Version 0.15.0 of the b4 patch-management tool is out. Highlights in this release include the

b4 review

workflow manager for maintainers (covered briefly in this article),

b4 dig

, which can find the original mailing-list submission behind a commit, three-way-merge support in

b4 shazam

, and more. See the release notes for details.

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From:		Konstantin Ryabitsev <konstantin-AT-linuxfoundation.org>
To:		users-AT-kernel.org, tools-AT-kernel.org
Subject:		b4 v0.15.0 released
Date:		Fri, 20 Mar 2026 16:47:14 -0400
Message-ID:		<20260320-portable-jaybird-of-focus-41fd66@lemur>

Hi, all:

B4 v0.15.0 is now available! Install or upgrade using your usual mechanism.

We're recommending the use of pipx now over pip, so if you want to start from scratch, you can use:

pipx install b4
# or, if you want the new shiny review tui stuff
pipx install b4\[tui\]

Full release notes: https://b4.docs.kernel.org/en/latest/releases.html Getting started guide with screencasts: https://b4.docs.kernel.org/en/latest/reviewer/getting-sta...

b4 review — TUI-based patch review workflow (technology preview)

The headline feature in this release is "b4 review", a terminal-based workflow for maintainers who receive, review, and accept patches from mailing lists. It ships as a technology preview (alpha): commands, keybindings, configuration options, and on-disk formats may change in incompatible ways between releases.

The TUI requires the optional "tui" dependency group:

pipx install b4\[tui\]

The workflow is built around a lightweight SQLite tracking database and per-series review branches. It comprises three cooperating TUI apps:

Tracking TUI Browse and manage tracked series with status indicators, take (apply) series using merge, linear, or cherry-pick strategies, compare revisions with range-diff, send thank-you messages, and archive completed series. The app groups series by lifecycle state (active, new, waiting, gone) and sorts by most-recent activity.

Review TUI Split-pane interface with a patch list and scrollable diff viewer. Add inline comments and code-review trailers, preview outgoing emails, invoke an external AI agent for automated review assistance, and send review replies — all without leaving the terminal.

Patchwork TUI Browse outstanding series from a Patchwork server, set state and archived flags, and track series into the local database for review.

Highlights:

• Series tracking and lifecycle management — track series from the CLI (b4 review track ), from your mail client, or from Patchwork. Series progress through new → reviewing → replied → accepted → thanked states.
• Revision discovery and upgrades — b4 automatically discovers older and newer revisions of a tracked series using change-id and in-reply-to chains. Upgrading to a newer revision preserves your review state and prior context.
• Inline commenting — press "r" in the review view to open $EDITOR with the full diff quoted. Write your comments below the relevant lines and b4 will format them as proper email replies. The diff view shows community follow-up comments from the mailing list alongside your own.
• AI agent integration — optionally invoke an external AI agent (Claude Code, Gemini CLI, OpenAI Codex CLI, or GitHub Copilot CLI) to produce a first-pass review. Agent findings remain private to you; you decide what, if anything, to include in your reply.
• Per-patch state machine — mark individual patches as done, skip, or draft to track your progress through large series. B4 automatically excludes skipped patches from cherry-pick selection and outgoing emails.
• Three take strategies — merge (creates a merge commit from the cover letter), linear (git am), or cherry-pick (select individual patches). B4 adds per-commit Signed-off-by and Link trailers on request.
• Snooze — defer a series until a specific date, duration, or git tag. B4 skips snoozed series during bulk updates and automatically wakes them when the snooze expires.
• Cross-machine synchronisation — push b4/review/* branches to a private remote and rescan on another machine to rebuild the tracking database from branch metadata.
• Mutt-style thread viewer — press "e" to browse the full email thread with tree art, attestation status display, and reply support. B4 tracks per-message flags (seen, flagged, answered) across sessions.
• Worktree support — enrolled repositories work correctly from worktrees; a configurable review-target-branch sets the default branch for take operations.
• Patchwork state synchronisation — when you have write access to a Patchwork instance, b4 automatically updates the remote series state as you progress through the review lifecycle.
• Prior review context — when upgrading to a new revision, b4 carries forward your previous review comments and notes so you can see what you said last time.
• Quick-reply — reply to follow-up messages directly from the review TUI or thread viewer without switching to your email client.

b4 dig — trace applied commits back to mailing list submissions

The new "b4 dig" command searches for the original mailing list submission of a commit that has already been applied to a git tree. It matches by patch-id, author, and subject to locate the original thread on lore.kernel.org.

b4 dig <commitish>
b4 dig --all-series HEAD~20..HEAD
b4 dig --who --save-mbox <commitish>

b4 shazam — three-way merge and conflict resolution

"b4 shazam -H" now performs a three-way merge when applying patches, which significantly improves the success rate for series that do not apply cleanly with a simple "git am". When conflicts do occur, the new --resolve flag drops you into an interactive conflict resolution session instead of aborting:

b4 shazam -H --resolve <msgid>

b4 prep — pre/post history-rewrite hooks

Two new configuration keys let you run commands before and after b4 rewrites history on a prep branch (for example, when updating the cover letter or applying trailers via git-filter-repo):

\[b4\]
    prep-pre-rewrite-hook = stg commit --all
    prep-post-rewrite-hook = stg repair

A non-zero exit from the pre-hook aborts the operation, which is useful for tools like StGit that need to commit their internal state first.

Other notable changes

• XOAUTH2 and bearer-token SMTP authentication
• Presubject support (b4.send-presubject / --set-presubject)
• Send-email alias expansion (sendemail.aliasesfile)
• Codespell integration in b4 prep --check
• Shallow same-thread support (b4.send-same-thread = shallow)
• Force cover letter for single-patch series (--force-cover-letter)
• Default Link domain changed to patch.msgid.link
• Full-index binary diffs (--full-index --binary)
• Clean multiple prep branches at once
• Thank-you self-copy (b4 ty --me-too)
• Range-diff arguments (--range-diff-opts)
• Trailer provenance display in b4 trailers

Thanks

Thanks to the following people for reporting bugs, suggesting features, reviewing patches, testing, and contributing code, and especially to Mark Brown for valiantly trying the very early, rough versions of b4 review workflows.

Alexey Minnekhanov, Andrew Cooper, Andy Shevchenko, Christian Heusel, Conor Dooley, Dave Marquardt, Geert Uytterhoeven, Jonathan Corbet, Junio C Hamano, Juri Lelli, Kevin Hilman, Krzysztof Kozlowski, Lee Jones, Linus Torvalds, Louis Chauvet, Luca Ceresoli, Manos Pitsidianakis, Marc Kleine-Budde, Mark Brown, Matthieu Baerts, Maxime Ripard, Michael S. Tsirkin, Miguel Ojeda, Nathan Chancellor, Panagiotis Vasilopoulos, Ricardo Ribalda, Rob Herring, Tamir Duberstein, Toke Høiland-Jørgensen.

Best regards,

KR

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