Second Brain 2

Second Brain 2 is a local-first knowledge repository toolkit for Markdown and Git. It uses deterministic SQLite FTS5 retrieval plus explicit structural signals. There are no embeddings, ANN indexes, model downloads, or similarity-service dependencies.

Quick start

$ pip install second-brain-opencode
$ mkdir knowledge && cd knowledge
$ git init -b main
$ sb2 init .
$ sb2 index rebuild --apply
$ sb2 search "project decision" --explain

Initialization creates a .secondbrain control directory and a wiki workspace without overwriting existing notes. Canonical changes are designed to be reviewed, validated, and committed through Git.

Security model

Repository content is untrusted data. Paths are constrained to the repository, generated local artifacts are write-protected, and remote egress is classification aware: restricted content cannot leave the machine and confidential content requires explicit confirmation by default.

Install the project-local OpenCode integration after reviewing its dry run:

$ sb2 opencode diff --repo .
$ sb2 opencode install --repo . --apply

See Quick start, architecture, CLI reference, OpenCode integration, team workflow, and security.

Development

$ python -m pytest --cov=second_brain --cov-fail-under=80
$ python -m ruff check src tests
$ python -m mypy src/second_brain

Licensed under the MIT License.