style: tabby tab styling with dashed inactive borders and hover invert

- Active tab: solid border on top/sides, bottom border matches background
  (connects to content area), bold text
- Inactive tabs: dashed borders in border-light color, muted text,
  transparent bottom border
- Inactive hover: invert (bg-fg text-bg) for clear clickability signal
- All three tabs behave identically on hover

src/popup/index.html

@@ -56,9 +56,37 @@
                     < Back
                 </button>
                 <h2 class="font-bold mb-2">Add Wallet</h2>
+
+                <!-- Mode selector tabs -->
+                <div
+                    class="flex border-b border-border mb-3"
+                    id="add-wallet-tabs"
+                >
+                    <button
+                        id="tab-mnemonic"
+                        class="px-3 py-1.5 cursor-pointer text-xs font-bold border border-border border-b-bg bg-bg -mb-px"
+                    >
+                        From Phrase
+                    </button>
+                    <button
+                        id="tab-privkey"
+                        class="px-3 py-1.5 cursor-pointer text-xs text-muted border border-dashed border-border-light border-b-transparent -mb-px hover:bg-fg hover:text-bg"
+                    >
+                        From Key
+                    </button>
+                    <button
+                        id="tab-xprv"
+                        class="px-3 py-1.5 cursor-pointer text-xs text-muted border border-dashed border-border-light border-b-transparent -mb-px hover:bg-fg hover:text-bg"
+                    >
+                        From xprv
+                    </button>
+                </div>
+
+                <!-- Mnemonic form section -->
+                <div id="add-wallet-section-mnemonic">
                     <p class="mb-2">
-                    Enter your 12 or 24 word recovery phrase below, or click the
-                    button to roll the die for a new one.
+                        Enter your 12 or 24 word recovery phrase below, or click
+                        the button to roll the die for a new one.
                     </p>
                     <div class="mb-1 flex justify-end">
                         <button
@@ -81,12 +109,51 @@
                         id="add-wallet-phrase-warning"
                         class="text-xs mb-2 border border-border border-dashed p-2 hidden"
                     >
-                    Write these words down and keep them safe. Anyone with them
-                    can take your funds; if you lose them, your wallet is gone.
+                        Write these words down and keep them safe. Anyone with
+                        them can take your funds; if you lose them, your wallet
+                        is gone.
                     </div>
+                </div>
+
+                <!-- Private key form section -->
+                <div id="add-wallet-section-privkey" class="hidden">
+                    <p class="mb-2">
+                        Paste your private key below. This wallet will have a
+                        single address.
+                    </p>
+                    <div class="mb-2">
+                        <input
+                            type="password"
+                            id="import-private-key"
+                            class="border border-border p-1 w-full font-mono text-sm bg-bg text-fg"
+                            placeholder="0x..."
+                        />
+                    </div>
+                </div>
+
+                <!-- Extended key (xprv) form section -->
+                <div id="add-wallet-section-xprv" class="hidden">
+                    <p class="mb-2">
+                        Paste your extended private key (xprv) below. This will
+                        import the HD wallet and scan for used addresses.
+                    </p>
+                    <div class="mb-2">
+                        <input
+                            type="password"
+                            id="import-xprv-key"
+                            class="border border-border p-1 w-full font-mono text-sm bg-bg text-fg"
+                            placeholder="xprv..."
+                        />
+                    </div>
+                </div>
+
+                <!-- Shared password fields -->
                 <div class="mb-2" id="add-wallet-password-section">
                     <label class="block mb-1">Choose a password</label>
-                    <p class="text-xs text-muted mb-1">
+                    <p
+                        class="text-xs text-muted mb-1"
+                        id="add-wallet-password-hint"
+                    >
                         This password encrypts your recovery phrase on this
                         device. You will need it to send funds.
                     </p>
@@ -107,64 +174,6 @@
                 <button
                     id="btn-add-wallet-confirm"
                     class="border border-border px-2 py-1 hover:bg-fg hover:text-bg cursor-pointer"
-                >
-                    Add
-                </button>
-                <div class="mt-3 text-xs text-muted">
-                    Have a private key instead?
-                    <button
-                        id="btn-add-wallet-import-key"
-                        class="underline cursor-pointer bg-transparent border-none text-fg text-xs font-mono p-0"
-                    >
-                        Import private key
-                    </button>
-                </div>
-            </div>
-
-            <!-- ============ IMPORT PRIVATE KEY ============ -->
-            <div id="view-import-key" class="view hidden">
-                <button
-                    id="btn-import-key-back"
-                    class="border border-border px-2 py-1 hover:bg-fg hover:text-bg cursor-pointer mb-2"
-                >
-                    &lt; Back
-                </button>
-                <h2 class="font-bold mb-2">Import Private Key</h2>
-                <p class="mb-2">
-                    Paste your private key below. This wallet will have a single
-                    address.
-                </p>
-                <div class="mb-2">
-                    <input
-                        type="password"
-                        id="import-private-key"
-                        class="border border-border p-1 w-full font-mono text-sm bg-bg text-fg"
-                        placeholder="0x..."
-                    />
-                </div>
-                <div class="mb-2" id="import-key-password-section">
-                    <label class="block mb-1">Choose a password</label>
-                    <p class="text-xs text-muted mb-1">
-                        This password encrypts your private key on this device.
-                        You will need it to send funds.
-                    </p>
-                    <input
-                        type="password"
-                        id="import-key-password"
-                        class="border border-border p-1 w-full font-mono text-sm bg-bg text-fg"
-                    />
-                </div>
-                <div class="mb-2" id="import-key-password-confirm-section">
-                    <label class="block mb-1">Confirm password</label>
-                    <input
-                        type="password"
-                        id="import-key-password-confirm"
-                        class="border border-border p-1 w-full font-mono text-sm bg-bg text-fg"
-                    />
-                </div>
-                <button
-                    id="btn-import-key-confirm"
-                    class="border border-border px-2 py-1 hover:bg-fg hover:text-bg cursor-pointer"
                 >
                     Import
                 </button>
@@ -496,6 +505,11 @@
                         class="border border-border p-1 w-full font-mono text-sm bg-bg text-fg"
                         placeholder="Address (0x...) or ENS name"
                     />
+                    <div
+                        id="send-to-error"
+                        class="text-xs"
+                        style="min-height: 1.25rem; color: #cc0000"
+                    ></div>
                 </div>
                 <div class="mb-2">
                     <div class="flex justify-between mb-1">

src/popup/index.js

@@ -10,7 +10,6 @@ const { $, showView } = require("./views/helpers");
 const home = require("./views/home");
 const welcome = require("./views/welcome");
 const addWallet = require("./views/addWallet");
-const importKey = require("./views/importKey");
 const addressDetail = require("./views/addressDetail");
 const addressToken = require("./views/addressToken");
 const send = require("./views/send");
@@ -54,7 +53,6 @@ const ctx = {
     renderWalletList,
     doRefreshAndRender,
     showAddWalletView: () => addWallet.show(),
-    showImportKeyView: () => importKey.show(),
     showAddressDetail: () => addressDetail.show(),
     showAddressToken: () => addressToken.show(),
     showAddTokenView: () => addToken.show(),
@@ -75,7 +73,6 @@ const RESTORABLE_VIEWS = new Set([
     "settings",
     "settings-addtoken",
     "transaction",
-    "confirm-tx",
     "success-tx",
     "error-tx",
 ]);
@@ -135,13 +132,6 @@ function restoreView() {
                 fallbackView();
             }
             break;
-        case "confirm-tx":
-            if (state.viewData && state.viewData.pendingTx) {
-                confirmTx.show(state.viewData.pendingTx);
-            } else {
-                fallbackView();
-            }
-            break;
         case "success-tx":
             if (state.viewData && state.viewData.hash) {
                 txStatus.renderSuccess();
@@ -217,7 +207,6 @@ async function init() {
 
     welcome.init(ctx);
     addWallet.init(ctx);
-    importKey.init(ctx);
     home.init(ctx);
     addressDetail.init(ctx);
     addressToken.init(ctx);

src/popup/views/addWallet.js

@@ -3,31 +3,80 @@ const {
     generateMnemonic,
     hdWalletFromMnemonic,
     isValidMnemonic,
+    addressFromPrivateKey,
+    hdWalletFromXprv,
+    isValidXprv,
 } = require("../../shared/wallet");
 const { encryptWithPassword } = require("../../shared/vault");
 const { state, saveState } = require("../../shared/state");
 const { scanForAddresses } = require("../../shared/balances");
 
+let currentMode = "mnemonic";
+
+const MODES = ["mnemonic", "privkey", "xprv"];
+
+const PASSWORD_HINTS = {
+    mnemonic:
+        "This password encrypts your recovery phrase on this device. You will need it to send funds.",
+    privkey:
+        "This password encrypts your private key on this device. You will need it to send funds.",
+    xprv: "This password encrypts your key on this device. You will need it to send funds.",
+};
+
+function switchMode(mode) {
+    currentMode = mode;
+    for (const m of MODES) {
+        $("add-wallet-section-" + m).classList.toggle("hidden", m !== mode);
+        const tab = $("tab-" + m);
+        const isActive = m === mode;
+        // Active: bold, solid border on top/sides, no bottom border (connects to content)
+        tab.classList.toggle("font-bold", isActive);
+        tab.classList.toggle("border-solid", isActive);
+        tab.classList.toggle("border-border", isActive);
+        tab.classList.toggle("border-b-bg", isActive);
+        tab.classList.toggle("bg-bg", isActive);
+        // Inactive: muted text, dashed border on top/sides, transparent bottom
+        tab.classList.toggle("text-muted", !isActive);
+        tab.classList.toggle("border-dashed", !isActive);
+        tab.classList.toggle("border-border-light", !isActive);
+        tab.classList.toggle("border-b-transparent", !isActive);
+    }
+    $("add-wallet-password-hint").textContent = PASSWORD_HINTS[mode];
+}
+
 function show() {
     $("wallet-mnemonic").value = "";
+    $("import-private-key").value = "";
+    $("import-xprv-key").value = "";
     $("add-wallet-password").value = "";
     $("add-wallet-password-confirm").value = "";
     $("add-wallet-phrase-warning").classList.add("hidden");
+    switchMode("mnemonic");
     showView("add-wallet");
 }
 
-function init(ctx) {
-    $("btn-generate-phrase").addEventListener("click", () => {
-        $("wallet-mnemonic").value = generateMnemonic();
-        $("add-wallet-phrase-warning").classList.remove("hidden");
-    });
+function validatePassword() {
+    const pw = $("add-wallet-password").value;
+    const pw2 = $("add-wallet-password-confirm").value;
+    if (!pw) {
+        showFlash("Please choose a password.");
+        return null;
+    }
+    if (pw.length < 12) {
+        showFlash("Password must be at least 12 characters.");
+        return null;
+    }
+    if (pw !== pw2) {
+        showFlash("Passwords do not match.");
+        return null;
+    }
+    return pw;
+}
 
-    $("btn-add-wallet-confirm").addEventListener("click", async () => {
+async function importMnemonic(ctx) {
     const mnemonic = $("wallet-mnemonic").value.trim();
     if (!mnemonic) {
-            showFlash(
-                "Enter a recovery phrase or press the die to generate one.",
-            );
+        showFlash("Enter a recovery phrase or press the die to generate one.");
         return;
     }
     const words = mnemonic.split(/\s+/);
@@ -43,33 +92,18 @@ function init(ctx) {
         showFlash("Invalid recovery phrase. Check for typos.");
         return;
     }
-        const pw = $("add-wallet-password").value;
-        const pw2 = $("add-wallet-password-confirm").value;
-        if (!pw) {
-            showFlash("Please choose a password.");
-            return;
-        }
-        if (pw.length < 12) {
-            showFlash("Password must be at least 12 characters.");
-            return;
-        }
-        if (pw !== pw2) {
-            showFlash("Passwords do not match.");
-            return;
-        }
+    const pw = validatePassword();
+    if (!pw) return;
     const { xpub, firstAddress } = hdWalletFromMnemonic(mnemonic);
     const duplicate = state.wallets.find(
         (w) =>
             w.type === "hd" &&
             w.addresses[0] &&
-                w.addresses[0].address.toLowerCase() ===
-                    firstAddress.toLowerCase(),
+            w.addresses[0].address.toLowerCase() === firstAddress.toLowerCase(),
     );
     if (duplicate) {
         showFlash(
-                "This recovery phrase is already added (" +
-                    duplicate.name +
-                    ").",
+            "This recovery phrase is already added (" + duplicate.name + ").",
         );
         return;
     }
@@ -109,8 +143,143 @@ function init(ctx) {
     }
 
     ctx.doRefreshAndRender();
+}
+
+async function importPrivateKey(ctx) {
+    const key = $("import-private-key").value.trim();
+    if (!key) {
+        showFlash("Please enter your private key.");
+        return;
+    }
+    let addr;
+    try {
+        addr = addressFromPrivateKey(key);
+    } catch (e) {
+        showFlash("Invalid private key.");
+        return;
+    }
+    const pw = validatePassword();
+    if (!pw) return;
+    const duplicate = state.wallets.find(
+        (w) =>
+            w.type === "key" &&
+            w.addresses[0] &&
+            w.addresses[0].address.toLowerCase() === addr.toLowerCase(),
+    );
+    if (duplicate) {
+        showFlash(
+            "This private key is already added (" + duplicate.name + ").",
+        );
+        return;
+    }
+    const encrypted = await encryptWithPassword(key, pw);
+    const walletNum = state.wallets.length + 1;
+    state.wallets.push({
+        type: "key",
+        name: "Wallet " + walletNum,
+        encryptedSecret: encrypted,
+        addresses: [{ address: addr, balance: "0.0000", tokenBalances: [] }],
+    });
+    state.hasWallet = true;
+    await saveState();
+    ctx.renderWalletList();
+    showView("main");
+
+    ctx.doRefreshAndRender();
+}
+
+async function importXprvKey(ctx) {
+    const xprv = $("import-xprv-key").value.trim();
+    if (!xprv) {
+        showFlash("Please enter your extended private key.");
+        return;
+    }
+    if (!isValidXprv(xprv)) {
+        showFlash("Invalid extended private key.");
+        return;
+    }
+    let result;
+    try {
+        result = hdWalletFromXprv(xprv);
+    } catch (e) {
+        showFlash("Invalid extended private key.");
+        return;
+    }
+    const { xpub, firstAddress } = result;
+    const duplicate = state.wallets.find(
+        (w) =>
+            (w.type === "hd" || w.type === "xprv") &&
+            w.addresses[0] &&
+            w.addresses[0].address.toLowerCase() === firstAddress.toLowerCase(),
+    );
+    if (duplicate) {
+        showFlash("This key is already added (" + duplicate.name + ").");
+        return;
+    }
+    const pw = validatePassword();
+    if (!pw) return;
+    const encrypted = await encryptWithPassword(xprv, pw);
+    const walletNum = state.wallets.length + 1;
+    const wallet = {
+        type: "xprv",
+        name: "Wallet " + walletNum,
+        xpub: xpub,
+        encryptedSecret: encrypted,
+        nextIndex: 1,
+        addresses: [
+            { address: firstAddress, balance: "0.0000", tokenBalances: [] },
+        ],
+    };
+    state.wallets.push(wallet);
+    state.hasWallet = true;
+    await saveState();
+    ctx.renderWalletList();
+    showView("main");
+
+    // Scan for used HD addresses beyond index 0.
+    showFlash("Scanning for addresses...", 30000);
+    const scan = await scanForAddresses(xpub, state.rpcUrl);
+    if (scan.addresses.length > 1) {
+        wallet.addresses = scan.addresses.map((a) => ({
+            address: a.address,
+            balance: "0.0000",
+            tokenBalances: [],
+        }));
+        wallet.nextIndex = scan.nextIndex;
+        await saveState();
+        ctx.renderWalletList();
+        showFlash("Found " + scan.addresses.length + " addresses.");
+    } else {
+        showFlash("Ready.", 1000);
+    }
+
+    ctx.doRefreshAndRender();
+}
+
+function init(ctx) {
+    // Tab click handlers
+    $("tab-mnemonic").addEventListener("click", () => switchMode("mnemonic"));
+    $("tab-privkey").addEventListener("click", () => switchMode("privkey"));
+    $("tab-xprv").addEventListener("click", () => switchMode("xprv"));
+
+    // Generate mnemonic
+    $("btn-generate-phrase").addEventListener("click", () => {
+        $("wallet-mnemonic").value = generateMnemonic();
+        $("add-wallet-phrase-warning").classList.remove("hidden");
     });
 
+    // Import / confirm
+    $("btn-add-wallet-confirm").addEventListener("click", async () => {
+        if (currentMode === "mnemonic") {
+            await importMnemonic(ctx);
+        } else if (currentMode === "privkey") {
+            await importPrivateKey(ctx);
+        } else if (currentMode === "xprv") {
+            await importXprvKey(ctx);
+        }
+    });
+
+    // Back button
     $("btn-add-wallet-back").addEventListener("click", () => {
         if (!state.hasWallet) {
             showView("welcome");
@@ -119,11 +288,6 @@ function init(ctx) {
             showView("main");
         }
     });
-
-    $("btn-add-wallet-import-key").addEventListener(
-        "click",
-        ctx.showImportKeyView,
-    );
 }
 
 module.exports = { init, show };

src/popup/views/addressDetail.js

@@ -15,7 +15,11 @@ const {
     filterTransactions,
 } = require("../../shared/transactions");
 const { resolveEnsNames } = require("../../shared/ens");
-const { updateSendBalance, renderSendTokenSelect } = require("./send");
+const {
+    updateSendBalance,
+    renderSendTokenSelect,
+    resetSendValidation,
+} = require("./send");
 const { log } = require("../../shared/log");
 const makeBlockie = require("ethereum-blockies-base64");
 const { decryptWithPassword } = require("../../shared/vault");
@@ -259,6 +263,7 @@ function init(_ctx) {
         $("send-token").classList.remove("hidden");
         $("send-token-static").classList.add("hidden");
         updateSendBalance();
+        resetSendValidation();
         showView("send");
     });
 

src/popup/views/addressToken.js

@@ -23,7 +23,11 @@ const {
     filterTransactions,
 } = require("../../shared/transactions");
 const { resolveEnsNames } = require("../../shared/ens");
-const { updateSendBalance, renderSendTokenSelect } = require("./send");
+const {
+    updateSendBalance,
+    renderSendTokenSelect,
+    resetSendValidation,
+} = require("./send");
 const { log } = require("../../shared/log");
 const makeBlockie = require("ethereum-blockies-base64");
 
@@ -372,6 +376,7 @@ function init(_ctx) {
             });
         }
         updateSendBalance();
+        resetSendValidation();
         showView("send");
     });
 

src/popup/views/confirmTx.js

@@ -14,11 +14,12 @@ const {
     showError,
     hideError,
     showView,
+    showFlash,
     addressTitle,
     addressDotHtml,
     escapeHtml,
 } = require("./helpers");
-const { state, saveState } = require("../../shared/state");
+const { state } = require("../../shared/state");
 const { getSignerForAddress } = require("../../shared/wallet");
 const { decryptWithPassword } = require("../../shared/vault");
 const { formatUsd, getPrice } = require("../../shared/prices");
@@ -95,11 +96,22 @@ function show(txInfo) {
     // Token contract section (ERC-20 only)
     const tokenSection = $("confirm-token-section");
     if (isErc20) {
+        const dot = addressDotHtml(txInfo.token);
         const link = etherscanTokenLink(txInfo.token);
         $("confirm-token-contract").innerHTML =
-            escapeHtml(txInfo.token) +
-            ` <a href="${link}" target="_blank" rel="noopener" class="inline-flex items-center">${EXT_ICON}</a>`;
+            `<div class="flex items-center">${dot}` +
+            `<span class="break-all underline decoration-dashed cursor-pointer" data-copy="${escapeHtml(txInfo.token)}">${escapeHtml(txInfo.token)}</span>` +
+            `<a href="${link}" target="_blank" rel="noopener" class="inline-flex items-center">${EXT_ICON}</a>` +
+            `</div>`;
         tokenSection.classList.remove("hidden");
+        // Attach click-to-copy on the contract address
+        const copyEl = tokenSection.querySelector("[data-copy]");
+        if (copyEl) {
+            copyEl.onclick = () => {
+                navigator.clipboard.writeText(copyEl.dataset.copy);
+                showFlash("Copied!");
+            };
+        }
     } else {
         tokenSection.classList.add("hidden");
     }
@@ -219,10 +231,6 @@ function show(txInfo) {
     $("confirm-fee-amount").textContent = "Estimating...";
     showView("confirm-tx");
 
-    // Persist txInfo so the view survives popup close/reopen
-    state.viewData = { pendingTx: txInfo };
-    saveState();
-
     estimateGas(txInfo);
 }
 

src/popup/views/helpers.js

@@ -13,7 +13,6 @@ const { state, saveState } = require("../../shared/state");
 const VIEWS = [
     "welcome",
     "add-wallet",
-    "import-key",
     "main",
     "address",
     "address-token",

src/popup/views/home.js

@@ -11,7 +11,11 @@ const {
     truncateMiddle,
 } = require("./helpers");
 const { state, saveState, currentAddress } = require("../../shared/state");
-const { updateSendBalance, renderSendTokenSelect } = require("./send");
+const {
+    updateSendBalance,
+    renderSendTokenSelect,
+    resetSendValidation,
+} = require("./send");
 const { deriveAddressFromXpub } = require("../../shared/wallet");
 const {
     formatUsd,
@@ -235,7 +239,7 @@ function render(ctx) {
         html += `<div>`;
         html += `<div class="flex justify-between items-center bg-section py-1 px-2" style="margin:0 -0.5rem">`;
         html += `<span class="font-bold cursor-pointer wallet-name underline decoration-dashed" data-wallet="${wi}">${wallet.name}</span>`;
-        if (wallet.type === "hd") {
+        if (wallet.type === "hd" || wallet.type === "xprv") {
             html += `<button class="btn-add-address border border-border px-1 hover:bg-fg hover:text-bg cursor-pointer text-xs" data-wallet="${wi}" title="Add another address to this wallet">+</button>`;
         }
         html += `</div>`;
@@ -388,6 +392,7 @@ function init(ctx) {
         $("send-token-static").classList.add("hidden");
         renderSendTokenSelect(addr);
         updateSendBalance();
+        resetSendValidation();
         showView("send");
     });
 

src/popup/views/importKey.js

@@ -1,69 +0,0 @@
-const { $, showView, showFlash } = require("./helpers");
-const { addressFromPrivateKey } = require("../../shared/wallet");
-const { encryptWithPassword } = require("../../shared/vault");
-const { state, saveState } = require("../../shared/state");
-
-function show() {
-    $("import-private-key").value = "";
-    $("import-key-password").value = "";
-    $("import-key-password-confirm").value = "";
-    showView("import-key");
-}
-
-function init(ctx) {
-    $("btn-import-key-confirm").addEventListener("click", async () => {
-        const key = $("import-private-key").value.trim();
-        if (!key) {
-            showFlash("Please enter your private key.");
-            return;
-        }
-        let addr;
-        try {
-            addr = addressFromPrivateKey(key);
-        } catch (e) {
-            showFlash("Invalid private key.");
-            return;
-        }
-        const pw = $("import-key-password").value;
-        const pw2 = $("import-key-password-confirm").value;
-        if (!pw) {
-            showFlash("Please choose a password.");
-            return;
-        }
-        if (pw.length < 12) {
-            showFlash("Password must be at least 12 characters.");
-            return;
-        }
-        if (pw !== pw2) {
-            showFlash("Passwords do not match.");
-            return;
-        }
-        const encrypted = await encryptWithPassword(key, pw);
-        const walletNum = state.wallets.length + 1;
-        state.wallets.push({
-            type: "key",
-            name: "Wallet " + walletNum,
-            encryptedSecret: encrypted,
-            addresses: [
-                { address: addr, balance: "0.0000", tokenBalances: [] },
-            ],
-        });
-        state.hasWallet = true;
-        await saveState();
-        ctx.renderWalletList();
-        showView("main");
-
-        ctx.doRefreshAndRender();
-    });
-
-    $("btn-import-key-back").addEventListener("click", () => {
-        if (!state.hasWallet) {
-            showView("welcome");
-        } else {
-            ctx.renderWalletList();
-            showView("main");
-        }
-    });
-}
-
-module.exports = { init, show };

src/popup/views/send.js

@@ -11,6 +11,107 @@ const { state, currentAddress } = require("../../shared/state");
 let ctx;
 const { getProvider } = require("../../shared/balances");
 const { KNOWN_SYMBOLS, resolveSymbol } = require("../../shared/tokenList");
+const { getAddress } = require("ethers");
+
+const ZERO_ADDRESS = "0x0000000000000000000000000000000000000000";
+
+/**
+ * Validate a destination address string.
+ * Returns { valid: true } or { valid: false, error: "..." }.
+ */
+function validateToAddress(value) {
+    const v = value.trim();
+    if (!v) return { valid: false, error: "" };
+
+    // ENS names: contains a dot and doesn't start with 0x
+    if (v.includes(".") && !v.startsWith("0x")) {
+        // Basic ENS format check: at least one label before and after dot
+        if (/^[a-zA-Z0-9-]+(\.[a-zA-Z0-9-]+)+$/.test(v)) {
+            return { valid: true };
+        }
+        return {
+            valid: false,
+            error: "Please enter a valid ENS name.",
+        };
+    }
+
+    // Must look like an Ethereum address
+    if (!/^0x[0-9a-fA-F]{40}$/.test(v)) {
+        return {
+            valid: false,
+            error: "Please enter a valid Ethereum address.",
+        };
+    }
+
+    // Reject zero address
+    if (v.toLowerCase() === ZERO_ADDRESS) {
+        return {
+            valid: false,
+            error: "Sending to the zero address is not allowed.",
+        };
+    }
+
+    // EIP-55 checksum validation: all-lowercase is ok, otherwise must match checksum
+    if (v !== v.toLowerCase()) {
+        try {
+            const checksummed = getAddress(v);
+            if (checksummed !== v) {
+                return {
+                    valid: false,
+                    error: "Address checksum is invalid. Please double-check the address.",
+                };
+            }
+        } catch {
+            return {
+                valid: false,
+                error: "Address checksum is invalid. Please double-check the address.",
+            };
+        }
+    }
+
+    // Warn if sending to own address
+    const addr = currentAddress();
+    if (addr && v.toLowerCase() === addr.address.toLowerCase()) {
+        // Allow but will warn — we return valid with a warning
+        return {
+            valid: true,
+            warning: "This is your own address. Are you sure?",
+        };
+    }
+
+    return { valid: true };
+}
+
+function updateToValidation() {
+    const input = $("send-to");
+    const errorEl = $("send-to-error");
+    const btn = $("btn-send-review");
+    const value = input.value.trim();
+
+    if (!value) {
+        errorEl.textContent = "";
+        btn.disabled = true;
+        btn.classList.add("opacity-50");
+        return;
+    }
+
+    const result = validateToAddress(value);
+    if (!result.valid) {
+        errorEl.textContent = result.error;
+        errorEl.style.color = "#cc0000";
+        btn.disabled = true;
+        btn.classList.add("opacity-50");
+    } else if (result.warning) {
+        errorEl.textContent = result.warning;
+        errorEl.style.color = "#b8860b";
+        btn.disabled = false;
+        btn.classList.remove("opacity-50");
+    } else {
+        errorEl.textContent = "";
+        btn.disabled = false;
+        btn.classList.remove("opacity-50");
+    }
+}
 
 const EXT_ICON =
     `<span style="display:inline-block;width:10px;height:10px;margin-left:4px;vertical-align:middle">` +
@@ -88,6 +189,13 @@ function init(_ctx) {
     ctx = _ctx;
     $("send-token").addEventListener("change", updateSendBalance);
 
+    // Initial state: disable review button until address is entered
+    $("btn-send-review").disabled = true;
+    $("btn-send-review").classList.add("opacity-50");
+
+    // Validate address on input
+    $("send-to").addEventListener("input", updateToValidation);
+
     $("btn-send-review").addEventListener("click", async () => {
         const to = $("send-to").value.trim();
         const amount = $("send-amount").value.trim();
@@ -95,6 +203,15 @@ function init(_ctx) {
             showFlash("Please enter a recipient address.");
             return;
         }
+
+        // Re-validate before proceeding
+        const validation = validateToAddress(to);
+        if (!validation.valid) {
+            showFlash(
+                validation.error || "Please enter a valid Ethereum address.",
+            );
+            return;
+        }
         if (!amount || isNaN(parseFloat(amount)) || parseFloat(amount) <= 0) {
             showFlash("Please enter a valid amount.");
             return;
@@ -159,4 +276,19 @@ function init(_ctx) {
     });
 }
 
-module.exports = { init, updateSendBalance, renderSendTokenSelect };
+function resetSendValidation() {
+    const errorEl = $("send-to-error");
+    const btn = $("btn-send-review");
+    if (errorEl) errorEl.textContent = "";
+    if (btn) {
+        btn.disabled = true;
+        btn.classList.add("opacity-50");
+    }
+}
+
+module.exports = {
+    init,
+    updateSendBalance,
+    renderSendTokenSelect,
+    resetSendValidation,
+};

src/shared/wallet.js

@@ -24,6 +24,26 @@ function hdWalletFromMnemonic(mnemonic) {
     return { xpub, firstAddress };
 }
 
+function hdWalletFromXprv(xprv) {
+    const root = HDNodeWallet.fromExtendedKey(xprv);
+    if (!root.privateKey) {
+        throw new Error("Not an extended private key (xprv).");
+    }
+    const node = root.derivePath("44'/60'/0'/0");
+    const xpub = node.neuter().extendedKey;
+    const firstAddress = node.deriveChild(0).address;
+    return { xpub, firstAddress };
+}
+
+function isValidXprv(key) {
+    try {
+        const node = HDNodeWallet.fromExtendedKey(key);
+        return !!node.privateKey;
+    } catch {
+        return false;
+    }
+}
+
 function addressFromPrivateKey(key) {
     const w = new Wallet(key);
     return w.address;
@@ -38,6 +58,11 @@ function getSignerForAddress(walletData, addrIndex, decryptedSecret) {
         );
         return node.deriveChild(addrIndex);
     }
+    if (walletData.type === "xprv") {
+        const root = HDNodeWallet.fromExtendedKey(decryptedSecret);
+        const node = root.derivePath("44'/60'/0'/0");
+        return node.deriveChild(addrIndex);
+    }
     return new Wallet(decryptedSecret);
 }
 
@@ -49,6 +74,8 @@ module.exports = {
     generateMnemonic,
     deriveAddressFromXpub,
     hdWalletFromMnemonic,
+    hdWalletFromXprv,
+    isValidXprv,
     addressFromPrivateKey,
     getSignerForAddress,
     isValidMnemonic,