fix: validate destination address on send view

- Validate Ethereum addresses (0x + 40 hex chars) and ENS names
- EIP-55 checksum validation for mixed-case addresses
- Block sending to zero address (0x0000...0000)
- Warn when sending to own address (allow but show warning)
- Inline error messages with reserved space (no layout shift)
- Disable Review button while address is invalid

Closes #67

src/popup/index.html

@@ -422,6 +422,11 @@
                         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">
@@ -637,10 +642,9 @@
                 <div class="flex justify-center mb-3">
                     <canvas id="receive-qr"></canvas>
                 </div>
-                <div
-                    class="border border-border p-2 break-all mb-3 text-xs cursor-pointer"
-                >
-                    <span id="receive-address-block" class="select-all"></span>
+                <div class="border border-border p-2 break-all mb-3 text-xs">
+                    <span id="receive-dot"></span>
+                    <span id="receive-address" class="select-all"></span>
                     <span id="receive-etherscan-link"></span>
                 </div>
                 <button

src/popup/views/receive.js

@@ -1,10 +1,4 @@
-const {
-    $,
-    showView,
-    showFlash,
-    formatAddressHtml,
-    addressTitle,
-} = require("./helpers");
+const { $, showView, showFlash, addressDotHtml } = require("./helpers");
 const { state, currentAddress } = require("../../shared/state");
 const QRCode = require("qrcode");
 
@@ -18,12 +12,8 @@ const EXT_ICON =
 function show() {
     const addr = currentAddress();
     const address = addr ? addr.address : "";
-    const title = address ? addressTitle(address, state.wallets) : null;
-    const ensName = addr ? addr.ensName || null : null;
-    $("receive-address-block").innerHTML = address
-        ? formatAddressHtml(address, ensName, null, title)
-        : "";
-    $("receive-address-block").dataset.full = address;
+    $("receive-dot").innerHTML = address ? addressDotHtml(address) : "";
+    $("receive-address").textContent = address;
     const link = address ? `https://etherscan.io/address/${address}` : "";
     $("receive-etherscan-link").innerHTML = link
         ? `<a href="${link}" target="_blank" rel="noopener" class="inline-flex items-center">${EXT_ICON}</a>`
@@ -60,16 +50,8 @@ function show() {
 }
 
 function init(ctx) {
-    $("receive-address-block").addEventListener("click", () => {
-        const addr = $("receive-address-block").dataset.full;
-        if (addr) {
-            navigator.clipboard.writeText(addr);
-            showFlash("Copied!");
-        }
-    });
-
     $("btn-receive-copy").addEventListener("click", () => {
-        const addr = $("receive-address-block").dataset.full;
+        const addr = $("receive-address").textContent;
         if (addr) {
             navigator.clipboard.writeText(addr);
             showFlash("Copied!");

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;

src/shared/transactions.js

@@ -153,14 +153,9 @@ async function fetchRecentTransactions(address, blockscoutUrl, count = 25) {
 
     // When a token transfer shares a hash with a normal tx, the normal tx
     // is the contract call (0 ETH) and the token transfer has the real
-    // amount and symbol. Preserve contract call metadata (direction, label,
-    // method) so swaps and other contract interactions display correctly.
-    //
-    // A single tx hash can produce multiple token transfers (e.g. a swap
-    // sends token A and receives token B). Use a composite key
-    // (hash:contractAddress) so every transfer is preserved. The original
-    // normal-tx entry (keyed by bare hash) is removed when at least one
-    // token transfer replaces it.
+    // amount and symbol. Replace the normal tx with the token transfer,
+    // but preserve contract call metadata (direction, label, method) so
+    // swaps and other contract interactions display correctly.
     for (const tt of ttJson.items || []) {
         const parsed = parseTokenTransfer(tt, addrLower);
         const existing = txsByHash.get(parsed.hash);
@@ -169,12 +164,8 @@ async function fetchRecentTransactions(address, blockscoutUrl, count = 25) {
             parsed.directionLabel = existing.directionLabel;
             parsed.isContractCall = true;
             parsed.method = existing.method;
-            // Remove the bare-hash normal tx so it isn't duplicated
-            txsByHash.delete(parsed.hash);
         }
-        // Use composite key so multiple token transfers per tx are kept
-        const compositeKey = parsed.hash + ":" + (parsed.contractAddress || "");
-        txsByHash.set(compositeKey, parsed);
+        txsByHash.set(parsed.hash, parsed);
     }
 
     const txs = [...txsByHash.values()];