fix: resolve token symbols from multiple sources (closes #51)

When tokenBalances doesn't contain an entry for a token (e.g. before
balances are fetched), the symbol fell back to '?' in addressToken
and send views.

Add resolveSymbol() helper that checks tokenBalances → TOKEN_BY_ADDRESS
(known tokens) → trackedTokens → truncated address as last resort.

Fixes USDC and other known tokens showing '?' when balance data
hasn't loaded yet.

.gitignore

@@ -25,3 +25,4 @@ dist/
 
 # Yarn
 .yarn-integrity
+package-lock.json

src/popup/index.html

@@ -999,18 +999,18 @@
                             class="text-xs"
                         ></div>
                     </div>
-                    <div id="tx-detail-rawdata-section" class="hidden">
-                        <div class="text-xs text-muted mb-1">Raw data</div>
-                        <div
-                            id="tx-detail-rawdata"
-                            class="text-xs break-all font-mono border border-border border-dashed p-2"
-                        ></div>
-                    </div>
                 </div>
                 <div class="mb-4">
                     <div class="text-xs text-muted mb-1">Transaction hash</div>
                     <div id="tx-detail-hash" class="text-xs break-all"></div>
                 </div>
+                <div id="tx-detail-rawdata-section" class="mb-4 hidden">
+                    <div class="text-xs text-muted mb-1">Raw data</div>
+                    <div
+                        id="tx-detail-rawdata"
+                        class="text-xs break-all font-mono border border-border border-dashed p-2"
+                    ></div>
+                </div>
             </div>
 
             <!-- ============ TRANSACTION APPROVAL ============ -->

src/popup/views/addressDetail.js

@@ -186,10 +186,14 @@ function renderTransactions(txs) {
     let html = "";
     let i = 0;
     for (const tx of txs) {
+        // For swap transactions, show the user's own labelled wallet
+        // address instead of the contract address (see issue #55).
         const counterparty =
-            tx.direction === "sent" || tx.direction === "contract"
-                ? tx.to
-                : tx.from;
+            tx.direction === "contract" && tx.directionLabel === "Swap"
+                ? tx.from
+                : tx.direction === "sent" || tx.direction === "contract"
+                  ? tx.to
+                  : tx.from;
         const ensName = ensNameMap.get(counterparty) || null;
         const title = addressTitle(counterparty, state.wallets);
         const dirLabel = tx.directionLabel;

src/popup/views/addressToken.js

@@ -12,7 +12,7 @@ const {
     balanceLine,
 } = require("./helpers");
 const { state, currentAddress, saveState } = require("../../shared/state");
-const { TOKEN_BY_ADDRESS } = require("../../shared/tokenList");
+const { TOKEN_BY_ADDRESS, resolveSymbol } = require("../../shared/tokenList");
 const {
     formatUsd,
     getPrice,
@@ -87,6 +87,7 @@ function show() {
 
     // Determine token symbol and balance
     let symbol, amount, price;
+    const knownToken = TOKEN_BY_ADDRESS.get(tokenId.toLowerCase());
     if (tokenId === "ETH") {
         symbol = "ETH";
         amount = parseFloat(addr.balance || "0");
@@ -95,7 +96,11 @@ function show() {
         const tb = (addr.tokenBalances || []).find(
             (t) => t.address.toLowerCase() === tokenId.toLowerCase(),
         );
-        symbol = tb ? tb.symbol : "?";
+        symbol = resolveSymbol(
+            tokenId,
+            addr.tokenBalances,
+            state.trackedTokens,
+        );
         amount = tb ? parseFloat(tb.balance || "0") : 0;
         price = getPrice(symbol);
     }
@@ -138,13 +143,32 @@ function show() {
         const tb = (addr.tokenBalances || []).find(
             (t) => t.address.toLowerCase() === tokenId.toLowerCase(),
         );
-        const tokenName = tb && tb.name ? escapeHtml(tb.name) : null;
-        const tokenSymbol = tb && tb.symbol ? escapeHtml(tb.symbol) : null;
-        const tokenDecimals = tb && tb.decimals != null ? tb.decimals : null;
+        const tracked = (state.trackedTokens || []).find(
+            (t) => t.address.toLowerCase() === tokenId.toLowerCase(),
+        );
+        const rawName =
+            (tb && tb.name) ||
+            (tracked && tracked.name) ||
+            (knownToken && knownToken.name) ||
+            null;
+        const rawSymbol =
+            (tb && tb.symbol) ||
+            (tracked && tracked.symbol) ||
+            (knownToken && knownToken.symbol) ||
+            null;
+        const tokenName = rawName ? escapeHtml(rawName) : null;
+        const tokenSymbol = rawSymbol ? escapeHtml(rawSymbol) : null;
+        const tokenDecimals =
+            tb && tb.decimals != null
+                ? tb.decimals
+                : tracked && tracked.decimals != null
+                  ? tracked.decimals
+                  : knownToken && knownToken.decimals != null
+                    ? knownToken.decimals
+                    : null;
         const tokenHolders = tb && tb.holders != null ? tb.holders : null;
         const dot = addressDotHtml(tokenId);
         const tokenLink = `https://etherscan.io/token/${escapeHtml(tokenId)}`;
-        const knownToken = TOKEN_BY_ADDRESS.get(tokenId.toLowerCase());
         const projectUrl = knownToken && knownToken.url ? knownToken.url : null;
         let infoHtml = `<div class="font-bold mb-2">Contract Address</div>`;
         infoHtml +=

src/popup/views/approval.js

@@ -78,10 +78,12 @@ function decodeCalldata(data, toAddress) {
                     "0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff",
                 );
                 const isUnlimited = rawAmount === maxUint;
+                const amountRaw = isUnlimited
+                    ? "Unlimited"
+                    : formatTxValue(formatUnits(rawAmount, tokenDecimals));
                 const amountStr = isUnlimited
                     ? "Unlimited"
-                    : formatTxValue(formatUnits(rawAmount, tokenDecimals)) +
-                      (tokenSymbol ? " " + tokenSymbol : "");
+                    : amountRaw + (tokenSymbol ? " " + tokenSymbol : "");
 
                 return {
                     name: "Token Approval",
@@ -100,7 +102,11 @@ function decodeCalldata(data, toAddress) {
                             value: spender,
                             address: spender,
                         },
-                        { label: "Amount", value: amountStr },
+                        {
+                            label: "Amount",
+                            value: amountStr,
+                            rawValue: amountRaw,
+                        },
                     ],
                 };
             }
@@ -108,9 +114,11 @@ function decodeCalldata(data, toAddress) {
             if (parsed.name === "transfer") {
                 const to = parsed.args[0];
                 const rawAmount = parsed.args[1];
+                const amountRaw = formatTxValue(
+                    formatUnits(rawAmount, tokenDecimals),
+                );
                 const amountStr =
-                    formatTxValue(formatUnits(rawAmount, tokenDecimals)) +
-                    (tokenSymbol ? " " + tokenSymbol : "");
+                    amountRaw + (tokenSymbol ? " " + tokenSymbol : "");
 
                 return {
                     name: "Token Transfer",
@@ -125,7 +133,11 @@ function decodeCalldata(data, toAddress) {
                             isToken: true,
                         },
                         { label: "Recipient", value: to, address: to },
-                        { label: "Amount", value: amountStr },
+                        {
+                            label: "Amount",
+                            value: amountStr,
+                            rawValue: amountRaw,
+                        },
                     ],
                 };
             }
@@ -163,7 +175,7 @@ function showTxApproval(details) {
                 pendingTxDetails.to = d.address;
             }
             if (d.label === "Amount") {
-                pendingTxDetails.amount = d.value;
+                pendingTxDetails.amount = d.rawValue || d.value;
             }
         }
         if (token) {

src/popup/views/home.js

@@ -103,10 +103,15 @@ function renderHomeTxList(ctx) {
     let html = "";
     let i = 0;
     for (const tx of homeTxs) {
+        // For swap transactions, show the user's own labelled wallet
+        // address (the one that initiated the swap) instead of the
+        // contract address which is not useful in the list view.
         const counterparty =
-            tx.direction === "sent" || tx.direction === "contract"
-                ? tx.to
-                : tx.from;
+            tx.direction === "contract" && tx.directionLabel === "Swap"
+                ? tx.from
+                : tx.direction === "sent" || tx.direction === "contract"
+                  ? tx.to
+                  : tx.from;
         const dirLabel = tx.directionLabel;
         const amountStr = tx.value
             ? escapeHtml(tx.value + " " + tx.symbol)

src/popup/views/send.js

@@ -10,7 +10,7 @@ const {
 const { state, currentAddress } = require("../../shared/state");
 let ctx;
 const { getProvider } = require("../../shared/balances");
-const { KNOWN_SYMBOLS } = require("../../shared/tokenList");
+const { KNOWN_SYMBOLS, resolveSymbol } = require("../../shared/tokenList");
 
 const EXT_ICON =
     `<span style="display:inline-block;width:10px;height:10px;margin-left:4px;vertical-align:middle">` +
@@ -73,7 +73,11 @@ function updateSendBalance() {
         const tb = (addr.tokenBalances || []).find(
             (t) => t.address.toLowerCase() === token.toLowerCase(),
         );
-        const symbol = tb ? tb.symbol : "?";
+        const symbol = resolveSymbol(
+            token,
+            addr.tokenBalances,
+            state.trackedTokens,
+        );
         const bal = tb ? tb.balance || "0" : "0";
         $("send-balance").textContent =
             "Current balance: " + bal + " " + symbol;
@@ -124,7 +128,11 @@ function init(_ctx) {
             const tb = (addr.tokenBalances || []).find(
                 (t) => t.address.toLowerCase() === token.toLowerCase(),
             );
-            tokenSymbol = tb ? tb.symbol : "?";
+            tokenSymbol = resolveSymbol(
+                token,
+                addr.tokenBalances,
+                state.trackedTokens,
+            );
             tokenBalance = tb ? tb.balance || "0" : "0";
         }
 

src/popup/views/transactionDetail.js

@@ -37,11 +37,19 @@ function blockieHtml(address) {
     return `<img src="${src}" width="48" height="48" style="image-rendering:pixelated;border-radius:50%;display:inline-block">`;
 }
 
+function etherscanLinkHtml(url) {
+    return (
+        `<a href="${url}" target="_blank" rel="noopener" ` +
+        `class="inline-flex items-center"` +
+        `>${EXT_ICON}</a>`
+    );
+}
+
 function txAddressHtml(address, ensName, title) {
     const blockie = blockieHtml(address);
     const dot = addressDotHtml(address);
     const link = `https://etherscan.io/address/${address}`;
-    const extLink = `<a href="${link}" target="_blank" rel="noopener" class="inline-flex items-center">${EXT_ICON}</a>`;
+    const extLink = etherscanLinkHtml(link);
     let html = `<div class="mb-1">${blockie}</div>`;
     if (title) {
         html += `<div class="font-bold">${escapeHtml(title)}</div>`;
@@ -50,10 +58,10 @@ function txAddressHtml(address, ensName, title) {
         html +=
             `<div class="flex items-center">${dot}` +
             copyableHtml(ensName, "") +
-            extLink +
             `</div>` +
-            `<div class="break-all">` +
+            `<div class="flex items-center">${dot}` +
             copyableHtml(address, "break-all") +
+            extLink +
             `</div>`;
     } else {
         html +=
@@ -67,7 +75,7 @@ function txAddressHtml(address, ensName, title) {
 
 function txHashHtml(hash) {
     const link = `https://etherscan.io/tx/${hash}`;
-    const extLink = `<a href="${link}" target="_blank" rel="noopener" class="inline-flex items-center">${EXT_ICON}</a>`;
+    const extLink = etherscanLinkHtml(link);
     return copyableHtml(hash, "break-all") + extLink;
 }
 
@@ -93,9 +101,6 @@ function show(tx) {
         },
     };
     render();
-    if (tx.isContractCall || tx.direction === "contract") {
-        loadCalldata(tx.hash, tx.to);
-    }
 }
 
 function render() {
@@ -144,9 +149,15 @@ function render() {
         if (headingEl) headingEl.textContent = "Transaction";
     }
 
-    // Hide calldata section by default; loadCalldata will show it if needed
+    // Hide calldata and raw data sections; re-fetch if this is a contract call
     const calldataSection = $("tx-detail-calldata-section");
     if (calldataSection) calldataSection.classList.add("hidden");
+    const rawDataSection = $("tx-detail-rawdata-section");
+    if (rawDataSection) rawDataSection.classList.add("hidden");
+
+    if (tx.isContractCall || tx.direction === "contract") {
+        loadCalldata(tx.hash, tx.to);
+    }
 
     $("tx-detail-time").textContent =
         isoDate(tx.timestamp) + " (" + timeAgo(tx.timestamp) + ")";
@@ -193,9 +204,20 @@ async function loadCalldata(txHash, toAddress) {
             for (const d of decoded.details || []) {
                 detailsHtml += `<div class="mb-2">`;
                 detailsHtml += `<div class="text-muted">${escapeHtml(d.label)}</div>`;
-                if (d.address) {
+                if (d.address && d.isToken) {
+                    // Token entry: show symbol on its own line, then dot + address + Etherscan link
                     const dot = addressDotHtml(d.address);
-                    detailsHtml += `<div>${dot}${copyableHtml(d.value, "break-all")}</div>`;
+                    const tokenSymbol = d.value.match(/^(\S+)\s*\(/)?.[1];
+                    if (tokenSymbol) {
+                        detailsHtml += `<div class="font-bold">${escapeHtml(tokenSymbol)}</div>`;
+                    }
+                    const etherscanUrl = `https://etherscan.io/token/${d.address}`;
+                    detailsHtml += `<div class="flex items-center">${dot}${copyableHtml(d.address, "break-all")}${etherscanLinkHtml(etherscanUrl)}</div>`;
+                } else if (d.address) {
+                    // Protocol/contract entry: show name + Etherscan link
+                    const dot = addressDotHtml(d.address);
+                    const etherscanUrl = `https://etherscan.io/address/${d.address}`;
+                    detailsHtml += `<div class="flex items-center">${dot}${copyableHtml(d.value, "break-all")}${etherscanLinkHtml(etherscanUrl)}</div>`;
                 } else {
                     detailsHtml += `<div class="font-bold">${escapeHtml(d.value)}</div>`;
                 }
@@ -219,13 +241,16 @@ async function loadCalldata(txHash, toAddress) {
 
         section.classList.remove("hidden");
 
-        // Bind copy handlers for new elements
-        section.querySelectorAll("[data-copy]").forEach((el) => {
-            el.onclick = () => {
-                navigator.clipboard.writeText(el.dataset.copy);
-                showFlash("Copied!");
-            };
-        });
+        // Bind copy handlers for new elements (including raw data now outside section)
+        const copyTargets = [section, rawSection].filter(Boolean);
+        for (const container of copyTargets) {
+            container.querySelectorAll("[data-copy]").forEach((el) => {
+                el.onclick = () => {
+                    navigator.clipboard.writeText(el.dataset.copy);
+                    showFlash("Copied!");
+                };
+            });
+        }
     } catch (e) {
         log.errorf("loadCalldata failed:", e.message);
     }

src/shared/balances.js

@@ -85,6 +85,7 @@ async function fetchTokenBalances(address, blockscoutUrl, trackedTokens) {
 
             balances.push({
                 address: item.token.address_hash,
+                name: item.token.name || "",
                 symbol: item.token.symbol || "???",
                 decimals: decimals,
                 balance: bal,

src/shared/tokenList.js

@@ -3645,10 +3645,27 @@ async function getTopTokenPrices(n) {
     return prices;
 }
 
+// Resolve a token symbol from multiple sources, never returning "?".
+function resolveSymbol(tokenAddress, tokenBalances, trackedTokens) {
+    const lower = (tokenAddress || "").toLowerCase();
+    const tb = (tokenBalances || []).find(
+        (t) => t.address.toLowerCase() === lower,
+    );
+    if (tb && tb.symbol) return tb.symbol;
+    const known = TOKEN_BY_ADDRESS.get(lower);
+    if (known && known.symbol) return known.symbol;
+    const tracked = (trackedTokens || []).find(
+        (t) => t.address.toLowerCase() === lower,
+    );
+    if (tracked && tracked.symbol) return tracked.symbol;
+    return lower.slice(0, 10) + "\u2026";
+}
+
 module.exports = {
     TOKENS,
     TOKEN_BY_ADDRESS,
     KNOWN_SYMBOLS,
     getTopTokens,
     getTopTokenPrices,
+    resolveSymbol,
 };

src/shared/uniswap.js

@@ -161,6 +161,157 @@ function decodeWrapEth(input) {
     }
 }
 
+// V4 inner action IDs
+const V4_SWAP_EXACT_IN_SINGLE = 0x06;
+const V4_SWAP_EXACT_IN = 0x07;
+const V4_SWAP_EXACT_OUT_SINGLE = 0x08;
+const V4_SWAP_EXACT_OUT = 0x09;
+const V4_SETTLE = 0x0b;
+const V4_TAKE = 0x0e;
+
+// 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,
+// and swap amounts from the swap sub-actions.
+function decodeV4Swap(input) {
+    try {
+        const d = coder.decode(["bytes", "bytes[]"], input);
+        const actions = getBytes(d[0]);
+        const params = d[1];
+
+        let settleToken = null;
+        let takeToken = null;
+        let amountIn = null;
+        let amountOutMin = null;
+
+        for (let i = 0; i < actions.length; i++) {
+            const actionId = actions[i];
+            try {
+                if (actionId === V4_SETTLE) {
+                    // SETTLE: (address currency, uint256 maxAmount, bool payerIsUser)
+                    const s = coder.decode(
+                        ["address", "uint256", "bool"],
+                        params[i],
+                    );
+                    settleToken = s[0];
+                } else if (actionId === V4_TAKE) {
+                    // TAKE: (address currency, address recipient, uint256 amount)
+                    const t = coder.decode(
+                        ["address", "address", "uint256"],
+                        params[i],
+                    );
+                    takeToken = t[0];
+                } else if (
+                    actionId === V4_SWAP_EXACT_IN ||
+                    actionId === V4_SWAP_EXACT_IN_SINGLE
+                ) {
+                    // Extract amounts from exact-in swap actions
+                    if (actionId === V4_SWAP_EXACT_IN) {
+                        // ExactInputParams: (address currencyIn,
+                        //   tuple(address,uint24,int24,address,bytes)[] path,
+                        //   uint128 amountIn, uint128 amountOutMin)
+                        try {
+                            const s = coder.decode(
+                                [
+                                    "tuple(address,tuple(address,uint24,int24,address,bytes)[],uint128,uint128)",
+                                ],
+                                params[i],
+                            );
+                            if (!settleToken) settleToken = s[0][0];
+                            const path = s[0][1];
+                            if (path.length > 0 && !takeToken) {
+                                takeToken = path[path.length - 1][0];
+                            }
+                            if (!amountIn) amountIn = s[0][2];
+                            if (!amountOutMin) amountOutMin = s[0][3];
+                        } catch {
+                            // Fall through — SETTLE/TAKE will provide tokens
+                        }
+                    } else {
+                        // ExactInputSingleParams: (tuple(address,address,uint24,int24,address) poolKey,
+                        //   bool zeroForOne, uint128 amountIn, uint128 amountOutMin, bytes hookData)
+                        try {
+                            const s = coder.decode(
+                                [
+                                    "tuple(tuple(address,address,uint24,int24,address),bool,uint128,uint128,bytes)",
+                                ],
+                                params[i],
+                            );
+                            const poolKey = s[0][0];
+                            const zeroForOne = s[0][1];
+                            if (!settleToken)
+                                settleToken = zeroForOne
+                                    ? poolKey[0]
+                                    : poolKey[1];
+                            if (!takeToken)
+                                takeToken = zeroForOne
+                                    ? poolKey[1]
+                                    : poolKey[0];
+                            if (!amountIn) amountIn = s[0][2];
+                            if (!amountOutMin) amountOutMin = s[0][3];
+                        } catch {
+                            // Fall through
+                        }
+                    }
+                } else if (
+                    actionId === V4_SWAP_EXACT_OUT ||
+                    actionId === V4_SWAP_EXACT_OUT_SINGLE
+                ) {
+                    if (actionId === V4_SWAP_EXACT_OUT) {
+                        try {
+                            const s = coder.decode(
+                                [
+                                    "tuple(address,tuple(address,uint24,int24,address,bytes)[],uint128,uint128)",
+                                ],
+                                params[i],
+                            );
+                            if (!takeToken) takeToken = s[0][0];
+                            const path = s[0][1];
+                            if (path.length > 0 && !settleToken) {
+                                settleToken = path[path.length - 1][0];
+                            }
+                        } catch {
+                            // Fall through
+                        }
+                    } else {
+                        try {
+                            const s = coder.decode(
+                                [
+                                    "tuple(tuple(address,address,uint24,int24,address),bool,uint128,uint128,bytes)",
+                                ],
+                                params[i],
+                            );
+                            const poolKey = s[0][0];
+                            const zeroForOne = s[0][1];
+                            if (!settleToken)
+                                settleToken = zeroForOne
+                                    ? poolKey[0]
+                                    : poolKey[1];
+                            if (!takeToken)
+                                takeToken = zeroForOne
+                                    ? poolKey[1]
+                                    : poolKey[0];
+                        } catch {
+                            // Fall through
+                        }
+                    }
+                }
+            } catch {
+                // Skip sub-actions we can't decode
+            }
+        }
+
+        return {
+            tokenIn: settleToken,
+            tokenOut: takeToken,
+            amountIn,
+            amountOutMin,
+        };
+    } catch {
+        return null;
+    }
+}
+
 // Try to decode a Universal Router execute() call.
 // Returns { name, description, details } matching the format used by
 // the approval UI, or null if the calldata is not a recognised execute().
@@ -233,6 +384,19 @@ function decode(data, toAddress) {
                     }
                 }
 
+                if (cmdId === 0x10) {
+                    const v4 = decodeV4Swap(inputs[i]);
+                    if (v4) {
+                        if (!inputToken && v4.tokenIn) inputToken = v4.tokenIn;
+                        if (!outputToken && v4.tokenOut)
+                            outputToken = v4.tokenOut;
+                        if (!inputAmount && v4.amountIn)
+                            inputAmount = v4.amountIn;
+                        if (!minOutput && v4.amountOutMin)
+                            minOutput = v4.amountOutMin;
+                    }
+                }
+
                 if (cmdId === 0x0c) {
                     hasUnwrapWeth = true;
                 }

tests/uniswap.test.js

@@ -1,9 +1,10 @@
-const { AbiCoder, Interface, solidityPacked } = require("ethers");
+const { AbiCoder, Interface, solidityPacked, getBytes } = require("ethers");
 const uniswap = require("../src/shared/uniswap");
 
 const ROUTER_ADDR = "0x66a9893cc07d91d95644aedd05d03f95e1dba8af";
 const USDT_ADDR = "0xdAC17F958D2ee523a2206206994597C13D831ec7";
 const WETH_ADDR = "0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2";
+const USDC_ADDR = "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48";
 const USER_ADDR = "0x66133E8ea0f5D1d612D2502a968757D1048c214a";
 
 // AutistMask's first-ever swap, 2026-02-27.
@@ -256,6 +257,87 @@ describe("uniswap decoder", () => {
         expect(amount.value).toBe("5.0000 USDT");
     });
 
+    // This test validates the decodeV4Swap() fix: a V4 ERC20→ERC20 swap
+    // (USDT→USDC) where the token addresses are ONLY discoverable inside
+    // the V4_SWAP sub-actions (SETTLE/TAKE). Before decodeV4Swap() was added,
+    // command 0x10 was opaque and this would decode as "Uniswap Swap" with
+    // no token info (or "ETH → ETH"). Now it correctly shows "USDT → USDC".
+    test("decodes V4_SWAP ERC20→ERC20 tokens via SETTLE/TAKE (regression: #59)", () => {
+        // Build a V4_SWAP input with SETTLE(USDT) + SWAP_EXACT_IN_SINGLE + TAKE(USDC)
+        const V4_SETTLE = 0x0b;
+        const V4_SWAP_EXACT_IN_SINGLE = 0x06;
+        const V4_TAKE = 0x0e;
+
+        // actions: SETTLE, SWAP_EXACT_IN_SINGLE, TAKE
+        const actions = new Uint8Array([
+            V4_SETTLE,
+            V4_SWAP_EXACT_IN_SINGLE,
+            V4_TAKE,
+        ]);
+
+        // SETTLE params: (address currency, uint256 maxAmount, bool payerIsUser)
+        const settleParam = coder.encode(
+            ["address", "uint256", "bool"],
+            [USDT_ADDR, 5000000n, true],
+        );
+
+        // SWAP_EXACT_IN_SINGLE params:
+        // (tuple(address,address,uint24,int24,address) poolKey, bool zeroForOne, uint128 amountIn, uint128 amountOutMin, bytes hookData)
+        const swapParam = coder.encode(
+            [
+                "tuple(tuple(address,address,uint24,int24,address),bool,uint128,uint128,bytes)",
+            ],
+            [
+                [
+                    [
+                        USDT_ADDR,
+                        USDC_ADDR,
+                        100, // fee
+                        1, // tickSpacing
+                        "0x0000000000000000000000000000000000000000", // hooks
+                    ],
+                    true, // zeroForOne
+                    5000000n, // amountIn (5 USDT)
+                    4900000n, // amountOutMin (4.9 USDC)
+                    "0x", // hookData
+                ],
+            ],
+        );
+
+        // TAKE params: (address currency, address recipient, uint256 amount)
+        const takeParam = coder.encode(
+            ["address", "address", "uint256"],
+            [USDC_ADDR, USER_ADDR, 0n],
+        );
+
+        // Encode the V4_SWAP input: (bytes actions, bytes[] params)
+        const v4Input = coder.encode(
+            ["bytes", "bytes[]"],
+            [actions, [settleParam, swapParam, takeParam]],
+        );
+
+        // Build execute() with PERMIT2_PERMIT (0x0a) + V4_SWAP (0x10)
+        // The permit provides the input token, but V4_SWAP must provide
+        // the OUTPUT token — without decodeV4Swap, output would be unknown.
+        const data = buildExecute(
+            solidityPacked(["uint8", "uint8"], [0x0a, 0x10]),
+            [encodePermit2(USDT_ADDR, 5000000n, ROUTER_ADDR), v4Input],
+            9999999999n,
+        );
+
+        const result = uniswap.decode(data, ROUTER_ADDR);
+        expect(result).not.toBeNull();
+        // Before decodeV4Swap fix: name would be "Swap USDT → ETH" or "Uniswap Swap"
+        // After fix: correctly identifies both tokens from V4 sub-actions
+        expect(result.name).toBe("Swap USDT \u2192 USDC");
+
+        const tokenIn = result.details.find((d) => d.label === "Token In");
+        expect(tokenIn.value).toContain("USDT");
+
+        const steps = result.details.find((d) => d.label === "Steps");
+        expect(steps.value).toContain("V4 Swap");
+    });
+
     test("handles unknown tokens gracefully", () => {
         const fakeToken = "0x1111111111111111111111111111111111111111";
         const data = buildExecute(