diff --git a/src/clients/base-client.ts b/src/clients/base-client.ts
new file mode 100644
index 0000000..f176bc9
--- /dev/null
+++ b/src/clients/base-client.ts
@@ -0,0 +1,77 @@
+// src/clients/base-client.ts
+import axios, { AxiosInstance, AxiosError } from 'axios';
+import { TokenConfigLoader, TokenConfig } from '../config.js';
+
+export interface ClientOptions {
+  timeout?: number;
+}
+
+export class BaseClient {
+  protected axiosInstance!: AxiosInstance;
+  private tokenSource: string | null = null;
+  private _initialized = false;
+  private _initPromise: Promise<void> | null = null;
+
+  constructor(options: ClientOptions = {}) {
+    this._initPromise = this._init(options);
+  }
+
+  private async _init(options: ClientOptions): Promise<void> {
+    try {
+      const config = await TokenConfigLoader.load();
+      this.tokenSource = config.source;
+      this.axiosInstance = axios.create({
+        baseURL: 'https://api.bitbucket.org/2.0',
+        headers: { 'Content-Type': 'application/json' },
+        auth: { username: config.email, password: config.token },
+        timeout: options.timeout || 30000,
+        maxRedirects: 5,
+      });
+      this.axiosInstance.interceptors.request.use(cfg => {
+        cfg.headers['User-Agent'] = 'Bitbucket-MCP-Server/1.0.0';
+        return cfg;
+      });
+      this.axiosInstance.interceptors.response.use(
+        r => r,
+        (error: AxiosError) => this._handleResponseError(error),
+      );
+      this._initialized = true;
+    } catch (error) {
+      throw new Error(`Unable to initialize Bitbucket client: ${error}`);
+    }
+  }
+
+  protected async ensureInitialized(): Promise<void> {
+    if (this._initialized) return;
+    await this._initPromise;
+  }
+
+  private async _handleResponseError(error: AxiosError): Promise<never> {
+    const status = error.response?.status;
+    if (status === 401) {
+      console.error('🔐 Bitbucket API Authentication Error (401)');
+      console.error(`   Token source: ${this.tokenSource || 'unknown'}`);
+      console.error(`   URL: ${error.config?.url}`);
+    } else if (status === 403) {
+      console.error('🚫 Bitbucket API Forbidden (403)');
+      console.error(`   URL: ${error.config?.url}`);
+    } else if (status === 429) {
+      const retryAfter = error.response?.headers['retry-after'];
+      const delay = retryAfter ? parseInt(retryAfter, 10) * 1000 : 5000;
+      console.log(`Rate limited. Retrying in ${delay}ms...`);
+      await this._sleep(delay);
+    }
+    throw error;
+  }
+
+  protected _sleep(ms: number): Promise<void> {
+    return new Promise(resolve => setTimeout(resolve, ms));
+  }
+
+  protected formatError(error: any): string {
+    if (error?.response?.status) {
+      return `HTTP ${error.response.status}: ${error.message}`;
+    }
+    return error?.message || 'Unknown error';
+  }
+}