diff --git a/src/lib/components/rule-actions/Relay-Actions.svelte b/src/lib/components/rule-actions/Relay-Actions.svelte
index 2169bc8e..cf181010 100644
--- a/src/lib/components/rule-actions/Relay-Actions.svelte
+++ b/src/lib/components/rule-actions/Relay-Actions.svelte
@@ -1,6 +1,12 @@
 <script lang="ts">
 	import { CwDropdown, CwInput } from '@cropwatchdevelopment/cwui';
 	import { m } from '$lib/paraglide/messages.js';
+	import {
+		MAX_TIMED_RELAY_SECONDS,
+		buildRelayPayload,
+		hexToBase64,
+		type ActionValue
+	} from './relay-payload';
 
 	interface DeviceOption {
 		label: string;
@@ -8,15 +14,6 @@
 		disabled?: boolean;
 	}
 
-	type ActionValue =
-		| 'ro1_on_timed'
-		| 'ro2_on_timed'
-		| 'both_on_timed'
-		| 'ro1_on_permanent'
-		| 'ro1_off_permanent'
-		| 'ro2_on_permanent'
-		| 'ro2_off_permanent';
-
 	interface ActionOption {
 		label: string;
 		value: ActionValue;
@@ -105,7 +102,9 @@
 	const isTimedAction = $derived(selectedAction.endsWith('_timed'));
 
 	const safeOnTimeSeconds = $derived(
-		Number.isFinite(onTimeSeconds) ? Math.max(1, Math.min(65, Math.trunc(onTimeSeconds))) : 5
+		Number.isFinite(onTimeSeconds)
+			? Math.max(1, Math.min(MAX_TIMED_RELAY_SECONDS, Math.trunc(onTimeSeconds)))
+			: 5
 	);
 
 	const payloadHex = $derived(buildRelayPayload(selectedAction, safeOnTimeSeconds));
@@ -138,87 +137,6 @@
 		}
 	});
 
-	function buildRelayPayload(action: ActionValue, seconds: number): string {
-		if (action.endsWith('_timed')) {
-			return buildTimedRelayPayload(action, seconds);
-		}
-		return buildPermanentRelayPayload(action);
-	}
-
-	function buildTimedRelayPayload(action: ActionValue, seconds: number): string {
-		const command = 0x05;
-
-		// Timeout behavior byte:
-		//   0x00 = after timeout, relay(s) switch to the inverted/opposite state
-		//   0x01 = after timeout, relay(s) return to their original pre-command state
-		// Use 0x00 so a timed "ON for N seconds" action always returns the relay to OFF,
-		// even if it was already ON when the rule fired.
-		const timeoutBehavior = 0x00;
-
-		// Dragino timed relay format uses one byte for RO1/RO2 state.
-		// 0b10 = Relay 1 ON/NC, Relay 2 OFF/NO
-		// 0b01 = Relay 1 OFF/NO, Relay 2 ON/NC
-		// 0b11 = Both ON/NC
-		const relayState = action === 'ro1_on_timed' ? 0b10 : action === 'ro2_on_timed' ? 0b01 : 0b11;
-
-		const milliseconds = seconds * 1000;
-
-		// Use 2-byte latch time for compatibility with older firmware.
-		// Max = 65535 ms, so this UI clamps to 65 seconds.
-		if (milliseconds > 0xffff) {
-			throw new Error('Timed relay payload exceeds 2-byte latch time limit.');
-		}
-
-		const timeHigh = (milliseconds >> 8) & 0xff;
-		const timeLow = milliseconds & 0xff;
-
-		return bytesToHex([command, timeoutBehavior, relayState, timeHigh, timeLow]);
-	}
-
-	function buildPermanentRelayPayload(action: ActionValue): string {
-		// Dragino fixed relay command: [0x03, relay1Byte, relay2Byte]
-		// 0x00 = OFF, 0x01 = ON, 0x11 = no action on that relay.
-		const command = 0x03;
-		const NO_ACTION = 0x11;
-
-		let relay1: number;
-		let relay2: number;
-		switch (action) {
-			case 'ro1_on_permanent':
-				relay1 = 0x01;
-				relay2 = NO_ACTION;
-				break;
-			case 'ro1_off_permanent':
-				relay1 = 0x00;
-				relay2 = NO_ACTION;
-				break;
-			case 'ro2_on_permanent':
-				relay1 = NO_ACTION;
-				relay2 = 0x01;
-				break;
-			case 'ro2_off_permanent':
-				relay1 = NO_ACTION;
-				relay2 = 0x00;
-				break;
-			default:
-				return '';
-		}
-
-		return bytesToHex([command, relay1, relay2]);
-	}
-
-	function bytesToHex(bytes: number[]): string {
-		return bytes
-			.map((byte) => byte.toString(16).padStart(2, '0'))
-			.join('')
-			.toUpperCase();
-	}
-
-	function hexToBase64(hex: string): string {
-		const bytes = hex.match(/.{1,2}/g)?.map((byte) => parseInt(byte, 16)) ?? [];
-		return btoa(String.fromCharCode(...bytes));
-	}
-
 	function handleSecondsInput(event: Event) {
 		const input = event.currentTarget as HTMLInputElement;
 		const value = Number(input.value);
@@ -248,7 +166,7 @@
 			placeholder="Enter time in seconds"
 			type="numeric"
 			min="1"
-			max="65"
+			max={String(MAX_TIMED_RELAY_SECONDS)}
 			value={String(onTimeSeconds)}
 			oninput={handleSecondsInput}
 		/>
diff --git a/src/lib/components/rule-actions/relay-payload.spec.ts b/src/lib/components/rule-actions/relay-payload.spec.ts
new file mode 100644
index 00000000..0443e1ad
--- /dev/null
+++ b/src/lib/components/rule-actions/relay-payload.spec.ts
@@ -0,0 +1,67 @@
+import { describe, expect, it } from 'vitest';
+import {
+	buildPermanentRelayPayload,
+	buildRelayPayload,
+	buildTimedRelayPayload,
+	hexToBase64
+} from './relay-payload';
+
+describe('buildTimedRelayPayload', () => {
+	it('builds the tested v1.7 payload for Relay 1 ON for 15 seconds', () => {
+		expect(buildTimedRelayPayload('ro1_on_timed', 15)).toBe('05011000003A98');
+	});
+
+	it('builds the payload for Relay 2 ON for 15 seconds', () => {
+		expect(buildTimedRelayPayload('ro2_on_timed', 15)).toBe('05010100003A98');
+	});
+
+	it('builds the payload for both relays ON for 15 seconds', () => {
+		expect(buildTimedRelayPayload('both_on_timed', 15)).toBe('05011100003A98');
+	});
+
+	it('uses timeoutBehavior 0x01 and never the old bad 0x00 payload', () => {
+		const payload = buildTimedRelayPayload('ro1_on_timed', 15);
+		expect(payload.slice(2, 4)).toBe('01');
+		expect(payload).not.toBe('0500023A98');
+	});
+
+	it('emits a 7-byte (4-byte latch time) payload', () => {
+		expect(buildTimedRelayPayload('ro1_on_timed', 15)).toHaveLength(14);
+	});
+
+	it('handles long latch times beyond the old 2-byte 65-second limit', () => {
+		// 24 hours = 86_400_000 ms = 0x05265C00
+		expect(buildTimedRelayPayload('ro1_on_timed', 86400)).toBe('05011005265C00');
+	});
+
+	it('throws on a non-positive latch time', () => {
+		expect(() => buildTimedRelayPayload('ro1_on_timed', 0)).toThrow();
+	});
+});
+
+describe('buildPermanentRelayPayload', () => {
+	it('builds permanent relay commands with the 0x03 command byte', () => {
+		expect(buildPermanentRelayPayload('ro1_on_permanent')).toBe('030111');
+		expect(buildPermanentRelayPayload('ro1_off_permanent')).toBe('030011');
+		expect(buildPermanentRelayPayload('ro2_on_permanent')).toBe('031101');
+		expect(buildPermanentRelayPayload('ro2_off_permanent')).toBe('031100');
+	});
+});
+
+describe('buildRelayPayload', () => {
+	it('routes timed actions to the timed builder', () => {
+		expect(buildRelayPayload('ro1_on_timed', 15)).toBe('05011000003A98');
+	});
+
+	it('routes permanent actions to the permanent builder', () => {
+		expect(buildRelayPayload('ro1_on_permanent', 15)).toBe('030111');
+	});
+});
+
+describe('hexToBase64', () => {
+	it('encodes the tested timed payloads to base64', () => {
+		expect(hexToBase64('05011000003A98')).toBe('BQEQAAA6mA==');
+		expect(hexToBase64('05010100003A98')).toBe('BQEBAAA6mA==');
+		expect(hexToBase64('05011100003A98')).toBe('BQERAAA6mA==');
+	});
+});
diff --git a/src/lib/components/rule-actions/relay-payload.ts b/src/lib/components/rule-actions/relay-payload.ts
new file mode 100644
index 00000000..621e6631
--- /dev/null
+++ b/src/lib/components/rule-actions/relay-payload.ts
@@ -0,0 +1,107 @@
+// Dragino LT-22222-L relay downlink payload builders.
+//
+// Reference: Dragino LT-22222-L LoRa I/O Controller User Manual (firmware v1.7).
+//   - 0x05 = timed relay control, 0x03 = permanent relay control.
+//   - Timed command layout: [0x05, timeoutBehavior, relayState, time1..time4].
+//   - timeoutBehavior 0x01 = return relays to original state after the latch time;
+//     0x00 = invert relays after the latch time.
+//   - relayState is one hex digit per relay (1 = NC/closed/ON, 0 = NO/open/OFF).
+//   - v1.6+ firmware uses a 4-byte big-endian latch time in milliseconds.
+
+export type ActionValue =
+	| 'ro1_on_timed'
+	| 'ro2_on_timed'
+	| 'both_on_timed'
+	| 'ro1_on_permanent'
+	| 'ro1_off_permanent'
+	| 'ro2_on_permanent'
+	| 'ro2_off_permanent';
+
+// 4-byte latch time (v1.6+ firmware) supports far more than the old 2-byte limit;
+// cap the UI at 24 hours rather than the previous 65-second clamp.
+export const MAX_TIMED_RELAY_SECONDS = 86400;
+
+export function bytesToHex(bytes: number[]): string {
+	return bytes
+		.map((byte) => byte.toString(16).padStart(2, '0'))
+		.join('')
+		.toUpperCase();
+}
+
+export function hexToBase64(hex: string): string {
+	const bytes = hex.match(/.{1,2}/g)?.map((byte) => parseInt(byte, 16)) ?? [];
+	return btoa(String.fromCharCode(...bytes));
+}
+
+export function buildTimedRelayPayload(action: ActionValue, seconds: number): string {
+	const command = 0x05;
+
+	// Use 0x01 so the relay returns to its original pre-command state after the
+	// latch time. Do NOT use 0x00 here — 0x00 means invert/opposite after timeout.
+	const timeoutBehavior = 0x01;
+
+	// The relay-state byte is not binary bit flags. It is Dragino's relay-state
+	// command byte, one hex digit per relay (1 = NC/closed/ON, 0 = NO/open/OFF):
+	//   0x10 = RO1 ON,  RO2 OFF
+	//   0x01 = RO1 OFF, RO2 ON
+	//   0x11 = RO1 ON,  RO2 ON
+	const relayState =
+		action === 'ro1_on_timed' ? 0x10 : action === 'ro2_on_timed' ? 0x01 : 0x11;
+
+	const milliseconds = seconds * 1000;
+
+	if (!Number.isFinite(milliseconds) || milliseconds < 1) {
+		throw new Error('Timed relay payload requires a positive latch time.');
+	}
+
+	if (milliseconds > 0xffffffff) {
+		throw new Error('Timed relay payload exceeds 4-byte latch time limit.');
+	}
+
+	// v1.6+ firmware (LT-22222-L v1.7) uses a 4-byte big-endian latch time.
+	const time1 = (milliseconds >>> 24) & 0xff;
+	const time2 = (milliseconds >>> 16) & 0xff;
+	const time3 = (milliseconds >>> 8) & 0xff;
+	const time4 = milliseconds & 0xff;
+
+	return bytesToHex([command, timeoutBehavior, relayState, time1, time2, time3, time4]);
+}
+
+export function buildPermanentRelayPayload(action: ActionValue): string {
+	// Dragino fixed relay command: [0x03, relay1Byte, relay2Byte]
+	// 0x00 = OFF, 0x01 = ON, 0x11 = no action on that relay.
+	const command = 0x03;
+	const NO_ACTION = 0x11;
+
+	let relay1: number;
+	let relay2: number;
+	switch (action) {
+		case 'ro1_on_permanent':
+			relay1 = 0x01;
+			relay2 = NO_ACTION;
+			break;
+		case 'ro1_off_permanent':
+			relay1 = 0x00;
+			relay2 = NO_ACTION;
+			break;
+		case 'ro2_on_permanent':
+			relay1 = NO_ACTION;
+			relay2 = 0x01;
+			break;
+		case 'ro2_off_permanent':
+			relay1 = NO_ACTION;
+			relay2 = 0x00;
+			break;
+		default:
+			return '';
+	}
+
+	return bytesToHex([command, relay1, relay2]);
+}
+
+export function buildRelayPayload(action: ActionValue, seconds: number): string {
+	if (action.endsWith('_timed')) {
+		return buildTimedRelayPayload(action, seconds);
+	}
+	return buildPermanentRelayPayload(action);
+}
diff --git a/src/lib/utils/recaptcha.ts b/src/lib/utils/recaptcha.ts
index 5f53567e..a65a51c3 100644
--- a/src/lib/utils/recaptcha.ts
+++ b/src/lib/utils/recaptcha.ts
@@ -20,6 +20,15 @@ const SCRIPT_ID = 'cw-recaptcha-enterprise';
 const SCRIPT_SRC_MATCHER = 'script[src*="recaptcha/enterprise.js"]';
 const READY_TIMEOUT_MS = 8_000;
 const EXECUTE_TIMEOUT_MS = 12_000;
+// A cold browser frequently fails the very first request to google.com with
+// `ERR_NAME_NOT_RESOLVED` before DNS is warm. Retry the script load a few
+// times with a short backoff so a transient failure doesn't hard-block login.
+const SCRIPT_LOAD_ATTEMPTS = 3;
+const SCRIPT_RETRY_BASE_DELAY_MS = 400;
+// `window.grecaptcha.enterprise` can lag slightly behind the script's `onload`.
+// Poll for it briefly rather than declaring failure on the first synchronous check.
+const API_AVAILABILITY_TIMEOUT_MS = 4_000;
+const API_POLL_INTERVAL_MS = 100;
 
 let status: RecaptchaStatus = 'idle';
 let inflightLoad: Promise<void> | null = null;
@@ -74,6 +83,12 @@ function removeRecaptchaArtifacts() {
 	}
 }
 
+function delay(ms: number): Promise<void> {
+	return new Promise((resolve) => {
+		window.setTimeout(resolve, ms);
+	});
+}
+
 async function withTimeout<T>(
 	promise: Promise<T>,
 	timeoutMs: number,
@@ -153,6 +168,42 @@ async function loadRecaptchaScriptElement(siteKey: string): Promise<void> {
 	});
 }
 
+async function loadRecaptchaScriptWithRetry(siteKey: string): Promise<void> {
+	let lastError: Error | null = null;
+
+	for (let attempt = 1; attempt <= SCRIPT_LOAD_ATTEMPTS; attempt += 1) {
+		try {
+			await loadRecaptchaScriptElement(siteKey);
+			return;
+		} catch (error) {
+			lastError = toError(error, 'reCAPTCHA script failed to load');
+			// Drop the failed <script> so the next attempt starts from a clean slate.
+			removeRecaptchaArtifacts();
+			if (attempt < SCRIPT_LOAD_ATTEMPTS) {
+				await delay(SCRIPT_RETRY_BASE_DELAY_MS * attempt);
+			}
+		}
+	}
+
+	throw lastError ?? new Error('reCAPTCHA script failed to load');
+}
+
+async function waitForEnterpriseApi(): Promise<void> {
+	if (hasUsableEnterpriseApi()) {
+		return;
+	}
+
+	const deadline = Date.now() + API_AVAILABILITY_TIMEOUT_MS;
+	while (Date.now() < deadline) {
+		await delay(API_POLL_INTERVAL_MS);
+		if (hasUsableEnterpriseApi()) {
+			return;
+		}
+	}
+
+	throw new Error('reCAPTCHA script loaded without a usable Enterprise API');
+}
+
 async function ensureRecaptchaReady(): Promise<void> {
 	const siteKey = getPublicSiteKey();
 	if (!siteKey) {
@@ -170,12 +221,8 @@ async function ensureRecaptchaReady(): Promise<void> {
 
 		inflightLoad = (async () => {
 			try {
-				await loadRecaptchaScriptElement(siteKey);
-
-				if (!hasUsableEnterpriseApi()) {
-					throw new Error('reCAPTCHA script loaded without a usable Enterprise API');
-				}
-
+				await loadRecaptchaScriptWithRetry(siteKey);
+				await waitForEnterpriseApi();
 				await waitForEnterpriseReady();
 				setStatus('ready');
 			} catch (error) {