Treat your AI as a coworker — ask questions about its changes in the same session that wrote the code.
/askdiff from inside any Claude Code session opens a GitHub-style diff
viewer in your browser. Hover a line, click +, type a question. The
answer streams back inline — and because each ask resumes the same
Claude Code session that wrote the code, the model already remembers
the file, the conversation, and why it made the change.
# 1. One-time skill install
npx -y askdiff install-skill
# 2. From any Claude Code session
/askdiff # working-tree changes
/askdiff last commit # HEAD~1..HEAD
/askdiff main vs feature/x # main…HEAD (PR-style)
/askdiff David's latest commit where he removed the xmpp integration # author + content searchThat's it. No API key, no global install, no config. The browser opens to a syntax-highlighted diff; comments stream back as the model thinks.
Developers often prompt AIs to write the code, then, if the diff becomes large enough, open draft GitHub PRs in order to review it better. Then, if there are any questions, take the diff back to the terminal, ask questions about it, and repeat.
Askdiff simplifies this process by combining the diff viewer and the Q&A interface into one seamless experience, directly integrated with the very same Claude Code session that wrote the code. It makes you treat the model truly as a coworker who already knows the entire context and the reasoning behind every single line of the diff.
Each ask spawns the claude CLI with --resume <your-session-id>.
So your question becomes a real turn in the running session's transcript:
- No diff sent to the model. The resumed session already has the full context that wrote the code; the prompt is just your question.
- No Anthropic API key needed. askdiff doesn't talk to the API —
it shells out to the
claudeCLI you've already auth'd via subscription or whatever. - No process cleanup. The server self-exits after 5 minutes of inactivity — close the browser tab and forget about it.
| Diff selection | Describe which diff to review in plain English — working tree, last commit, branch comparisons, arbitrary refs. |
| Inline comments | Click the + gutter button to comment on any line. Drag to comment on a range. |
| Streaming answers | Tokens stream in as Claude generates them — same model context that wrote the code. |
| Threaded discussions | Multiple asks per line, each its own thread, all anchored to the diff. |
Anything after /askdiff is a description — Claude figures out the
right git diff invocation, writes the result to a temp file, and
points the server at it. Some examples:
| You type | What you'll review |
|---|---|
/askdiff |
working-tree changes (uncommitted + untracked) |
/askdiff last commit |
HEAD~1..HEAD |
/askdiff last 3 commits |
HEAD~3..HEAD |
/askdiff the 5th latest commit |
the single commit at HEAD~4 |
/askdiff main vs feature/x |
main…HEAD (three-dot, PR-style) |
/askdiff abc123 vs def456 |
abc123..def456 |
/askdiff staged |
git diff --cached |
/askdiff the commit where I added the favicon |
Claude searches commit messages, diff content, or file history to find it |
Defaults when ambiguous:
- "branch X against branch Y" between named refs ⇒ three-dot (PR semantics).
- Two arbitrary commits ⇒ two-dot (literal tree diff).
- "Nth latest commit" ⇒ that single commit's changes.
The TopBar shows what diff you're reviewing as a small label
(e.g. Working tree, HEAD~1..HEAD, main…feature/x).
Re-invoking refreshes. Run /askdiff again from the same session
and the previous server is killed, the diff is recomputed, and the
existing browser tab auto-reconnects on the same port. For working-tree
diffs, an amber banner appears if any reviewed file has been edited
since the diff was captured, prompting you to re-run /askdiff.
Hover any line in the diff. A + button appears in the gutter.
Click it for a single-line question, or click and drag to range over
multiple lines. The comment widget renders below the selected lines;
type a question and hit Cmd/Ctrl+Enter (or click Send).
Tokens stream in as the model generates them — usually starting within
~1 second, typing speed-of-thought. Click Stop mid-stream to abort.
Markdown is rendered live, including syntax-highlighted code blocks
in any of 30+ languages.
Each line can have multiple ask/answer pairs. They render as a threaded conversation inline with the diff, so you can ask a follow-up without losing context.
All optional. Set as env vars before running npx -y askdiff — or
let the skill resolve them automatically.
| Variable | Default | Notes |
|---|---|---|
PORT |
7837 |
Auto-bumps if taken. |
ASKDIFF_SESSION_ID |
(resolved from $PPID) |
Force a specific Claude Code session UUID. |
ASKDIFF_PROJECT_CWD |
(parent CC manifest, then process.cwd()) |
Project directory to diff. |
ASKDIFF_MODEL |
(inherits resumed session's model) | Override the Claude model for asks. |
CLAUDE_CONFIG_DIR |
~/.claude |
Where Claude Code stores sessions/, projects/. |
CLI flags also work (askdiff --port 7838 --no-open --session <uuid>).
Run askdiff --help for the full list.
When you next run /askdiff and a newer version is on npm, the skill
prints UPDATE_AVAILABLE: pinned=X latest=Y and asks whether to
upgrade or proceed. Upgrade is one command:
npx -y askdiff@latest install-skill --forceThis rewrites the skill to pin to the new version. The first
subsequent /askdiff runs the upgraded CLI.
install-skill writes one file: ~/.claude/skills/askdiff/SKILL.md.
That's the entire surface area in your CC config.
In this repo (for contributors) there is one more:
/askdiff-dev— local Vite dev server with HMR + tsx-run WS server. Use when editingpackages/serverorpackages/ui-browser. Re-invoking/askdiff-dev(or/askdiff) from the same session kills the previous server, reuses its port, and points at a freshly-written diff — that's the refresh path. The WS server idle-shuts after 5 min with no clients.
The npm package (packages/cli) is a single esbuild-bundled Node
binary that hosts an HTTP server (serving the prebuilt UI bundle in
dist/ui/) and a WebSocket on the same port at /ws. The CLI
imports startServer from @askdiff/server, which spawns
claude --resume per ask and forwards text_delta events to the
client. The browser UI (packages/ui-browser) is React 19 + Vite +
Tailwind v4 + zustand, with react-diff-view for rendering and
refractor for syntax highlighting.
git clone https://github.com/narghev/askdiff
cd askdiff
pnpm install
pnpm test
pnpm lint
pnpm run buildFrom a Claude Code session in this repo:
/askdiff-dev # first launch: Vite + WS server with HMR
/askdiff-dev # again: kills the WS server, restarts on same port with a fresh diff
/askdiff-dev last commit # description-driven: HEAD~1..HEAD
The WS server idle-shuts after 5 min with no connected clients; Vite is
intentionally persistent (HMR is the whole point). Kill Vite via
Activity Monitor or pkill -f 'ui-browser.*vite' on the rare occasion
you want it gone.
To exercise the production-shaped binary locally:
pnpm run build
node packages/cli/dist/index.js --port 7838"Claude session: (none — set ASKDIFF_SESSION_ID or use --session)"
The skill couldn't read the parent CC manifest. You're either running
askdiff from outside a Claude Code session (no $PPID.json in
~/.claude/sessions/), or CLAUDE_CONFIG_DIR points somewhere
else. Pass --session <uuid> explicitly to override.
"Port 7837 is already in use"
Another askdiff (from a different session) is running, or something
else grabbed the port. Same-session re-invocations don't hit this —
they reuse their session's saved port. Pass --port 7838 to force a
specific port, or wait 5 min for the idle WS server to self-terminate.
Browser opens, UI loads, but never connects
The WS upgrade is failing. Check /tmp/askdiff.<suffix>.log (where
<suffix> is your CC session UUID) — usually it's an old UI cached
against a new server (reload the browser tab) or a hung
claude --resume subprocess (check ps aux | grep claude).
/askdiff doesn't appear in Claude Code's skill picker
Run npx -y askdiff install-skill to write
~/.claude/skills/askdiff/SKILL.md. If it's there but still missing,
restart Claude Code or run /reload-plugins.