I setup my own mini obsidian with openai/claude api using sqlite, and it's been really useful. I have folders/subfolders with their own schemas and conventions using plain AGENT.md files, and even setup custom agents to hold specific instruction sets and access control systems. A subset of tools to navivate, search, edit, combined with the agents plugin spec, gives me a pretty flexible workflow, and the ability to extend functionality with MCP, 3rd party providers. I'm using vercel's ai sdk, so i can switch providers and use any AI model in openrouter or local GPU.

Ofcourse you could just use obsidian with some extension like claudian, or plain markdown files and vscode, or even claude/codex apps, but they all have their own quirks, and they'll cost alot more per token usage, subscription plans.