diff --git a/.agents/skills/lodash-es-runtime-guards/SKILL.md b/.agents/skills/lodash-es-runtime-guards/SKILL.md
new file mode 100644
index 0000000..0c3eae7
--- /dev/null
+++ b/.agents/skills/lodash-es-runtime-guards/SKILL.md
@@ -0,0 +1,74 @@
+# lodash-es-runtime-guards
+
+Replace runtime `typeof` checks and ad-hoc empty-string checks with `lodash-es` predicates.
+
+## When to Use
+
+- You see runtime checks like `typeof value === 'string'`.
+- You see object guards like `value && typeof value === 'object'`.
+- You see emptiness checks like `value.trim() !== ''` or `value.trim() === ''`.
+- You want consistent guard style across app, server, IPC, and tests.
+
+## Do Not Replace
+
+- Type-level `typeof` (TypeScript only), for example:
+  - `ReturnType<typeof fn>`
+  - `keyof typeof CONST_MAP`
+  - `z.infer<typeof Schema>`
+
+These are compile-time types and must remain as-is.
+
+## Guard Mapping
+
+- `typeof x === 'string'` -> `isString(x)`
+- `typeof x !== 'string'` -> `!isString(x)`
+- `typeof x === 'number'` -> `isNumber(x)`
+- `typeof x === 'boolean'` -> `isBoolean(x)`
+- `typeof x === 'function'` -> `isFunction(x)`
+- `typeof x === 'undefined'` -> `isUndefined(x)`
+- `x && typeof x === 'object'` -> `isObjectLike(x)`
+- `typeof x === 'object' && x !== null` -> `isObjectLike(x)`
+- `typeof x === 'object' && !Array.isArray(x)` -> `isObjectLike(x) && !isArray(x)`
+
+## String Emptiness Pattern
+
+- Prefer:
+  - `isEmpty(value.trim())`
+- Instead of:
+  - `value.trim() === ''`
+  - `value.trim() !== ''`
+  - `value.trim().length === 0`
+
+## Import Style
+
+- Use named imports from `lodash-es`:
+
+```ts
+import { isString, isNumber, isObjectLike, isEmpty } from 'lodash-es';
+```
+
+- Do not use full-package imports.
+- Reuse existing imports in file; avoid duplicate imports.
+
+## Refactor Checklist
+
+1. Replace runtime checks first, preserving behavior.
+2. Keep array/object branching semantics unchanged.
+3. Re-scan:
+
+```bash
+rg -n "typeof\s+[^\n]+(?:===|!==)\s*'" src
+```
+
+4. Confirm only type-level `typeof` remains:
+
+```bash
+rg -n "\btypeof\b" src
+```
+
+5. Run verification:
+
+```bash
+npm run type-check
+```
+
diff --git a/src/components/CloudAccountList.tsx b/src/components/CloudAccountList.tsx
index 68edc7d..ae46216 100644
--- a/src/components/CloudAccountList.tsx
+++ b/src/components/CloudAccountList.tsx
@@ -71,7 +71,7 @@ import {
   SelectTrigger,
   SelectValue,
 } from '@/components/ui/select';
-import { filter, flatMap, isEmpty, size, sumBy } from 'lodash-es';
+import { filter, flatMap, isEmpty, isNumber, size, sumBy } from 'lodash-es';
 import {
   clampQuotaPercentage,
   getQuotaStatus,
@@ -313,7 +313,7 @@ export function CloudAccountList() {
       {
         onSuccess: (updatedAccount) => {
           const credits = updatedAccount.quota?.ai_credits?.credits;
-          if (typeof credits === 'number') {
+          if (isNumber(credits)) {
             toast({
               title: t('cloud.toast.quotaRefreshed'),
               description: `AI credits: $${credits.toFixed(2)}`,
diff --git a/src/components/ui/dropdown-menu.tsx b/src/components/ui/dropdown-menu.tsx
index 22bacc7..9fc1bad 100644
--- a/src/components/ui/dropdown-menu.tsx
+++ b/src/components/ui/dropdown-menu.tsx
@@ -1,5 +1,6 @@
 import * as React from 'react';
 import * as DropdownMenuPrimitive from '@radix-ui/react-dropdown-menu';
+import { isNumber, isObjectLike } from 'lodash-es';
 import { Check, ChevronRight, Circle } from 'lucide-react';
 import { cn } from '@/lib/utils';
 
@@ -52,11 +53,11 @@ const DropdownMenuContent = React.forwardRef<
     collisionPadding?: number | Partial<Record<'top' | 'right' | 'bottom' | 'left', number>>;
   }
 >(({ className, sideOffset = 4, collisionPadding = 8, ...props }, ref) => {
-  if (typeof collisionPadding === 'number') {
+  if (isNumber(collisionPadding)) {
     if (collisionPadding < 0) {
       throw new Error('collisionPadding must be a non-negative number');
     }
-  } else if (typeof collisionPadding === 'object' && collisionPadding !== null) {
+  } else if (isObjectLike(collisionPadding)) {
     for (const key of Object.keys(collisionPadding)) {
       if ((collisionPadding as any)[key] < 0) {
         throw new Error(`collisionPadding.${key} must be a non-negative number`);
diff --git a/src/ipc/cloud/handler.ts b/src/ipc/cloud/handler.ts
index b2cb54d..03cffbe 100644
--- a/src/ipc/cloud/handler.ts
+++ b/src/ipc/cloud/handler.ts
@@ -6,6 +6,7 @@ import { logger } from '../../utils/logger';
 
 import { shell } from 'electron';
 import fs from 'fs';
+import { isEmpty, isString } from 'lodash-es';
 import { updateTrayMenu } from '../../ipc/tray/handler';
 import {
   ensureGlobalOriginalFromCurrentStorage,
@@ -46,7 +47,7 @@ function isEnterpriseClient(clientKey?: string): boolean {
 }
 
 function normalizeProjectId(projectId?: string): string | null {
-  if (typeof projectId !== 'string') {
+  if (!isString(projectId)) {
     return null;
   }
   const normalized = projectId.trim();
@@ -148,7 +149,7 @@ async function clearAccountStatus(account: CloudAccount): Promise<void> {
 
 function hydrateActiveOAuthClientFromSettings(): void {
   const preferredClientKey = CloudAccountRepo.getSetting<string>(ACTIVE_OAUTH_CLIENT_KEY_SETTING, '');
-  if (preferredClientKey && preferredClientKey.trim() !== '') {
+  if (isString(preferredClientKey) && !isEmpty(preferredClientKey.trim())) {
     try {
       GoogleAPIService.setActiveOAuthClientKey(preferredClientKey);
     } catch (error) {
@@ -195,7 +196,7 @@ async function backfillMissingOAuthClientKeyForLegacyAccounts(
     }
 
     const projectMissing =
-      typeof account.token.project_id !== 'string' || account.token.project_id.trim() === '';
+      !isString(account.token.project_id) || isEmpty(account.token.project_id.trim());
     if (activeClientKey === ENTERPRISE_OAUTH_CLIENT_KEY && projectMissing) {
       skippedEnterpriseGuardCount += 1;
       continue;
@@ -232,7 +233,7 @@ export async function addGoogleAccount(
   oauthClientKey?: string,
 ): Promise<CloudAccount> {
   try {
-    if (oauthClientKey && oauthClientKey.trim() !== '') {
+    if (isString(oauthClientKey) && !isEmpty(oauthClientKey.trim())) {
       setActiveOAuthClient(oauthClientKey);
     } else {
       hydrateActiveOAuthClientFromSettings();
@@ -684,7 +685,7 @@ export async function forcePollCloudMonitor(): Promise<void> {
 }
 
 export async function startAuthFlow(oauthClientKey?: string): Promise<void> {
-  if (oauthClientKey && oauthClientKey.trim() !== '') {
+  if (isString(oauthClientKey) && !isEmpty(oauthClientKey.trim())) {
     setActiveOAuthClient(oauthClientKey);
   } else {
     hydrateActiveOAuthClientFromSettings();
diff --git a/src/ipc/database/cloudHandler.ts b/src/ipc/database/cloudHandler.ts
index a64e934..a8063e2 100644
--- a/src/ipc/database/cloudHandler.ts
+++ b/src/ipc/database/cloudHandler.ts
@@ -4,6 +4,7 @@ import fs from 'fs';
 import { v4 as uuidv4 } from 'uuid';
 import { desc, eq } from 'drizzle-orm';
 import type { BetterSQLite3Database } from 'drizzle-orm/better-sqlite3';
+import { isNumber, isObjectLike, isPlainObject, isString } from 'lodash-es';
 import { getCloudAccountsDbPath, getAntigravityDbPaths } from '../../utils/paths';
 import { logger } from '../../utils/logger';
 import {
@@ -35,14 +36,14 @@ type DrizzleExecutor = Pick<
 >;
 
 function isSqliteBusyError(error: unknown): boolean {
-  if (!error || typeof error !== 'object') {
+  if (!isObjectLike(error)) {
     return false;
   }
   const err = error as { code?: string; message?: string };
   if (err.code && SQLITE_BUSY_CODES.has(err.code)) {
     return true;
   }
-  if (typeof err.message === 'string') {
+  if (isString(err.message)) {
     return err.message.includes('SQLITE_BUSY') || err.message.includes('SQLITE_LOCKED');
   }
   return false;
@@ -168,17 +169,13 @@ interface MigrationStats {
   failedFields: number;
 }
 
-function isRecord(value: unknown): value is Record<string, unknown> {
-  return Boolean(value) && typeof value === 'object' && !Array.isArray(value);
-}
-
 function readStringCandidate(
   source: Record<string, unknown>,
   ...keys: string[]
 ): string | undefined {
   for (const key of keys) {
     const candidate = source[key];
-    if (typeof candidate === 'string' && candidate.length > 0) {
+    if (isString(candidate) && candidate.length > 0) {
       return candidate;
     }
   }
@@ -186,14 +183,15 @@ function readStringCandidate(
 }
 
 function normalizeDeviceProfile(value: unknown): DeviceProfile | undefined {
-  if (!isRecord(value)) {
+  if (!isPlainObject(value)) {
     return undefined;
   }
+  const valueRecord = value as Record<string, unknown>;
 
-  const machineId = readStringCandidate(value, 'machineId', 'machine_id');
-  const macMachineId = readStringCandidate(value, 'macMachineId', 'mac_machine_id');
-  const devDeviceId = readStringCandidate(value, 'devDeviceId', 'dev_device_id');
-  const sqmId = readStringCandidate(value, 'sqmId', 'sqm_id');
+  const machineId = readStringCandidate(valueRecord, 'machineId', 'machine_id');
+  const macMachineId = readStringCandidate(valueRecord, 'macMachineId', 'mac_machine_id');
+  const devDeviceId = readStringCandidate(valueRecord, 'devDeviceId', 'dev_device_id');
+  const sqmId = readStringCandidate(valueRecord, 'sqmId', 'sqm_id');
 
   if (!machineId || !macMachineId || !devDeviceId || !sqmId) {
     return undefined;
@@ -217,45 +215,47 @@ function areDeviceProfilesEqual(left: DeviceProfile, right: DeviceProfile): bool
 }
 
 function readVersionedProfilePayload(value: unknown): unknown {
-  if (!isRecord(value)) {
+  if (!isPlainObject(value)) {
     return value;
   }
-  if (!('schemaVersion' in value)) {
+  const valueRecord = value as Record<string, unknown>;
+  if (!('schemaVersion' in valueRecord)) {
     return value;
   }
 
-  const schemaVersion = value.schemaVersion;
-  if (typeof schemaVersion !== 'number' || !Number.isFinite(schemaVersion)) {
+  const schemaVersion = valueRecord.schemaVersion;
+  if (!isNumber(schemaVersion) || !Number.isFinite(schemaVersion)) {
     throw new Error('invalid_device_profile_schema_version');
   }
   if (schemaVersion !== DEVICE_PAYLOAD_SCHEMA_VERSION) {
     throw new Error(`unsupported_device_profile_schema_version:${schemaVersion}`);
   }
-  if (!('profile' in value)) {
+  if (!('profile' in valueRecord)) {
     throw new Error('invalid_device_profile_payload');
   }
-  return value.profile;
+  return valueRecord.profile;
 }
 
 function readVersionedHistoryPayload(value: unknown): unknown {
-  if (!isRecord(value)) {
+  if (!isPlainObject(value)) {
     return value;
   }
-  if (!('schemaVersion' in value)) {
+  const valueRecord = value as Record<string, unknown>;
+  if (!('schemaVersion' in valueRecord)) {
     return value;
   }
 
-  const schemaVersion = value.schemaVersion;
-  if (typeof schemaVersion !== 'number' || !Number.isFinite(schemaVersion)) {
+  const schemaVersion = valueRecord.schemaVersion;
+  if (!isNumber(schemaVersion) || !Number.isFinite(schemaVersion)) {
     throw new Error('invalid_device_history_schema_version');
   }
   if (schemaVersion !== DEVICE_PAYLOAD_SCHEMA_VERSION) {
     throw new Error(`unsupported_device_history_schema_version:${schemaVersion}`);
   }
-  if (!('history' in value)) {
+  if (!('history' in valueRecord)) {
     throw new Error('invalid_device_history_payload');
   }
-  return value.history;
+  return valueRecord.history;
 }
 
 function serializeDeviceProfile(profile: DeviceProfile | undefined): string | null {
@@ -285,23 +285,25 @@ function normalizeDeviceHistory(value: unknown): DeviceProfileVersion[] | undefi
 
   const normalized: DeviceProfileVersion[] = [];
   for (const item of value) {
-    if (!isRecord(item)) {
+    if (!isPlainObject(item)) {
       continue;
     }
+    const itemRecord = item as Record<string, unknown>;
 
-    const profile = normalizeDeviceProfile(item.profile);
+    const profile = normalizeDeviceProfile(itemRecord.profile);
     if (!profile) {
       continue;
     }
 
-    const id = typeof item.id === 'string' && item.id.length > 0 ? item.id : uuidv4();
-    const createdAtCandidate = item.createdAt;
+    const id = isString(itemRecord.id) && itemRecord.id.length > 0 ? itemRecord.id : uuidv4();
+    const createdAtCandidate = itemRecord.createdAt;
     const createdAt =
-      typeof createdAtCandidate === 'number' && Number.isFinite(createdAtCandidate)
+      isNumber(createdAtCandidate) && Number.isFinite(createdAtCandidate)
         ? Math.floor(createdAtCandidate)
         : Math.floor(Date.now() / 1000);
-    const label = typeof item.label === 'string' && item.label.length > 0 ? item.label : 'legacy';
-    const isCurrent = item.isCurrent === true;
+    const label =
+      isString(itemRecord.label) && itemRecord.label.length > 0 ? itemRecord.label : 'legacy';
+    const isCurrent = itemRecord.isCurrent === true;
 
     normalized.push({
       id,
diff --git a/src/ipc/database/handler.ts b/src/ipc/database/handler.ts
index fa0d369..fa44ac2 100644
--- a/src/ipc/database/handler.ts
+++ b/src/ipc/database/handler.ts
@@ -2,6 +2,7 @@ import Database from 'better-sqlite3';
 import fs from 'fs';
 import path from 'path';
 import { eq } from 'drizzle-orm';
+import { isString } from 'lodash-es';
 import { AccountBackupData, AccountInfo } from '../../types/account';
 import { ItemTableValueRowSchema, type ItemTableKey } from '../../types/db';
 import { logger } from '../../utils/logger';
@@ -192,8 +193,8 @@ export function getCurrentAccountInfo(): AccountInfo {
     // Helper to find email in object
     const findEmail = (obj: { email?: string; user?: { email?: string } }): string => {
       if (!obj) return '';
-      if (typeof obj.email === 'string') return obj.email;
-      if (obj.user && typeof obj.user.email === 'string') return obj.user.email;
+      if (isString(obj.email)) return obj.email;
+      if (obj.user && isString(obj.user.email)) return obj.user.email;
       return '';
     };
 
@@ -323,7 +324,7 @@ function _restoreSingleDb(dbPath: string, backup: AccountBackupData): boolean {
       for (const key of KEYS_TO_BACKUP) {
         if (key in backup.data) {
           const value = backup.data[key];
-          const stringValue = typeof value === 'string' ? value : JSON.stringify(value);
+          const stringValue = isString(value) ? value : JSON.stringify(value);
           tx.insert(itemTable)
             .values({ key, value: stringValue })
             .onConflictDoUpdate({
diff --git a/src/ipc/device/handler.ts b/src/ipc/device/handler.ts
index 09a99fd..bac4241 100644
--- a/src/ipc/device/handler.ts
+++ b/src/ipc/device/handler.ts
@@ -2,6 +2,7 @@ import Database from 'better-sqlite3';
 import fs from 'fs';
 import path from 'path';
 import { createHash, randomBytes } from 'crypto';
+import { isBoolean, isNumber, isObjectLike, isString } from 'lodash-es';
 import { type DeviceProfile } from '../../types/account';
 import { logger } from '../../utils/logger';
 import { getAgentDir, getAntigravityDbPaths, getAntigravityStoragePaths } from '../../utils/paths';
@@ -76,14 +77,14 @@ const deviceHardeningState: DeviceHardeningState = {
 };
 
 function isSqliteBusyError(error: unknown): boolean {
-  if (!error || typeof error !== 'object') {
+  if (!isObjectLike(error)) {
     return false;
   }
   const candidate = error as { code?: string; message?: string };
   if (candidate.code === 'SQLITE_BUSY' || candidate.code === 'SQLITE_LOCKED') {
     return true;
   }
-  if (typeof candidate.message === 'string') {
+  if (isString(candidate.message)) {
     return candidate.message.includes('SQLITE_BUSY') || candidate.message.includes('SQLITE_LOCKED');
   }
   return false;
@@ -139,8 +140,8 @@ function readLastKnownGoodMarker(): LastKnownGoodMarker | null {
     if (
       parsed &&
       parsed.version === 1 &&
-      typeof parsed.savedAt === 'number' &&
-      typeof parsed.hasStateDb === 'boolean'
+      isNumber(parsed.savedAt) &&
+      isBoolean(parsed.hasStateDb)
     ) {
       return {
         version: 1,
@@ -157,7 +158,7 @@ function readLastKnownGoodMarker(): LastKnownGoodMarker | null {
 function parseStorageJson(storagePath: string): Record<string, unknown> {
   const content = fs.readFileSync(storagePath, 'utf-8');
   const parsed = JSON.parse(content);
-  if (!parsed || typeof parsed !== 'object' || Array.isArray(parsed)) {
+  if (!isObjectLike(parsed) || Array.isArray(parsed)) {
     throw new Error('storage.json top-level value must be an object');
   }
   return parsed as Record<string, unknown>;
@@ -165,15 +166,15 @@ function parseStorageJson(storagePath: string): Record<string, unknown> {
 
 function getTelemetryField(storage: Record<string, unknown>, key: string): string | null {
   const telemetry = storage.telemetry;
-  if (telemetry && typeof telemetry === 'object' && !Array.isArray(telemetry)) {
+  if (isObjectLike(telemetry) && !Array.isArray(telemetry)) {
     const nestedValue = (telemetry as Record<string, unknown>)[key];
-    if (typeof nestedValue === 'string' && nestedValue.length > 0) {
+    if (isString(nestedValue) && nestedValue.length > 0) {
       return nestedValue;
     }
   }
 
   const flatValue = storage[`telemetry.${key}`];
-  if (typeof flatValue === 'string' && flatValue.length > 0) {
+  if (isString(flatValue) && flatValue.length > 0) {
     return flatValue;
   }
 
@@ -183,7 +184,7 @@ function getTelemetryField(storage: Record<string, unknown>, key: string): strin
 function ensureTelemetryObject(storage: Record<string, unknown>): Record<string, unknown> {
   if (
     !storage.telemetry ||
-    typeof storage.telemetry !== 'object' ||
+    !isObjectLike(storage.telemetry) ||
     Array.isArray(storage.telemetry)
   ) {
     storage.telemetry = {};
@@ -223,7 +224,7 @@ function readStateServiceMachineIdValue(dbPath: string): string | null {
     const row = db
       .prepare("SELECT value FROM ItemTable WHERE key = 'storage.serviceMachineId' LIMIT 1")
       .get() as { value?: unknown } | undefined;
-    if (!row || typeof row.value !== 'string' || row.value.length === 0) {
+    if (!row || !isString(row.value) || row.value.length === 0) {
       return null;
     }
     return row.value;
diff --git a/src/ipc/manager.ts b/src/ipc/manager.ts
index fbc403d..16d1e49 100644
--- a/src/ipc/manager.ts
+++ b/src/ipc/manager.ts
@@ -1,4 +1,5 @@
 import { IPC_CHANNELS } from '@/constants';
+import { isString } from 'lodash-es';
 
 // Custom IPC Client that correctly builds method paths
 function createIPCClient(port: MessagePort) {
@@ -10,7 +11,7 @@ function createIPCClient(port: MessagePort) {
 
   port.onmessage = (event) => {
     try {
-      const data = typeof event.data === 'string' ? JSON.parse(event.data) : event.data;
+      const data = isString(event.data) ? JSON.parse(event.data) : event.data;
 
       const id = data.i || data.id;
       const pending = pendingRequests.get(id);
diff --git a/src/ipc/process/handler.ts b/src/ipc/process/handler.ts
index 7702534..2296fe4 100644
--- a/src/ipc/process/handler.ts
+++ b/src/ipc/process/handler.ts
@@ -1,6 +1,7 @@
 import { exec, execSync, spawn } from 'child_process';
 import { promisify } from 'util';
 import findProcess, { ProcessInfo } from 'find-process';
+import { isNumber } from 'lodash-es';
 import { getAntigravityExecutablePath, isWsl } from '../../utils/paths';
 import { logger } from '../../utils/logger';
 
@@ -98,7 +99,7 @@ export async function isProcessRunning(): Promise<boolean> {
 
     const processMap = new Map<number, ProcessInfo>();
     for (const proc of allMatches) {
-      if (typeof proc.pid === 'number') {
+      if (isNumber(proc.pid)) {
         processMap.set(proc.pid, proc);
       }
     }
diff --git a/src/lib/antigravity/ClaudeRequestMapper.ts b/src/lib/antigravity/ClaudeRequestMapper.ts
index 8a1ad63..11921f6 100644
--- a/src/lib/antigravity/ClaudeRequestMapper.ts
+++ b/src/lib/antigravity/ClaudeRequestMapper.ts
@@ -1,5 +1,5 @@
 import { v4 as uuidv4 } from 'uuid';
-import { isPlainObject, isString } from 'lodash-es';
+import { isEmpty, isPlainObject, isString } from 'lodash-es';
 import { mapClaudeModelToGemini, normalizeGeminiModelAlias } from './ModelMapping';
 import { getMaxOutputTokens, getThinkingBudget } from './ModelSpecs';
 import { cleanJsonSchema, normalizeObjectJsonSchema } from './JsonSchemaUtils';
@@ -518,7 +518,7 @@ function buildContents(
 
     for (const block of contentBlocks) {
       if (block.type === 'text') {
-        if (block.text && block.text !== '(no content)' && block.text.trim() !== '')
+        if (block.text && block.text !== '(no content)' && !isEmpty(block.text.trim()))
           parts.push({ text: block.text.trim() });
       } else if (block.type === 'thinking') {
         const part: any = { text: block.thinking, thought: true };
@@ -553,7 +553,7 @@ function buildContents(
             .filter((b: any) => b.type === 'text')
             .map((b: any) => b.text)
             .join('\n');
-        if (mergedContent.trim().length === 0)
+        if (isEmpty(mergedContent.trim()))
           mergedContent = block.is_error
             ? 'Tool execution failed with no output.'
             : 'Command executed successfully.';
diff --git a/src/lib/antigravity/JsonSchemaUtils.ts b/src/lib/antigravity/JsonSchemaUtils.ts
index f7c7f0f..ed49a47 100644
--- a/src/lib/antigravity/JsonSchemaUtils.ts
+++ b/src/lib/antigravity/JsonSchemaUtils.ts
@@ -1,3 +1,5 @@
+import { isArray, isBoolean, isNumber, isObjectLike, isString } from 'lodash-es';
+
 /**
  * Recursively cleans JSON Schema to meet Gemini interface requirements
  *
@@ -9,7 +11,7 @@
  */
 export function cleanJsonSchema(value: any) {
   // 0. Preprocessing: Expand $ref (Schema Flattening)
-  if (value && typeof value === 'object' && !Array.isArray(value)) {
+  if (isObjectLike(value) && !isArray(value)) {
     const defs: Record<string, any> = {};
 
     // Extract $defs or definitions
@@ -34,21 +36,21 @@ export function cleanJsonSchema(value: any) {
 
 export function normalizeObjectJsonSchema(schema: unknown): Record<string, unknown> {
   const fallbackSchema: Record<string, unknown> = { type: 'object', properties: {} };
-  if (!schema || typeof schema !== 'object' || Array.isArray(schema)) {
+  if (!isObjectLike(schema) || isArray(schema)) {
     return fallbackSchema;
   }
 
   const normalizedSchema = JSON.parse(JSON.stringify(schema)) as Record<string, unknown>;
   cleanJsonSchema(normalizedSchema);
 
-  if (typeof normalizedSchema.type !== 'string') {
+  if (!isString(normalizedSchema.type)) {
     normalizedSchema.type = 'object';
   }
   if (
     normalizedSchema.type === 'object' &&
     (!normalizedSchema.properties ||
-      typeof normalizedSchema.properties !== 'object' ||
-      Array.isArray(normalizedSchema.properties))
+      !isObjectLike(normalizedSchema.properties) ||
+      isArray(normalizedSchema.properties))
   ) {
     normalizedSchema.properties = {};
   }
@@ -60,10 +62,10 @@ export function normalizeObjectJsonSchema(schema: unknown): Record<string, unkno
  * Recursively expand $ref
  */
 function flattenRefs(map: any, defs: Record<string, any>) {
-  if (!map || typeof map !== 'object') return;
+  if (!isObjectLike(map)) return;
 
   // Check and replace $ref
-  if (typeof map['$ref'] === 'string') {
+  if (isString(map['$ref'])) {
     const refPath = map['$ref'];
     // Parse reference name (e.g. #/$defs/MyType -> MyType)
     const parts = refPath.split('/');
@@ -74,7 +76,7 @@ function flattenRefs(map: any, defs: Record<string, any>) {
       // $ref nodes should not have other properties, remove $ref directly
       delete map['$ref'];
 
-      if (defSchema && typeof defSchema === 'object') {
+      if (isObjectLike(defSchema)) {
         for (const [k, v] of Object.entries(defSchema)) {
           // Only insert if the key does not exist in current map (avoid overwrite)
           if (map[k] === undefined) {
@@ -93,7 +95,7 @@ function flattenRefs(map: any, defs: Record<string, any>) {
   for (const k in map) {
     if (Object.prototype.hasOwnProperty.call(map, k)) {
       const v = map[k];
-      if (typeof v === 'object' && v !== null) {
+      if (isObjectLike(v)) {
         flattenRefs(v, defs);
       }
     }
@@ -101,11 +103,11 @@ function flattenRefs(map: any, defs: Record<string, any>) {
 }
 
 function cleanJsonSchemaRecursive(value: any) {
-  if (!value || typeof value !== 'object') {
+  if (!isObjectLike(value)) {
     return;
   }
 
-  if (Array.isArray(value)) {
+  if (isArray(value)) {
     // Array: Recursively process each element
     for (const v of value) {
       cleanJsonSchemaRecursive(v);
@@ -142,7 +144,7 @@ function cleanJsonSchemaRecursive(value: any) {
       if (map[field] !== undefined) {
         const val = map[field];
         // Only migrate if value is primitive type
-        if (typeof val === 'string' || typeof val === 'number' || typeof val === 'boolean') {
+        if (isString(val) || isNumber(val) || isBoolean(val)) {
           constraints.push(`${label}: ${val}`);
           delete map[field];
         } else {
@@ -188,13 +190,13 @@ function cleanJsonSchemaRecursive(value: any) {
     // 5. Handle type field (Gemini requires single lowercase string)
     if (map['type']) {
       const typeVal = map['type'];
-      if (typeof typeVal === 'string') {
+      if (isString(typeVal)) {
         map['type'] = typeVal.toLowerCase();
-      } else if (Array.isArray(typeVal)) {
+      } else if (isArray(typeVal)) {
         // Union type downgrade: take the first non-null type
         let selectedType = 'string';
         for (const item of typeVal) {
-          if (typeof item === 'string' && item !== 'null') {
+          if (isString(item) && item !== 'null') {
             selectedType = item.toLowerCase();
             break;
           }
diff --git a/src/lib/antigravity/ModelMapping.ts b/src/lib/antigravity/ModelMapping.ts
index 4628b42..61431cb 100644
--- a/src/lib/antigravity/ModelMapping.ts
+++ b/src/lib/antigravity/ModelMapping.ts
@@ -1,3 +1,4 @@
+import { isEmpty, isString } from 'lodash-es';
 import { logger } from '../../utils/logger';
 
 const PUBLIC_SUPPORTED_MODELS = [
@@ -94,7 +95,7 @@ export function getSupportedModels(): string[] {
 }
 
 export function updateDynamicForwardingRules(oldModel: string, newModel: string): void {
-  if (typeof oldModel !== 'string' || typeof newModel !== 'string') {
+  if (!isString(oldModel) || !isString(newModel)) {
     return;
   }
   const normalizedOld = oldModel.trim();
@@ -140,7 +141,7 @@ export function getAllDynamicModels(
 
   if (dynamicModelIds) {
     for (const dynamicModelId of dynamicModelIds) {
-      if (typeof dynamicModelId === 'string' && dynamicModelId.trim() !== '') {
+      if (isString(dynamicModelId) && !isEmpty(dynamicModelId.trim())) {
         modelIds.add(dynamicModelId.trim());
       }
     }
@@ -150,7 +151,7 @@ export function getAllDynamicModels(
 }
 
 export function mapClaudeModelToGemini(input: string): string {
-  if (!input || typeof input !== 'string') {
+  if (!isString(input) || isEmpty(input)) {
     return '';
   }
   const mappedModel = CLAUDE_TO_GEMINI[input];
diff --git a/src/lib/antigravity/ModelSpecs.ts b/src/lib/antigravity/ModelSpecs.ts
index 5d9523b..d71c3de 100644
--- a/src/lib/antigravity/ModelSpecs.ts
+++ b/src/lib/antigravity/ModelSpecs.ts
@@ -1,4 +1,5 @@
 import modelSpecsJson from './model-specs';
+import { isNumber } from 'lodash-es';
 
 type ModelSpec = {
   max_output_tokens?: number;
@@ -24,7 +25,7 @@ export function resolveModelAlias(modelId: string): string {
 export function getMaxOutputTokens(modelId: string): number {
   const resolved = resolveModelAlias(modelId);
   const fromSpec = SPECS.models[resolved]?.max_output_tokens;
-  if (typeof fromSpec === 'number' && Number.isFinite(fromSpec) && fromSpec > 0) {
+  if (isNumber(fromSpec) && Number.isFinite(fromSpec) && fromSpec > 0) {
     return Math.floor(fromSpec);
   }
   return DEFAULT_MAX_OUTPUT_TOKENS;
@@ -33,7 +34,7 @@ export function getMaxOutputTokens(modelId: string): number {
 export function getThinkingBudget(modelId: string): number {
   const resolved = resolveModelAlias(modelId);
   const fromSpec = SPECS.models[resolved]?.thinking_budget;
-  if (typeof fromSpec === 'number' && Number.isFinite(fromSpec) && fromSpec >= 0) {
+  if (isNumber(fromSpec) && Number.isFinite(fromSpec) && fromSpec >= 0) {
     return Math.floor(fromSpec);
   }
   return DEFAULT_THINKING_BUDGET;
diff --git a/src/lib/antigravity/QuotaService.ts b/src/lib/antigravity/QuotaService.ts
index ea42e21..4d74d4a 100644
--- a/src/lib/antigravity/QuotaService.ts
+++ b/src/lib/antigravity/QuotaService.ts
@@ -1,4 +1,5 @@
 import axios, { AxiosInstance } from 'axios';
+import { isNumber } from 'lodash-es';
 import { QuotaData, LoadProjectResponse, QuotaApiResponse } from './types';
 import { logger } from '../../utils/logger';
 
@@ -162,7 +163,7 @@ export class QuotaService {
             };
           }
 
-          if (hasNextEndpoint && (status === 429 || (typeof status === 'number' && status >= 500))) {
+          if (hasNextEndpoint && (status === 429 || (isNumber(status) && status >= 500))) {
             logger.warn(
               `Quota API ${endpoint} returned ${status}, falling back to next endpoint`,
             );
@@ -173,7 +174,7 @@ export class QuotaService {
 
           logger.warn(`API Error: ${status} - ${text}`);
           lastError = new Error(`HTTP ${status} - ${text}`);
-          shouldFallback = typeof status !== 'number';
+          shouldFallback = !isNumber(status);
         } else {
           logger.warn(`Request Failed at ${endpoint}: ${error.message}`);
           lastError = error instanceof Error ? error : new Error(String(error));
diff --git a/src/server/guards/api-key-auth.util.ts b/src/server/guards/api-key-auth.util.ts
index f0147fa..60f2dca 100644
--- a/src/server/guards/api-key-auth.util.ts
+++ b/src/server/guards/api-key-auth.util.ts
@@ -1,9 +1,11 @@
+import { isEmpty, isString } from 'lodash-es';
+
 export type RequestHeaderValue = string | string[] | undefined;
 
 export type RequestHeaders = Record<string, RequestHeaderValue>;
 
 export function hasConfiguredApiKey(apiKey: string | undefined): apiKey is string {
-  return typeof apiKey === 'string' && apiKey.trim() !== '';
+  return isString(apiKey) && !isEmpty(apiKey.trim());
 }
 
 export function extractApiKeyToken(headers: RequestHeaders): string | null {
@@ -29,16 +31,16 @@ export function extractApiKeyToken(headers: RequestHeaders): string | null {
 }
 
 function readHeaderValue(headerValue: RequestHeaderValue): string | null {
-  if (typeof headerValue === 'string') {
+  if (isString(headerValue)) {
     const trimmedValue = headerValue.trim();
-    return trimmedValue !== '' ? trimmedValue : null;
+    return !isEmpty(trimmedValue) ? trimmedValue : null;
   }
 
   if (Array.isArray(headerValue)) {
     for (const value of headerValue) {
-      if (typeof value === 'string') {
+      if (isString(value)) {
         const trimmedValue = value.trim();
-        if (trimmedValue !== '') {
+        if (!isEmpty(trimmedValue)) {
           return trimmedValue;
         }
       }
diff --git a/src/server/modules/proxy/clients/gemini.client.ts b/src/server/modules/proxy/clients/gemini.client.ts
index 9a1a233..91c21fc 100644
--- a/src/server/modules/proxy/clients/gemini.client.ts
+++ b/src/server/modules/proxy/clients/gemini.client.ts
@@ -1,6 +1,6 @@
 import { Injectable, Logger } from '@nestjs/common';
 import axios, { AxiosProxyConfig, AxiosRequestConfig, AxiosResponse } from 'axios';
-import { isNil } from 'lodash-es';
+import { isEmpty, isFunction, isNil, isObjectLike, isString } from 'lodash-es';
 import { GeminiRequest, GeminiResponse } from '../interfaces/request-interfaces';
 import { GeminiInternalRequest } from '../../../../lib/antigravity/types';
 import { getServerConfig } from '../../../server-config';
@@ -131,10 +131,10 @@ export class GeminiClient {
       extraHeaders,
     );
     const payload = response.data;
-    if (payload && typeof payload === 'object' && 'response' in payload) {
-      return payload.response;
+    if (isObjectLike(payload) && 'response' in payload) {
+      return (payload as { response: GeminiResponse }).response;
     }
-    return payload;
+    return payload as GeminiResponse;
   }
 
   private getInternalBaseUrls(): string[] {
@@ -255,7 +255,7 @@ export class GeminiClient {
       return fromObject;
     }
 
-    if (typeof responseData === 'string') {
+    if (isString(responseData)) {
       return this.extractAxiosErrorMessageFromText(responseData);
     }
 
@@ -272,20 +272,20 @@ export class GeminiClient {
   }
 
   private extractAxiosErrorMessageFromObject(responseData: unknown): string | null {
-    if (!responseData || typeof responseData !== 'object' || this.isReadableStream(responseData)) {
+    if (!isObjectLike(responseData) || this.isReadableStream(responseData)) {
       return null;
     }
 
     const errorRecord = (responseData as { error?: unknown }).error;
-    if (errorRecord && typeof errorRecord === 'object') {
+    if (isObjectLike(errorRecord)) {
       const message = (errorRecord as { message?: unknown }).message;
-      if (typeof message === 'string' && message.trim() !== '') {
+      if (isString(message) && !isEmpty(message.trim())) {
         return message.trim();
       }
     }
 
     const message = (responseData as { message?: unknown }).message;
-    if (typeof message === 'string' && message.trim() !== '') {
+    if (isString(message) && !isEmpty(message.trim())) {
       return message.trim();
     }
 
@@ -333,11 +333,7 @@ export class GeminiClient {
   }
 
   private isReadableStream(value: unknown): value is NodeJS.ReadableStream {
-    return (
-      Boolean(value) &&
-      typeof value === 'object' &&
-      typeof (value as { pipe?: unknown }).pipe === 'function'
-    );
+    return isObjectLike(value) && isFunction((value as { pipe?: unknown }).pipe);
   }
 
   private async readStreamAsText(stream: NodeJS.ReadableStream): Promise<string | null> {
@@ -407,17 +403,17 @@ export class GeminiClient {
   }
 
   private extractRetryAfterHeader(headers: unknown): string | undefined {
-    if (!headers || typeof headers !== 'object') {
+    if (!isObjectLike(headers)) {
       return undefined;
     }
 
     const retryAfter = (headers as Record<string, unknown>)['retry-after'];
-    if (typeof retryAfter === 'string' && retryAfter.trim() !== '') {
+    if (isString(retryAfter) && !isEmpty(retryAfter.trim())) {
       return retryAfter.trim();
     }
     if (Array.isArray(retryAfter) && retryAfter.length > 0) {
       const first = retryAfter[0];
-      if (typeof first === 'string' && first.trim() !== '') {
+      if (isString(first) && !isEmpty(first.trim())) {
         return first.trim();
       }
     }
@@ -439,7 +435,7 @@ export class GeminiClient {
     try {
       const seen = new WeakSet();
       return JSON.stringify(obj, (key, value) => {
-        if (typeof value === 'object' && value !== null) {
+        if (isObjectLike(value)) {
           if (seen.has(value)) return '[Circular]';
           seen.add(value);
         }
diff --git a/src/server/modules/proxy/clients/upstream-error.ts b/src/server/modules/proxy/clients/upstream-error.ts
index f515f3a..12d72c0 100644
--- a/src/server/modules/proxy/clients/upstream-error.ts
+++ b/src/server/modules/proxy/clients/upstream-error.ts
@@ -1,3 +1,5 @@
+import { isNumber, isObjectLike, isString } from 'lodash-es';
+
 export interface UpstreamErrorHeaders {
   retryAfter?: string;
 }
@@ -16,10 +18,10 @@ export class UpstreamRequestError extends Error {
     super(params.message);
     this.name = 'UpstreamRequestError';
 
-    if (params.status && typeof params.status !== 'number') {
+    if (params.status && !isNumber(params.status)) {
       throw new TypeError('status must be a number');
     }
-    if (params.headers && typeof params.headers !== 'object') {
+    if (params.headers && !isObjectLike(params.headers)) {
       throw new TypeError('headers must be an object');
     }
 
@@ -27,7 +29,7 @@ export class UpstreamRequestError extends Error {
     this.headers = params.headers;
 
     // Sanitize and limit body size
-    if (typeof params.body === 'string') {
+    if (isString(params.body)) {
       const sanitized = params.body.replace(/<[^>]*>?/gm, '');
       this.body = sanitized.substring(0, 1000);
     } else {
diff --git a/src/server/modules/proxy/gemini.controller.ts b/src/server/modules/proxy/gemini.controller.ts
index a6c289f..dacb439 100644
--- a/src/server/modules/proxy/gemini.controller.ts
+++ b/src/server/modules/proxy/gemini.controller.ts
@@ -11,7 +11,7 @@ import {
   Optional,
 } from '@nestjs/common';
 import { FastifyReply } from 'fastify';
-import { isEmpty } from 'lodash-es';
+import { isEmpty, isFunction, isNumber, isString } from 'lodash-es';
 import { Observable } from 'rxjs';
 
 import { ProxyGuard } from './proxy.guard';
@@ -198,7 +198,7 @@ export class GeminiController {
     const candidates = (response.candidates ?? []).map((candidate, index) => ({
       content: candidate.content,
       finishReason: candidate.finishReason,
-      index: typeof candidate.index === 'number' ? candidate.index : index,
+      index: isNumber(candidate.index) ? candidate.index : index,
     }));
 
     const normalized: GeminiResponse = {
@@ -246,8 +246,8 @@ export class GeminiController {
   private writeObservableSseResponse(res: FastifyReply, stream: Observable<unknown>): void {
     if (
       !res.raw ||
-      typeof res.raw.writeHead !== 'function' ||
-      typeof res.raw.write !== 'function'
+      !isFunction(res.raw.writeHead) ||
+      !isFunction(res.raw.write)
     ) {
       res.header('Content-Type', 'text/event-stream');
       res.header('Cache-Control', 'no-cache');
@@ -271,7 +271,7 @@ export class GeminiController {
         if (res.raw.writableEnded) {
           return;
         }
-        const payload = typeof chunk === 'string' ? chunk : String(chunk ?? '');
+        const payload = isString(chunk) ? chunk : String(chunk ?? '');
         res.raw.write(payload);
       },
       error: (error) => {
@@ -302,6 +302,6 @@ export class GeminiController {
   }
 
   private supportsReplyHijack(reply: FastifyReply): reply is FastifyReply & { hijack: () => void } {
-    return typeof (reply as { hijack?: unknown }).hijack === 'function';
+    return isFunction((reply as { hijack?: unknown }).hijack);
   }
 }
diff --git a/src/server/modules/proxy/proxy.controller.ts b/src/server/modules/proxy/proxy.controller.ts
index 6aec030..e839a44 100644
--- a/src/server/modules/proxy/proxy.controller.ts
+++ b/src/server/modules/proxy/proxy.controller.ts
@@ -12,7 +12,7 @@ import {
   Optional,
 } from '@nestjs/common';
 import { FastifyReply, FastifyRequest } from 'fastify';
-import { isNil, isPlainObject, isString } from 'lodash-es';
+import { isEmpty, isFunction, isNil, isObjectLike, isPlainObject, isString } from 'lodash-es';
 import { ProxyService } from './proxy.service';
 import { Observable } from 'rxjs';
 import {
@@ -339,7 +339,7 @@ export class ProxyController {
   private toLegacyTextCompletionsResponse(response: OpenAIChatResponse): Record<string, unknown> {
     const choice = response.choices?.[0];
     const content = choice?.message?.content;
-    const text = typeof content === 'string' ? content : '';
+    const text = isString(content) ? content : '';
 
     return {
       id: response.id,
@@ -397,7 +397,7 @@ export class ProxyController {
     stream?: boolean;
   }): OpenAIChatRequest {
     const messages: OpenAIChatRequest['messages'] = [];
-    if (body.instructions && body.instructions.trim() !== '') {
+    if (isString(body.instructions) && !isEmpty(body.instructions.trim())) {
       messages.push({
         role: 'system',
         content: body.instructions,
@@ -484,7 +484,7 @@ export class ProxyController {
           continue;
         }
       }
-    } else if (typeof body.input === 'string') {
+    } else if (isString(body.input)) {
       messages.push({
         role: 'user',
         content: body.input,
@@ -716,18 +716,14 @@ export class ProxyController {
   }
 
   private isObservableLike(value: unknown): value is Observable<unknown> {
-    return (
-      Boolean(value) &&
-      typeof value === 'object' &&
-      typeof (value as { subscribe?: unknown }).subscribe === 'function'
-    );
+    return isObjectLike(value) && isFunction((value as { subscribe?: unknown }).subscribe);
   }
 
   private writeSseResponse(res: FastifyReply, stream: Observable<unknown>): void {
     if (
       !res.raw ||
-      typeof res.raw.writeHead !== 'function' ||
-      typeof res.raw.write !== 'function'
+      !isFunction(res.raw.writeHead) ||
+      !isFunction(res.raw.write)
     ) {
       res.header('Content-Type', 'text/event-stream');
       res.header('Cache-Control', 'no-cache');
@@ -736,7 +732,7 @@ export class ProxyController {
       return;
     }
 
-    if (typeof (res as { hijack?: () => void }).hijack === 'function') {
+    if (isFunction((res as { hijack?: () => void }).hijack)) {
       (res as { hijack: () => void }).hijack();
     }
 
@@ -751,7 +747,7 @@ export class ProxyController {
         if (res.raw.writableEnded) {
           return;
         }
-        const payload = typeof chunk === 'string' ? chunk : String(chunk ?? '');
+        const payload = isString(chunk) ? chunk : String(chunk ?? '');
         res.raw.write(payload);
       },
       error: (error) => {
@@ -804,7 +800,7 @@ export class ProxyController {
       }
 
       const content = result.choices?.[0]?.message?.content;
-      const image = this.extractInlineBase64Image(typeof content === 'string' ? content : '');
+      const image = this.extractInlineBase64Image(isString(content) ? content : '');
       if (!image) {
         this.logProxyEndpointError(
           '/v1/images/generations',
@@ -908,7 +904,7 @@ export class ProxyController {
 
     if (!userMessage) {
       parts.push({ text: fallbackPrompt || 'Please generate an image based on this request.' });
-    } else if (typeof userMessage.content === 'string') {
+    } else if (isString(userMessage.content)) {
       parts.push({
         text:
           userMessage.content ||
@@ -917,7 +913,7 @@ export class ProxyController {
       });
     } else {
       for (const block of userMessage.content) {
-        if (block.type === 'text' && typeof block.text === 'string' && block.text.trim() !== '') {
+        if (block.type === 'text' && isString(block.text) && !isEmpty(block.text.trim())) {
           textParts.push(block.text);
         }
         if (block.type === 'image_url') {
@@ -964,7 +960,7 @@ export class ProxyController {
 
   private hasMultipartBoundary(req: FastifyRequest): boolean {
     const contentType = req.headers['content-type'];
-    if (typeof contentType !== 'string') {
+    if (!isString(contentType)) {
       return false;
     }
 
diff --git a/src/server/modules/proxy/proxy.service.ts b/src/server/modules/proxy/proxy.service.ts
index 2d50fab..007359e 100644
--- a/src/server/modules/proxy/proxy.service.ts
+++ b/src/server/modules/proxy/proxy.service.ts
@@ -1,5 +1,5 @@
 import { Injectable, Logger, Inject } from '@nestjs/common';
-import { isEmpty, isNil, isPlainObject, isString } from 'lodash-es';
+import { isEmpty, isNil, isNumber, isPlainObject, isString } from 'lodash-es';
 import { TokenManagerService } from './token-manager.service';
 import { GeminiClient } from './clients/gemini.client';
 import { v4 as uuidv4 } from 'uuid';
@@ -511,7 +511,7 @@ export class ProxyService {
   private getModelOutputCap(accountId: string, model: string): number {
     const normalizedModel = this.normalizeModelIdentifier(model);
     const dynamicCap = this.tokenManager.getModelOutputLimitForAccount(accountId, normalizedModel);
-    if (typeof dynamicCap === 'number' && Number.isFinite(dynamicCap) && dynamicCap > 0) {
+    if (isNumber(dynamicCap) && Number.isFinite(dynamicCap) && dynamicCap > 0) {
       return Math.floor(dynamicCap);
     }
     return getMaxOutputTokens(normalizedModel);
@@ -523,7 +523,7 @@ export class ProxyService {
       accountId,
       normalizedModel,
     );
-    if (typeof dynamicBudget === 'number' && Number.isFinite(dynamicBudget) && dynamicBudget >= 0) {
+    if (isNumber(dynamicBudget) && Number.isFinite(dynamicBudget) && dynamicBudget >= 0) {
       return Math.floor(dynamicBudget);
     }
     return getThinkingBudget(normalizedModel);
@@ -548,12 +548,12 @@ export class ProxyService {
       | undefined;
     const adaptiveSentinel =
       thinkingConfig &&
-      (typeof thinkingConfig.thinkingLevel === 'string' ||
+      (isString(thinkingConfig.thinkingLevel) ||
         thinkingConfig.thinkingBudget === -1 ||
         thinkingConfig.thinkingBudget === 32768);
 
     if (thinkingConfig) {
-      if (!isClaudeModel && typeof thinkingConfig.thinkingLevel === 'string') {
+      if (!isClaudeModel && isString(thinkingConfig.thinkingLevel)) {
         const converted = this.resolveThinkingLevelBudget(thinkingConfig.thinkingLevel);
         if (converted !== undefined) {
           thinkingConfig.thinkingBudget = converted;
@@ -561,12 +561,12 @@ export class ProxyService {
         delete thinkingConfig.thinkingLevel;
       }
 
-      if (typeof thinkingConfig.thinkingBudget === 'number' && thinkingConfig.thinkingBudget < 0) {
+      if (isNumber(thinkingConfig.thinkingBudget) && thinkingConfig.thinkingBudget < 0) {
         thinkingConfig.thinkingBudget = Math.min(thinkingBudgetCap, 24576);
       }
 
       if (
-        typeof thinkingConfig.thinkingBudget === 'number' &&
+        isNumber(thinkingConfig.thinkingBudget) &&
         Number.isFinite(thinkingConfig.thinkingBudget)
       ) {
         thinkingConfig.thinkingBudget = Math.min(
@@ -595,7 +595,7 @@ export class ProxyService {
     }
 
     if (
-      typeof generationConfig.maxOutputTokens === 'number' &&
+      isNumber(generationConfig.maxOutputTokens) &&
       Number.isFinite(generationConfig.maxOutputTokens)
     ) {
       generationConfig.maxOutputTokens = Math.min(
@@ -634,7 +634,7 @@ export class ProxyService {
       ? response.candidates.map((candidate, index) => ({
           content: candidate?.content,
           finishReason: candidate?.finishReason,
-          index: typeof candidate?.index === 'number' ? candidate.index : index,
+          index: isNumber(candidate?.index) ? candidate.index : index,
         }))
       : [];
 
@@ -1115,7 +1115,7 @@ export class ProxyService {
       const choice = response.choices?.[0];
       const finishReason = choice?.finish_reason ?? 'stop';
       const content =
-        choice?.message && typeof choice.message.content === 'string' ? choice.message.content : '';
+        choice?.message && isString(choice.message.content) ? choice.message.content : '';
       const chunkSize = 80;
 
       if (content.length === 0) {
@@ -1216,7 +1216,7 @@ export class ProxyService {
       systemInstruction: request.systemInstruction
         ? {
             parts: request.systemInstruction.parts
-              .filter((part): part is { text: string } => typeof part.text === 'string')
+              .filter((part): part is { text: string } => isString(part.text))
               .map((part) => ({ text: part.text })),
           }
         : undefined,
@@ -1294,7 +1294,7 @@ export class ProxyService {
   private convertOpenAIPartsToAnthropicContent(
     content: OpenAIChatRequest['messages'][number]['content'],
   ): AnthropicContent[] {
-    if (typeof content === 'string') {
+    if (isString(content)) {
       return content.trim() ? [{ type: 'text', text: content }] : [];
     }
 
@@ -1328,7 +1328,7 @@ export class ProxyService {
   private extractOpenAITextContent(
     content: OpenAIChatRequest['messages'][number]['content'],
   ): string {
-    if (typeof content === 'string') {
+    if (isString(content)) {
       return content;
     }
 
@@ -1339,14 +1339,14 @@ export class ProxyService {
   }
 
   private parseOpenAIFunctionArguments(argumentsString: string): Record<string, unknown> {
-    if (!argumentsString || argumentsString.trim() === '') {
+    if (isEmpty(argumentsString.trim())) {
       return {};
     }
 
     try {
       const parsed = JSON.parse(argumentsString);
-      if (this.isRecord(parsed)) {
-        return parsed;
+      if (isPlainObject(parsed)) {
+        return parsed as Record<string, unknown>;
       }
       return { value: parsed };
     } catch {
@@ -1446,7 +1446,7 @@ export class ProxyService {
   }
 
   private normalizeToolCallArguments(input: unknown): string {
-    if (typeof input === 'string') {
+    if (isString(input)) {
       return input;
     }
     if (isNil(input)) {
@@ -1730,7 +1730,7 @@ export class ProxyService {
     const metadata = request.metadata;
     const sessionCandidate =
       metadata?.session_id ?? metadata?.sessionId ?? metadata?.user_id ?? metadata?.userId;
-    if (!isString(sessionCandidate) || sessionCandidate.trim() === '') {
+    if (!isString(sessionCandidate) || isEmpty(sessionCandidate.trim())) {
       return undefined;
     }
     return `anthropic:${sessionCandidate.trim()}`;
@@ -1740,17 +1740,13 @@ export class ProxyService {
     const extra = request.extra;
     const sessionCandidate =
       extra?.session_id ?? extra?.sessionId ?? extra?.user_id ?? extra?.userId;
-    if (!isString(sessionCandidate) || sessionCandidate.trim() === '') {
+    if (!isString(sessionCandidate) || isEmpty(sessionCandidate.trim())) {
       return undefined;
     }
     return `openai:${sessionCandidate.trim()}`;
   }
 
-  private isRecord(value: unknown): value is Record<string, unknown> {
+  private isGeminiPart(value: unknown): value is InternalGeminiPart {
     return isPlainObject(value);
   }
-
-  private isGeminiPart(value: unknown): value is InternalGeminiPart {
-    return this.isRecord(value);
-  }
 }
diff --git a/src/server/modules/proxy/rate-limit-tracker.ts b/src/server/modules/proxy/rate-limit-tracker.ts
index 9e3a753..78189c7 100644
--- a/src/server/modules/proxy/rate-limit-tracker.ts
+++ b/src/server/modules/proxy/rate-limit-tracker.ts
@@ -1,3 +1,5 @@
+import { isEmpty, isNumber, isObjectLike, isString } from 'lodash-es';
+
 export enum RateLimitReason {
   QuotaExhausted = 'quota_exhausted',
   RateLimitExceeded = 'rate_limit_exceeded',
@@ -68,7 +70,7 @@ function tryParseGoogleErrorBody(body: string | undefined): ParsedGoogleErrorBod
 
   try {
     const parsed = JSON.parse(trimmed) as ParsedGoogleErrorBody;
-    if (!parsed || typeof parsed !== 'object') {
+    if (!isObjectLike(parsed)) {
       return null;
     }
     return parsed;
@@ -96,7 +98,7 @@ export class RateLimitTracker {
   private readonly failureCounts = new Map<string, FailureCountEntry>();
 
   private buildLockoutKey(accountId: string, model?: string): string {
-    if (model && model.trim() !== '') {
+    if (!isEmpty(model?.trim() ?? '')) {
       return `${accountId}:${model}`;
     }
     return accountId;
@@ -150,7 +152,7 @@ export class RateLimitTracker {
     model?: string,
   ): void {
     const retryAfterSec = Math.max(2, Math.ceil((resetTimeMs - Date.now()) / 1000));
-    const key = model && model.trim() !== '' ? this.buildLockoutKey(accountId, model) : accountId;
+    const key = !isEmpty(model?.trim() ?? '') ? this.buildLockoutKey(accountId, model) : accountId;
     this.lockoutByKey.set(key, {
       resetTimeMs,
       retryAfterSec,
@@ -240,7 +242,7 @@ export class RateLimitTracker {
     const parsedBody = tryParseGoogleErrorBody(body);
     const details = Array.isArray(parsedBody?.error?.details) ? parsedBody?.error?.details : [];
     for (const detail of details) {
-      if (typeof detail.reason !== 'string' || detail.reason.trim() === '') {
+      if (!isString(detail.reason) || isEmpty(detail.reason.trim())) {
         continue;
       }
       const mappedReason = mapGoogleReasonToTrackerReason(detail.reason);
@@ -354,7 +356,7 @@ export class RateLimitTracker {
     const parsedBody = tryParseGoogleErrorBody(body);
     const details = Array.isArray(parsedBody?.error?.details) ? parsedBody.error.details : [];
     for (const detail of details) {
-      if (typeof detail.retryDelay === 'string' && detail.retryDelay.trim() !== '') {
+      if (isString(detail.retryDelay) && !isEmpty(detail.retryDelay.trim())) {
         const parsedDelay = parseDurationToSeconds(detail.retryDelay);
         if (parsedDelay !== null) {
           return parsedDelay;
@@ -362,8 +364,8 @@ export class RateLimitTracker {
       }
 
       if (
-        typeof detail.metadata?.retryDelay === 'string' &&
-        detail.metadata.retryDelay.trim() !== ''
+        isString(detail.metadata?.retryDelay) &&
+        !isEmpty(detail.metadata.retryDelay.trim())
       ) {
         const parsedDelay = parseDurationToSeconds(detail.metadata.retryDelay);
         if (parsedDelay !== null) {
@@ -372,8 +374,8 @@ export class RateLimitTracker {
       }
 
       if (
-        typeof detail.metadata?.quotaResetDelay === 'string' &&
-        detail.metadata.quotaResetDelay.trim() !== ''
+        isString(detail.metadata?.quotaResetDelay) &&
+        !isEmpty(detail.metadata.quotaResetDelay.trim())
       ) {
         const parsedDelay = parseDurationToSeconds(detail.metadata.quotaResetDelay);
         if (parsedDelay !== null) {
@@ -383,7 +385,7 @@ export class RateLimitTracker {
     }
 
     const retryAfter = parsedBody?.error?.retry_after;
-    if (typeof retryAfter === 'number' && retryAfter > 0) {
+    if (isNumber(retryAfter) && retryAfter > 0) {
       return Math.ceil(retryAfter);
     }
 
diff --git a/src/server/modules/proxy/request-user-agent.ts b/src/server/modules/proxy/request-user-agent.ts
index f8b77ba..8974b62 100644
--- a/src/server/modules/proxy/request-user-agent.ts
+++ b/src/server/modules/proxy/request-user-agent.ts
@@ -1,4 +1,5 @@
 import axios from 'axios';
+import { isString } from 'lodash-es';
 import { getAntigravityVersion } from '../../../utils/antigravityVersion';
 import { logger } from '../../../utils/logger';
 
@@ -20,7 +21,7 @@ let cachedUserAgentResolution: UserAgentResolution | null = null;
 let pendingUserAgentResolution: Promise<UserAgentResolution> | null = null;
 
 function normalizeNonEmptyString(value: string | null | undefined): string | null {
-  if (typeof value !== 'string') {
+  if (!isString(value)) {
     return null;
   }
 
@@ -125,7 +126,7 @@ async function fetchTextPayload(url: string): Promise<string | null> {
       },
     });
 
-    if (typeof response.data === 'string') {
+    if (isString(response.data)) {
       return response.data;
     }
 
diff --git a/src/server/modules/proxy/token-manager.service.ts b/src/server/modules/proxy/token-manager.service.ts
index 6a35ebe..a289f66 100644
--- a/src/server/modules/proxy/token-manager.service.ts
+++ b/src/server/modules/proxy/token-manager.service.ts
@@ -1,4 +1,5 @@
 import { Injectable, Logger, OnModuleInit } from '@nestjs/common';
+import { isEmpty, isNumber, isString } from 'lodash-es';
 import { CloudAccountRepo } from '../../../ipc/database/cloudHandler';
 import { CloudAccount, CloudQuotaData } from '../../../types/cloudAccount';
 import { GoogleAPIService } from '../../../services/GoogleAPIService';
@@ -36,7 +37,7 @@ interface GetNextTokenOptions {
 type TokenEntry = [string, TokenData];
 
 function normalizeProjectId(projectId: string | null | undefined): string | undefined {
-  if (typeof projectId !== 'string') {
+  if (!isString(projectId)) {
     return undefined;
   }
 
@@ -53,7 +54,7 @@ function normalizeProjectId(projectId: string | null | undefined): string | unde
 }
 
 function normalizeModelId(modelId: string | null | undefined): string | undefined {
-  if (typeof modelId !== 'string') {
+  if (!isString(modelId)) {
     return undefined;
   }
   const normalized = modelId.replace(/^models\//i, '').trim();
@@ -61,7 +62,7 @@ function normalizeModelId(modelId: string | null | undefined): string | undefine
 }
 
 function normalizeClientKey(clientKey: string | undefined): string | undefined {
-  if (typeof clientKey !== 'string') {
+  if (!isString(clientKey)) {
     return undefined;
   }
   const normalized = clientKey.trim().toLowerCase();
@@ -190,7 +191,7 @@ export class TokenManagerService implements OnModuleInit {
     const accountId = this.resolveAccountId(params.accountIdOrEmail) ?? params.accountIdOrEmail;
     const normalizedModel = normalizeModelId(params.model);
     const hasExplicitRetryWindow =
-      Boolean(params.retryAfter && params.retryAfter.trim() !== '') ||
+      Boolean(isString(params.retryAfter) && !isEmpty(params.retryAfter.trim())) ||
       Boolean(params.body && params.body.includes('quotaResetDelay'));
 
     if (!hasExplicitRetryWindow && (params.status ?? 0) === 429) {
@@ -215,7 +216,7 @@ export class TokenManagerService implements OnModuleInit {
         if (
           parsed.reason !== RateLimitReason.QuotaExhausted ||
           !parsed.model ||
-          parsed.model.trim() === ''
+          isEmpty(parsed.model.trim())
         ) {
           this.accountCooldowns.set(accountId, Date.now() + parsed.retryAfterSec * 1000);
         }
@@ -258,7 +259,7 @@ export class TokenManagerService implements OnModuleInit {
     if (
       parsed.reason !== RateLimitReason.QuotaExhausted ||
       !parsed.model ||
-      parsed.model.trim() === ''
+      isEmpty(parsed.model.trim())
     ) {
       this.accountCooldowns.set(accountId, Date.now() + parsed.retryAfterSec * 1000);
     }
@@ -661,14 +662,14 @@ export class TokenManagerService implements OnModuleInit {
 
       const limitCandidate = modelInfo.max_output_tokens ?? modelInfo.max_tokens;
       if (
-        typeof limitCandidate === 'number' &&
+        isNumber(limitCandidate) &&
         Number.isFinite(limitCandidate) &&
         limitCandidate > 0
       ) {
         modelLimits[normalizedModel] = Math.floor(limitCandidate);
       }
 
-      if (typeof modelInfo.resetTime === 'string' && modelInfo.resetTime.trim() !== '') {
+      if (isString(modelInfo.resetTime) && !isEmpty(modelInfo.resetTime.trim())) {
         modelResetTimes[normalizedModel] = modelInfo.resetTime;
       }
     }
@@ -692,7 +693,7 @@ export class TokenManagerService implements OnModuleInit {
   }
 
   private findEarliestQuotaResetTime(modelResetTimes: Record<string, string>): string | null {
-    const validTimes = Object.values(modelResetTimes).filter((value) => value.trim() !== '');
+    const validTimes = Object.values(modelResetTimes).filter((value) => !isEmpty(value.trim()));
     if (validTimes.length === 0) {
       return null;
     }
@@ -1084,7 +1085,7 @@ export class TokenManagerService implements OnModuleInit {
         continue;
       }
       const budget = modelInfo?.thinking_budget;
-      if (typeof budget === 'number' && Number.isFinite(budget) && budget >= 0) {
+      if (isNumber(budget) && Number.isFinite(budget) && budget >= 0) {
         return Math.floor(budget);
       }
     }
diff --git a/src/services/GoogleAPIService.ts b/src/services/GoogleAPIService.ts
index eb71884..a0e34fa 100644
--- a/src/services/GoogleAPIService.ts
+++ b/src/services/GoogleAPIService.ts
@@ -8,7 +8,7 @@ import {
   FALLBACK_VERSION,
   resolveLocalInstalledVersion,
 } from '@/server/modules/proxy/request-user-agent';
-import { isNumber, isString } from 'lodash-es';
+import { isEmpty, isNumber, isString, isUndefined } from 'lodash-es';
 
 // --- Constants & Config ---
 
@@ -81,7 +81,7 @@ function buildOAuthClientRegistry(): OAuthClientRegistry {
   ];
 
   const rawExtraClients = process.env[OAUTH_CLIENTS_ENV];
-  if (isString(rawExtraClients) && rawExtraClients.trim() !== '') {
+  if (isString(rawExtraClients) && !isEmpty(rawExtraClients.trim())) {
     for (const entry of rawExtraClients.split(';')) {
       const trimmed = entry.trim();
       if (trimmed === '') {
@@ -180,7 +180,7 @@ function selectAuthClient(clientKey?: string): OAuthClientConfig {
     throw new Error('No OAuth clients configured');
   }
 
-  if (clientKey && clientKey.trim() !== '') {
+  if (isString(clientKey) && !isEmpty(clientKey.trim())) {
     const selected = getClientByKey(registry.clients, clientKey);
     if (!selected) {
       throw new Error(`Unknown OAuth client key: ${clientKey}`);
@@ -345,20 +345,20 @@ function buildInternalApiHeaders(accessToken: string): Record<string, string> {
 
 function resolveSubscriptionTier(payload: LoadProjectResponse): string | undefined {
   const paidTier = payload.paidTier;
-  if (paidTier?.name && paidTier.name.trim() !== '') {
+  if (isString(paidTier?.name) && !isEmpty(paidTier.name.trim())) {
     return paidTier.name;
   }
-  if (paidTier?.id && paidTier.id.trim() !== '') {
+  if (isString(paidTier?.id) && !isEmpty(paidTier.id.trim())) {
     return paidTier.id;
   }
 
   const ineligible = Array.isArray(payload.ineligibleTiers) && payload.ineligibleTiers.length > 0;
   if (!ineligible) {
     const currentTier = payload.currentTier;
-    if (currentTier?.name && currentTier.name.trim() !== '') {
+    if (isString(currentTier?.name) && !isEmpty(currentTier.name.trim())) {
       return currentTier.name;
     }
-    if (currentTier?.id && currentTier.id.trim() !== '') {
+    if (isString(currentTier?.id) && !isEmpty(currentTier.id.trim())) {
       return currentTier.id;
     }
   }
@@ -366,10 +366,10 @@ function resolveSubscriptionTier(payload: LoadProjectResponse): string | undefin
   if (Array.isArray(payload.allowedTiers)) {
     const preferredAllowedTier =
       payload.allowedTiers.find((tier) => tier.is_default === true) ?? payload.allowedTiers[0];
-    if (preferredAllowedTier?.name && preferredAllowedTier.name.trim() !== '') {
+    if (isString(preferredAllowedTier?.name) && !isEmpty(preferredAllowedTier.name.trim())) {
       return ineligible ? `${preferredAllowedTier.name} (Restricted)` : preferredAllowedTier.name;
     }
-    if (preferredAllowedTier?.id && preferredAllowedTier.id.trim() !== '') {
+    if (isString(preferredAllowedTier?.id) && !isEmpty(preferredAllowedTier.id.trim())) {
       return ineligible ? `${preferredAllowedTier.id} (Restricted)` : preferredAllowedTier.id;
     }
   }
@@ -410,7 +410,7 @@ function toModelForwardingRules(
 
   const forwardingRules: Record<string, string> = {};
   for (const [oldModelId, deprecatedInfo] of Object.entries(deprecatedModelIds)) {
-    if (typeof deprecatedInfo.newModelId === 'string' && deprecatedInfo.newModelId !== '') {
+    if (isString(deprecatedInfo.newModelId) && deprecatedInfo.newModelId !== '') {
       forwardingRules[oldModelId] = deprecatedInfo.newModelId;
     }
   }
@@ -423,7 +423,7 @@ function parseCreditAmount(value: string | number | undefined): number {
     return value;
   }
 
-  if (typeof value === 'string') {
+  if (isString(value)) {
     const parsed = Number.parseInt(value, 10);
     if (Number.isFinite(parsed)) {
       return parsed;
@@ -448,7 +448,7 @@ function toAiCredits(
         ? payload.remainingCredits
         : undefined;
 
-  if (typeof creditsValue === 'undefined') {
+  if (isUndefined(creditsValue)) {
     return null;
   }
 
@@ -517,10 +517,10 @@ export class GoogleAPIService {
   ): string | undefined {
     const resolved = refreshedClientKey ?? currentToken.oauth_client_key;
     const projectMissing =
-      typeof currentToken.project_id !== 'string' || currentToken.project_id.trim() === '';
+      !isString(currentToken.project_id) || isEmpty(currentToken.project_id.trim());
 
     if (
-      typeof currentToken.oauth_client_key !== 'string' &&
+      !isString(currentToken.oauth_client_key) &&
       projectMissing &&
       resolved &&
       normalizeClientKey(resolved) === DEFAULT_OAUTH_CLIENT_KEY
@@ -812,7 +812,7 @@ export class GoogleAPIService {
 
         if (response.ok) {
           const data = (await response.json()) as LoadProjectResponse;
-          if (typeof data.cloudaicompanionProject === 'string') {
+          if (isString(data.cloudaicompanionProject)) {
             projectId = data.cloudaicompanionProject;
           }
           subscriptionTier = resolveSubscriptionTier(data);
diff --git a/src/tests/e2e/app.spec.ts b/src/tests/e2e/app.spec.ts
index 874fd6a..56b31e0 100644
--- a/src/tests/e2e/app.spec.ts
+++ b/src/tests/e2e/app.spec.ts
@@ -6,17 +6,18 @@ const injectCloudAccountsFailureScript = `
 (() => {
   const START_ORPC_SERVER = 'start-orpc-server';
   const originalPostMessage = window.postMessage.bind(window);
+  const isStringValue = (value) => Object.prototype.toString.call(value) === '[object String]';
 
   window.postMessage = function (message, targetOrigin, transfer) {
     if (message === START_ORPC_SERVER && Array.isArray(transfer) && transfer[0]) {
       const serverPort = transfer[0];
-      if (typeof serverPort.start === 'function') {
+      if (serverPort.start instanceof Function) {
         serverPort.start();
       }
 
       serverPort.onmessage = (event) => {
         try {
-          const request = typeof event.data === 'string' ? JSON.parse(event.data) : event.data;
+          const request = isStringValue(event.data) ? JSON.parse(event.data) : event.data;
           const requestId = request && (request.i || request.id);
           const requestUrl = (request && request.p && request.p.u) || '';
 
diff --git a/src/tests/scripts/project-id-request-validation.ts b/src/tests/scripts/project-id-request-validation.ts
index 73ce324..e32b7b3 100644
--- a/src/tests/scripts/project-id-request-validation.ts
+++ b/src/tests/scripts/project-id-request-validation.ts
@@ -1,4 +1,5 @@
 import assert from 'node:assert/strict';
+import { isEmpty, isString } from 'lodash-es';
 
 import { transformClaudeRequestIn } from '../../lib/antigravity/ClaudeRequestMapper';
 import { ProxyService } from '../../server/modules/proxy/proxy.service';
@@ -34,7 +35,7 @@ class TestableProxyService extends ProxyService {
 
 function getEnv(name: string, fallback?: string): string {
   const value = process.env[name];
-  if (value && value.trim() !== '') {
+  if (isString(value) && !isEmpty(value.trim())) {
     return value;
   }
   if (fallback !== undefined) {
@@ -46,7 +47,7 @@ function getEnv(name: string, fallback?: string): string {
 function getEnvFromList(names: string[], fallback?: string): string {
   for (const name of names) {
     const value = process.env[name];
-    if (value && value.trim() !== '') {
+    if (isString(value) && !isEmpty(value.trim())) {
       return value;
     }
   }
@@ -60,7 +61,7 @@ function getLiveHeaders(apiKey?: string): Record<string, string> {
   const headers: Record<string, string> = {
     'Content-Type': 'application/json',
   };
-  if (apiKey && apiKey.trim() !== '') {
+  if (isString(apiKey) && !isEmpty(apiKey.trim())) {
     headers.Authorization = apiKey.startsWith('Bearer ') ? apiKey : `Bearer ${apiKey}`;
   }
   return headers;
@@ -271,7 +272,7 @@ async function validateRuntimeAnthropicRequestFromRealTokenManager(): Promise<vo
   const captured = capturedBody as Record<string, unknown>;
   const tokenProjectId = selectedToken?.token?.project_id;
   const normalizedTokenProjectId =
-    typeof tokenProjectId === 'string' && tokenProjectId.trim() !== ''
+    isString(tokenProjectId) && !isEmpty(tokenProjectId.trim())
       ? tokenProjectId.trim()
       : undefined;
 
diff --git a/src/tests/unit/google-api-timeout.test.ts b/src/tests/unit/google-api-timeout.test.ts
index 379ddd9..6bae1c7 100644
--- a/src/tests/unit/google-api-timeout.test.ts
+++ b/src/tests/unit/google-api-timeout.test.ts
@@ -1,4 +1,5 @@
 import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
+import { isString } from 'lodash-es';
 
 // Mock module to test timeout behavior
 describe('GoogleAPIService Timeout', () => {
@@ -92,13 +93,13 @@ describe('GoogleAPIService OAuth clients', () => {
   });
 
   afterEach(() => {
-    if (typeof originalOauthClientsEnv === 'string') {
+    if (isString(originalOauthClientsEnv)) {
       process.env.ANTIGRAVITY_OAUTH_CLIENTS = originalOauthClientsEnv;
     } else {
       delete process.env.ANTIGRAVITY_OAUTH_CLIENTS;
     }
 
-    if (typeof originalActiveOauthClientEnv === 'string') {
+    if (isString(originalActiveOauthClientEnv)) {
       process.env.ANTIGRAVITY_OAUTH_CLIENT_KEY = originalActiveOauthClientEnv;
     } else {
       delete process.env.ANTIGRAVITY_OAUTH_CLIENT_KEY;
diff --git a/src/tests/unit/setup.ts b/src/tests/unit/setup.ts
index 566edc0..c3864a8 100644
--- a/src/tests/unit/setup.ts
+++ b/src/tests/unit/setup.ts
@@ -1,11 +1,12 @@
 import '@testing-library/jest-dom';
 import * as matchers from '@testing-library/jest-dom/matchers';
+import { isUndefined } from 'lodash-es';
 import { expect, vi } from 'vitest';
 
 expect.extend(matchers);
 
 // Mock window and localStorage for Node environment
-if (typeof window === 'undefined') {
+if (isUndefined((globalThis as { window?: unknown }).window)) {
   global.window = {
     matchMedia: vi.fn().mockImplementation((query) => ({
       matches: false,
diff --git a/src/utils/account-status.ts b/src/utils/account-status.ts
index 92c1b32..73b6d85 100644
--- a/src/utils/account-status.ts
+++ b/src/utils/account-status.ts
@@ -1,3 +1,5 @@
+import { isString } from 'lodash-es';
+
 export const RATE_LIMIT_HINTS = [
   'resource_exhausted',
   'too many requests',
@@ -40,7 +42,7 @@ export function extractErrorMessage(error: unknown): string {
   if (error instanceof Error) {
     return error.message;
   }
-  if (typeof error === 'string') {
+  if (isString(error)) {
     return error;
   }
   return String(error);
diff --git a/src/utils/errorMessages.ts b/src/utils/errorMessages.ts
index af22484..3872afc 100644
--- a/src/utils/errorMessages.ts
+++ b/src/utils/errorMessages.ts
@@ -1,4 +1,5 @@
 import type { TFunction } from 'i18next';
+import { isObjectLike } from 'lodash-es';
 
 const KEYCHAIN_ERROR_CODE = 'ERR_KEYCHAIN_UNAVAILABLE';
 const KEYCHAIN_HINT_TRANSLOCATION = 'HINT_APP_TRANSLOCATION';
@@ -60,7 +61,7 @@ export function getLocalizedErrorMessage(error: unknown, t: TFunction): string {
     return rawMessage;
   }
 
-  if (error && typeof error === 'object' && 'message' in error) {
+  if (isObjectLike(error)) {
     const rawMessage = String((error as { message?: unknown }).message ?? '');
     const [code, hint] = rawMessage.split('|');
     if (code === KEYCHAIN_ERROR_CODE) {
diff --git a/src/utils/googleAuthSubmission.ts b/src/utils/googleAuthSubmission.ts
index 526e01d..d096d44 100644
--- a/src/utils/googleAuthSubmission.ts
+++ b/src/utils/googleAuthSubmission.ts
@@ -1,3 +1,5 @@
+import { isEmpty } from 'lodash-es';
+
 export function shouldAutoSubmitGoogleAuthCode(params: {
   authCode: string;
   isAddDialogOpen: boolean;
@@ -5,7 +7,7 @@ export function shouldAutoSubmitGoogleAuthCode(params: {
   lastSubmittedAuthCode: string | null;
 }): boolean {
   return (
-    params.authCode.trim() !== '' &&
+    !isEmpty(params.authCode.trim()) &&
     params.isAddDialogOpen &&
     !params.isPending &&
     params.authCode !== params.lastSubmittedAuthCode
diff --git a/src/utils/logger.ts b/src/utils/logger.ts
index bfff4bf..4ff6924 100644
--- a/src/utils/logger.ts
+++ b/src/utils/logger.ts
@@ -1,5 +1,6 @@
 import fs from 'fs';
 import path from 'path';
+import { isObjectLike } from 'lodash-es';
 import winston from 'winston';
 import DailyRotateFile from 'winston-daily-rotate-file';
 import { getAgentDir } from './paths';
@@ -42,7 +43,7 @@ function safeStringify(obj: unknown): string {
       };
     }
     // Handle circular references
-    if (typeof value === 'object' && value !== null) {
+    if (isObjectLike(value)) {
       if (seen.has(value)) {
         return '[Circular]';
       }
@@ -143,7 +144,7 @@ class Logger {
 
   private formatArgs(args: unknown[]): string {
     return args
-      .map((arg) => (typeof arg === 'object' ? safeStringify(arg) : String(arg)))
+      .map((arg) => (isObjectLike(arg) ? safeStringify(arg) : String(arg)))
       .join(' ');
   }
 
diff --git a/src/utils/sensitiveDataMasking.ts b/src/utils/sensitiveDataMasking.ts
index 5bc11df..1714470 100644
--- a/src/utils/sensitiveDataMasking.ts
+++ b/src/utils/sensitiveDataMasking.ts
@@ -1,3 +1,5 @@
+import { isObjectLike, isString } from 'lodash-es';
+
 /**
  * Keys to mask in logs to avoid exposing sensitive data.
  */
@@ -39,10 +41,10 @@ function sanitizeWithSeen(obj: unknown, seen: WeakSet<object>): unknown {
     return obj;
   }
 
-  if (typeof obj === 'string') {
+  if (isString(obj)) {
     try {
       const parsed = JSON.parse(obj);
-      if (typeof parsed === 'object' && parsed !== null) {
+      if (isObjectLike(parsed)) {
         return JSON.stringify(sanitizeWithSeen(parsed, seen));
       }
     } catch {
@@ -59,7 +61,7 @@ function sanitizeWithSeen(obj: unknown, seen: WeakSet<object>): unknown {
     return obj.map((item) => sanitizeWithSeen(item, seen));
   }
 
-  if (typeof obj === 'object') {
+  if (isObjectLike(obj)) {
     if (seen.has(obj)) {
       return CIRCULAR_PLACEHOLDER;
     }
@@ -94,7 +96,7 @@ export function safeStringifyPacket(obj: unknown): string {
   const sanitized = sanitizeObject(obj);
   const seen = new WeakSet();
   return JSON.stringify(sanitized, (key, value) => {
-    if (typeof value === 'object' && value !== null) {
+    if (isObjectLike(value)) {
       if (seen.has(value)) {
         return '[Circular]';
       }