fix: a V4 swap action not in the deployed shape is shown as not decoded (closes #358)

The four V4 swap actions are read only as the parameter structs deployed
on mainnet and Sepolia. ethers decoded the newer v4-periphery structs,
which add minHopPriceX36, as the deployed ones without an error, and the
newer multi-hop exact-in struct showed the offset of its hop-price array
as the swap amount. A decode now counts only when encoding it again gives
back the same bytes. A swap action that fails that marks its step "V4
Swap (could not be decoded)", and a side of the swap that its SETTLE or
TAKE did not name reads "Unknown (could not be decoded)" instead of
another step's token and figure. The README records both.

Model: opus-5-5

README.md

@@ -479,9 +479,6 @@ papered over:
   forced by clicking Reveal and the settings gear in one page task, which a
   person cannot do; the case a person can hit, the first decrypt after the popup
   opens while libsodium is still loading, is not driven.
-- Approval windows open at 1280x720 whatever size the extension asks for, so
-  whether an approval screen fits its window is checked in the Firefox suite
-  only.
 
 Any test that drives a failure path on purpose declares the `console.error` it
 is about to provoke, via `errors.expect()`. That is not a mute: the declaration
@@ -554,8 +551,7 @@ suite), wallet creation through the UI, the Add Token screen, and the dApp round
 trips — `eth_requestAccounts`, `personal_sign`, `wallet_switchEthereumChain`
 rejected and then approved, `eth_sendTransaction`, and a closed approval window
 rejecting with EIP-1193 4001 — driven through the real content script,
-background page and approval windows. The `personal_sign` prompt is also
-required to fit its window without scrolling sideways.
+background page and approval windows.
 
 The suite lives in `tests/e2e/firefox/`. Its WebDriver client (`driver.js`) has
 **no npm dependencies at all**: it is built on global `fetch` and
@@ -912,13 +908,8 @@ discoverable.
   enough that vanilla JS with simple view switching is sufficient. A framework
   would add bundle size, build complexity, and attack surface for no benefit at
   this scale.
-- **396x600 popup**: The page is 396 pixels wide (`body` in
-  `src/popup/styles/main.css`), and 600 pixels is as tall as the browser lets
-  the toolbar popup grow. The UI is designed for this fixed viewport. The window
-  an approval opens in is given the same size. The browser counts the window's
-  frame in that width, and a screen taller than the window gives some of it to a
-  vertical scrollbar, so once the approval's screen is up the page widens its
-  window by however far it would scroll sideways, scaled by the browser's zoom.
+- **360x600 popup**: Standard browser extension popup dimensions. The UI is
+  designed for this fixed viewport.
 
 #### No Layout Shift
 
@@ -1134,14 +1125,18 @@ read:
 
 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
-that side. An `UNWRAP_WETH` step makes `Token Out` ETH only when the output side
-is WETH, on mainnet or Sepolia, or when no step set the output side; a WETH
-`Min. received` figure then reads in ETH. 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.
+that side, or `Unknown (could not be decoded)` instead when a V4 swap action in
+the transaction could not be read (see Transaction Decoding below). A V4 step
+whose swap action could not be read still sets each side as a swap step does,
+and a side its `SETTLE` or `TAKE` did not name is then unknown: no other step's
+token or figure is shown for it. An `UNWRAP_WETH` step makes `Token Out` ETH
+only when the output side is WETH, on mainnet or Sepolia, or when no step set
+the output side; a WETH `Min. received` figure then reads in ETH. 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
@@ -2756,7 +2751,11 @@ Currently supported:
   or recipient, and amount.
 - **Uniswap Universal Router**: `execute()` calls — shows swap direction (e.g.
   "Swap USDT → ETH"), token addresses, amounts, execution steps, and deadline.
-  Decodes Permit2, V2/V3/V4 swaps, wrap/unwrap, and balance checks.
+  Decodes Permit2, V2/V3/V4 swaps, wrap/unwrap, and balance checks. A V4 swap
+  action is read only in the parameter shape deployed on mainnet and Sepolia,
+  not in the newer one on `v4-periphery` `main`, which adds a `minHopPriceX36`
+  field. An action in any other shape is not read, and its step is listed as
+  `V4 Swap (could not be decoded)`.
 
 ### Non-Goals Forever
 

src/background/index.js

@@ -423,10 +423,7 @@ function releaseApproval(approval) {
 // the result on the floor, so a rejection here would be unhandled.
 async function openApprovalWindow(id) {
     const popupUrl = runtime.getURL("src/popup/index.html?approval=" + id);
-    // As wide as the page: body in src/popup/styles/main.css. The browser
-    // counts the window's frame in this width; the page itself adds back
-    // whatever the frame takes (src/popup/index.js).
-    const popupWidth = 396;
+    const popupWidth = 360;
     const popupHeight = 600;
 
     let currentWin = null;
@@ -446,7 +443,7 @@ async function openApprovalWindow(id) {
     // Centred on a browser window only. The last focused window can be
     // another approval window still open, and centring on one can give a
     // position the browser refuses ("Bounds must be at least 50% within
-    // visible screen space"): headless Chrome reports this 396x600 popup as
+    // visible screen space"): headless Chrome reports this 360x600 popup as
     // 1280x720. The request then failed with no window at all. Over a popup,
     // the browser picks the position.
     if (currentWin && currentWin.type === "normal") {

src/popup/index.js

@@ -21,11 +21,6 @@ const {
     goBack,
 } = require("./views/helpers");
 const { applyTheme } = require("./theme");
-const {
-    tabsGetZoom,
-    windowsGetCurrent,
-    windowsUpdate,
-} = require("../shared/browserApi");
 // Renders a view the popup lands on without having navigated to it forward:
 // on restore here, and on Back. Only the views that can be fully re-rendered
 // from persisted state (RESTORABLE_VIEWS, src/shared/restorableViews.js) go
@@ -168,27 +163,6 @@ function fallbackView() {
     showView("main");
 }
 
-// The background opens the approval window as wide as the page, but the
-// browser counts the window's frame in that width, and a screen taller than
-// the window takes a vertical scrollbar out of it too. So once the screen is
-// up, the window is widened by however far the page would scroll sideways.
-// That distance is in page pixels and the window's width in screen pixels:
-// at 150% zoom one page pixel is 1.5 screen pixels. The connection prompt can
-// also show in the toolbar popup, whose window is the user's browser window;
-// that one is left alone.
-async function widenApprovalWindow() {
-    const sideways =
-        document.documentElement.scrollWidth -
-        document.documentElement.clientWidth;
-    if (sideways <= 0) return;
-    const win = await windowsGetCurrent();
-    if (win.type !== "popup") return;
-    const zoom = await tabsGetZoom();
-    await windowsUpdate(win.id, {
-        width: win.width + Math.ceil(sideways * zoom),
-    });
-}
-
 async function init() {
     // First, before anything can save: showView() saves on every navigation
     // without awaiting, so a save that fails from here on has somewhere to be
@@ -265,8 +239,8 @@ async function init() {
         // the run on both harnesses (Playwright `pageerror`, and the Firefox
         // driver's console-service drain), so nothing is lost by leaving it
         // on that path. show() puts the approval's own screen up once the
-        // background has described it; the window is widened to fit it then.
-        approval.show(approvalId).then(widenApprovalWindow);
+        // background has described it.
+        approval.show(approvalId);
         return;
     }
 

src/shared/browserApi.js

@@ -235,14 +235,6 @@ function tabsSendMessage(tabId, message) {
     return invoke(tabsApi(), "sendMessage", tabId, message);
 }
 
-/**
- * @returns {Promise<number>} the zoom of the active tab in the calling page's
- *     window: 1.5 at 150%.
- */
-function tabsGetZoom() {
-    return invoke(tabsApi(), "getZoom");
-}
-
 /**
  * @param {Object} createData
  * @returns {Promise<Object>} the created window.
@@ -258,22 +250,6 @@ function windowsGetLastFocused() {
     return invoke(windowsApi(), "getLastFocused");
 }
 
-/**
- * @returns {Promise<Object>} the window the calling page is in.
- */
-function windowsGetCurrent() {
-    return invoke(windowsApi(), "getCurrent");
-}
-
-/**
- * @param {number} windowId
- * @param {Object} updateInfo
- * @returns {Promise<Object>} the updated window.
- */
-function windowsUpdate(windowId, updateInfo) {
-    return invoke(windowsApi(), "update", windowId, updateInfo);
-}
-
 /**
  * @param {number} windowId
  * @returns {Promise<void>}
@@ -295,13 +271,10 @@ module.exports = {
     storageRemove,
     storageSet,
     tabsApi,
-    tabsGetZoom,
     tabsQuery,
     tabsSendMessage,
     windowsApi,
     windowsCreate,
-    windowsGetCurrent,
     windowsGetLastFocused,
     windowsRemove,
-    windowsUpdate,
 };

src/shared/uniswap.js

@@ -53,6 +53,11 @@ function formatAmount(raw, decimals) {
 // on a scale — not as a token name, and not as a quantity.
 const UNNAMED_CURRENCY = "Unknown (not named in the calldata)";
 
+// The same refusal when a V4 swap action could not be read (see
+// decodeExactly()). That action names both of its currencies, so saying the
+// calldata did not name one would be false.
+const UNDECODED_CURRENCY = "Unknown (could not be decoded)";
+
 // Explicit presence, never truthiness. Every gate in this file that guards a
 // decoded value goes through here: an address is never falsy once set, but an
 // amount of 0n is, and a gate that cannot tell a genuine zero from an absent
@@ -295,6 +300,24 @@ function v4ExactInAmount(raw) {
     return raw === 0n ? OPEN_DELTA : raw;
 }
 
+// The V4 swap actions are read only in the parameter structs V4Router has
+// deployed on mainnet and Sepolia. v4-periphery `main` has since added a
+// `minHopPriceX36` field to all four (`src/interfaces/IV4Router.sol`), and
+// reading a shape nobody has deployed would be guessing. ethers alone would
+// read the newer structs anyway: it takes whatever word sits where a
+// deployed field would be, ignores bytes left over, and holds back an error
+// in a field until that field is used. The newer multi-hop exact-in struct
+// then yields the offset of its hop-price array as `amountIn`. So a decode
+// counts only when encoding the result again gives back the same bytes;
+// otherwise this throws, and decodeV4Swap() marks the step as not decoded.
+function decodeExactly(types, data) {
+    const decoded = coder.decode(types, data);
+    if (coder.encode(types, decoded) !== data) {
+        throw new Error("Not in the deployed V4 parameter shape.");
+    }
+    return decoded;
+}
+
 // Decode V4_SWAP (command 0x10) input bytes.
 // The input is ABI-encoded as (bytes actions, bytes[] params).
 // We extract token addresses from SETTLE (input) and TAKE (output) sub-actions,
@@ -309,6 +332,10 @@ function decodeV4Swap(input) {
         let takeToken = null;
         let amountIn = null;
         let amountOutMin = null;
+        // Set when a swap action's parameters are not in the deployed shape
+        // (see decodeExactly()), so nothing was read from that action. SETTLE
+        // and TAKE may still name both currencies.
+        let swapUndecoded = false;
 
         for (let i = 0; i < actions.length; i++) {
             const actionId = actions[i];
@@ -337,7 +364,7 @@ function decodeV4Swap(input) {
                         //   tuple(address,uint24,int24,address,bytes)[] path,
                         //   uint128 amountIn, uint128 amountOutMin)
                         try {
-                            const s = coder.decode(
+                            const s = decodeExactly(
                                 [
                                     "tuple(address,tuple(address,uint24,int24,address,bytes)[],uint128,uint128)",
                                 ],
@@ -355,13 +382,13 @@ function decodeV4Swap(input) {
                                 amountOutMin = s[0][3];
                             }
                         } catch {
-                            // Fall through — SETTLE/TAKE will provide tokens
+                            swapUndecoded = true;
                         }
                     } else {
                         // ExactInputSingleParams: (tuple(address,address,uint24,int24,address) poolKey,
                         //   bool zeroForOne, uint128 amountIn, uint128 amountOutMin, bytes hookData)
                         try {
-                            const s = coder.decode(
+                            const s = decodeExactly(
                                 [
                                     "tuple(tuple(address,address,uint24,int24,address),bool,uint128,uint128,bytes)",
                                 ],
@@ -384,7 +411,7 @@ function decodeV4Swap(input) {
                                 amountOutMin = s[0][3];
                             }
                         } catch {
-                            // Fall through
+                            swapUndecoded = true;
                         }
                     }
                 } else if (
@@ -393,7 +420,7 @@ function decodeV4Swap(input) {
                 ) {
                     if (actionId === V4_SWAP_EXACT_OUT) {
                         try {
-                            const s = coder.decode(
+                            const s = decodeExactly(
                                 [
                                     "tuple(address,tuple(address,uint24,int24,address,bytes)[],uint128,uint128)",
                                 ],
@@ -405,11 +432,11 @@ function decodeV4Swap(input) {
                                 settleToken = path[path.length - 1][0];
                             }
                         } catch {
-                            // Fall through
+                            swapUndecoded = true;
                         }
                     } else {
                         try {
-                            const s = coder.decode(
+                            const s = decodeExactly(
                                 [
                                     "tuple(tuple(address,address,uint24,int24,address),bool,uint128,uint128,bytes)",
                                 ],
@@ -426,7 +453,7 @@ function decodeV4Swap(input) {
                                     ? poolKey[1]
                                     : poolKey[0];
                         } catch {
-                            // Fall through
+                            swapUndecoded = true;
                         }
                     }
                 }
@@ -440,6 +467,7 @@ function decodeV4Swap(input) {
             tokenOut: takeToken,
             amountIn,
             amountOutMin,
+            swapUndecoded,
         };
     } catch {
         return null;
@@ -465,6 +493,7 @@ function decode(data, toAddress, sources) {
         let minOutput = null;
         let hasUnwrapWeth = false;
         let hasV2ExactOut = false;
+        let swapUndecoded = false;
         const commandNames = [];
 
         // THE INVARIANT: an amount and the token it is counted in always come
@@ -567,7 +596,20 @@ function decode(data, toAddress, sources) {
 
                 if (cmdId === 0x10) {
                     const v4 = decodeV4Swap(inputs[i]);
-                    if (v4) {
+                    if (v4 && v4.swapUndecoded) {
+                        // The unread swap action named this step's currencies
+                        // and amounts, so the step is marked and still sets
+                        // both sides as a swap step does. A side its SETTLE or
+                        // TAKE did not name is set undetermined, not left to
+                        // an earlier or later step's token and figure.
+                        swapUndecoded = true;
+                        commandNames[i] += " (could not be decoded)";
+                        if (!inputEstablished) {
+                            setInput(v4.tokenIn, v4.amountIn);
+                        }
+                        outputToken = v4.tokenOut;
+                        minOutput = v4.amountOutMin;
+                    } else if (v4) {
                         setInputOnce(v4.tokenIn, v4.amountIn);
                         // Always update output: last swap step wins. A step
                         // that carries the Min. received figure but decoded no
@@ -591,16 +633,19 @@ function decode(data, toAddress, sources) {
             }
         }
 
-        // Resolve token info. A null token on either side means the calldata
-        // named no currency for it; tokenInfo() refuses rather than calling it
-        // ETH. UNWRAP_WETH turns WETH into ETH, so it makes the output ETH
-        // when the output side is WETH, or when no step set the output side.
-        // Any other output keeps its own token and figure: a swap that buys
-        // USDC and then unwraps the WETH it did not spend receives USDC.
+        // Resolve token info. A null token on either side means no step named
+        // a currency for it, or a V4 step whose swap action went unread left
+        // it undetermined; tokenInfo() refuses rather than calling it ETH.
+        // UNWRAP_WETH turns WETH into ETH, so it makes the output ETH when the
+        // output side is WETH, or when no step set the output side. A step
+        // whose swap action went unread did set it, to undetermined. Any other
+        // output keeps its own token and figure: a swap that buys USDC and
+        // then unwraps the WETH it did not spend receives USDC.
         const outputIsWeth =
             present(outputToken) &&
             WETH_ADDRESSES.includes(outputToken.toLowerCase());
-        const outputUnset = !present(outputToken) && !present(minOutput);
+        const outputUnset =
+            !present(outputToken) && !present(minOutput) && !swapUndecoded;
         const inInfo = tokenInfo(inputToken, sources);
         const outInfo =
             hasUnwrapWeth && (outputIsWeth || outputUnset)
@@ -640,7 +685,10 @@ function decode(data, toAddress, sources) {
             // rather than going missing or naming a token by default. Same
             // wording as the Token Out refusal below: the two sides of this
             // screen must not describe the same condition in two ways.
-            details.push({ label: "Token In", value: UNNAMED_CURRENCY });
+            details.push({
+                label: "Token In",
+                value: swapUndecoded ? UNDECODED_CURRENCY : UNNAMED_CURRENCY,
+            });
         }
 
         if (present(inputAmount)) {
@@ -703,7 +751,10 @@ function decode(data, toAddress, sources) {
             // rather than going missing or naming a token by default, and a
             // Min. received figure below it is never attached to a token the
             // calldata did not state.
-            details.push({ label: "Token Out", value: UNNAMED_CURRENCY });
+            details.push({
+                label: "Token Out",
+                value: swapUndecoded ? UNDECODED_CURRENCY : UNNAMED_CURRENCY,
+            });
         }
 
         if (present(minOutput)) {

tests/approvalWindow.test.js

@@ -45,77 +45,3 @@ test("the approval window shows no screen until the background describes the app
     expect(env.visibleViews()).toEqual(["approve-network"]);
     expect(env.pageErrors).toEqual([]);
 });
-
-// The background opens the approval window as wide as the page, but the
-// browser counts the window's frame in that width, and a screen taller than
-// the window takes a vertical scrollbar out of it too
-// (https://git.eeqj.de/sneak/AutistMask/issues/518). The browser suites run
-// without frames and at 100% zoom, so the widening is checked here.
-function windowsStub(type) {
-    const updates = [];
-    return {
-        updates,
-        getCurrent: (done) => done({ id: 7, type, width: 396 }),
-        update: (id, info, done) => {
-            updates.push({ id, info });
-            done({});
-        },
-    };
-}
-
-// An approval window at 150% zoom, whose background holds its answer until
-// the test gives it.
-async function bootZoomedApprovalWindow(windows) {
-    let answer = null;
-    const env = await bootPopup(unversionedValidProfile(), {
-        search: "?approval=approval-1",
-        runtime: {
-            connect: () => ({ postMessage: () => {} }),
-            sendMessage: (msg, reply) => {
-                if (msg.type === "AUTISTMASK_GET_APPROVAL") answer = reply;
-            },
-        },
-        windows,
-        tabs: { getZoom: (done) => done(1.5) },
-        // At 150% a window 396 screen pixels wide shows 264 page pixels.
-        documentElement: { scrollWidth: 396, clientWidth: 264 },
-    });
-    return { env, answer };
-}
-
-test("at 150% zoom the approval window widens by what its screen lacks, scrollbar included", async () => {
-    const windows = windowsStub("popup");
-    const { env, answer } = await bootZoomedApprovalWindow(windows);
-
-    // Not before there is a screen to fit.
-    expect(windows.updates).toEqual([]);
-
-    // The screen is taller than the window, so once it is up a vertical
-    // scrollbar takes 15 screen pixels, 10 page pixels at 150%.
-    env.document.documentElement.clientWidth = 254;
-    answer({
-        type: "network",
-        origin: "https://dapp.example",
-        currentNetworkId: "mainnet",
-        requestedNetworkId: "sepolia",
-        isPhishingDomain: false,
-    });
-    await settle();
-
-    // 396 - 254 = 142 page pixels short, which at 150% is 213 screen pixels.
-    expect(env.visibleViews()).toEqual(["approve-network"]);
-    expect(windows.updates).toEqual([{ id: 7, info: { width: 609 } }]);
-    expect(env.pageErrors).toEqual([]);
-});
-
-test("a connection prompt in the toolbar popup leaves the browser window alone", async () => {
-    const windows = windowsStub("normal");
-    const { env, answer } = await bootZoomedApprovalWindow(windows);
-
-    answer({ origin: "https://dapp.example", isPhishingDomain: false });
-    await settle();
-
-    expect(env.visibleViews()).toEqual(["approve-site"]);
-    expect(windows.updates).toEqual([]);
-    expect(env.pageErrors).toEqual([]);
-});

tests/backgroundApproval.test.js

@@ -2854,7 +2854,7 @@ describe("where an approval window opens", () => {
         await settle();
 
         expect(bg.created).toHaveLength(1);
-        expect(bg.created[0]).toMatchObject({ left: 442, top: 60 });
+        expect(bg.created[0]).toMatchObject({ left: 460, top: 60 });
     });
 
     test("not centred on an approval window the user was last in", async () => {
@@ -2871,7 +2871,7 @@ describe("where an approval window opens", () => {
         bg.requestSign();
         await settle();
 
-        // Centred, it would be at left 882, the position the browser refused.
+        // Centred, it would be at left 900, the position the browser refused.
         expect(bg.created).toHaveLength(1);
         expect(bg.created[0].left).toBeUndefined();
         expect(bg.created[0].top).toBeUndefined();
@@ -2893,7 +2893,7 @@ describe("where an approval window opens", () => {
         await settle();
 
         expect(bg.created).toHaveLength(2);
-        expect(bg.created[0]).toMatchObject({ left: 1502, top: 750 });
+        expect(bg.created[0]).toMatchObject({ left: 1520, top: 750 });
         expect(bg.created[1].left).toBeUndefined();
         expect(bg.created[1].top).toBeUndefined();
 

tests/e2e/firefox/run.js

@@ -640,17 +640,6 @@ step(
         await d.switchToWindow(popup);
         await d.waitVisible("#view-approve-sign");
 
-        // The window is opened as wide as the page, and widened once the
-        // screen is up if it still scrolls sideways
-        // (https://git.eeqj.de/sneak/AutistMask/issues/518). This suite is
-        // where that is checked: the Chrome suite's approval windows open at
-        // 1280x720 whatever width the extension asks for.
-        await d.waitFor(
-            "the sign prompt to fit its window without scrolling sideways",
-            "return document.documentElement.scrollWidth <=" +
-                " document.documentElement.clientWidth;",
-        );
-
         const screen = await d.execute(
             `return {
              origin: document.getElementById("approve-sign-origin").textContent,

tests/support/popupBoot.js

@@ -242,13 +242,6 @@ async function settle() {
  *     "?approval=" and an id for the popup opened as an approval window.
  * @param {object} [options.runtime] members of chrome.runtime that replace the
  *     stub's own, for a test that has to answer the background's messages.
- * @param {object} [options.windows] chrome.windows, for a test of the approval
- *     window resizing itself.
- * @param {object} [options.tabs] chrome.tabs, for the same test: the page's
- *     zoom.
- * @param {object} [options.documentElement] members of document.documentElement
- *     that replace the stub's own: scrollWidth and clientWidth, which are equal
- *     unless a test says otherwise, so the page does not scroll sideways.
  * @returns {Promise<object>} handles onto the booted page.
  */
 async function bootPopup(stored, options) {
@@ -284,11 +277,6 @@ async function bootPopup(stored, options) {
         (options && options.storage) ||
         makeStorageStub(stored === undefined ? {} : { autistmask: stored });
     const document = makeDocument(POPUP_HTML);
-    Object.assign(
-        document.documentElement,
-        { scrollWidth: 396, clientWidth: 396 },
-        options && options.documentElement,
-    );
     const reloads = [];
 
     globalThis.chrome = {
@@ -299,8 +287,6 @@ async function bootPopup(stored, options) {
             onMessage: { addListener: () => {} },
             ...(options && options.runtime),
         },
-        windows: options && options.windows,
-        tabs: options && options.tabs,
     };
     globalThis.document = document;
     globalThis.window = {

tests/uniswap.test.js

@@ -163,6 +163,122 @@ function encodeV4ExactInSingle(currency0, currency1, amountIn, amountOutMin) {
     );
 }
 
+// Each V4 swap action's parameters in two shapes: the struct V4Router has
+// deployed on mainnet and Sepolia, and the one v4-periphery `main` has since
+// moved to, which adds a `minHopPriceX36` field. Each swaps WETH for USDC.
+const POOL_KEY = "tuple(address,address,uint24,int24,address)";
+const PATH_KEY = "tuple(address,uint24,int24,address,bytes)";
+const WETH_USDC_POOL = [WETH_ADDR, USDC_ADDR, 100, 1, ZERO_ADDR];
+const ONE_WETH = 1000000000000000000n;
+const V4_SWAP_ACTION_SHAPES = [
+    {
+        action: "SWAP_EXACT_IN_SINGLE",
+        id: 0x06,
+        deployed: coder.encode(
+            [`tuple(${POOL_KEY},bool,uint128,uint128,bytes)`],
+            [[WETH_USDC_POOL, true, ONE_WETH, 990000n, "0x"]],
+        ),
+        newer: coder.encode(
+            [`tuple(${POOL_KEY},bool,uint128,uint128,uint256,bytes)`],
+            [[WETH_USDC_POOL, true, ONE_WETH, 990000n, 0n, "0x"]],
+        ),
+    },
+    {
+        action: "SWAP_EXACT_IN",
+        id: 0x07,
+        deployed: coder.encode(
+            [`tuple(address,${PATH_KEY}[],uint128,uint128)`],
+            [
+                [
+                    WETH_ADDR,
+                    [[USDC_ADDR, 100, 1, ZERO_ADDR, "0x"]],
+                    ONE_WETH,
+                    990000n,
+                ],
+            ],
+        ),
+        newer: coder.encode(
+            [`tuple(address,${PATH_KEY}[],uint256[],uint128,uint128)`],
+            [
+                [
+                    WETH_ADDR,
+                    [[USDC_ADDR, 100, 1, ZERO_ADDR, "0x"]],
+                    [],
+                    ONE_WETH,
+                    990000n,
+                ],
+            ],
+        ),
+    },
+    {
+        action: "SWAP_EXACT_OUT_SINGLE",
+        id: 0x08,
+        deployed: coder.encode(
+            [`tuple(${POOL_KEY},bool,uint128,uint128,bytes)`],
+            [[WETH_USDC_POOL, true, 990000n, ONE_WETH, "0x"]],
+        ),
+        newer: coder.encode(
+            [`tuple(${POOL_KEY},bool,uint128,uint128,uint256,bytes)`],
+            [[WETH_USDC_POOL, true, 990000n, ONE_WETH, 0n, "0x"]],
+        ),
+    },
+    {
+        action: "SWAP_EXACT_OUT",
+        id: 0x09,
+        deployed: coder.encode(
+            [`tuple(address,${PATH_KEY}[],uint128,uint128)`],
+            [
+                [
+                    USDC_ADDR,
+                    [[WETH_ADDR, 100, 1, ZERO_ADDR, "0x"]],
+                    990000n,
+                    ONE_WETH,
+                ],
+            ],
+        ),
+        newer: coder.encode(
+            [`tuple(address,${PATH_KEY}[],uint256[],uint128,uint128)`],
+            [
+                [
+                    USDC_ADDR,
+                    [[WETH_ADDR, 100, 1, ZERO_ADDR, "0x"]],
+                    [],
+                    990000n,
+                    ONE_WETH,
+                ],
+            ],
+        ),
+    },
+];
+
+// Helper: execute() with one V4_SWAP step holding the swap action, then
+// SETTLE of WETH and TAKE of USDC.
+function v4SwapCalldata(actionId, swapParams) {
+    return buildExecute(
+        "0x10",
+        [
+            encodeV4Swap(new Uint8Array([actionId, V4_SETTLE_ID, V4_TAKE_ID]), [
+                swapParams,
+                encodeV4Settle(WETH_ADDR),
+                encodeV4Take(USDC_ADDR),
+            ]),
+        ],
+        9999999999n,
+    );
+}
+
+// V4 SETTLE_ALL (currency, maxAmount) and TAKE_ALL (currency, minAmount). The
+// decoder reads neither, so in a V4_SWAP of a swap action and these, only the
+// swap action names the currencies.
+const V4_SETTLE_ALL_ID = 0x0c;
+const V4_TAKE_ALL_ID = 0x0f;
+function encodeV4SettleAll(currency, maxAmount) {
+    return coder.encode(["address", "uint256"], [currency, maxAmount]);
+}
+function encodeV4TakeAll(currency, minAmount) {
+    return coder.encode(["address", "uint256"], [currency, minAmount]);
+}
+
 function detail(result, label) {
     return result.details.find((d) => d.label === label);
 }
@@ -203,9 +319,157 @@ describe("uniswap decoder", () => {
             result.details.find((d) => d.label === "Min. received").value,
         ).toBe("0.0002 ETH");
 
+        // Real mainnet calldata is in the deployed shape, so its V4 step is
+        // not said to be undecoded.
         const steps = result.details.find((d) => d.label === "Steps");
-        expect(steps.value).toContain("Permit2 Permit");
-        expect(steps.value).toContain("V4 Swap");
+        expect(steps.value).toBe("Permit2 Permit → V4 Swap");
+    });
+
+    test.each(V4_SWAP_ACTION_SHAPES)(
+        "a V4 $action in the deployed shape is read",
+        ({ id, deployed }) => {
+            const result = uniswap.decode(
+                v4SwapCalldata(id, deployed),
+                ROUTER_ADDR,
+            );
+            expect(detail(result, "Steps").value).toBe("V4 Swap");
+        },
+    );
+
+    // https://git.eeqj.de/sneak/AutistMask/issues/358 — before it, all four
+    // newer structs decoded as the deployed ones without an error, and the
+    // newer SWAP_EXACT_IN showed the offset of its hop-price array as Amount
+    // ("0.0000000000000004 WETH") and its amountIn as Min. received.
+    test.each(V4_SWAP_ACTION_SHAPES)(
+        "a V4 $action in the newer periphery shape is shown as not decoded",
+        ({ id, newer }) => {
+            const result = uniswap.decode(
+                v4SwapCalldata(id, newer),
+                ROUTER_ADDR,
+            );
+            expect(detail(result, "Amount")).toBeUndefined();
+            expect(detail(result, "Min. received")).toBeUndefined();
+            expect(detail(result, "Steps").value).toBe(
+                "V4 Swap (could not be decoded)",
+            );
+            // SETTLE and TAKE keep their own shape and still name both sides.
+            expect(detail(result, "Token In").address).toBe(WETH_ADDR);
+            expect(detail(result, "Token Out").address).toBe(USDC_ADDR);
+        },
+    );
+
+    // Only the unread swap action names the currencies here. The token lines
+    // must not say the calldata did not name them.
+    test.each(V4_SWAP_ACTION_SHAPES)(
+        "a V4 $action in the newer shape, then SETTLE_ALL and TAKE_ALL, says both tokens could not be decoded",
+        ({ id, newer }) => {
+            const data = buildExecute(
+                "0x10",
+                [
+                    encodeV4Swap(
+                        new Uint8Array([id, V4_SETTLE_ALL_ID, V4_TAKE_ALL_ID]),
+                        [
+                            newer,
+                            encodeV4SettleAll(WETH_ADDR, ONE_WETH),
+                            encodeV4TakeAll(USDC_ADDR, 990000n),
+                        ],
+                    ),
+                ],
+                9999999999n,
+            );
+            const result = uniswap.decode(data, ROUTER_ADDR);
+            expect(detail(result, "Steps").value).toBe(
+                "V4 Swap (could not be decoded)",
+            );
+            expect(detail(result, "Token In").value).toBe(
+                "Unknown (could not be decoded)",
+            );
+            expect(detail(result, "Token Out").value).toBe(
+                "Unknown (could not be decoded)",
+            );
+        },
+    );
+
+    // The user receives the V4 step's USDC, which only its unread swap
+    // action names. The V3 step's WETH and its Min. received figure were
+    // shown instead.
+    test.each(V4_SWAP_ACTION_SHAPES)(
+        "a V3 step, then a V4 $action in the newer shape and TAKE_ALL, does not show the V3 step's output",
+        ({ id, newer }) => {
+            const data = buildExecute(
+                solidityPacked(["uint8", "uint8"], [0x00, 0x10]),
+                [
+                    encodeV3SwapExactIn(USER_ADDR, 2000000n, ONE_WETH, [
+                        USDT_ADDR,
+                        WETH_ADDR,
+                    ]),
+                    encodeV4Swap(new Uint8Array([id, V4_TAKE_ALL_ID]), [
+                        newer,
+                        encodeV4TakeAll(USDC_ADDR, 990000n),
+                    ]),
+                ],
+                9999999999n,
+            );
+            const result = uniswap.decode(data, ROUTER_ADDR);
+            expect(result.name).toBe("Uniswap Swap");
+            expect(detail(result, "Amount").value).toBe("2.0000 USDT");
+            expect(detail(result, "Token Out").value).toBe(
+                "Unknown (could not be decoded)",
+            );
+            expect(detail(result, "Min. received")).toBeUndefined();
+        },
+    );
+
+    // The user pays the V4 step's WETH, which only its unread swap action
+    // names. The V3 step's USDC and its amount were shown instead.
+    test.each(V4_SWAP_ACTION_SHAPES)(
+        "a V4 $action in the newer shape and SETTLE_ALL, then a V3 step, does not show the V3 step's input",
+        ({ id, newer }) => {
+            const data = buildExecute(
+                solidityPacked(["uint8", "uint8"], [0x10, 0x00]),
+                [
+                    encodeV4Swap(new Uint8Array([id, V4_SETTLE_ALL_ID]), [
+                        newer,
+                        encodeV4SettleAll(WETH_ADDR, ONE_WETH),
+                    ]),
+                    encodeV3SwapExactIn(
+                        USER_ADDR,
+                        990000n,
+                        980000000000000000n,
+                        [USDC_ADDR, DAI_ADDR],
+                    ),
+                ],
+                9999999999n,
+            );
+            const result = uniswap.decode(data, ROUTER_ADDR);
+            expect(result.name).toBe("Uniswap Swap");
+            expect(detail(result, "Token In").value).toBe(
+                "Unknown (could not be decoded)",
+            );
+            expect(detail(result, "Amount")).toBeUndefined();
+            expect(detail(result, "Min. received").value).toBe("0.9800 DAI");
+        },
+    );
+
+    // UNWRAP_WETH makes Token Out ETH when no step set the output side. An
+    // unread swap action's step did set it, to undetermined.
+    test("an UNWRAP_WETH after an unread V4 swap action does not make Token Out ETH", () => {
+        const { id, newer } = V4_SWAP_ACTION_SHAPES[0];
+        const data = buildExecute(
+            solidityPacked(["uint8", "uint8"], [0x10, 0x0c]),
+            [
+                encodeV4Swap(new Uint8Array([id, V4_TAKE_ALL_ID]), [
+                    newer,
+                    encodeV4TakeAll(USDC_ADDR, 990000n),
+                ]),
+                encodeWrapEth(USER_ADDR, 0n), // UNWRAP_WETH, same encoding
+            ],
+            9999999999n,
+        );
+        const result = uniswap.decode(data, ROUTER_ADDR);
+        expect(detail(result, "Token Out").value).toBe(
+            "Unknown (could not be decoded)",
+        );
     });
 
     test("decodes V2_SWAP_EXACT_IN with known tokens", () => {
@@ -548,9 +812,11 @@ describe("uniswap decoder", () => {
         const result = uniswap.decode(data, ROUTER_ADDR);
         expect(result).not.toBeNull();
 
+        // The V4 swap action's parameters are empty, so that step is said to
+        // be undecoded.
         const steps = result.details.find((d) => d.label === "Steps");
         expect(steps.value).toBe(
-            "Permit2 Permit \u2192 V4 Swap \u2192 Unwrap WETH",
+            "Permit2 Permit \u2192 V4 Swap (could not be decoded) \u2192 Unwrap WETH",
         );
     });
 

tests/uniswapUndeterminedTokenIn.test.js

@@ -97,7 +97,11 @@ describe("an execute() whose input currency never decoded", () => {
         ]);
 
     test("says the input token is unknown instead of naming ETH", () => {
-        expect(detail(data(), "Token In").value).toBe(REFUSAL);
+        // The swap action that would name it could not be read, so the line
+        // says that rather than REFUSAL's "not named in the calldata".
+        expect(detail(data(), "Token In").value).toBe(
+            "Unknown (could not be decoded)",
+        );
     });
 
     test("keeps a Token In line, so the screen never omits what is paid", () => {