Building a good LLM prompt is not a one-shot task. You assemble pieces, a system message, a few examples, some context, the actual instruction and then you iterate. You compress things that are too long, test whether the output still holds up, check how many tokens you are spending, and save versions so you can roll back when something breaks. Most developers do this in a text editor, a notebook, or scattered across a handful of scripts. There is no single place where you can see the whole context window, manipulate it visually, compress a block, run a live test, and save a snapshot, all without switching tools. ContextCraft is that place. It is a canvas-based interactive workbench for assembling, compressing, testing, and versioning LLM context windows. It runs locally, connects to Ollama for local compression and testing, supports OpenRouter for cloud LLM testing, and exports directly to OpenAI, Anthropic, LangChain, and JSON formats.…