B2

A notes app for research. Plain Markdown in a folder you own, with an AI layer that finds the connections you haven't made yet, explains them, and answers questions from your notes with citations you can check.

B2 is my daily notes app, built to replace Obsidian. Obsidian is a good place to keep notes and a poor place to think with them. B2 keeps what Obsidian gets right (plain files, any editor, no lock-in) and adds the part research needs: help seeing what your notes have in common, how they bear on each other, and what they actually say.

What it does

• Shows the connections you haven't made. Beside every note is a ranked list of related notes it isn't linked to yet. Click Why? and a model explains what the two have in common, citing the passages.
• Lets you say how ideas relate. Link two notes and type the link: references, supports or contradicts. Similarity can tell that two notes are about the same thing; only you know whether one backs the other up or argues against it.
• Searches honestly. Keyword and semantic search together. When the vault holds no evidence for a query, B2 says "no matches" instead of showing its nearest guesses.
• Answers from your notes, with sources. Ask a question and get a streamed answer grounded only in your notes, each [n] pointing back to the passage it came from.
• Works with agents. Every CLI command has a --json form, and the vault is plain Markdown on disk, so an agent can search, read and walk the graph the way you do.
• Is a real editor. Live-preview Markdown, [[wikilink]] completion, images, a graph view, a file tree over your real folders, and full keyboard control with rebindable keys.

What it promises

• Your notes stay yours. The vault is a folder of Markdown that reads fine in Obsidian or any editor. B2's index lives in .b2/ and can be deleted and rebuilt at any time.
• No surprise writes. Opening, reading and indexing a vault change nothing. B2 writes only when you ask it to (a link, a move, a save), and never into the body of a note on its own.
• Local first. Embeddings run on your machine. Chat uses a local model through Ollama by default; a cloud model is something you choose.
• Refactor without fear. Move or rename a note through B2 and every link to it is rewritten to match.

Get started

make doctor                        # checks Rust, Node, the Tauri CLI and the build toolchain
make init                          # one time: download the embedding model
B2_VAULT_PATH=~/notes make app     # open the desktop app on a folder of Markdown

Point it at an existing Obsidian vault or any folder of .md files. For chat, install Ollama and run ollama pull gemma4:e2b.

The same engine runs from the terminal:

make install                       # puts `b2` on your PATH
b2 -C ~/notes search "spaced repetition"
b2 -C ~/notes similar notes/memory
b2 -C ~/notes ask "what have I written about sleep and memory?"

The quick start has the walkthrough, every command and every setting. B2 runs from source on macOS today; an installable build is #23.

How it's built

A Rust workspace. b2-core is the whole engine: it turns a folder of Markdown into a SQLite index (full-text search, vectors and a typed link graph) that is a pure projection of the files. The b2 CLI and the Tauri desktop app are two thin front ends over the same typed API. The real models sit behind small seams (b2-embed for embeddings, b2-llm for chat) and the engine is tested without them.

Two ideas shape every decision:

• The vault is the truth; the index is disposable. Drop the index, rebuild it, get the same thing back.
• Build for tomorrow's model. Do the least today's model needs, behind a seam, so the next one is an upgrade and not a rewrite.

Docs

Doc	What it covers
Quick start	Using B2: the walkthrough, commands, config, environment variables.
Data model	What a vault holds: notes, links, the verbs, resources.
Architecture	How it's built: the crates, the index, the flows.
Invariants	What must always be true, cited by id. Wins any conflict.
Decisions	The few key decisions, and why.
Evals	How search, discovery and chat quality are measured.

Develop

make check     # the fast loop: format, lint, engine and frontend tests
make ci        # exactly what GitHub Actions runs; run it before pushing
make           # every target, grouped

The build-out is done, so new work starts from daily use: an observed issue saying what I was doing, what I expected and what happened. Ground rules for contributors and agents are in CLAUDE.md, with the desktop crate's own in crates/b2-desktop/CLAUDE.md.