Diffsmith

Diffsmith is a local, human-in-the-loop AI code review cockpit for GitHub pull requests and GitLab merge requests.

It fetches a PR/MR diff, asks a selected AI CLI to draft review findings, validates the output, and opens a terminal UI where you inspect, edit, approve, dismiss, and copy comments manually.

Diffsmith is not an auto-comment bot. The reviewer stays in control.

Diffsmith has no server. The selected model CLI may still send diffs to its own provider, so users must choose a model that is acceptable for the repository being reviewed.

Current Status

v0.1.0-rc1 released (M8). The product is built end-to-end: GitHub + GitLab providers; Codex, Claude, and Antigravity model adapters running in parallel with synthesis via a lead model; three-pane TUI; clipboard/export; inline review-thread posting back to GitHub PRs and GitLab MRs (gated by explicit confirmation); dedup-before-post against existing diffsmith threads; prompt-injection-resilient parser. See CHANGELOG.md for the v0.1.0 release notes.

Product Thesis

Most AI review tools fail by posting noisy comments directly into pull requests. Diffsmith takes the opposite approach:

• Local-first CLI/TUI.
• Explicit model selection at startup via an interactive picker.
• Suggested review comments are drafts.
• Every suggested review comment is editable.
• Posting is opt-in per finding (p in the TUI) and requires an explicit y confirmation before any network call.
• No backend.
• No auto-posting.

V1 Command

diffsmith review <github-pr-url|gitlab-mr-url>     # review a specific PR/MR
diffsmith                                          # inbox: pick from your repo's open PRs/MRs

At startup, diffsmith probes which AI CLIs are installed (codex, claude, and agy for Antigravity) and shows an interactive picker. Any subset can be selected; their findings are merged by a synthesis pass via the highest-priority surviving model (priority order: codex → claude → antigravity). The Antigravity adapter requires a one-time interactive agy login (after which its OAuth token persists); see internal/model/antigravitycli/doc.go.

To sharpen findings, diffsmith also sends the PR/MR description and the acceptance criteria from any issues the PR/MR formally closes (resolved via gh/glab) so reviewers can flag scope drift and unmet criteria. This is on by default; pass --no-context for a diff-only review that withholds the description and skips the linked-issue fetch. Context fetching is never a gate — if it fails, the review proceeds and the reason is surfaced in the run summary.

Large diffs can exceed the per-model input budget (1 MiB by default). Pass --exclude <pattern> (repeatable) to drop noise files from the review — lockfiles, vendored deps, generated code — before the prompt is built: a trailing / excludes a directory tree at any depth (vendor/), a pattern without / matches basenames anywhere (*.lock), anything else is a full-path glob (internal/gen/*.go). Exclusions are surfaced in the run summary, never silent, and excluding every changed file is an error rather than an empty review.

--include <pattern> (repeatable) is the allowlist counterpart: it keeps only the matching files and drops the rest, using the same pattern rules. It runs first, then --exclude carves exceptions out of the kept set — so --include 'internal/' --exclude 'internal/gen/' reviews everything under internal/ except the generated tree. Like exclusions, the narrowing is surfaced in the run summary, and an --include that matches no changed file is an error rather than an empty review.

After review, p in the TUI marks findings for upstream posting. On quit, diffsmith asks for explicit y confirmation, then posts approved findings as inline review threads on the PR/MR. Findings whose (file, line) already has a diffsmith thread upstream are skipped with a summary line; pass --repost to bypass that dedup gate.

Install

One-line install (macOS and Linux)

curl -fsSL https://raw.githubusercontent.com/selyafi/diffsmith/main/install.sh | sh

The script detects your OS and architecture, downloads the matching tarball from the latest GitHub Release, verifies its SHA256 against the published SHA256SUMS, and installs the binary to /usr/local/bin (or $HOME/.local/bin if /usr/local/bin is not writable without sudo).

To pin a specific version or change the install directory:

DIFFSMITH_VERSION=v0.1.0 INSTALL_DIR="$HOME/bin" \
  curl -fsSL https://raw.githubusercontent.com/selyafi/diffsmith/main/install.sh | sh

Via go install

If you have Go 1.24+ installed:

go install github.com/selyafi/diffsmith/cmd/diffsmith@latest

Manual download

Grab the tarball for your platform from the latest release, extract it, and move the diffsmith binary somewhere on your PATH.

Updating

Re-run the install command — install.sh always resolves to the most recent release, so running it again upgrades in place. For go install, repeat the @latest invocation.

Verifying

diffsmith --version

Uninstalling

rm "$(command -v diffsmith)"

V1 Dependencies

For repository access:

• gh for GitHub pull requests
• glab for GitLab merge requests

For AI review:

• codex, claude, or agy (Antigravity) CLI — at least one must be installed and authenticated. The picker shows which are available at startup; all selected models run in parallel and a lead model synthesizes the final findings.
• agy requires a one-time interactive login (run agy once); after that its OAuth token persists and diffsmith drives it non-interactively.

V1 Workflow

1. Detect GitHub or GitLab from the URL.
2. Fetch PR/MR metadata and diff through gh or glab.
3. Normalize changed files, hunks, and line positions.
4. Send a structured review prompt to each selected AI CLI in parallel.
5. Parse each model's output as JSON findings (defensively — fenced or prose-wrapped output is unwrapped before parsing).
6. Synthesize findings across models via a lead model that picks, merges, and rewrites.
7. Validate findings against the diff (anchor file/line into the diff index).
8. Show findings in a three-pane TUI; let the reviewer edit, approve, dismiss, copy, or mark for posting.
9. On quit, with explicit y confirmation, post approved findings as inline review threads on the upstream PR/MR — skipping any whose (file, line) already has a diffsmith thread.

V1 Non-Goals

• No automatic posting — every post requires explicit y confirmation.
• No CI bot mode.
• No hosted service.
• No session resume.
• No automatic patch application.
• No team policy engine.

License

MIT — see LICENSE. Diffsmith bundles no third-party code under a different license; runtime dependencies are listed in go.mod.