Show HN: Substage – Natural language command bar for Finder windows on Mac (selkie.design)

Hey all!

I’m a solo indie dev and I’ve been working on Substage – a Mac app that docks under your Finder window and lets you interact with your files using natural language. Stuff like:

• Convert to webp

• zip these up

• Author of this PDF?

• Download this file: <url>

• Is this really a PNG?

• What's 5 foot 9 in cm?

• Open in TextMate

Substage converts your prompt into a Terminal command using an LLM (GPT-4o, Claude, Gemini, Mistral, or your own local model), runs it, and summarises the output. If it detects something risky, it’ll pause for confirmation before running. Commands run locally on your Mac – Substage doesn’t access your files directly, just the metadata and paths you select. However, if you end up executing something like `cat yourFile.txt`, then it'll send that output to the LLM for summarization.

You can use the built-in models with a subscription, or use your own API keys for OpenAI, Anthropic, Google, or Mistral with a one-off purchase. It also supports local models via Ollama or LM Studio if you prefer not to send anything off-device.

I built it for myself initially – I’m primarily an indie game developer (co-founder of inkle), and I constantly need to wrangle videos, images, text files, and metadata. I’m okay with basic command line work, but I’ll never remember all the arguments to ffmpeg!

Very open to thoughts and feedback!