push(t);
@@ -2196,8 +2249,9 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
         // V2's already-paid zero, neither of which is a quantity at all (see
         // OPEN_DELTA and ALREADY_PAID), and an unbounded permit. Those two
         // tests come first — the sentinels are not bigints and cannot be
-        // compared with one.
+        // compared with one. `atMost` marks an amount that is only the most a
-        const spentText = (amount, info) => {
+        // take may be (see userPaid).
+        const spentText = (amount, info, atMost) => {
             if (amount === OPEN_DELTA) {
                 return { raw: OPEN_DELTA_AMOUNT, display: OPEN_DELTA_AMOUNT };
             }
@@ -2210,7 +2264,7 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
             if (amount >= MAX_UINT160) {
                 return { raw: "Unlimited", display: "Unlimited" };
             }
-            if (hasV2OrV3ExactOut) {
+            if (hasV2OrV3ExactOut || atMost) {
                 // A V2 or V3 exact-out swap spends at most this figure,
                 // whichever steps gave it (an amountInMax, the WRAP_ETH of a
                 // swap paid in ETH, a permit, or several steps' total), so it
@@ -2270,7 +2324,8 @@ function decode(data, toAddress, chainId, sources, fromAddress) {
             details.push({
                 label: "Moved from the sender",
                 value: present(s.amount)
-                    ? spentText(s.amount, tokenInfo(s.token, sources)).display
+                    ? spentText(s.amount, tokenInfo(s.token, sources), s.atMost)
+                          .display
                     : UNDECODED_CURRENCY,
             });
             if (present(s.token)) {

tests/uniswap.test.js

@@ -3439,6 +3439,129 @@ describe("uniswap decoder", () => {
                 ]);
             });
         });
+
+        // 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
+        // SETTLE of 1 ETH that names the router as payer gave no ETH line.
+        describe("a V4 SETTLE of ETH that names the router as payer", () => {
+            const ONE_ETH = 1000000000000000000n;
+            // A V4 swap of `amount` of ETH for USDC. The SETTLE names the
+            // router as payer.
+            const v4EthFromRouter = (amount) =>
+                encodeV4Swap(
+                    new Uint8Array([
+                        V4_SWAP_EXACT_IN_SINGLE_ID,
+                        V4_SETTLE_ID,
+                        V4_TAKE_ALL_ID,
+                    ]),
+                    [
+                        encodeV4ExactInSingle(ZERO_ADDR, USDC_ADDR, amount, 1n),
+                        settle(ZERO_ADDR, amount, false),
+                        encodeV4TakeAll(USDC_ADDR, 1n),
+                    ],
+                );
+
+            test("after a V3 exact-in of 600 USDT, shows the 1 ETH moved from the sender", () => {
+                const result = decodeSteps(
+                    [0x00, 0x10],
+                    [V3_600, v4EthFromRouter(ONE_ETH)],
+                );
+                expect(linesBetweenTokens(result)).toEqual([
+                    ["Amount", "600.0000 USDT"],
+                    ["Moved from the sender", "1.0000 ETH"],
+                    ["Token moved", "ETH"],
+                    ["Moved to", "The swap step that spends it"],
+                ]);
+            });
+
+            // The UNWRAP_WETH leaves ETH in the router. The SETTLE may spend
+            // that ETH before the transaction's value.
+            test("after an UNWRAP_WETH into the router, shows at most 1 ETH moved from the sender", () => {
+                const result = decodeSteps(
+                    [0x00, 0x0c, 0x10],
+                    [
+                        encodeV3SwapExactIn(ROUTER_ADDR, USDT_600, 1n, [
+                            USDT_ADDR,
+                            WETH_ADDR,
+                        ]),
+                        encodeWrapEth(ROUTER_ADDR, 0n), // UNWRAP_WETH, same encoding
+                        v4EthFromRouter(ONE_ETH),
+                    ],
+                );
+                expect(linesBetweenTokens(result)).toEqual([
+                    ["Amount", "600.0000 USDT"],
+                    ["Moved from the sender", "Up to 1.0000 ETH"],
+                    ["Token moved", "ETH"],
+                    ["Moved to", "The swap step that spends it"],
+                ]);
+            });
+
+            test("after a WRAP_ETH of 0.5 ETH, adds the SETTLE's 0.5 ETH to the Amount line", () => {
+                const result = decodeSteps(
+                    [0x0b, 0x10],
+                    [
+                        encodeWrapEth(ROUTER_ADDR, ONE_ETH / 2n),
+                        v4EthFromRouter(ONE_ETH / 2n),
+                    ],
+                );
+                expect(linesBetweenTokens(result)).toEqual([
+                    ["Amount", "1.0000 ETH"],
+                ]);
+            });
+
+            // The WRAP_ETH sets Token In to ETH, and the UNWRAP_WETH leaves
+            // ETH in the router. The SETTLE may spend that ETH before the
+            // transaction's value, so its 1 ETH never joins the Amount line.
+            test("after a WRAP_ETH and an UNWRAP_WETH into the router, keeps the Amount line and shows at most 1 ETH moved from the sender", () => {
+                const result = decodeSteps(
+                    [0x0b, 0x0c, 0x10],
+                    [
+                        encodeWrapEth(ROUTER_ADDR, ONE_ETH / 2n),
+                        encodeWrapEth(ROUTER_ADDR, 0n), // UNWRAP_WETH, same encoding
+                        v4EthFromRouter(ONE_ETH),
+                    ],
+                );
+                expect(linesBetweenTokens(result)).toEqual([
+                    ["Amount", "0.5000 ETH"],
+                    ["Moved from the sender", "Up to 1.0000 ETH"],
+                    ["Token moved", "ETH"],
+                    ["Moved to", "The swap step that spends it"],
+                ]);
+            });
+
+            // A SETTLE of CONTRACT_BALANCE pays all the router holds, an
+            // amount the calldata does not state.
+            test("of CONTRACT_BALANCE, on the step that sets the input side, shows an unknown amount moved from the sender", () => {
+                const result = decodeSteps(
+                    [0x10],
+                    [
+                        encodeV4Swap(
+                            new Uint8Array([
+                                V4_SWAP_EXACT_IN_SINGLE_ID,
+                                V4_SETTLE_ID,
+                                V4_TAKE_ALL_ID,
+                            ]),
+                            [
+                                encodeV4ExactInSingle(
+                                    ZERO_ADDR,
+                                    USDC_ADDR,
+                                    ONE_ETH,
+                                    1n,
+                                ),
+                                settle(ZERO_ADDR, 2n ** 255n, false), // CONTRACT_BALANCE
+                                encodeV4TakeAll(USDC_ADDR, 1n),
+                            ],
+                        ),
+                    ],
+                );
+                expect(linesBetweenTokens(result)).toEqual([
+                    ["Moved from the sender", UNDECODED],
+                    ["Token moved", "ETH"],
+                    ["Moved to", "The swap step that spends it"],
+                ]);
+            });
+        });
     });
 
     // https://git.eeqj.de/sneak/AutistMask/issues/359 — the output half, in

tests/uniswapRecipient.test.js

@@ -1661,9 +1661,18 @@ describe("any token left in the router is not received", () => {
             ),
             min: "1990.0000 USDC",
         },
-        {
+    ])("$kind reads as a swap paid to the user", ({ data, min }) => {
-            kind: "a swap paying WETH to the router, an UNWRAP_WETH into the router, then a V4 swap settling all the ETH from the router",
+        const result = decode(data);
-            data: execute(
+        expect(labels(result)).toEqual(PAID_TO_USER);
+        expect(detail(result, "Min. received").value).toBe(min);
+    });
+
+    // https://git.eeqj.de/sneak/AutistMask/issues/682 — the SETTLE spends all
+    // the router's ETH, the transaction's value included, so the sender pays
+    // an amount the calldata does not state.
+    test("a swap paying WETH to the router, an UNWRAP_WETH into the router, then a V4 swap settling all the ETH from the router reads as a swap paid to the user", () => {
+        const result = decode(
+            execute(
                 swapToWeth(ADDRESS_THIS),
                 unwrapWeth(ADDRESS_THIS),
                 v4Swap(
@@ -1672,12 +1681,23 @@ describe("any token left in the router is not received", () => {
                     takeAll(USDC),
                 ),
             ),
-            min: "1990.0000 USDC",
+        );
-        },
+        expect(labels(result)).toEqual([
-    ])("$kind reads as a swap paid to the user", ({ data, min }) => {
+            "Protocol",
-        const result = decode(data);
+            "Token In",
-        expect(labels(result)).toEqual(PAID_TO_USER);
+            "Amount",
-        expect(detail(result, "Min. received").value).toBe(min);
+            "Moved from the sender",
+            "Token moved",
+            "Moved to",
+            "Token Out",
+            "Min. received",
+            "Steps",
+            "Deadline",
+        ]);
+        expect(detail(result, "Moved from the sender").value).toBe(
+            "Unknown (could not be decoded)",
+        );
+        expect(detail(result, "Min. received").value).toBe("1990.0000 USDC");
     });
 });