Bitsandbytes CLAUDE.md

> Sourced from [bitsandbytes-foundation/bitsandbytes](https://github.com/bitsandbytes-foundation/bitsandbytes) — [MIT](https://github.com/bitsandbytes-foundation/bitsandbytes/blob/a57d8e27c23c9005fe8b032770aff86f2baf19c8/CLAUDE.md).

# MANDATORY: Use git worktrees for all branch work

NEVER work on a fix or feature branch inside the main `~/git/bitsandbytes` checkout. Always create a worktree first:

```bash
cd ~/git/bitsandbytes
git worktree add ~/git/bnb-fix-<NUMBER> -b fix/issue-<NUMBER>
cd ~/git/bnb-fix-<NUMBER>
```

This keeps the main checkout clean and allows parallel sessions. If you are already inside a worktree directory, you do not need to create another one.

**Before creating a worktree**, check the worktree registry for existing ones — see the Git Worktrees section in `~/.claude/CLAUDE.md`. Bitsandbytes-specific naming conventions: `agents/worktree_guide.md`. General worktree guide: `~/git/lab_tools/worktree_guide.md`.

# MANDATORY: Check for existing PRs before starting work

Before working on any issue, check whether a PR already exists:

```bash
gh pr list --search "issue-number OR keyword" --state open
```

If a PR exists, review and build on it instead of starting from scratch. Do not create duplicate work.

# MANDATORY: Run linting before every pull request

Before pushing a PR branch, you MUST run the full pre-commit suite. CI will reject PRs that fail any check:

```bash
pre-commit run --all-files
```

This runs ruff, ruff format, typos, trailing-whitespace, clang-format, and all other CI lint hooks. Review and commit any changes it makes. Do NOT run only `ruff check` and `ruff format` — those are just 2 of 10 hooks. Full details: `agents/linting_guide.md`

# Testing: only run relevant tests

Do NOT run the full test suite — it takes 10+ minutes. Instead, run only the tests that cover the code you changed:

```bash
pytest tests/test_relevant_file.py -v --tb=short -k "relevant_test_name"
```

The full suite will be run separately. Best practices and known issues: `agents/testing_guide.md`

# Agent Dispatch (the "Dispatcher" role)

To triage open GitHub issues, generate prompt files, and launch parallel worker agents, read `agents/dispatch_guide.md`. If told "you're the Dispatcher" or "please read the Dispatch Guide," that's what this refers to. The dispatch workflow uses the GitHub issue tools in `agents/` — see `agents/github_tools_guide.md` for the bitsandbytes-specific reference.

# Issue maintenance and triage

To identify and close stale, duplicate, or resolved issues: `agents/issue_maintenance_guide.md`. Common closeable patterns (old CUDA setup, Windows pre-support, third-party app issues, etc.) are cataloged in `agents/issue_patterns.md`.

# Pull request review

When tasked with reviewing a pull request, you MUST read these guides before starting the review:

1. `agents/pr_review_guide.md` — The complete review workflow (classification, checklists, verdict format, and posting instructions). This is the primary guide; follow its steps sequentially.
2. `agents/architecture_guide.md` — Codebase architecture and patterns
3. `agents/code_standards.md` — Code quality expectations
4. `agents/api_surface.md` — Public API catalog (for detecting breaking changes)
5. `agents/downstream_integrations.md` — How Transformers, PEFT, Accelerate, TGI, and vLLM depend on bitsandbytes (for assessing downstream impact)
6. `agents/security_guide.md` — Trust model and security checklist (especially for external contributor PRs)

For CUDA kernel changes, also read `agents/kbit_gemm_context.md`. The PR review guide references all of these at the appropriate steps.