diff --git a/src/services/api/index.ts b/src/services/api/index.ts
index 86f0348..e46373c 100644
--- a/src/services/api/index.ts
+++ b/src/services/api/index.ts
@@ -38,9 +38,11 @@ export const apiService = {
       )
     );
   },
-  post: (url: string, data: any) => apiClient.post(url, data),
-  put: (url: string, data: any) => apiClient.put(url, data),
-  delete: (url: string) => apiClient.delete(url),
+  /** #801: Generic response type so callers can infer the response shape. */
+  post: <T = unknown>(url: string, data: unknown) => apiClient.post<T>(url, data),
+  put: <T = unknown>(url: string, data: unknown) => apiClient.put<T>(url, data),
+  patch: <T = unknown>(url: string, data: unknown) => apiClient.patch<T>(url, data),
+  delete: <T = unknown>(url: string) => apiClient.delete<T>(url),
 };
 
 export { default as apiClient } from './axios.config';
diff --git a/src/services/api/requestQueue.ts b/src/services/api/requestQueue.ts
index a8598b2..7dd5e5c 100644
--- a/src/services/api/requestQueue.ts
+++ b/src/services/api/requestQueue.ts
@@ -1,4 +1,5 @@
 import AsyncStorage from '@react-native-async-storage/async-storage';
+import type { ApiClient } from '../../types/apiClient';
 import { InternalAxiosRequestConfig } from 'axios';
 import * as Network from 'expo-network';
 
@@ -64,7 +65,8 @@ class RequestQueue {
   private listeners: ((count: number) => void)[] = [];
   private monitoringInterval: ReturnType<typeof setInterval> | null = null;
   private networkListener: (() => void) | null = null;
-  private apiClient: any | null = null;
+  // #802: typed as ApiClient to prevent passing arbitrary objects
+  private apiClient: ApiClient | null = null;
   private metrics: QueueMetrics = {
     totalQueued: 0,
     byPriority: { critical: 0, high: 0, normal: 0, low: 0 },
@@ -202,7 +204,7 @@ class RequestQueue {
     }
   }
 
-  async processQueue(apiClient?: any): Promise<void> {
+  async processQueue(apiClient?: ApiClient): Promise<void> {
     if (this.isProcessing) return;
 
     if (apiClient) {
@@ -283,7 +285,7 @@ class RequestQueue {
       .catch(() => {});
   }
 
-  startMonitoring(apiClient?: any): void {
+  startMonitoring(apiClient?: ApiClient): void {
     if (apiClient) {
       this.apiClient = apiClient;
     }
diff --git a/src/store/createStore.ts b/src/store/createStore.ts
index c12732c..977a85a 100644
--- a/src/store/createStore.ts
+++ b/src/store/createStore.ts
@@ -45,13 +45,15 @@ export const createStore = <T extends object>(
         storage: createJSONStorage(() => asyncMMKVStorage),
         partialize,
         migrate,
-        onRehydrateStorage: (state) => {
-          return (state, error) => {
+        onRehydrateStorage: (_initialState) => {
+          // #803: explicitly type both params so implicit `any` is eliminated.
+          // `error` is `Error | undefined` per the Zustand persist middleware signature.
+          return (_rehydratedState: T | undefined, error: Error | undefined) => {
             if (error) {
               appLogger.errorSync('an error happened during hydration', error instanceof Error ? error : new Error(String(error)))
               logger.errorSync('an error happened during hydration', error as Error)
             }
-          }
+          };
         },
       }),
       { name: `Teach-This-${name}` }
diff --git a/src/types/apiClient.ts b/src/types/apiClient.ts
new file mode 100644
index 0000000..6b357d2
--- /dev/null
+++ b/src/types/apiClient.ts
@@ -0,0 +1,20 @@
+// src/types/apiClient.ts
+// Typed interface that RequestQueue uses to replay queued requests.
+// The exported `apiClient` from axios.config.ts satisfies this interface.
+
+import type { AxiosResponse, InternalAxiosRequestConfig } from 'axios';
+
+/**
+ * Minimum contract required by RequestQueue to execute queued HTTP requests.
+ *
+ * Typed as a callable (for replaying raw configs) plus named method overloads
+ * so TypeScript can verify the actual apiClient satisfies it at compile time.
+ */
+export interface ApiClient {
+  (config: InternalAxiosRequestConfig): Promise<AxiosResponse>;
+  get<T = unknown>(url: string, config?: object): Promise<AxiosResponse<T>>;
+  post<T = unknown>(url: string, data?: unknown, config?: object): Promise<AxiosResponse<T>>;
+  put<T = unknown>(url: string, data?: unknown, config?: object): Promise<AxiosResponse<T>>;
+  patch<T = unknown>(url: string, data?: unknown, config?: object): Promise<AxiosResponse<T>>;
+  delete<T = unknown>(url: string, config?: object): Promise<AxiosResponse<T>>;
+}
diff --git a/src/types/axios.d.ts b/src/types/axios.d.ts
new file mode 100644
index 0000000..d33cf10
--- /dev/null
+++ b/src/types/axios.d.ts
@@ -0,0 +1,33 @@
+// src/types/axios.d.ts
+// Module augmentation for custom Axios request config properties.
+// This is the single source of truth — no more `as any` casts needed.
+
+import 'axios';
+
+declare module 'axios' {
+  interface InternalAxiosRequestConfig {
+    /**
+     * Set to `true` once a 401 has triggered a token-refresh attempt for this
+     * request, preventing infinite refresh loops.
+     */
+    _retry?: boolean;
+
+    /**
+     * Running count of retry attempts for 429 (rate-limit) and 5xx (server
+     * error) responses. Starts at 0 and increments before each retry.
+     */
+    _retryCount?: number;
+
+    /**
+     * Epoch milliseconds recorded when the request was dispatched. Used to
+     * calculate response latency in the response interceptor.
+     */
+    _requestStartMs?: number;
+
+    /**
+     * Performance timing finish callback injected by the request interceptor.
+     * Set to `undefined` after first use to avoid double-reporting on retries.
+     */
+    _timingFinish?: ((success: boolean, statusCode?: number) => unknown) | undefined;
+  }
+}