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">
@@ -531,6 +536,7 @@
             <!-- ============ TX SUCCESS ============ -->
             <div id="view-success-tx" class="view hidden">
                 <h2 class="font-bold mb-2">Transaction Confirmed</h2>
+                <div id="success-tx-decoded" class="mb-3 hidden text-xs"></div>
                 <div class="mb-3">
                     <div class="text-xs text-muted mb-1">Amount</div>
                     <div id="success-tx-summary" class="font-bold"></div>

src/popup/views/approval.js

@@ -184,6 +184,15 @@ function showTxApproval(details) {
         }
     }
 
+    // Carry decoded calldata info through to success/error views
+    if (decoded) {
+        pendingTxDetails.decoded = {
+            name: decoded.name,
+            description: decoded.description,
+            details: decoded.details,
+        };
+    }
+
     $("approve-tx-hostname").textContent = details.hostname;
     $("approve-tx-from").innerHTML = approvalAddressHtml(state.activeAddress);
 

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, TOKEN_BY_ADDRESS } = 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">` +
@@ -92,6 +193,13 @@ 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();
@@ -99,6 +207,15 @@ 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/popup/views/transactionDetail.js

@@ -143,11 +143,10 @@ function render() {
             typeEl.textContent = tx.directionLabel;
             typeSection.classList.remove("hidden");
         }
-        if (headingEl) headingEl.textContent = tx.directionLabel;
     } else {
         if (typeSection) typeSection.classList.add("hidden");
-        if (headingEl) headingEl.textContent = "Transaction";
     }
+    if (headingEl) headingEl.textContent = "Transaction";
 
     // Hide calldata and raw data sections; re-fetch if this is a contract call
     const calldataSection = $("tx-detail-calldata-section");

src/popup/views/txStatus.js

@@ -8,6 +8,7 @@ const {
     addressTitle,
     escapeHtml,
 } = require("./helpers");
+const { TOKEN_BY_ADDRESS } = require("../../shared/tokenList");
 const { state, saveState } = require("../../shared/state");
 const { getProvider } = require("../../shared/balances");
 const { log } = require("../../shared/log");
@@ -121,11 +122,51 @@ function showSuccess(txInfo, txHash, blockNumber) {
         to: txInfo.to,
         hash: txHash,
         blockNumber: blockNumber,
+        decoded: txInfo.decoded || null,
     };
     renderSuccess();
     ctx.doRefreshAndRender();
 }
 
+function tokenLabel(address) {
+    const t = TOKEN_BY_ADDRESS.get(address.toLowerCase());
+    return t ? t.symbol : null;
+}
+
+function etherscanTokenLink(address) {
+    return `https://etherscan.io/token/${address}`;
+}
+
+function decodedDetailsHtml(decoded) {
+    if (!decoded || !decoded.details) return "";
+    let html = "";
+    if (decoded.name) {
+        html += `<div class="mb-2"><div class="text-xs text-muted mb-1">Action</div>`;
+        html += `<div class="font-bold">${escapeHtml(decoded.name)}</div></div>`;
+    }
+    if (decoded.description) {
+        html += `<div class="mb-2"><div class="text-xs text-muted mb-1">Description</div>`;
+        html += `<div>${escapeHtml(decoded.description)}</div></div>`;
+    }
+    for (const d of decoded.details) {
+        html += `<div class="mb-2">`;
+        html += `<div class="text-xs text-muted mb-1">${escapeHtml(d.label)}</div>`;
+        if (d.address) {
+            if (d.isToken) {
+                const sym = tokenLabel(d.address) || "Unknown token";
+                html += `<div class="font-bold">${escapeHtml(sym)}</div>`;
+                html += toAddressHtml(d.address);
+            } else {
+                html += toAddressHtml(d.address);
+            }
+        } else {
+            html += `<div class="font-bold">${escapeHtml(d.value)}</div>`;
+        }
+        html += `</div>`;
+    }
+    return html;
+}
+
 function renderSuccess() {
     const d = state.viewData;
     if (!d || !d.hash) return;
@@ -133,6 +174,16 @@ function renderSuccess() {
     $("success-tx-to").innerHTML = toAddressHtml(d.to);
     $("success-tx-block").textContent = String(d.blockNumber);
     $("success-tx-hash").innerHTML = txHashHtml(d.hash);
+
+    // Show decoded calldata details if present
+    const decodedEl = $("success-tx-decoded");
+    if (decodedEl && d.decoded) {
+        decodedEl.innerHTML = decodedDetailsHtml(d.decoded);
+        decodedEl.classList.remove("hidden");
+    } else if (decodedEl) {
+        decodedEl.classList.add("hidden");
+    }
+
     attachCopyHandlers("view-success-tx");
     showView("success-tx");
 }