EidoStack
Browser workspace for comparing LLM responses side by side using your own API keys
EidoStack is a workspace for evaluating and choosing between AI models. It runs one prompt against two models at once and shows the responses side by side, alongside token usage, estimated cost and how much of the context window each one consumed.
Provider access is bring-your-own-key for OpenAI, Anthropic and Google AI. Keys are encrypted in the browser under a master password and requests are made client-side, so they are not held by EidoStack.
System prompts are configurable per chat, and chats can be organised into folders for repeated comparisons.
Pricing: Monthly / yearly subscriptions
What is EidoStack?
EidoStack is a browser-based workspace for deciding which model to use. It is aimed at the evaluation step rather than production monitoring: run the same prompt against two models, read both answers next to each other, and see what each one cost.
How it works
Connect OpenAI, Anthropic or Google AI with your own API keys. Comparison mode sends one prompt to two selected models simultaneously and renders the responses side by side. Each response carries its token count and estimated cost, and a context view shows estimated tokens against the selected model's context window, with full, windowed or summarised context strategies.
System prompts are set per chat, so the effect of an instruction change can be observed directly. Chats are auto-named and organised in folders.
Key handling
Provider keys are encrypted in the browser under a master password and stored in browser storage; plaintext keys stay in memory only while a session is unlocked. Provider requests are issued from the browser with those credentials, so keys do not pass through EidoStack's servers. Encrypted vault backup and restore are supported.
Pricing
The free tier allows one configured provider, five chats and 50 messages per chat, with token, cost and context inspection, but no comparison mode. Pro lifts those limits, enabling unlimited providers and chats plus comparison mode. The pricing page shows $99/year with a monthly option; the terms of service state $10 per month, so confirm the current rate at checkout before subscribing. Both figures read 31 August 2026.
Who it is for
Developers choosing between models for a specific application, particularly where the decision turns on cost and context consumption as much as answer quality. It is a manual side-by-side tool rather than an automated eval harness: there are no scored test suites or regression runs, so it complements rather than replaces a framework like Promptfoo or DeepEval.
EidoStack Alternatives
Explore 47 products in the Observability & Analytics category. View all EidoStack alternatives.
Weckr
Tracks LLM cost and margin per end customer, with spending caps that fire before the call
RAGAS
Open-source evaluation and testing framework for LLM and RAG applications
Work on EidoStack? Feature it at the top of Observability & Analytics.
Is your product missing?