diff --git a/src/core/listing/apply.ts b/src/core/listing/apply.ts
index bdb7d626..b61bb566 100644
--- a/src/core/listing/apply.ts
+++ b/src/core/listing/apply.ts
@@ -1,5 +1,6 @@
 import type { AndroidLocaleInfo, AppleLocaleInfo, StoreConfig } from '../store/storeConfig.js';
 import type { DraftListing, ListingBrief, LocaleDraft } from '../types/listing.js';
+import type { MutableDeep } from '../types/mutable.js';
 /**
  * App Store field limits, in characters. `keywords` is the limit on the *comma-joined* string (Apple
  * counts the serialized field, and `storeConfig` joins with `", "`), not the count of keywords.
@@ -23,11 +24,11 @@ const clampText = (listingText: string, maxCharacters: number): string => {
   return listingText.slice(0, maxCharacters).trimEnd();
 };
 /** The comma-joined serialization Apple counts against the 100-char keyword limit. */
-export const serializeKeywords = (keywords: string[]): string => {
+export const serializeKeywords = (keywords: readonly string[]): string => {
   return keywords.join(', ');
 };
 /** Keep keywords from the front until adding the next would overflow the joined-string limit. */
-const clampKeywords = (keywords: string[], maxCharacters: number): string[] => {
+const clampKeywords = (keywords: readonly string[], maxCharacters: number): string[] => {
   const keptKeywords: string[] = [];
   for (const keyword of keywords) {
     if (serializeKeywords([...keptKeywords, keyword]).length > maxCharacters) break;
@@ -47,7 +48,7 @@ export const clampDraft = (
   warnings: string[];
 } => {
   const warningMessages: string[] = [];
-  const clampedDraft: DraftListing = {};
+  const clampedDraft: MutableDeep<DraftListing> = {};
   /** Clamp one optional text field, recording a warning when it was over the limit. */
   const fitText = (
     listingText: string | undefined,
@@ -98,7 +99,7 @@ export const briefFor = (
   currentListing: AppleLocaleInfo | undefined,
   aboutOverride: string | undefined,
 ): ListingBrief => {
-  const listingBrief: ListingBrief = { locale: localeName, appName: displayName };
+  const listingBrief: MutableDeep<ListingBrief> = { locale: localeName, appName: displayName };
   let aboutText = aboutOverride;
   if (aboutText === undefined && currentListing !== undefined)
     aboutText = currentListing.promotionalText;
@@ -135,6 +136,38 @@ export const deriveAndroidLocale = (listingDraft: DraftListing): AndroidLocaleIn
  * fields (so untouched fields and other locales survive), per targeted platform. The App Store fields
  * map 1:1; the Play fields are derived via {@link deriveAndroidLocale}. Returns a new config.
  */
+/** Merge a draft over one locale's existing App Store listing, copying keywords into a mutable array. */
+const mergeAppleLocale = (
+  existingLocale: AppleLocaleInfo | undefined,
+  listingDraft: DraftListing,
+): AppleLocaleInfo => {
+  const mergedLocale: MutableDeep<AppleLocaleInfo> = {};
+  if (existingLocale !== undefined) {
+    if (existingLocale.title !== undefined) mergedLocale.title = existingLocale.title;
+    if (existingLocale.subtitle !== undefined) mergedLocale.subtitle = existingLocale.subtitle;
+    if (existingLocale.description !== undefined)
+      mergedLocale.description = existingLocale.description;
+    if (existingLocale.keywords !== undefined) mergedLocale.keywords = [...existingLocale.keywords];
+    if (existingLocale.releaseNotes !== undefined)
+      mergedLocale.releaseNotes = existingLocale.releaseNotes;
+    if (existingLocale.promotionalText !== undefined)
+      mergedLocale.promotionalText = existingLocale.promotionalText;
+    if (existingLocale.marketingUrl !== undefined)
+      mergedLocale.marketingUrl = existingLocale.marketingUrl;
+    if (existingLocale.supportUrl !== undefined)
+      mergedLocale.supportUrl = existingLocale.supportUrl;
+    if (existingLocale.privacyPolicyUrl !== undefined)
+      mergedLocale.privacyPolicyUrl = existingLocale.privacyPolicyUrl;
+  }
+  if (listingDraft.title !== undefined) mergedLocale.title = listingDraft.title;
+  if (listingDraft.subtitle !== undefined) mergedLocale.subtitle = listingDraft.subtitle;
+  if (listingDraft.description !== undefined) mergedLocale.description = listingDraft.description;
+  if (listingDraft.promotionalText !== undefined)
+    mergedLocale.promotionalText = listingDraft.promotionalText;
+  if (listingDraft.keywords !== undefined) mergedLocale.keywords = [...listingDraft.keywords];
+  return mergedLocale;
+};
+
 export const applyDraft = (
   storeConfiguration: StoreConfig,
   localeName: string,
@@ -148,12 +181,11 @@ export const applyDraft = (
   if (listingTargets.ios) {
     let appleListing = storeConfiguration.apple;
     if (appleListing === undefined) appleListing = { info: {} };
+    const localeInfo: Record<string, AppleLocaleInfo> = { ...appleListing.info };
+    localeInfo[localeName] = mergeAppleLocale(appleListing.info[localeName], listingDraft);
     updatedStoreConfiguration.apple = {
       ...appleListing,
-      info: {
-        ...appleListing.info,
-        [localeName]: { ...appleListing.info[localeName], ...listingDraft },
-      },
+      info: localeInfo,
     };
   }
   if (listingTargets.android) {
diff --git a/src/core/listing/generator.ts b/src/core/listing/generator.ts
index b587da3a..84650725 100644
--- a/src/core/listing/generator.ts
+++ b/src/core/listing/generator.ts
@@ -3,6 +3,7 @@ import { Data, Effect, Redacted, Schema } from 'effect';
 import { LaunchEnvironment, type LaunchEnvironmentService } from '../services/environment.js';
 import type { DraftListing, ListingBrief, ListingGenerator } from '../types/listing.js';
 import { APPLE_LIMITS, serializeKeywords } from './apply.js';
+import type { MutableDeep } from '../types/mutable.js';
 
 const GeneratedListingSchema = Schema.Struct({
   title: Schema.optionalWith(Schema.String, { exact: true }),
@@ -138,7 +139,7 @@ export const parseDraftListing = (
     stripJsonFence(completionText),
   ).pipe(
     Effect.map((generatedListing) => {
-      const listingDraft: DraftListing = {};
+      const listingDraft: MutableDeep<DraftListing> = {};
       const title = normalizeGeneratedText(generatedListing.title);
       if (title !== undefined) listingDraft.title = title;
       const subtitle = normalizeGeneratedText(generatedListing.subtitle);
diff --git a/src/core/privacy/parse.ts b/src/core/privacy/parse.ts
index d578d206..ab7786ea 100644
--- a/src/core/privacy/parse.ts
+++ b/src/core/privacy/parse.ts
@@ -12,7 +12,7 @@ const CollectedDataTypeSchema = Schema.Struct({
 const USAGE_DESCRIPTION_RE =
   /<key>(NS\w*UsageDescription)<\/key>\s*(?:<string>([^<]*)<\/string>|<string\s*\/>)/g;
 /** De-duplicate while preserving first-seen order. */
-const unique = (strings: string[]): string[] => {
+const unique = (strings: readonly string[]): string[] => {
   return [...new Set(strings)];
 };
 /** Collect every `<string>...</string>` inside an XML fragment. */
diff --git a/src/core/privacy/reconcile.ts b/src/core/privacy/reconcile.ts
index 73e2e920..959b6ff5 100644
--- a/src/core/privacy/reconcile.ts
+++ b/src/core/privacy/reconcile.ts
@@ -138,7 +138,7 @@ export const reconcilePrivacy = (app: string, surface: PrivacySurface): PrivacyF
  */
 export const buildPrivacyReport = (
   findings: PrivacyFinding[],
-  scanned: string[],
+  scanned: readonly string[],
 ): PrivacyReport => {
   let exitCode: PrivacyReport['exitCode'] = READINESS_EXIT.ok;
   if (findings.some((finding) => finding.severity === 'blocker')) exitCode = READINESS_EXIT.blocker;
diff --git a/src/core/store/accessibility.ts b/src/core/store/accessibility.ts
index 3bc77906..39f825a9 100644
--- a/src/core/store/accessibility.ts
+++ b/src/core/store/accessibility.ts
@@ -9,6 +9,7 @@ import {
 import { appRecordMissing, plan, type ReconcileContext } from './reconcile.js';
 import { errorMessage } from '../services/errorMessage.js';
 import type { PlannedAction } from '../types/reconcile.js';
+import type { MutableDeep } from '../types/mutable.js';
 import {
   decodeStoreSurfaceConfig,
   loadStoreSurfaceConfig,
@@ -126,7 +127,7 @@ const supportEquals = (
 };
 /** Expand omitted accessibility flags to `false`. */
 const normalizeSupport = (support: AccessibilitySupport): AccessibilitySupport => {
-  const normalizedSupport: AccessibilitySupport = {};
+  const normalizedSupport: MutableDeep<AccessibilitySupport> = {};
   for (const key of ACCESSIBILITY_SUPPORT_KEYS) normalizedSupport[key] = support[key] === true;
   return normalizedSupport;
 };
diff --git a/src/core/store/appEvents.ts b/src/core/store/appEvents.ts
index 7b9eb73b..4b69ddc8 100644
--- a/src/core/store/appEvents.ts
+++ b/src/core/store/appEvents.ts
@@ -1,4 +1,5 @@
 import { Data, Effect } from 'effect';
+import type { MutableDeep } from '../types/mutable.js';
 import type {
   AppEventLocalizationInput,
   AppEventLocalizationResource,
@@ -191,7 +192,7 @@ export const createEvent = (
       appEventsStore.getAppId(bundleId),
     );
     if (appId === null) return yield* Effect.fail(missingAppRecord(bundleId));
-    const eventAttributes: NewAppEvent = { referenceName };
+    const eventAttributes: MutableDeep<NewAppEvent> = { referenceName };
     if (badge !== undefined) eventAttributes.badge = badge;
     if (eventRequest.primaryLocale !== undefined) {
       eventAttributes.primaryLocale = eventRequest.primaryLocale.trim();
@@ -224,7 +225,7 @@ export const localizeEvent = (
         }),
       );
     }
-    const localizationAttributes: AppEventLocalizationInput = {};
+    const localizationAttributes: MutableDeep<AppEventLocalizationInput> = {};
     if (localizationRequest.name !== undefined) {
       localizationAttributes.name = localizationRequest.name;
     }
diff --git a/src/core/store/ascScreenshots.ts b/src/core/store/ascScreenshots.ts
index 9c9900ff..e98e11cf 100644
--- a/src/core/store/ascScreenshots.ts
+++ b/src/core/store/ascScreenshots.ts
@@ -64,7 +64,7 @@ export type ScreenshotReconcileInput = {
 };
 /** Group members by a derived string key. */
 const groupBy = <Member>(
-  members: Member[],
+  members: readonly Member[],
   keyOf: (member: Member) => string,
 ): Map<string, Member[]> => {
   const groups = new Map<string, Member[]>();
@@ -122,7 +122,7 @@ const reconcileAppScreenshots = (
   api: ScreenshotsApi,
   log: ActionLog,
   appId: string,
-  screenshots: LocalScreenshot[],
+  screenshots: readonly LocalScreenshot[],
 ): Effect.Effect<void, unknown> =>
   Effect.gen(function* () {
     const versionId = yield* api.getEditableVersionId(appId);
@@ -178,7 +178,7 @@ const reconcileScreenshotSet = (
   existingSet: ScreenshotSetResource | undefined,
   displayType: string,
   locale: string,
-  screenshots: LocalScreenshot[],
+  screenshots: readonly LocalScreenshot[],
 ): Effect.Effect<void, unknown> =>
   Effect.gen(function* () {
     const label = appleDisplayTypeLabel(displayType);
@@ -227,7 +227,7 @@ const reconcileSubscriptionReviewScreenshots = (
   api: ScreenshotsApi,
   log: ActionLog,
   appId: string,
-  reviewScreenshots: SubscriptionReviewScreenshot[],
+  reviewScreenshots: readonly SubscriptionReviewScreenshot[],
 ): Effect.Effect<void, unknown> =>
   Effect.gen(function* () {
     const subscriptionIdByProduct = new Map<string, string>();
@@ -365,7 +365,7 @@ const reconcilePreviewSet = (
   existingSet: PreviewSetResource | undefined,
   previewType: string,
   locale: string,
-  previews: LocalPreview[],
+  previews: readonly LocalPreview[],
 ): Effect.Effect<void, unknown> =>
   Effect.gen(function* () {
     const label = applePreviewTypeLabel(previewType);
diff --git a/src/core/store/ascSync.ts b/src/core/store/ascSync.ts
index e0b3ad0c..858ebe88 100644
--- a/src/core/store/ascSync.ts
+++ b/src/core/store/ascSync.ts
@@ -300,7 +300,7 @@ export const reconcileApp = (
     const catalogContext = emptyCatalogContext(api, input.dryRun, input.allowDestructive);
     const appId = yield* requireAppStoreRecordId(api, input.bundleId);
     yield* reconcileCapabilities(catalogContext, input.bundleId, input.capabilities);
-    let desiredInAppPurchases: InAppPurchaseConfig[] = [];
+    let desiredInAppPurchases: readonly InAppPurchaseConfig[] = [];
     if (input.products.inAppPurchases !== undefined) {
       desiredInAppPurchases = input.products.inAppPurchases;
     }
@@ -372,7 +372,7 @@ const reconcileCapabilities = (
 const reconcileInAppPurchases = (
   catalogContext: CatalogReconcileContext,
   appId: string,
-  desiredPurchases: InAppPurchaseConfig[],
+  desiredPurchases: readonly InAppPurchaseConfig[],
 ): Effect.Effect<void, unknown> =>
   Effect.gen(function* () {
     if (desiredPurchases.length === 0) return;
diff --git a/src/core/store/availability.ts b/src/core/store/availability.ts
index 0edf34f9..a8b7256d 100644
--- a/src/core/store/availability.ts
+++ b/src/core/store/availability.ts
@@ -68,7 +68,7 @@ export type AvailabilityReconcileInput = {
   dryRun: boolean;
 };
 /** Uppercase, trim, and de-duplicate a list of territory codes into a stable set. */
-const normalizeTerritories = (territories: string[]): Set<string> => {
+const normalizeTerritories = (territories: readonly string[]): Set<string> => {
   return new Set(territories.map((code) => code.trim().toUpperCase()));
 };
 /** Sorted difference `a \ b` - codes in `a` not in `b`. */
diff --git a/src/core/store/gameCenter.ts b/src/core/store/gameCenter.ts
index 8f158709..72879b01 100644
--- a/src/core/store/gameCenter.ts
+++ b/src/core/store/gameCenter.ts
@@ -17,6 +17,7 @@ import type {
   GameCenterConfig,
   LeaderboardConfig,
 } from '../types/storeSurface.js';
+import type { MutableDeep } from '../types/mutable.js';
 import {
   decodeStoreSurfaceConfig,
   loadStoreSurfaceConfig,
@@ -199,7 +200,7 @@ const localizationLocale = (locale: string | undefined): string => {
  * Connect) rather than failed.
  */
 const applyLocalization = (
-  localizationAction: PlannedAction,
+  localizationAction: MutableDeep<PlannedAction>,
   versionId: string | null,
   vendorIdentifier: string,
   writeLocalization: (confirmedVersionId: string) => Effect.Effect<void, unknown>,
@@ -287,7 +288,7 @@ const reconcileAchievements = (
   reconcileContext: ReconcileContext,
   api: AscGameCenterApi,
   detail: NonNullable<EnsuredDetail>,
-  declaredAchievements: AchievementConfig[],
+  declaredAchievements: readonly AchievementConfig[],
 ): Effect.Effect<void, unknown> =>
   Effect.gen(function* () {
     let existingIdentifiers = new Set<string>();
@@ -333,7 +334,7 @@ const reconcileLeaderboards = (
   reconcileContext: ReconcileContext,
   api: AscGameCenterApi,
   detail: NonNullable<EnsuredDetail>,
-  declaredLeaderboards: LeaderboardConfig[],
+  declaredLeaderboards: readonly LeaderboardConfig[],
 ): Effect.Effect<void, unknown> =>
   Effect.gen(function* () {
     let existingIdentifiers = new Set<string>();
@@ -395,9 +396,9 @@ export const reconcileGameCenter = (
       );
       return { bundleId: reconcileInput.bundleId, actions: reconcileContext.actions };
     }
-    let achievements: AchievementConfig[] = [];
+    let achievements: readonly AchievementConfig[] = [];
     if (gameCenterConfig.achievements !== undefined) achievements = gameCenterConfig.achievements;
-    let leaderboards: LeaderboardConfig[] = [];
+    let leaderboards: readonly LeaderboardConfig[] = [];
     if (gameCenterConfig.leaderboards !== undefined) leaderboards = gameCenterConfig.leaderboards;
     yield* reconcileAchievements(reconcileContext, api, detail, achievements);
     yield* reconcileLeaderboards(reconcileContext, api, detail, leaderboards);
diff --git a/src/core/store/offers.test.ts b/src/core/store/offers.test.ts
index 97fdcec0..cbea3c93 100644
--- a/src/core/store/offers.test.ts
+++ b/src/core/store/offers.test.ts
@@ -39,7 +39,7 @@ class FakeOffersApi implements AscOffersApi {
   readonly createdWinBack: WinBackOfferCreate[] = [];
   readonly createdPromoted: PromotedPurchaseCreate[] = [];
   introCreateCount = 0;
-  reorderedTo: string[] | null = null;
+  reorderedTo: readonly string[] | null = null;
   getAppId(): Effect.Effect<string | null> {
     return Effect.succeed(this.appId);
   }
@@ -115,7 +115,7 @@ class FakeOffersApi implements AscOffersApi {
       visibleForAllUsers: input.visibleForAllUsers,
     });
   }
-  reorderPromotedPurchases(_appId: string, orderedIds: string[]): Effect.Effect<void> {
+  reorderPromotedPurchases(_appId: string, orderedIds: readonly string[]): Effect.Effect<void> {
     this.reorderedTo = orderedIds;
     return Effect.void;
   }
diff --git a/src/core/store/offers.ts b/src/core/store/offers.ts
index 205cf220..fd8569ca 100644
--- a/src/core/store/offers.ts
+++ b/src/core/store/offers.ts
@@ -26,6 +26,7 @@ import type {
   SubscriptionConfig,
   WinBackOfferConfig,
 } from '../types/catalog.js';
+import type { MutableDeep } from '../types/mutable.js';
 import { errorMessage } from '../services/errorMessage.js';
 import { act, makeAppRecordFailure, plan, skip, type ReconcileContext } from './reconcile.js';
 
@@ -88,7 +89,7 @@ const makeOfferPricePointFailure = Data.tagged<OfferPricePointFailure>('OfferPri
 const resolvePrices = (
   api: AscOffersApi,
   subscriptionId: string,
-  prices: OfferPrice[],
+  prices: readonly OfferPrice[],
 ): Effect.Effect<ResolvedOfferPrice[], OfferPricePointFailure | unknown> =>
   Effect.gen(function* () {
     const resolved: ResolvedOfferPrice[] = [];
@@ -116,7 +117,10 @@ const resolvePrices = (
  * Validate a price-bearing offer (offer code, promotional, win-back) at the boundary: `FREE_TRIAL` must
  * carry no prices; any other mode needs at least one. Returns a human reason when invalid, else null.
  */
-const priceModeError = (offerMode: string, prices: OfferPrice[] | undefined): string | null => {
+const priceModeError = (
+  offerMode: string,
+  prices: readonly OfferPrice[] | undefined,
+): string | null => {
   let priceCount = 0;
   if (prices !== undefined) priceCount = prices.length;
   if (offerMode === 'FREE_TRIAL') {
@@ -132,12 +136,12 @@ const createWithResolvedPrices = (
   offersContext: OffersContext,
   subscriptionId: string,
   description: string,
-  prices: OfferPrice[] | undefined,
+  prices: readonly OfferPrice[] | undefined,
   write: (resolvedPrices: ResolvedOfferPrice[]) => Effect.Effect<void, unknown>,
 ): Effect.Effect<void> =>
   act(offersContext, description, () =>
     Effect.gen(function* () {
-      let offerPrices: OfferPrice[] = [];
+      let offerPrices: readonly OfferPrice[] = [];
       if (prices !== undefined) offerPrices = prices;
       const resolvedPrices = yield* resolvePrices(offersContext.api, subscriptionId, offerPrices);
       yield* write(resolvedPrices);
@@ -149,7 +153,7 @@ const reconcileOfferCodes = (
   offersContext: OffersContext,
   subscriptionId: string,
   productId: string,
-  desired: OfferCodeConfig[],
+  desired: readonly OfferCodeConfig[],
 ): Effect.Effect<void, unknown> =>
   Effect.gen(function* () {
     const codes = yield* offersContext.api.listSubscriptionOfferCodes(subscriptionId);
@@ -188,7 +192,7 @@ const reconcilePromotionalOffers = (
   offersContext: OffersContext,
   subscriptionId: string,
   productId: string,
-  desired: PromotionalOfferConfig[],
+  desired: readonly PromotionalOfferConfig[],
 ): Effect.Effect<void, unknown> =>
   Effect.gen(function* () {
     const offers = yield* offersContext.api.listPromotionalOffers(subscriptionId);
@@ -229,7 +233,7 @@ const reconcileIntroductoryOffers = (
   offersContext: OffersContext,
   subscriptionId: string,
   productId: string,
-  desired: IntroductoryOfferConfig[],
+  desired: readonly IntroductoryOfferConfig[],
 ): Effect.Effect<void, unknown> =>
   Effect.gen(function* () {
     const introductoryOffers = yield* offersContext.api.listIntroductoryOffers(subscriptionId);
@@ -267,7 +271,7 @@ const reconcileIntroductoryOffers = (
               ]);
               if (resolvedPrices[0] !== undefined) resolvedPrice = resolvedPrices[0];
             }
-            const introductoryOffer: IntroductoryOfferCreate = {
+            const introductoryOffer: MutableDeep<IntroductoryOfferCreate> = {
               subscriptionId,
               duration: offer.duration,
               offerMode: offer.offerMode,
@@ -288,7 +292,7 @@ const reconcileWinBackOffers = (
   offersContext: OffersContext,
   subscriptionId: string,
   productId: string,
-  desired: WinBackOfferConfig[],
+  desired: readonly WinBackOfferConfig[],
 ): Effect.Effect<void, unknown> =>
   Effect.gen(function* () {
     const winBackOffers = yield* offersContext.api.listWinBackOffers(subscriptionId);
@@ -318,7 +322,7 @@ const reconcileWinBackOffers = (
         (resolvedPrices) => {
           let priority: WinBackOfferCreate['priority'] = 'NORMAL';
           if (offer.priority !== undefined) priority = offer.priority;
-          const create: WinBackOfferCreate = {
+          const create: MutableDeep<WinBackOfferCreate> = {
             subscriptionId,
             offerId: offer.offerId,
             referenceName: offer.referenceName,
@@ -422,7 +426,7 @@ const reconcilePromotedPurchases = (
         declaredOrder.push(existingPromotionId);
         continue;
       }
-      const create: PromotedPurchaseCreate = {
+      const create: MutableDeep<PromotedPurchaseCreate> = {
         appId,
         visibleForAllUsers: true,
         enabled: true,
@@ -513,17 +517,17 @@ export const reconcileOffers = (
           );
           continue;
         }
-        let offerCodes: OfferCodeConfig[] = [];
+        let offerCodes: readonly OfferCodeConfig[] = [];
         if (subscription.offerCodes !== undefined) offerCodes = subscription.offerCodes;
-        let promotionalOffers: PromotionalOfferConfig[] = [];
+        let promotionalOffers: readonly PromotionalOfferConfig[] = [];
         if (subscription.promotionalOffers !== undefined) {
           promotionalOffers = subscription.promotionalOffers;
         }
-        let introductoryOffers: IntroductoryOfferConfig[] = [];
+        let introductoryOffers: readonly IntroductoryOfferConfig[] = [];
         if (subscription.introductoryOffers !== undefined) {
           introductoryOffers = subscription.introductoryOffers;
         }
-        let winBackOffers: WinBackOfferConfig[] = [];
+        let winBackOffers: readonly WinBackOfferConfig[] = [];
         if (subscription.winBackOffers !== undefined) {
           winBackOffers = subscription.winBackOffers;
         }
diff --git a/src/core/store/playProducts.ts b/src/core/store/playProducts.ts
index 76c1d160..9df0b501 100644
--- a/src/core/store/playProducts.ts
+++ b/src/core/store/playProducts.ts
@@ -4,6 +4,7 @@ import type { InAppPurchaseConfig, PlayPriceConfig } from '../types/catalog.js';
 import type { PlannedAction } from '../types/reconcile.js';
 import { plan, type ReconcileContext } from './reconcile.js';
 import { errorMessage } from '../services/errorMessage.js';
+import type { MutableDeep } from '../types/mutable.js';
 /** Play's purchase type for a one-off managed (non-subscription) product. */
 const MANAGED_PRODUCT = 'managedUser';
 /** Status Launch publishes products as - declaring a `play` override means "this product should be sellable". */
@@ -85,7 +86,7 @@ export const toPlayProduct = (
       prices[region] = toMoney(price);
     }
   }
-  const desiredProduct: InAppProductResource = {
+  const desiredProduct: MutableDeep<InAppProductResource> = {
     sku,
     status: ACTIVE_STATUS,
     purchaseType: MANAGED_PRODUCT,
diff --git a/src/core/store/playSubscriptions.ts b/src/core/store/playSubscriptions.ts
index 68a52b76..24ae40e9 100644
--- a/src/core/store/playSubscriptions.ts
+++ b/src/core/store/playSubscriptions.ts
@@ -14,6 +14,7 @@ import type {
   SubscriptionConfig,
   SubscriptionPeriod,
 } from '../types/catalog.js';
+import type { MutableDeep } from '../types/mutable.js';
 import type { PlannedAction } from '../types/reconcile.js';
 import { plan, type ReconcileContext } from './reconcile.js';
 import { errorMessage } from '../services/errorMessage.js';
@@ -110,7 +111,9 @@ export const unitsToMicros = (money: PlayMoneyUnits): string => {
 };
 
 /** Map shared localizations to Play subscription listings (Play requires a description; fall back to title). */
-const listingsFromLocalizations = (localizations: ProductLocalization[]): SubscriptionListing[] => {
+const listingsFromLocalizations = (
+  localizations: readonly ProductLocalization[],
+): SubscriptionListing[] => {
   return localizations.map((localization) => {
     let description = localization.name;
     if (localization.description !== undefined) description = localization.description;
@@ -124,8 +127,8 @@ const listingsFromLocalizations = (localizations: ProductLocalization[]): Subscr
 
 /** Whether every desired listing has a title/description-equal counterpart already live. */
 const listingsInSync = (
-  existing: SubscriptionListing[],
-  desired: SubscriptionListing[],
+  existing: readonly SubscriptionListing[],
+  desired: readonly SubscriptionListing[],
 ): boolean => {
   const byLanguage = new Map(existing.map((listing) => [listing.languageCode, listing]));
   return desired.every((listing) => {
@@ -137,8 +140,8 @@ const listingsInSync = (
 
 /** Merge desired listings over live ones by language so a patch never drops locales Launch does not manage. */
 const mergeListings = (
-  existing: SubscriptionListing[],
-  desired: SubscriptionListing[],
+  existing: readonly SubscriptionListing[],
+  desired: readonly SubscriptionListing[],
 ): SubscriptionListing[] => {
   const byLanguage = new Map(existing.map((listing) => [listing.languageCode, listing]));
   for (const listing of desired) {
@@ -168,14 +171,14 @@ const basePlanFromConfig = (
 
 /** Re-encode a live base plan for a patch that only appends a new one - drop output-only `state`. */
 const resendableBasePlan = (basePlan: BasePlan): BasePlan => {
-  const resendablePlan: BasePlan = { basePlanId: basePlan.basePlanId };
+  const resendablePlan: MutableDeep<BasePlan> = { basePlanId: basePlan.basePlanId };
   if (basePlan.autoRenewingBasePlanType !== undefined) {
     resendablePlan.autoRenewingBasePlanType = basePlan.autoRenewingBasePlanType;
   }
   if (basePlan.regionalConfigs !== undefined) {
-    resendablePlan.regionalConfigs = basePlan.regionalConfigs;
+    resendablePlan.regionalConfigs = [...basePlan.regionalConfigs];
   }
-  if (basePlan.offerTags !== undefined) resendablePlan.offerTags = basePlan.offerTags;
+  if (basePlan.offerTags !== undefined) resendablePlan.offerTags = [...basePlan.offerTags];
   return resendablePlan;
 };
 
@@ -195,7 +198,7 @@ const makePlayOfferConfigFailure = Data.tagged<PlayOfferConfigFailure>('PlayOffe
 export const offerFromConfig = (
   productId: string,
   basePlanId: string,
-  basePlanRegions: string[],
+  basePlanRegions: readonly string[],
   config: PlaySubscriptionOfferConfig,
 ): Effect.Effect<SubscriptionOfferResource, PlayOfferConfigFailure> => {
   const phases: SubscriptionOfferPhase[] = [];
@@ -259,8 +262,8 @@ const offersFromConfigs = (
   reconcileContext: ReconcileContext,
   productId: string,
   basePlanId: string,
-  basePlanRegions: string[],
-  configs: PlaySubscriptionOfferConfig[],
+  basePlanRegions: readonly string[],
+  configs: readonly PlaySubscriptionOfferConfig[],
 ): Effect.Effect<SubscriptionOfferResource[]> =>
   Effect.gen(function* () {
     const offers: SubscriptionOfferResource[] = [];
@@ -294,10 +297,10 @@ const offersFromConfigs = (
 type DesiredSubscription = {
   productId: string;
   basePlanId: string;
-  listings: SubscriptionListing[];
+  listings: readonly SubscriptionListing[];
   basePlan: BasePlan;
-  basePlanRegions: string[];
-  offerConfigs: PlaySubscriptionOfferConfig[];
+  basePlanRegions: readonly string[];
+  offerConfigs: readonly PlaySubscriptionOfferConfig[];
 };
 
 /** Project one catalog subscription into the Play shape Launch will create or patch. */
@@ -310,7 +313,7 @@ const desiredSubscriptionFromConfig = (
   if (playOverrides.productId !== undefined) productId = playOverrides.productId;
   let basePlanId = PERIOD_ISO[subscription.subscriptionPeriod].toLowerCase();
   if (playOverrides.basePlanId !== undefined) basePlanId = playOverrides.basePlanId;
-  let offerConfigs: PlaySubscriptionOfferConfig[] = [];
+  let offerConfigs: readonly PlaySubscriptionOfferConfig[] = [];
   if (playOverrides.offers !== undefined) offerConfigs = playOverrides.offers;
   return {
     productId,
@@ -427,7 +430,7 @@ const reconcileExistingSubscription = (
   desired: DesiredSubscription,
 ): Effect.Effect<void> =>
   Effect.gen(function* () {
-    let existingListings: SubscriptionListing[] = [];
+    let existingListings: readonly SubscriptionListing[] = [];
     if (existing.listings !== undefined) existingListings = existing.listings;
     if (!listingsInSync(existingListings, desired.listings)) {
       const mergedListings = mergeListings(existingListings, desired.listings);
@@ -444,7 +447,7 @@ const reconcileExistingSubscription = (
       }
     }
 
-    let existingBasePlans: BasePlan[] = [];
+    let existingBasePlans: readonly BasePlan[] = [];
     if (existing.basePlans !== undefined) existingBasePlans = existing.basePlans;
     const liveBasePlan = existingBasePlans.find(
       (basePlan) => basePlan.basePlanId === desired.basePlanId,
diff --git a/src/core/store/playTracks.ts b/src/core/store/playTracks.ts
index 0dc1ac85..475efaf7 100644
--- a/src/core/store/playTracks.ts
+++ b/src/core/store/playTracks.ts
@@ -1,5 +1,6 @@
 import { Data, Effect, Schema } from 'effect';
 import type { PlayRelease } from '../types/googlePlay.js';
+import type { MutableDeep } from '../types/mutable.js';
 
 /** Play release statuses accepted by the Android Publisher API. */
 export const RELEASE_STATUSES = ['draft', 'inProgress', 'halted', 'completed'] as const;
@@ -105,7 +106,7 @@ export const buildRelease = (
       }),
     );
   }
-  const playRelease: PlayRelease = {
+  const playRelease: MutableDeep<PlayRelease> = {
     status: releaseInput.status,
     versionCodes: [...releaseInput.versionCodes],
   };
diff --git a/src/core/store/reconcile.ts b/src/core/store/reconcile.ts
index 8930c96b..5fead184 100644
--- a/src/core/store/reconcile.ts
+++ b/src/core/store/reconcile.ts
@@ -1,10 +1,11 @@
 import { Data, Effect } from 'effect';
 import { errorMessage } from '../services/errorMessage.js';
 import type { PlannedAction } from '../types/reconcile.js';
+import type { MutableDeep } from '../types/mutable.js';
 
 /** Mutable state for one reconciliation pass. */
 export type ReconcileContext = {
-  actions: PlannedAction[];
+  actions: MutableDeep<PlannedAction>[];
   dryRun: boolean;
 };
 
@@ -23,7 +24,11 @@ export const act = (
   description: string,
   runAction: () => Effect.Effect<void, unknown>,
 ): Effect.Effect<void> => {
-  const plannedAction: PlannedAction = { description, destructive: false, status: 'planned' };
+  const plannedAction: MutableDeep<PlannedAction> = {
+    description,
+    destructive: false,
+    status: 'planned',
+  };
   reconcileContext.actions.push(plannedAction);
   if (reconcileContext.dryRun) return Effect.void;
   return runAction().pipe(
@@ -40,8 +45,15 @@ export const act = (
 };
 
 /** Record a planned action and return its mutable status handle. */
-export const plan = (reconcileContext: ReconcileContext, description: string): PlannedAction => {
-  const plannedAction: PlannedAction = { description, destructive: false, status: 'planned' };
+export const plan = (
+  reconcileContext: ReconcileContext,
+  description: string,
+): MutableDeep<PlannedAction> => {
+  const plannedAction: MutableDeep<PlannedAction> = {
+    description,
+    destructive: false,
+    status: 'planned',
+  };
   reconcileContext.actions.push(plannedAction);
   return plannedAction;
 };
@@ -72,7 +84,7 @@ export const skip = (reconcileContext: ReconcileContext, description: string): v
 };
 /** Tally a reconcile report's action statuses for the run-summary footer (applied / failed / skipped). */
 export const summarize = (
-  actions: PlannedAction[],
+  actions: readonly PlannedAction[],
 ): {
   applied: number;
   failed: number;
diff --git a/src/core/store/reportsCommand.ts b/src/core/store/reportsCommand.ts
index 1585b5c6..79147e63 100644
--- a/src/core/store/reportsCommand.ts
+++ b/src/core/store/reportsCommand.ts
@@ -14,6 +14,7 @@ import {
   parseTsv,
 } from './reports.js';
 import { resolveStoreBundleId, type StoreAppSelectionRequirements } from './selectStoreApp.js';
+import type { MutableDeep } from '../types/mutable.js';
 
 const SalesReportsCommandInputSchema = Schema.Struct({
   operation: Schema.Literal('sales'),
@@ -244,7 +245,7 @@ const downloadSalesReports = (
     yield* Effect.forEach(
       reportDates,
       (reportDate) => {
-        const reportQuery: SalesReportQuery = {
+        const reportQuery: MutableDeep<SalesReportQuery> = {
           vendorNumber,
           frequency: commandInput.frequency,
           reportType: commandInput.reportType,
@@ -282,7 +283,7 @@ const downloadFinanceReport = (
     const vendorNumber = yield* selectVendorNumber(commandInput.vendorNumber);
     const outputDirectory = yield* projectOutputDirectory(commandInput.out);
     const appleStore = yield* loadActiveAppleStore();
-    const reportQuery: FinanceReportQuery = {
+    const reportQuery: MutableDeep<FinanceReportQuery> = {
       vendorNumber,
       reportDate: commandInput.date,
       regionCode: commandInput.region,
diff --git a/src/core/store/syncJobs.ts b/src/core/store/syncJobs.ts
index 0efc5d74..60b45db0 100644
--- a/src/core/store/syncJobs.ts
+++ b/src/core/store/syncJobs.ts
@@ -87,9 +87,9 @@ export const makeAppSelectionFailure = Data.tagged<AppSelectionFailure>('AppSele
 
 /** Resolve discovered apps from an optional comma-separated selector. */
 export const selectApps = (
-  apps: AppDescriptor[],
+  apps: readonly AppDescriptor[],
   selector: string | undefined,
-): Effect.Effect<AppDescriptor[], AppSelectionFailure> => {
+): Effect.Effect<readonly AppDescriptor[], AppSelectionFailure> => {
   if (selector === undefined) return Effect.succeed(apps);
   if (selector === '') return Effect.succeed(apps);
   const selectedNames = selector
@@ -113,7 +113,7 @@ export const selectApps = (
   });
 };
 /** Build the job list, dropping apps with no iOS bundle id and nothing (capabilities, products, listing, or assets) to sync. */
-export const buildJobs = (apps: AppDescriptor[], config: LaunchConfig) =>
+export const buildJobs = (apps: readonly AppDescriptor[], config: LaunchConfig) =>
   Effect.gen(function* () {
     const jobs: SyncJob[] = [];
     for (const app of apps) {
diff --git a/src/core/store/syncRun.ts b/src/core/store/syncRun.ts
index f0ce27f4..85fda8e7 100644
--- a/src/core/store/syncRun.ts
+++ b/src/core/store/syncRun.ts
@@ -38,7 +38,7 @@ export type SyncAppReport = {
   app: string;
   bundleId: string;
   error?: string;
-  actions?: PlannedAction[];
+  actions?: readonly PlannedAction[];
   summary?: {
     applied: number;
     failed: number;
@@ -187,8 +187,14 @@ export const reconcileJob = (
     };
     if (job.listing) reconcileInput.listing = job.listing;
     const report = yield* reconcileApp(client, reconcileInput);
-    report.actions.push(...(yield* reconcileAssetActions(client, job, dryRun, allowDestructive)));
-    return { job, report };
+    const assetActions = yield* reconcileAssetActions(client, job, dryRun, allowDestructive);
+    return {
+      job,
+      report: {
+        ...report,
+        actions: [...report.actions, ...assetActions],
+      },
+    };
   }).pipe(
     Effect.catchAll((failure) =>
       Effect.succeed({
diff --git a/src/core/store/team.ts b/src/core/store/team.ts
index b1195976..a11bd2c9 100644
--- a/src/core/store/team.ts
+++ b/src/core/store/team.ts
@@ -81,7 +81,7 @@ export const getTeam = (teamClient: AscTeamApi): Effect.Effect<Team, TeamFailure
   ).pipe(Effect.mapError((cause) => teamFailure('list', cause)));
 
 /** Normalize comma-separated role fragments into Apple's canonical role names. */
-const normalizeRoles = (declaredRoles: string[]): string[] => {
+const normalizeRoles = (declaredRoles: readonly string[]): string[] => {
   const normalizedRoles = new Set<string>();
   for (const declaredRole of declaredRoles) {
     const normalizedRole = declaredRole.trim().toUpperCase();
diff --git a/src/core/store/walletIds.ts b/src/core/store/walletIds.ts
index f9f37752..0425b362 100644
--- a/src/core/store/walletIds.ts
+++ b/src/core/store/walletIds.ts
@@ -68,7 +68,7 @@ const reconcileFamily = (
   reconcileContext: ReconcileContext,
   label: string,
   existing: Set<string>,
-  declared: WalletIdConfig[],
+  declared: readonly WalletIdConfig[],
   create: (identifier: string, name: string) => Effect.Effect<void, unknown>,
 ): Effect.Effect<void> =>
   Effect.gen(function* () {