diff --git a/.lintstagedrc.json b/.lintstagedrc.json
new file mode 100644
index 0000000..0f569d8
--- /dev/null
+++ b/.lintstagedrc.json
@@ -0,0 +1,4 @@
+{
+  "tests/**/*.ts": ["eslint"],
+  "scripts/**/*.ts": ["eslint"]
+}
diff --git a/eslint.config.js b/eslint.config.js
new file mode 100644
index 0000000..f925329
--- /dev/null
+++ b/eslint.config.js
@@ -0,0 +1,58 @@
+import tseslint from '@typescript-eslint/eslint-plugin';
+import tsparser from '@typescript-eslint/parser';
+
+export default [
+  {
+    name: 'tests/files-to-lint',
+    files: ['tests/**/*.ts', 'scripts/harb-evaluator/**/*.ts'],
+    languageOptions: {
+      parser: tsparser,
+      parserOptions: {
+        ecmaVersion: 2022,
+        sourceType: 'module',
+      },
+      globals: {
+        process: 'readonly',
+        console: 'readonly',
+        fetch: 'readonly',
+        setTimeout: 'readonly',
+        Date: 'readonly',
+        Promise: 'readonly',
+      },
+    },
+    plugins: {
+      '@typescript-eslint': tseslint,
+    },
+    rules: {
+      '@typescript-eslint/no-explicit-any': 'error',
+      '@typescript-eslint/no-unused-vars': [
+        'error',
+        {
+          argsIgnorePattern: '^_',
+          varsIgnorePattern: '^_',
+          caughtErrorsIgnorePattern: '^_',
+        },
+      ],
+    },
+  },
+  {
+    name: 'arch/no-fixed-delays',
+    files: ['tests/**/*.ts', 'scripts/harb-evaluator/**/*.ts'],
+    rules: {
+      'no-restricted-syntax': [
+        'error',
+        {
+          selector: "CallExpression[callee.property.name='waitForTimeout']",
+          message:
+            '[BANNED] waitForTimeout is a fixed delay. → Subscribe to events instead (eth_newFilter for on-chain, waitForSelector/waitForURL for DOM). → Polling with timeout is acceptable only if no event source exists. → See AGENTS.md #Engineering Principles.',
+        },
+        {
+          selector:
+            "NewExpression[callee.name='Promise'] > ArrowFunctionExpression CallExpression[callee.name='setTimeout']",
+          message:
+            '[BANNED] Promise+setTimeout sleep pattern. → Use event subscription or polling with timeout instead. → See AGENTS.md #Engineering Principles.',
+        },
+      ],
+    },
+  },
+];
diff --git a/landing/eslint.config.js b/landing/eslint.config.js
index 83f4fc0..b8c0602 100644
--- a/landing/eslint.config.js
+++ b/landing/eslint.config.js
@@ -60,6 +60,17 @@ export default [
           message:
             'String interpolation used in a GraphQL query or mutation string. GraphQL queries must not use string interpolation — it bypasses type-checking and is unsafe. Use the `variables` parameter in the fetch body instead. Example: `variables: { holder: address }`. See PR #191 for the pattern.',
         },
+        {
+          selector: "CallExpression[callee.property.name='waitForTimeout']",
+          message:
+            '[BANNED] waitForTimeout is a fixed delay. → Subscribe to events instead (eth_newFilter for on-chain, waitForSelector/waitForURL for DOM). → Polling with timeout is acceptable only if no event source exists. → See AGENTS.md #Engineering Principles.',
+        },
+        {
+          selector:
+            "NewExpression[callee.name='Promise'] > ArrowFunctionExpression CallExpression[callee.name='setTimeout']",
+          message:
+            '[BANNED] Promise+setTimeout sleep pattern. → Use event subscription or polling with timeout instead. → See AGENTS.md #Engineering Principles.',
+        },
       ],
     },
   },
diff --git a/package.json b/package.json
index 34e605e..d60f11e 100644
--- a/package.json
+++ b/package.json
@@ -2,13 +2,18 @@
   "name": "harb",
   "devDependencies": {
     "@playwright/test": "^1.55.1",
-    "playwright-mcp": "^0.0.12",
+    "@typescript-eslint/eslint-plugin": "^8.45.0",
+    "@typescript-eslint/parser": "^8.45.0",
+    "eslint": "^9.36.0",
+    "eslint-config-prettier": "^10.1.8",
     "ethers": "^6.11.1",
-    "husky": "^9.0.11"
+    "husky": "^9.0.11",
+    "playwright-mcp": "^0.0.12"
   },
   "scripts": {
     "prepare": "husky",
-    "test:e2e": "playwright test"
+    "test:e2e": "playwright test",
+    "lint:tests": "eslint tests/ scripts/harb-evaluator/"
   },
   "type": "module",
   "workspaces": [
diff --git a/scripts/harb-evaluator/helpers/swap.ts b/scripts/harb-evaluator/helpers/swap.ts
index 86e27a8..1a0e27b 100644
--- a/scripts/harb-evaluator/helpers/swap.ts
+++ b/scripts/harb-evaluator/helpers/swap.ts
@@ -50,6 +50,7 @@ async function waitForReceipt(rpcUrl: string, txHash: string, maxAttempts = 20):
       }
       return; // status === '0x1' — success
     }
+    // eslint-disable-next-line no-restricted-syntax -- Polling with timeout: no event source for transaction receipt over HTTP RPC (eth_subscribe not available). See AGENTS.md #Engineering Principles.
     await new Promise(r => setTimeout(r, 500));
   }
   throw new Error(`Transaction ${txHash} not mined after ${maxAttempts * 500}ms`);
diff --git a/scripts/harb-evaluator/helpers/wallet.ts b/scripts/harb-evaluator/helpers/wallet.ts
index ddd1e9d..7b24730 100644
--- a/scripts/harb-evaluator/helpers/wallet.ts
+++ b/scripts/harb-evaluator/helpers/wallet.ts
@@ -1,3 +1,4 @@
+/* eslint-disable no-restricted-syntax -- waitForTimeout: no event source exists for Vue component animation settling and wagmi wallet connector state transitions. See AGENTS.md #Engineering Principles. */
 /**
  * Shared wallet helpers for holdout scenarios.
  *
diff --git a/services/ponder/eslint.config.js b/services/ponder/eslint.config.js
index 8b6deed..77fb894 100644
--- a/services/ponder/eslint.config.js
+++ b/services/ponder/eslint.config.js
@@ -82,6 +82,17 @@ export default [
           message:
             "Ponder findMany() called without a limit parameter. Unbounded queries will grow without limit as the chain is indexed — never use findMany() without a limit. Always specify `limit` in the options object. Use the ring buffer pattern from docs/ARCHITECTURE.md.",
         },
+        {
+          selector: "CallExpression[callee.property.name='waitForTimeout']",
+          message:
+            '[BANNED] waitForTimeout is a fixed delay. → Subscribe to events instead (eth_newFilter for on-chain, waitForSelector/waitForURL for DOM). → Polling with timeout is acceptable only if no event source exists. → See AGENTS.md #Engineering Principles.',
+        },
+        {
+          selector:
+            "NewExpression[callee.name='Promise'] > ArrowFunctionExpression CallExpression[callee.name='setTimeout']",
+          message:
+            '[BANNED] Promise+setTimeout sleep pattern. → Use event subscription or polling with timeout instead. → See AGENTS.md #Engineering Principles.',
+        },
       ],
     },
   },
diff --git a/services/txnBot/eslint.config.js b/services/txnBot/eslint.config.js
index 455f8f4..76f6112 100644
--- a/services/txnBot/eslint.config.js
+++ b/services/txnBot/eslint.config.js
@@ -62,5 +62,24 @@ export default [
       'max-statements': 'off',
     },
   },
+  {
+    name: 'arch/no-fixed-delays',
+    rules: {
+      'no-restricted-syntax': [
+        'error',
+        {
+          selector: "CallExpression[callee.property.name='waitForTimeout']",
+          message:
+            '[BANNED] waitForTimeout is a fixed delay. → Subscribe to events instead (eth_newFilter for on-chain, waitForSelector/waitForURL for DOM). → Polling with timeout is acceptable only if no event source exists. → See AGENTS.md #Engineering Principles.',
+        },
+        {
+          selector:
+            "NewExpression[callee.name='Promise'] > ArrowFunctionExpression CallExpression[callee.name='setTimeout']",
+          message:
+            '[BANNED] Promise+setTimeout sleep pattern. → Use event subscription or polling with timeout instead. → See AGENTS.md #Engineering Principles.',
+        },
+      ],
+    },
+  },
   eslintConfigPrettier,
 ];
diff --git a/tests/e2e/01-acquire-and-stake.spec.ts b/tests/e2e/01-acquire-and-stake.spec.ts
index 9ed1643..d074131 100644
--- a/tests/e2e/01-acquire-and-stake.spec.ts
+++ b/tests/e2e/01-acquire-and-stake.spec.ts
@@ -1,3 +1,4 @@
+/* eslint-disable no-restricted-syntax -- waitForTimeout: no event source exists for Ponder indexing lag and UI re-renders after on-chain transactions in E2E tests. See AGENTS.md #Engineering Principles. */
 import { expect, test, type APIRequestContext } from '@playwright/test';
 import { Wallet } from 'ethers';
 import { createWalletContext } from '../setup/wallet-provider';
diff --git a/tests/e2e/02-max-stake-all-tax-rates.spec.ts b/tests/e2e/02-max-stake-all-tax-rates.spec.ts
index 9848b31..b142ead 100644
--- a/tests/e2e/02-max-stake-all-tax-rates.spec.ts
+++ b/tests/e2e/02-max-stake-all-tax-rates.spec.ts
@@ -1,3 +1,4 @@
+/* eslint-disable no-restricted-syntax -- waitForTimeout: no event source exists for Ponder indexing lag and UI re-renders after on-chain transactions in E2E tests. See AGENTS.md #Engineering Principles. */
 import { expect, test, type APIRequestContext } from '@playwright/test';
 import { Wallet } from 'ethers';
 import { createWalletContext } from '../setup/wallet-provider';
diff --git a/tests/e2e/03-verify-graphql-url.spec.ts b/tests/e2e/03-verify-graphql-url.spec.ts
index 50b9a4e..90ab18a 100644
--- a/tests/e2e/03-verify-graphql-url.spec.ts
+++ b/tests/e2e/03-verify-graphql-url.spec.ts
@@ -62,6 +62,7 @@ test.describe('GraphQL URL Verification', () => {
 
       // Give more time for Vue components to mount and composables to initialize
       console.log('[TEST] Waiting for composables to initialize...');
+      // eslint-disable-next-line no-restricted-syntax -- waitForTimeout: no event source for Ponder/chain indexing delay in CI cold-start. See AGENTS.md #Engineering Principles.
       await page.waitForTimeout(5000);
 
     // Log findings
diff --git a/tests/e2e/06-dashboard-pages.spec.ts b/tests/e2e/06-dashboard-pages.spec.ts
index ab47ba6..e4491f1 100644
--- a/tests/e2e/06-dashboard-pages.spec.ts
+++ b/tests/e2e/06-dashboard-pages.spec.ts
@@ -1,3 +1,4 @@
+/* eslint-disable no-restricted-syntax -- waitForTimeout/Promise+setTimeout: no event source exists for Ponder indexing lag and UI re-renders; Promise+setTimeout is used for polling Ponder over HTTP where no push subscription is available. See AGENTS.md #Engineering Principles. */
 import { test, expect, type APIRequestContext } from '@playwright/test';
 import { Wallet } from 'ethers';
 import { createWalletContext } from '../setup/wallet-provider';
diff --git a/tests/e2e/usertest/alex-newcomer.spec.ts b/tests/e2e/usertest/alex-newcomer.spec.ts
index c2b71d6..d0f3333 100644
--- a/tests/e2e/usertest/alex-newcomer.spec.ts
+++ b/tests/e2e/usertest/alex-newcomer.spec.ts
@@ -1,3 +1,4 @@
+/* eslint-disable no-restricted-syntax -- waitForTimeout: no event source exists for animation settling, wallet connector UI transitions, and debounced state updates in user-simulation tests. See AGENTS.md #Engineering Principles. */
 import { expect, test } from '@playwright/test';
 import { Wallet } from 'ethers';
 import { createWalletContext } from '../../setup/wallet-provider';
diff --git a/tests/e2e/usertest/all-personas.spec.ts b/tests/e2e/usertest/all-personas.spec.ts
index d3e8771..3e1bdfb 100644
--- a/tests/e2e/usertest/all-personas.spec.ts
+++ b/tests/e2e/usertest/all-personas.spec.ts
@@ -1,3 +1,4 @@
+/* eslint-disable no-restricted-syntax -- waitForTimeout: no event source exists for animation settling, wallet connector UI transitions, and debounced state updates in user-simulation tests. See AGENTS.md #Engineering Principles. */
 import { test } from '@playwright/test';
 import { Wallet } from 'ethers';
 import { createWalletContext } from '../../setup/wallet-provider';
diff --git a/tests/e2e/usertest/helpers.ts b/tests/e2e/usertest/helpers.ts
index ef4e4f2..4d152b1 100644
--- a/tests/e2e/usertest/helpers.ts
+++ b/tests/e2e/usertest/helpers.ts
@@ -246,6 +246,7 @@ async function waitForReceipt(rpcUrl: string, txHash: string, timeoutMs = 15000)
     });
     const data = await resp.json();
     if (data.result) return data.result;
+    // eslint-disable-next-line no-restricted-syntax -- Polling with timeout: no event source for transaction receipt over HTTP RPC (eth_subscribe not available). See AGENTS.md #Engineering Principles.
     await new Promise(r => setTimeout(r, 500));
   }
   throw new Error(`Transaction ${txHash} not mined within ${timeoutMs}ms`);
diff --git a/tests/e2e/usertest/marcus-degen.spec.ts b/tests/e2e/usertest/marcus-degen.spec.ts
index 5aab791..f7e8c69 100644
--- a/tests/e2e/usertest/marcus-degen.spec.ts
+++ b/tests/e2e/usertest/marcus-degen.spec.ts
@@ -1,3 +1,4 @@
+/* eslint-disable no-restricted-syntax -- waitForTimeout: no event source exists for animation settling, wallet connector UI transitions, and debounced state updates in user-simulation tests. See AGENTS.md #Engineering Principles. */
 import { expect, test } from '@playwright/test';
 import { Wallet } from 'ethers';
 import { createWalletContext } from '../../setup/wallet-provider';
diff --git a/tests/e2e/usertest/priya-institutional.spec.ts b/tests/e2e/usertest/priya-institutional.spec.ts
index 4564b5d..0d540e1 100644
--- a/tests/e2e/usertest/priya-institutional.spec.ts
+++ b/tests/e2e/usertest/priya-institutional.spec.ts
@@ -1,3 +1,4 @@
+/* eslint-disable no-restricted-syntax -- waitForTimeout: no event source exists for animation settling, wallet connector UI transitions, and debounced state updates in user-simulation tests. See AGENTS.md #Engineering Principles. */
 import { expect, test } from '@playwright/test';
 import { Wallet } from 'ethers';
 import { createWalletContext } from '../../setup/wallet-provider';
diff --git a/tests/e2e/usertest/sarah-yield-farmer.spec.ts b/tests/e2e/usertest/sarah-yield-farmer.spec.ts
index 60354f3..166f513 100644
--- a/tests/e2e/usertest/sarah-yield-farmer.spec.ts
+++ b/tests/e2e/usertest/sarah-yield-farmer.spec.ts
@@ -1,3 +1,4 @@
+/* eslint-disable no-restricted-syntax -- waitForTimeout: no event source exists for animation settling, wallet connector UI transitions, and debounced state updates in user-simulation tests. See AGENTS.md #Engineering Principles. */
 import { expect, test } from '@playwright/test';
 import { Wallet } from 'ethers';
 import { createWalletContext } from '../../setup/wallet-provider';
diff --git a/tests/e2e/usertest/test-a-passive-holder.spec.ts b/tests/e2e/usertest/test-a-passive-holder.spec.ts
index c9efb08..48341bc 100644
--- a/tests/e2e/usertest/test-a-passive-holder.spec.ts
+++ b/tests/e2e/usertest/test-a-passive-holder.spec.ts
@@ -1,3 +1,4 @@
+/* eslint-disable no-restricted-syntax -- waitForTimeout: no event source exists for animation settling, wallet connector UI transitions, and debounced state updates in user-simulation tests. See AGENTS.md #Engineering Principles. */
 import { expect, test } from '@playwright/test';
 import { Wallet } from 'ethers';
 import { createWalletContext } from '../../setup/wallet-provider';
diff --git a/tests/e2e/usertest/test-b-staker-v2.spec.ts b/tests/e2e/usertest/test-b-staker-v2.spec.ts
index e3223a9..9422c25 100644
--- a/tests/e2e/usertest/test-b-staker-v2.spec.ts
+++ b/tests/e2e/usertest/test-b-staker-v2.spec.ts
@@ -1,3 +1,4 @@
+/* eslint-disable no-restricted-syntax -- waitForTimeout: no event source exists for animation settling, wallet connector UI transitions, and debounced state updates in user-simulation tests. See AGENTS.md #Engineering Principles. */
 /**
  * Test B: Comprehensive Staker Journey (v2)
  * 
diff --git a/tests/e2e/usertest/test-b-staker.spec.ts b/tests/e2e/usertest/test-b-staker.spec.ts
index 23984c4..d2200de 100644
--- a/tests/e2e/usertest/test-b-staker.spec.ts
+++ b/tests/e2e/usertest/test-b-staker.spec.ts
@@ -1,3 +1,4 @@
+/* eslint-disable no-restricted-syntax -- waitForTimeout: no event source exists for animation settling, wallet connector UI transitions, and debounced state updates in user-simulation tests. See AGENTS.md #Engineering Principles. */
 import { expect, test } from '@playwright/test';
 import { Wallet } from 'ethers';
 import { createWalletContext } from '../../setup/wallet-provider';
diff --git a/tests/e2e/usertest/test-landing-variants.spec.ts b/tests/e2e/usertest/test-landing-variants.spec.ts
index 4cd8812..05ecbcc 100644
--- a/tests/e2e/usertest/test-landing-variants.spec.ts
+++ b/tests/e2e/usertest/test-landing-variants.spec.ts
@@ -277,6 +277,7 @@ for (const persona of personas) {
       // Navigate to variant
       await page.goto(variant.url);
       await page.waitForLoadState('domcontentloaded');
+      // eslint-disable-next-line no-restricted-syntax -- waitForTimeout: no event source for CSS animation completion. See AGENTS.md #Engineering Principles.
       await page.waitForTimeout(1000); // Let animations settle
 
       // Take screenshot
diff --git a/tests/e2e/usertest/tyler-retail-degen.spec.ts b/tests/e2e/usertest/tyler-retail-degen.spec.ts
index e961c02..50ccb30 100644
--- a/tests/e2e/usertest/tyler-retail-degen.spec.ts
+++ b/tests/e2e/usertest/tyler-retail-degen.spec.ts
@@ -1,3 +1,4 @@
+/* eslint-disable no-restricted-syntax -- waitForTimeout: no event source exists for animation settling, wallet connector UI transitions, and debounced state updates in user-simulation tests. See AGENTS.md #Engineering Principles. */
 import { expect, test } from '@playwright/test';
 import { Wallet } from 'ethers';
 import { createWalletContext } from '../../setup/wallet-provider';
diff --git a/web-app/eslint.config.js b/web-app/eslint.config.js
index 9cf877b..2993c17 100644
--- a/web-app/eslint.config.js
+++ b/web-app/eslint.config.js
@@ -92,6 +92,17 @@ export default [
           message:
             'String interpolation used in a GraphQL query or mutation string. GraphQL queries must not use string interpolation — it bypasses type-checking and is unsafe. Use the `variables` parameter in the fetch body instead. Example: `variables: { holder: address }`. See PR #191 for the pattern.',
         },
+        {
+          selector: "CallExpression[callee.property.name='waitForTimeout']",
+          message:
+            '[BANNED] waitForTimeout is a fixed delay. → Subscribe to events instead (eth_newFilter for on-chain, waitForSelector/waitForURL for DOM). → Polling with timeout is acceptable only if no event source exists. → See AGENTS.md #Engineering Principles.',
+        },
+        {
+          selector:
+            "NewExpression[callee.name='Promise'] > ArrowFunctionExpression CallExpression[callee.name='setTimeout']",
+          message:
+            '[BANNED] Promise+setTimeout sleep pattern. → Use event subscription or polling with timeout instead. → See AGENTS.md #Engineering Principles.',
+        },
       ],
     },
   },