diff --git a/scripts/harb-evaluator/helpers/swap.ts b/scripts/harb-evaluator/helpers/swap.ts
index cde36c9..01b83a9 100644
--- a/scripts/harb-evaluator/helpers/swap.ts
+++ b/scripts/harb-evaluator/helpers/swap.ts
@@ -174,35 +174,40 @@ export async function buyKrk(page: Page, ethAmount: string, opts?: BuyKrkOptions
  *
  * Drives the real sell widget UI (requires the #456 sell tab).
  *
- * If config is provided, queries WETH balance before and after the sell and
- * returns the delta. Otherwise returns 0n (caller is responsible for verification).
+ * If config is provided, creates an eth_newFilter for WETH Transfer events to the
+ * account before clicking Sell, polls eth_getFilterLogs until the event arrives
+ * (confirming the swap is mined), then returns the WETH balance delta. Otherwise
+ * returns 0n (caller is responsible for verification).
  *
  * @param page - Playwright page with injected wallet
  * @param amount - KRK amount to sell (as string). Use 'max' to click the Max button.
  * @param screenshotPrefix - Optional prefix for screenshot filenames
- * @param config - Optional config to query WETH received after sell
+ * @param config - Optional config for on-chain WETH receipt confirmation
  * @returns WETH received (balance diff) or 0n if config is not provided
  */
 export async function sellKrk(
   page: Page,
   amount: string,
   screenshotPrefix?: string,
-  config?: SellConfig,
+  config?: Pick<SellConfig, 'rpcUrl' | 'accountAddress'>,
 ): Promise<bigint> {
   console.log(`[swap] Selling ${amount} KRK via get-krk page sell widget...`);
   await navigateSPA(page, '/app/get-krk');
+  await expect(page.getByRole('heading', { name: 'Get $KRK Tokens' })).toBeVisible({ timeout: 10_000 });
 
   const sellTab = page.getByTestId('swap-mode-sell');
   await expect(sellTab).toBeVisible({ timeout: 10_000 });
   await sellTab.click();
 
+  const sellInput = page.getByTestId('swap-sell-amount-input');
   if (amount === 'max') {
     const maxButton = page.locator('.max-button');
     await expect(maxButton).toBeVisible({ timeout: 5_000 });
     await maxButton.click();
+    // setMax() is async — wait for the composable to populate the input via loadKrkBalance()
+    await expect(sellInput).not.toHaveValue('', { timeout: 10_000 });
     console.log('[swap] Clicked Max button');
   } else {
-    const sellInput = page.getByTestId('swap-sell-amount-input');
     await expect(sellInput).toBeVisible({ timeout: 5_000 });
     await sellInput.fill(amount);
     console.log(`[swap] Filled sell amount: ${amount}`);
@@ -210,6 +215,23 @@ export async function sellKrk(
 
   const wethBefore = config ? await erc20BalanceOf(config.rpcUrl, WETH, config.accountAddress) : 0n;
 
+  // Create WETH Transfer event filter BEFORE the sell (if config provided)
+  let filterId: string | undefined;
+  if (config) {
+    filterId = (await rpcCall(config.rpcUrl, 'eth_newFilter', [
+      {
+        address: WETH,
+        topics: [
+          TRANSFER_TOPIC,
+          null, // any sender (pool/router)
+          '0x' + config.accountAddress.slice(2).padStart(64, '0'), // to our account
+        ],
+        fromBlock: 'latest',
+      },
+    ])) as string;
+    console.log(`[swap] WETH Transfer filter created: ${filterId}`);
+  }
+
   if (screenshotPrefix) {
     await page.screenshot({ path: `test-results/${screenshotPrefix}-before-sell.png` });
   }
@@ -228,7 +250,28 @@ export async function sellKrk(
     console.log('[swap] Button state not observed (sell may have completed instantly)');
   }
   await expect(sellButton).toHaveText('Sell KRK', { timeout: 60_000 });
-  console.log('[swap] Sell completed');
+  console.log('[swap] Sell completed (UI idle)');
+
+  // Wait for on-chain confirmation via WETH Transfer event
+  if (config && filterId) {
+    console.log('[swap] Waiting for WETH Transfer event...');
+    const deadline = Date.now() + 15_000;
+    let received = false;
+    while (Date.now() < deadline) {
+      const logs = (await rpcCall(config.rpcUrl, 'eth_getFilterLogs', [filterId])) as unknown[];
+      if (logs && logs.length > 0) {
+        received = true;
+        console.log(`[swap] WETH Transfer event received (${logs.length} log(s))`);
+        break;
+      }
+      // eslint-disable-next-line no-restricted-syntax -- Polling with timeout: eth_getFilterLogs is HTTP-only polling (not push). See AGENTS.md #Engineering Principles.
+      await new Promise(r => setTimeout(r, 200));
+    }
+    await rpcCall(config.rpcUrl, 'eth_uninstallFilter', [filterId]).catch(() => {});
+    if (!received) {
+      throw new Error(`No WETH Transfer event received within 15s after selling ${amount} KRK`);
+    }
+  }
 
   if (screenshotPrefix) {
     await page.screenshot({ path: `test-results/${screenshotPrefix}-after-sell.png` });