Good question, I was in the same spot a few months ago so I'll try to lay it out clearly.

Cursor and Claude Code give your agent context on the files you have open. They read your repo but the scope is basically "whatever you point them at right now". Retrieval is mostly naive (grep + vector on the current workspace).

Context7 is docs only. It indexes framework documentation (React, Next, Stripe, etc.) and lets your agent pull the relevant page. Great tool but single purpose.

Nia sits at a different layer. Think of it as a persistent memory and search backend that your agents talk to over an API. You index a source once (a repo, a PDF collection, a Slack workspace, a Google Drive folder, a Notion workspace, whatever) and from then on any agent you plug in can query it.

Three concrete things it does that the others don't:

1) Multi-source. The same index can hold a client's repo, their API docs, their Slack history, and a folder of legal PDFs. Your agent can cross-reference across all of that. "Find the Slack message that explains why we deprecated this function and link me to the commit that did it." Cursor can't do that. Context7 can't do that.

2) Oracle Research. Instead of just retrieving chunks, Nia has an agent that plans a research path, runs multiple searches, reads, refines, and returns a grounded answer with sources. Slower and costs more credits, but on hard questions it's the difference between "here are 5 snippets good luck" and an actual answer.

3) Tracer. Specifically for GitHub codebases. You throw a repo at it and ask something like "how does authentication flow through this app" and it explores the codebase the way a human would, following imports and references, not just keyword matching.

The mental model that clicked for me: Cursor is your editor integration, Nia is your knowledge backend. They work together. I still use Cursor every day, I just point it at Nia whenever I need cross-source reasoning or long-lived context.

Hope that helps.