What this is: A plugin for your coding agent that guides you through the birth of a product, from purpose to market.

Backstory: I've built digital products for almost 30 years, and I've seen the same story evolve over and over. We built something nobody wanted or asked for. The only "proof" we had, was someone's gut feeling. Finding product-market-fit on a gut feeling is expensive and long-lasting. The constant refactoring and new alignments often meant adding some duct tape, chewing gum, pins and needles keeping it all together. Now I see the same thing happening using AI. At speed. Everybody building what no one asked for at 10x the speed, ending up with the same shaky structures. Because we let the agents continue our own guessing discipline, in an amplified state.

Where this is different: Most other product-focused plugins I've seen focus on the output and the delivery. Mycelium starts further upstream so that you are sure the product you think about building is actually worth building. The focus throughout the loops is to deliver value through outcome, not output. The agent needs to learn what to build and test its riskiest assumption before it gets to write any code.

Real life stories: (1) A mathematician at NTNU gave it a spin on Vibe+Mistral, albeit I developed it for Claude Code first and foremost. He created a MiniLisp interpreter with it, and published it on GitHub (https://github.com/dagfinndybvig/minilisp). For him it was more of an educational project, for me a proof of concept. (2) Mycelium stopped me from creating a file viewer that nobody but me ever wanted. The facts are available as a receipt in the repo (https://github.com/haabe/mycelium/blob/main/docs/receipts/ca...)

The plugin is still living in its early days. I'm developing it dogfooding it on itself. Any feedback you might have is most welcome, good and bad.

I did post about Mycelium on HN months ago, but I forgot to use the "Show HN" tag in the title. Mycelium has changed a lot since then. The original post is at https://news.ycombinator.com/item?id=47723889

If you're curious, and want to take it for a ride, you can do so by installing it through the plugin's own marketplace. You will need a coding agent, such as Claude Code, and access to a working LLM model. /plugin marketplace add haabe/mycelium /plugin install mycelium@haabe-mycelium /mycelium:start # one command: setup + 10-minute discovery

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