fix: reset validation state when navigating to send view

Clear the error/warning text and disable the review button when entering
the send view from home, address detail, or address token views. This
prevents stale validation messages from persisting after leaving and
returning to the send view.

src/popup/index.html

@@ -496,6 +496,11 @@
                         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/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/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,
@@ -388,6 +392,7 @@ function init(ctx) {
         $("send-token-static").classList.add("hidden");
         renderSendTokenSelect(addr);
         updateSendBalance();
+        resetSendValidation();
         showView("send");
     });
 

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,
+};