Besidka is a bring-your-own-key (BYOK) chat application that allows users to interact with multiple large language models, including GPT, Gemini, Claude, and DeepSeek, using their own API keys. The app operates without a subscription; instead, it displays the cost of each message and charges only for actual usage, with no markup added by the service. It is open-source and self-hostable, giving users control over their data and infrastructure. The application supports desktop and mobile use as an installable progressive web app (PWA) with push notifications. Each response shows the model, token count, and cost. Users can choose between light and dark themes. The app works with API keys from seven different AI providers and optionally supports gateways such as OpenRouter, Vercel, and Cloudflare. Additional features include web search with configurable pricing tiers (Lite, Auto, Deep), projects that incorporate memory, files, and notes, a profile memory that users can review and edit, and optional safety checks using a TypeSafe AI key. Users can search past conversations, view highlighted code and rendered diagrams, follow reasoning steps, generate images within the chat, conduct deep research with full traceability, and manage uploaded files through a built-in file manager. Typical use cases involve daily tasks such as search, translation, working with PDFs, generating images, and writing code. The workflow requires users to sign up, obtain an API key from a provider’s developer console, and add that key to Besidka. The app is designed for individuals who already pay for subscription services like ChatGPT Plus or Claude Pro but rarely consume their full limits, or for anyone who prefers a pay-per-use model across multiple models in a single interface without committing to a recurring fee. Because users manage their own API keys, no additional payment card or prepaid credit is needed within Besidka itself. Technically, Besidka requires users to have basic familiarity with creating API keys from supported providers. The application is self-hostable and fully open source, meaning users can deploy it on their own infrastructure if desired. There is no server-side storage of API keys; the keys are stored locally on the user’s device. The app provides full transparency on pricing by showing the cost of every message, and it does not impose any subscription tier or usage caps beyond what the API providers themselves enforce.