diff --git a/server/src/internal/balances/trackWebhooks/checkUsageAlerts.ts b/server/src/internal/balances/trackWebhooks/checkUsageAlerts.ts
index 1d17274f8..9d34c37fd 100644
--- a/server/src/internal/balances/trackWebhooks/checkUsageAlerts.ts
+++ b/server/src/internal/balances/trackWebhooks/checkUsageAlerts.ts
@@ -1,5 +1,6 @@
 import {
 	type ApiBalanceV1,
+	AppEnv,
 	type DbUsageAlert,
 	type Feature,
 	type FullCustomer,
@@ -206,8 +207,12 @@ export const checkUsageAlerts = async ({
 		scope: "customer",
 	});
 
-	// 2. Org-level alerts (apply to all customers; evaluated against customer-level balance)
-	const orgAlerts = ctx.org.config?.usage_alerts ?? [];
+	// 2. Org-level alerts (apply to all customers; evaluated against customer-level balance).
+	// Env-scoped: sandbox reads sandbox_usage_alerts, live reads usage_alerts.
+	const orgAlerts =
+		ctx.env === AppEnv.Sandbox
+			? (ctx.org.config?.sandbox_usage_alerts ?? [])
+			: (ctx.org.config?.usage_alerts ?? []);
 	if (orgAlerts.length > 0) {
 		await processAlerts({
 			ctx,
diff --git a/server/src/internal/migrations/v2/preview/previewMigrateCustomer/buildBalanceChanges.ts b/server/src/internal/migrations/v2/preview/previewMigrateCustomer/buildBalanceChanges.ts
index d7e61ad85..4ff7ef4e3 100644
--- a/server/src/internal/migrations/v2/preview/previewMigrateCustomer/buildBalanceChanges.ts
+++ b/server/src/internal/migrations/v2/preview/previewMigrateCustomer/buildBalanceChanges.ts
@@ -1,5 +1,37 @@
 import type { ApiBalanceV1 } from "@autumn/shared";
-import type { PreviewBalanceChange } from "./types/index.js";
+import type { PreviewBalance, PreviewBalanceChange } from "./types/index.js";
+
+const balanceSubset = (balance: ApiBalanceV1 | undefined): PreviewBalance => ({
+	granted: balance?.granted ?? 0,
+	remaining: balance?.remaining ?? 0,
+	usage: balance?.usage ?? 0,
+	unlimited: balance?.unlimited ?? false,
+	next_reset_at: balance?.next_reset_at ?? null,
+});
+
+const TRACKED_FIELDS: ReadonlyArray<keyof PreviewBalance> = [
+	"granted",
+	"remaining",
+	"usage",
+	"unlimited",
+	"next_reset_at",
+];
+
+const diffPreviousAttributes = ({
+	before,
+	after,
+}: {
+	before: PreviewBalance;
+	after: PreviewBalance;
+}): Record<string, unknown> => {
+	const previous: Record<string, unknown> = {};
+	for (const field of TRACKED_FIELDS) {
+		if (before[field] !== after[field]) {
+			previous[field] = before[field];
+		}
+	}
+	return previous;
+};
 
 export const buildBalanceChanges = ({
 	beforeBalances,
@@ -14,31 +46,25 @@ export const buildBalanceChanges = ({
 	]);
 
 	return Array.from(featureIds).flatMap((featureId) => {
-		const before = beforeBalances[featureId];
 		const after = afterBalances[featureId];
-		const beforeSnapshot = {
-			granted: before?.granted ?? 0,
-			remaining: before?.remaining ?? 0,
-			usage: before?.usage ?? 0,
-		};
-		const afterSnapshot = {
-			granted: after?.granted ?? 0,
-			remaining: after?.remaining ?? 0,
-			usage: after?.usage ?? 0,
-		};
+		// Feature disappeared post-migration → flag_changes / plan_changes own
+		// that signal; we don't emit a balance_change carrying nothing.
+		if (!after) return [];
 
-		if (
-			beforeSnapshot.granted === afterSnapshot.granted &&
-			beforeSnapshot.remaining === afterSnapshot.remaining &&
-			beforeSnapshot.usage === afterSnapshot.usage
-		)
-			return [];
+		const before = balanceSubset(beforeBalances[featureId]);
+		const balance = balanceSubset(after);
+		const previous_attributes = diffPreviousAttributes({
+			before,
+			after: balance,
+		});
+
+		if (Object.keys(previous_attributes).length === 0) return [];
 
 		return [
 			{
 				feature_id: featureId,
-				...afterSnapshot,
-				before: beforeSnapshot,
+				balance,
+				previous_attributes,
 			},
 		];
 	});
diff --git a/server/src/internal/migrations/v2/preview/previewMigrateCustomer/buildPlanChanges.ts b/server/src/internal/migrations/v2/preview/previewMigrateCustomer/buildPlanChanges.ts
index 9768a36fb..ce5c0d341 100644
--- a/server/src/internal/migrations/v2/preview/previewMigrateCustomer/buildPlanChanges.ts
+++ b/server/src/internal/migrations/v2/preview/previewMigrateCustomer/buildPlanChanges.ts
@@ -1,4 +1,8 @@
-import type { AutumnBillingPlan, FullCusProduct } from "@autumn/shared";
+import type {
+	AutumnBillingPlan,
+	FullCusProduct,
+	FullCustomerEntitlement,
+} from "@autumn/shared";
 import {
 	getDeleteCustomerProducts,
 	getPatchCustomerProducts,
@@ -23,20 +27,88 @@ const customerProductToPlanChange = ({
 	item_changes: itemChanges,
 });
 
+const buildUpdatedPreviousAttributes = ({
+	oldCustomerEntitlement,
+	newCustomerEntitlement,
+}: {
+	oldCustomerEntitlement: FullCustomerEntitlement;
+	newCustomerEntitlement: FullCustomerEntitlement;
+}): Record<string, unknown> => {
+	const previous: Record<string, unknown> = {};
+
+	const oldIncluded = oldCustomerEntitlement.entitlement.allowance ?? null;
+	const newIncluded = newCustomerEntitlement.entitlement.allowance ?? null;
+	if (oldIncluded !== newIncluded) previous.included = oldIncluded;
+
+	const oldUnlimited = Boolean(oldCustomerEntitlement.unlimited);
+	const newUnlimited = Boolean(newCustomerEntitlement.unlimited);
+	if (oldUnlimited !== newUnlimited) previous.unlimited = oldUnlimited;
+
+	return previous;
+};
+
+/**
+ * Pair up patch-level insert/delete customer_entitlements that share a
+ * `feature_id` and emit a single `"updated"` item_change for each pair.
+ * Unpaired inserts/deletes stay as their own `"created"` / `"deleted"`
+ * entries. When multiple cusEnts for the same feature are touched (e.g.
+ * monthly + lifetime), they pair in arrival order; the dashboard sees N
+ * `"updated"` entries for that feature.
+ */
 const buildPatchItemChanges = ({
 	patch,
 }: {
 	patch: NonNullable<AutumnBillingPlan["patchCustomerProducts"]>[number];
-}): PreviewPlanItemChange[] => [
-	...patch.insertCustomerEntitlements.map((customerEntitlement) => ({
-		action: "created" as const,
-		feature_id: customerEntitlement.entitlement.feature.id,
-	})),
-	...patch.deleteCustomerEntitlements.map((customerEntitlement) => ({
-		action: "deleted" as const,
-		feature_id: customerEntitlement.entitlement.feature.id,
-	})),
-];
+}): PreviewPlanItemChange[] => {
+	const changes: PreviewPlanItemChange[] = [];
+
+	const insertsByFeature = new Map<string, FullCustomerEntitlement[]>();
+	for (const insert of patch.insertCustomerEntitlements) {
+		const featureId = insert.entitlement.feature.id;
+		const existing = insertsByFeature.get(featureId) ?? [];
+		existing.push(insert);
+		insertsByFeature.set(featureId, existing);
+	}
+
+	const remainingDeletes: FullCustomerEntitlement[] = [];
+	for (const deleted of patch.deleteCustomerEntitlements) {
+		const featureId = deleted.entitlement.feature.id;
+		const matchingInserts = insertsByFeature.get(featureId);
+		const paired = matchingInserts?.shift();
+		if (paired) {
+			changes.push({
+				action: "updated",
+				feature_id: featureId,
+				previous_attributes: buildUpdatedPreviousAttributes({
+					oldCustomerEntitlement: deleted,
+					newCustomerEntitlement: paired,
+				}),
+			});
+			continue;
+		}
+		remainingDeletes.push(deleted);
+	}
+
+	for (const inserts of insertsByFeature.values()) {
+		for (const insert of inserts) {
+			changes.push({
+				action: "created",
+				feature_id: insert.entitlement.feature.id,
+				previous_attributes: {},
+			});
+		}
+	}
+
+	for (const deleted of remainingDeletes) {
+		changes.push({
+			action: "deleted",
+			feature_id: deleted.entitlement.feature.id,
+			previous_attributes: {},
+		});
+	}
+
+	return changes;
+};
 
 export const buildPlanChanges = ({
 	autumnBillingPlan,
diff --git a/server/src/internal/migrations/v2/preview/previewMigrateCustomer/types/previewBalanceChange.ts b/server/src/internal/migrations/v2/preview/previewMigrateCustomer/types/previewBalanceChange.ts
index 8cf3b5929..62639a727 100644
--- a/server/src/internal/migrations/v2/preview/previewMigrateCustomer/types/previewBalanceChange.ts
+++ b/server/src/internal/migrations/v2/preview/previewMigrateCustomer/types/previewBalanceChange.ts
@@ -1,17 +1,27 @@
 import { z } from "zod/v4";
 
-const PreviewBalanceSnapshotSchema = z.object({
+/**
+ * Per-feature balance change in a migration preview.
+ *
+ * Shape mirrors the `billing.updated` webhook: `balance` is a small subset
+ * of `ApiBalanceV1` representing the post-migration state, plus
+ * `previous_attributes` (sparse — only fields whose value differs from
+ * pre-migration). The dashboard can render "granted: 100 → 250" by overlaying
+ * `previous_attributes` on top of the snapshot.
+ */
+export const PreviewBalanceSchema = z.object({
 	granted: z.number(),
 	remaining: z.number(),
 	usage: z.number(),
+	unlimited: z.boolean(),
+	next_reset_at: z.number().nullable(),
 });
 
 export const PreviewBalanceChangeSchema = z.object({
 	feature_id: z.string(),
-	granted: z.number(),
-	remaining: z.number(),
-	usage: z.number(),
-	before: PreviewBalanceSnapshotSchema,
+	balance: PreviewBalanceSchema,
+	previous_attributes: z.record(z.string(), z.unknown()).default({}),
 });
 
+export type PreviewBalance = z.infer<typeof PreviewBalanceSchema>;
 export type PreviewBalanceChange = z.infer<typeof PreviewBalanceChangeSchema>;
diff --git a/server/src/internal/migrations/v2/preview/previewMigrateCustomer/types/previewPlanChange.ts b/server/src/internal/migrations/v2/preview/previewMigrateCustomer/types/previewPlanChange.ts
index b097ce902..58947c09b 100644
--- a/server/src/internal/migrations/v2/preview/previewMigrateCustomer/types/previewPlanChange.ts
+++ b/server/src/internal/migrations/v2/preview/previewMigrateCustomer/types/previewPlanChange.ts
@@ -1,8 +1,9 @@
 import { z } from "zod/v4";
 
 export const PreviewPlanItemChangeSchema = z.object({
-	action: z.enum(["created", "deleted"]),
+	action: z.enum(["created", "updated", "deleted"]),
 	feature_id: z.string(),
+	previous_attributes: z.record(z.string(), z.unknown()).default({}),
 });
 
 export const PreviewPlanChangeSchema = z.object({
diff --git a/server/tests/integration/balances/track/usage-alerts/usage-alert-org-env.test.ts b/server/tests/integration/balances/track/usage-alerts/usage-alert-org-env.test.ts
new file mode 100644
index 000000000..920715f98
--- /dev/null
+++ b/server/tests/integration/balances/track/usage-alerts/usage-alert-org-env.test.ts
@@ -0,0 +1,251 @@
+/**
+ * TDD coverage for env-discriminated org usage alerts.
+ *
+ * Contract under test:
+ *   New types/fields:
+ *     - OrgConfig.sandbox_usage_alerts: DbUsageAlert[]
+ *   New behaviors:
+ *     - In sandbox env, checkUsageAlerts reads ctx.org.config.sandbox_usage_alerts.
+ *     - In sandbox env, ctx.org.config.usage_alerts (the live field) is IGNORED
+ *       — alerts on it do NOT fire.
+ *   Side effects:
+ *     - A sandbox_usage_alerts entry produces a Svix balances.usage_alert_triggered
+ *       webhook when its threshold is crossed.
+ *     - A usage_alerts entry alone produces NO webhook when the runtime is sandbox.
+ *
+ * Pre-impl red:
+ *   - OrgConfig.sandbox_usage_alerts type doesn't exist → TS error.
+ *   - checkUsageAlerts still reads ctx.org.config.usage_alerts unconditionally,
+ *     so test 2 (which expects no webhook from usage_alerts in sandbox) fails.
+ *
+ * Post-impl green: both behaviors hold once OrgConfigSchema gains
+ * sandbox_usage_alerts and checkUsageAlerts switches on ctx.env.
+ */
+
+import { afterAll, afterEach, beforeAll, expect, test } from "bun:test";
+import type { DbUsageAlert } from "@autumn/shared";
+import {
+	getTestSvixAppId,
+	setupWebhookTest,
+	type WebhookTestSetup,
+	waitForWebhook,
+} from "@tests/integration/utils/svixWebhookTestUtils.js";
+import { TestFeature } from "@tests/setup/v2Features.js";
+import { items } from "@tests/utils/fixtures/items.js";
+import { products } from "@tests/utils/fixtures/products.js";
+import defaultCtx from "@tests/utils/testInitUtils/createTestContext.js";
+import { initScenario, s } from "@tests/utils/testInitUtils/initScenario.js";
+import chalk from "chalk";
+import { db } from "@/db/initDrizzle.js";
+import { OrgService } from "@/internal/orgs/OrgService.js";
+
+type BalancesUsageAlertTriggeredPayload = {
+	type: string;
+	data: {
+		customer_id: string;
+		feature_id: string;
+		entity_id?: string;
+		usage_alert: {
+			name?: string;
+			threshold: number;
+			threshold_type: string;
+		};
+	};
+};
+
+let webhook: WebhookTestSetup;
+let playToken: string;
+
+beforeAll(async () => {
+	const appId = getTestSvixAppId({ svixConfig: defaultCtx.org.svix_config });
+	webhook = await setupWebhookTest({
+		appId,
+		filterTypes: ["balances.usage_alert_triggered"],
+	});
+	playToken = webhook.playToken;
+});
+
+afterAll(async () => {
+	await webhook?.cleanup();
+	await setOrgAlerts({ sandbox: [], live: [] });
+});
+
+afterEach(async () => {
+	await setOrgAlerts({ sandbox: [], live: [] });
+});
+
+async function setOrgAlerts({
+	sandbox,
+	live,
+}: {
+	sandbox: DbUsageAlert[];
+	live: DbUsageAlert[];
+}) {
+	await OrgService.update({
+		db,
+		orgId: defaultCtx.org.id,
+		updates: {
+			config: {
+				...defaultCtx.org.config,
+				sandbox_usage_alerts: sandbox,
+				usage_alerts: live,
+			},
+		},
+	});
+}
+
+// ── Contract assertion 1: sandbox_usage_alerts fires in sandbox env ──
+
+test(`${chalk.yellowBright("org-alert-env1: sandbox_usage_alerts triggers webhook in sandbox env")}`, async () => {
+	const messagesItem = items.monthlyMessages({ includedUsage: 1000 });
+	const prod = products.base({
+		id: "org-ua-env-sandbox-fires",
+		items: [messagesItem],
+	});
+
+	await setOrgAlerts({
+		sandbox: [
+			{
+				feature_id: TestFeature.Messages,
+				threshold: 500,
+				threshold_type: "usage",
+				enabled: true,
+				name: "sandbox-only-alert",
+			},
+		],
+		live: [],
+	});
+
+	const { customerId, autumnV2_1 } = await initScenario({
+		customerId: "org-usage-alert-env-sandbox-fires",
+		setup: [s.customer({ testClock: false }), s.products({ list: [prod] })],
+		actions: [s.attach({ productId: prod.id })],
+	});
+
+	await autumnV2_1.track({
+		customer_id: customerId,
+		feature_id: TestFeature.Messages,
+		value: 600,
+	});
+
+	const result = await waitForWebhook<BalancesUsageAlertTriggeredPayload>({
+		token: playToken,
+		predicate: (payload) =>
+			payload.type === "balances.usage_alert_triggered" &&
+			payload.data?.customer_id === customerId &&
+			payload.data?.usage_alert?.name === "sandbox-only-alert",
+		timeoutMs: 15000,
+	});
+
+	expect(result).not.toBeNull();
+	expect(result!.payload.data.usage_alert.threshold).toBe(500);
+});
+
+// ── Contract assertion 2: usage_alerts (live field) does NOT fire in sandbox ──
+
+test(`${chalk.yellowBright("org-alert-env2: usage_alerts (live field) is ignored in sandbox env")}`, async () => {
+	const messagesItem = items.monthlyMessages({ includedUsage: 1000 });
+	const prod = products.base({
+		id: "org-ua-env-live-ignored",
+		items: [messagesItem],
+	});
+
+	await setOrgAlerts({
+		sandbox: [],
+		live: [
+			{
+				feature_id: TestFeature.Messages,
+				threshold: 400,
+				threshold_type: "usage",
+				enabled: true,
+				name: "live-only-alert-should-not-fire",
+			},
+		],
+	});
+
+	const { customerId, autumnV2_1 } = await initScenario({
+		customerId: "org-usage-alert-env-live-ignored",
+		setup: [s.customer({ testClock: false }), s.products({ list: [prod] })],
+		actions: [s.attach({ productId: prod.id })],
+	});
+
+	await autumnV2_1.track({
+		customer_id: customerId,
+		feature_id: TestFeature.Messages,
+		value: 700,
+	});
+
+	const result = await waitForWebhook<BalancesUsageAlertTriggeredPayload>({
+		token: playToken,
+		predicate: (payload) =>
+			payload.type === "balances.usage_alert_triggered" &&
+			payload.data?.customer_id === customerId &&
+			payload.data?.usage_alert?.name === "live-only-alert-should-not-fire",
+		timeoutMs: 8000,
+	});
+
+	expect(result).toBeNull();
+});
+
+// ── Contract assertion 3: only the sandbox entry fires when both fields are set ──
+
+test(`${chalk.yellowBright("org-alert-env3: with both fields set in sandbox, only sandbox_usage_alerts triggers")}`, async () => {
+	const messagesItem = items.monthlyMessages({ includedUsage: 1000 });
+	const prod = products.base({
+		id: "org-ua-env-both-set",
+		items: [messagesItem],
+	});
+
+	await setOrgAlerts({
+		sandbox: [
+			{
+				feature_id: TestFeature.Messages,
+				threshold: 300,
+				threshold_type: "usage",
+				enabled: true,
+				name: "sandbox-side",
+			},
+		],
+		live: [
+			{
+				feature_id: TestFeature.Messages,
+				threshold: 300,
+				threshold_type: "usage",
+				enabled: true,
+				name: "live-side",
+			},
+		],
+	});
+
+	const { customerId, autumnV2_1 } = await initScenario({
+		customerId: "org-usage-alert-env-both",
+		setup: [s.customer({ testClock: false }), s.products({ list: [prod] })],
+		actions: [s.attach({ productId: prod.id })],
+	});
+
+	await autumnV2_1.track({
+		customer_id: customerId,
+		feature_id: TestFeature.Messages,
+		value: 500,
+	});
+
+	const sandboxResult = await waitForWebhook<BalancesUsageAlertTriggeredPayload>({
+		token: playToken,
+		predicate: (payload) =>
+			payload.type === "balances.usage_alert_triggered" &&
+			payload.data?.customer_id === customerId &&
+			payload.data?.usage_alert?.name === "sandbox-side",
+		timeoutMs: 15000,
+	});
+	expect(sandboxResult).not.toBeNull();
+
+	const liveResult = await waitForWebhook<BalancesUsageAlertTriggeredPayload>({
+		token: playToken,
+		predicate: (payload) =>
+			payload.type === "balances.usage_alert_triggered" &&
+			payload.data?.customer_id === customerId &&
+			payload.data?.usage_alert?.name === "live-side",
+		timeoutMs: 6000,
+	});
+	expect(liveResult).toBeNull();
+});
diff --git a/server/tests/integration/balances/track/usage-alerts/usage-alert-org-over-100pct.test.ts b/server/tests/integration/balances/track/usage-alerts/usage-alert-org-over-100pct.test.ts
index 21dff927f..4cdc3181e 100644
--- a/server/tests/integration/balances/track/usage-alerts/usage-alert-org-over-100pct.test.ts
+++ b/server/tests/integration/balances/track/usage-alerts/usage-alert-org-over-100pct.test.ts
@@ -68,13 +68,15 @@ afterEach(async () => {
 });
 
 async function setOrgUsageAlerts(usageAlerts: DbUsageAlert[]) {
+	// Tests run in AppEnv.Sandbox — checkUsageAlerts reads
+	// sandbox_usage_alerts, not the live `usage_alerts` field.
 	await OrgService.update({
 		db,
 		orgId: defaultCtx.org.id,
 		updates: {
 			config: {
 				...defaultCtx.org.config,
-				usage_alerts: usageAlerts,
+				sandbox_usage_alerts: usageAlerts,
 			},
 		},
 	});
diff --git a/server/tests/integration/balances/track/usage-alerts/usage-alert-org.test.ts b/server/tests/integration/balances/track/usage-alerts/usage-alert-org.test.ts
index 1e19c6132..13a4e3329 100644
--- a/server/tests/integration/balances/track/usage-alerts/usage-alert-org.test.ts
+++ b/server/tests/integration/balances/track/usage-alerts/usage-alert-org.test.ts
@@ -92,13 +92,15 @@ afterEach(async () => {
 });
 
 async function setOrgUsageAlerts(usageAlerts: DbUsageAlert[]) {
+	// Tests run in AppEnv.Sandbox — checkUsageAlerts reads
+	// sandbox_usage_alerts, not the live `usage_alerts` field.
 	await OrgService.update({
 		db,
 		orgId: defaultCtx.org.id,
 		updates: {
 			config: {
 				...defaultCtx.org.config,
-				usage_alerts: usageAlerts,
+				sandbox_usage_alerts: usageAlerts,
 			},
 		},
 	});
diff --git a/server/tests/integration/billing/migrations-v2/preview/migrate-customer-preview-update-items.test.ts b/server/tests/integration/billing/migrations-v2/preview/migrate-customer-preview-update-items.test.ts
new file mode 100644
index 000000000..998d00f8c
--- /dev/null
+++ b/server/tests/integration/billing/migrations-v2/preview/migrate-customer-preview-update-items.test.ts
@@ -0,0 +1,290 @@
+/**
+ * TDD coverage for migrateCustomer preview shape on update_items migrations.
+ *
+ * Contract under test:
+ *   New types/fields:
+ *     - balance_changes[i] is a full ApiBalanceV1 snapshot (object, feature_id,
+ *       granted, remaining, usage, breakdown[], rollovers[], next_reset_at...)
+ *       plus a sparse `previous_attributes` carrying the OLD values of fields
+ *       that changed.
+ *     - The legacy `before: { granted, remaining, usage }` shape is gone.
+ *   New behaviors:
+ *     - For a no-usage `update_items` bump (included 100 → 250), preview emits
+ *       a single balance_change with new granted/remaining = 250 and
+ *       previous_attributes.granted = previous_attributes.remaining = 100.
+ *     - Fields that stayed the same (e.g. usage = 0 before and after) are
+ *       omitted from previous_attributes.
+ *     - When `update_items` lowers included but tracked usage is preserved,
+ *       the balance_change reflects new remaining, with previous_attributes
+ *       containing the old granted (and old remaining if it differs).
+ *     - Migration that doesn't touch a given feature does NOT emit a
+ *       balance_change for it.
+ */
+
+import { expect, test } from "bun:test";
+import { TestFeature } from "@tests/setup/v2Features";
+import { items } from "@tests/utils/fixtures/items";
+import { products } from "@tests/utils/fixtures/products";
+import { initScenario, s } from "@tests/utils/testInitUtils/initScenario";
+import chalk from "chalk";
+
+type MigrationClient = Awaited<ReturnType<typeof initScenario>>["autumnV2_2"];
+
+const timeout = (ms: number) =>
+	new Promise((resolve) => setTimeout(resolve, ms));
+
+const deepParse = (value: unknown): unknown => {
+	if (typeof value === "string") {
+		const trimmed = value.trim();
+		if (
+			(trimmed.startsWith("{") && trimmed.endsWith("}")) ||
+			(trimmed.startsWith("[") && trimmed.endsWith("]"))
+		) {
+			try {
+				return deepParse(JSON.parse(value));
+			} catch {
+				return value;
+			}
+		}
+		return value;
+	}
+	if (Array.isArray(value)) return value.map(deepParse);
+	if (value && typeof value === "object") {
+		const result: Record<string, unknown> = {};
+		for (const [k, v] of Object.entries(value)) result[k] = deepParse(v);
+		return result;
+	}
+	return value;
+};
+
+const parseResponse = (response: unknown): Record<string, unknown> => {
+	const parsed = deepParse(response);
+	if (parsed && typeof parsed === "object" && !Array.isArray(parsed))
+		return parsed as Record<string, unknown>;
+	throw new Error(`Invalid migration event response: ${String(response)}`);
+};
+
+const waitForPreview = async ({
+	autumnV2_2,
+	migrationId,
+	migrationRunId,
+	timeoutMs = 45_000,
+}: {
+	autumnV2_2: MigrationClient;
+	migrationId: string;
+	migrationRunId: string;
+	timeoutMs?: number;
+}): Promise<Record<string, unknown>> => {
+	const start = Date.now();
+	let lastError: unknown;
+	while (Date.now() - start < timeoutMs) {
+		try {
+			const events = await autumnV2_2.migrationsV2.listItemEvents({
+				migrationId,
+				migrationRunId,
+			});
+			const event = events.list[0];
+			if (!event) throw new Error("No migration item event found");
+			const response = parseResponse(event.response);
+			const preview = response.preview;
+			if (!preview) throw new Error("Migration item event missing preview");
+			return preview as Record<string, unknown>;
+		} catch (error) {
+			lastError = error;
+			await timeout(1_000);
+		}
+	}
+	throw new Error(
+		`Timed out waiting for migration preview: ${
+			lastError instanceof Error ? lastError.message : String(lastError)
+		}`,
+	);
+};
+
+const runPreviewMigration = async ({
+	autumnV2_2,
+	migrationId,
+	filter,
+	operations,
+}: {
+	autumnV2_2: MigrationClient;
+	migrationId: string;
+	filter: Parameters<
+		MigrationClient["migrationsV2"]["deleteAndCreate"]
+	>[0]["filter"];
+	operations: Parameters<
+		MigrationClient["migrationsV2"]["deleteAndCreate"]
+	>[0]["operations"];
+}) => {
+	const migration = await autumnV2_2.migrationsV2.deleteAndCreate({
+		id: migrationId,
+		filter,
+		operations,
+	});
+	const runResponse = await autumnV2_2.migrationsV2.run({
+		id: migration.id,
+		dry_run: true,
+	});
+	return waitForPreview({
+		autumnV2_2,
+		migrationId: migration.id,
+		migrationRunId: runResponse.run_id,
+	});
+};
+
+test(`${chalk.yellowBright("migrations preview: update_items emits ApiBalanceV1 snapshot + previous_attributes for the touched feature")}`, async () => {
+	const suffix = Date.now();
+	const customerId = `migration-preview-update-items-${suffix}`;
+	const freePlan = products.base({
+		id: `migration-preview-update-items-plan-${suffix}`,
+		items: [
+			items.monthlyMessages({ includedUsage: 100 }),
+			items.monthlyCredits({ includedUsage: 50 }),
+		],
+	});
+
+	const { autumnV2_2 } = await initScenario({
+		customerId,
+		setup: [s.customer(), s.products({ list: [freePlan] })],
+		actions: [s.billing.attach({ productId: freePlan.id })],
+	});
+
+	const preview = await runPreviewMigration({
+		autumnV2_2,
+		migrationId: `${customerId}-mig`,
+		filter: { customer: { plan: { plan_id: freePlan.id } } },
+		operations: {
+			customer: [
+				{
+					type: "update_plan",
+					plan_filter: { plan_id: freePlan.id },
+					customize: {
+						update_items: [
+							{ filter: { feature_id: TestFeature.Messages }, included: 250 },
+						],
+					},
+				},
+			],
+		},
+	});
+
+	const balanceChanges = preview.balance_changes as Array<
+		Record<string, unknown>
+	>;
+
+	// Untouched Credits feature → no entry.
+	expect(
+		balanceChanges.some((change) => change.feature_id === TestFeature.Credits),
+	).toBe(false);
+
+	const messagesChange = balanceChanges.find(
+		(change) => change.feature_id === TestFeature.Messages,
+	);
+	expect(messagesChange, "expected a balance change for messages").toBeDefined();
+
+	const balance = messagesChange?.balance as Record<string, unknown>;
+	expect(balance).toBeDefined();
+	expect(balance).toMatchObject({
+		granted: 250,
+		remaining: 250,
+		usage: 0,
+	});
+	expect(balance).toHaveProperty("unlimited");
+	expect(balance).toHaveProperty("next_reset_at");
+
+	// previous_attributes lives at the balance-change level, NOT inside balance.
+	expect(balance).not.toHaveProperty("previous_attributes");
+	const previous = messagesChange?.previous_attributes as Record<
+		string,
+		unknown
+	>;
+	expect(previous).toBeDefined();
+	expect(previous.granted).toBe(100);
+	expect(previous.remaining).toBe(100);
+
+	// usage was 0 before and after — must NOT appear in previous_attributes.
+	expect(previous).not.toHaveProperty("usage");
+
+	// Top-level shape: just feature_id + balance + previous_attributes. No
+	// legacy before/granted at the top level.
+	expect(messagesChange).not.toHaveProperty("granted");
+	expect(messagesChange).not.toHaveProperty("before");
+
+	// update_items collapses to a single "updated" item_change with the old
+	// included value in previous_attributes.
+	const planChanges = preview.plan_changes as Array<Record<string, unknown>>;
+	const patch = planChanges.find(
+		(change) => change.action === "updated" && change.plan_id === freePlan.id,
+	);
+	expect(patch).toBeDefined();
+	const itemChanges = patch?.item_changes as Array<Record<string, unknown>>;
+	const messagesItem = itemChanges.find(
+		(item) => item.feature_id === TestFeature.Messages,
+	);
+	expect(messagesItem).toEqual(
+		expect.objectContaining({
+			action: "updated",
+			feature_id: TestFeature.Messages,
+			previous_attributes: expect.objectContaining({ included: 100 }),
+		}),
+	);
+});
+
+test(`${chalk.yellowBright("migrations preview: update_items with carried usage surfaces previous granted but not previous usage")}`, async () => {
+	const suffix = Date.now();
+	const customerId = `migration-preview-update-items-usage-${suffix}`;
+	const freePlan = products.base({
+		id: `migration-preview-update-items-usage-plan-${suffix}`,
+		items: [items.monthlyMessages({ includedUsage: 100 })],
+	});
+
+	const { autumnV2_2 } = await initScenario({
+		customerId,
+		setup: [s.customer(), s.products({ list: [freePlan] })],
+		actions: [
+			s.billing.attach({ productId: freePlan.id }),
+			s.track({ featureId: TestFeature.Messages, value: 30, timeout: 2000 }),
+		],
+	});
+
+	const preview = await runPreviewMigration({
+		autumnV2_2,
+		migrationId: `${customerId}-mig`,
+		filter: { customer: { plan: { plan_id: freePlan.id } } },
+		operations: {
+			customer: [
+				{
+					type: "update_plan",
+					plan_filter: { plan_id: freePlan.id },
+					customize: {
+						update_items: [
+							{ filter: { feature_id: TestFeature.Messages }, included: 300 },
+						],
+					},
+				},
+			],
+		},
+	});
+
+	const balanceChanges = preview.balance_changes as Array<
+		Record<string, unknown>
+	>;
+	const change = balanceChanges.find(
+		(b) => b.feature_id === TestFeature.Messages,
+	);
+	expect(change).toBeDefined();
+
+	const balance = change?.balance as Record<string, unknown>;
+	// new: granted=300, remaining=270 (300-30 carried usage), usage=30
+	expect(balance).toMatchObject({
+		granted: 300,
+		remaining: 270,
+		usage: 30,
+	});
+
+	const previous = change?.previous_attributes as Record<string, unknown>;
+	// previous: granted=100, remaining=70 (100-30), usage=30 (same)
+	expect(previous.granted).toBe(100);
+	expect(previous.remaining).toBe(70);
+	expect(previous).not.toHaveProperty("usage");
+});
diff --git a/server/tests/integration/billing/migrations-v2/preview/migrate-customer-preview.test.ts b/server/tests/integration/billing/migrations-v2/preview/migrate-customer-preview.test.ts
index 36bda2cf7..b1c18678e 100644
--- a/server/tests/integration/billing/migrations-v2/preview/migrate-customer-preview.test.ts
+++ b/server/tests/integration/billing/migrations-v2/preview/migrate-customer-preview.test.ts
@@ -18,26 +18,29 @@ import { products } from "@tests/utils/fixtures/products";
 import { initScenario, s } from "@tests/utils/testInitUtils/initScenario";
 import chalk from "chalk";
 
+type PreviewPlanItemChange = {
+	action: "created" | "updated" | "deleted";
+	feature_id: string;
+	previous_attributes: Record<string, unknown>;
+};
+
 type PreviewPlanChange = {
 	action: "created" | "updated" | "deleted";
 	plan_id: string;
 	entity_id?: string | null;
-	item_changes: Array<{
-		action: "created" | "deleted";
-		feature_id: string;
-	}>;
+	item_changes: PreviewPlanItemChange[];
 };
 
 type PreviewBalanceChange = {
 	feature_id: string;
-	granted: number;
-	remaining: number;
-	usage: number;
-	before: {
+	balance: {
 		granted: number;
 		remaining: number;
 		usage: number;
+		unlimited: boolean;
+		next_reset_at: number | null;
 	};
+	previous_attributes: Record<string, unknown>;
 };
 
 type PreviewFlagChange = {
@@ -58,10 +61,39 @@ type MigrationClient = Awaited<ReturnType<typeof initScenario>>["autumnV2_2"];
 const timeout = (ms: number) =>
 	new Promise((resolve) => setTimeout(resolve, ms));
 
+/**
+ * Tinybird's `t.json` storage round-trips nested values as JSON-encoded
+ * strings at one or more levels. Walk the tree, JSON.parse any string that
+ * looks like a JSON object/array, and return a fully-parsed structure.
+ */
+const deepParse = (value: unknown): unknown => {
+	if (typeof value === "string") {
+		const trimmed = value.trim();
+		if (
+			(trimmed.startsWith("{") && trimmed.endsWith("}")) ||
+			(trimmed.startsWith("[") && trimmed.endsWith("]"))
+		) {
+			try {
+				return deepParse(JSON.parse(value));
+			} catch {
+				return value;
+			}
+		}
+		return value;
+	}
+	if (Array.isArray(value)) return value.map(deepParse);
+	if (value && typeof value === "object") {
+		const result: Record<string, unknown> = {};
+		for (const [k, v] of Object.entries(value)) result[k] = deepParse(v);
+		return result;
+	}
+	return value;
+};
+
 const parseResponse = (response: unknown): Record<string, unknown> => {
-	if (typeof response === "string") return JSON.parse(response);
-	if (response && typeof response === "object")
-		return response as Record<string, unknown>;
+	const parsed = deepParse(response);
+	if (parsed && typeof parsed === "object" && !Array.isArray(parsed))
+		return parsed as Record<string, unknown>;
 	throw new Error(`Invalid migration event response: ${String(response)}`);
 };
 
@@ -182,8 +214,16 @@ test(`${chalk.yellowBright("migrations preview: boolean item add/remove emits fl
 			action: "updated",
 			plan_id: freePlan.id,
 			item_changes: expect.arrayContaining([
-				{ action: "deleted", feature_id: TestFeature.AdminRights },
-				{ action: "created", feature_id: TestFeature.Dashboard },
+				{
+					action: "deleted",
+					feature_id: TestFeature.AdminRights,
+					previous_attributes: {},
+				},
+				{
+					action: "created",
+					feature_id: TestFeature.Dashboard,
+					previous_attributes: {},
+				},
 			]),
 		}),
 	]);
@@ -231,32 +271,44 @@ test(`${chalk.yellowBright("migrations preview: metered grant replacement emits
 	});
 
 	expect(preview.flag_changes).toEqual([]);
-	expect(preview.balance_changes).toEqual([
-		{
+	expect(preview.balance_changes.length).toBe(1);
+	expect(preview.balance_changes[0]).toEqual(
+		expect.objectContaining({
 			feature_id: TestFeature.Credits,
-			granted: 300,
-			remaining: 300,
-			usage: 0,
-			before: {
+			balance: expect.objectContaining({
+				granted: 300,
+				remaining: 300,
+				usage: 0,
+			}),
+			previous_attributes: expect.objectContaining({
 				granted: 100,
 				remaining: 100,
-				usage: 0,
-			},
-		},
-	]);
+			}),
+		}),
+	);
+	// usage stayed at 0 — must NOT appear in previous_attributes
+	expect(
+		preview.balance_changes[0].previous_attributes,
+	).not.toHaveProperty("usage");
 	expect(
 		preview.balance_changes.some(
 			(change) => change.feature_id === TestFeature.Messages,
 		),
 	).toBe(false);
+	// remove + add on the same feature collapses into a single "updated" item_change
 	expect(preview.plan_changes).toEqual([
 		expect.objectContaining({
 			action: "updated",
 			plan_id: freePlan.id,
-			item_changes: expect.arrayContaining([
-				{ action: "deleted", feature_id: TestFeature.Credits },
-				{ action: "created", feature_id: TestFeature.Credits },
-			]),
+			item_changes: [
+				expect.objectContaining({
+					action: "updated",
+					feature_id: TestFeature.Credits,
+					previous_attributes: expect.objectContaining({
+						included: 100,
+					}),
+				}),
+			],
 		}),
 	]);
 });
@@ -302,25 +354,27 @@ test(`${chalk.yellowBright("migrations preview: version update emits plan, balan
 		expect.arrayContaining([
 			expect.objectContaining({
 				feature_id: TestFeature.Messages,
-				granted: 200,
-				remaining: 200,
-				usage: 0,
-				before: {
+				balance: expect.objectContaining({
+					granted: 200,
+					remaining: 200,
+					usage: 0,
+				}),
+				previous_attributes: expect.objectContaining({
 					granted: 100,
 					remaining: 100,
-					usage: 0,
-				},
+				}),
 			}),
 			expect.objectContaining({
 				feature_id: TestFeature.Credits,
-				granted: 50,
-				remaining: 50,
-				usage: 0,
-				before: {
+				balance: expect.objectContaining({
+					granted: 50,
+					remaining: 50,
+					usage: 0,
+				}),
+				previous_attributes: expect.objectContaining({
 					granted: 0,
 					remaining: 0,
-					usage: 0,
-				},
+				}),
 			}),
 		]),
 	);
diff --git a/shared/models/orgModels/orgConfig.ts b/shared/models/orgModels/orgConfig.ts
index a7e2f151b..8b1ecea3a 100644
--- a/shared/models/orgModels/orgConfig.ts
+++ b/shared/models/orgModels/orgConfig.ts
@@ -3,6 +3,9 @@ import { DbUsageAlertSchema } from "../cusModels/billingControls/usageAlert.js";
 
 export const OrgConfigSchema = z.object({
 	usage_alerts: z.array(DbUsageAlertSchema).optional().default([]),
+	/** Sandbox-env-only usage alerts. `checkUsageAlerts` reads this list when
+	 *  `ctx.env === AppEnv.Sandbox` and `usage_alerts` when env is live. */
+	sandbox_usage_alerts: z.array(DbUsageAlertSchema).optional().default([]),
 
 	bill_upgrade_immediately: z.boolean().default(true),
 	convert_to_charge_automatically: z.boolean().default(true),