surshar / claude-code

Claude Code is an agentic coding tool that lives in your terminal, understands your codebase, and helps you code faster by executing routine tasks, explaining complex code, and handling git workflows - all through natural language commands.

Built by Anthropic · github.com/anthropics

claude-code / mods / diff / README.md

Alice T'Poteatdiff: a resumed session with edits opens the pane before any new edit, /clear leaves it up, and the session line follows the engine's start (#95587) 7974a70 · on Sep 20, 2026 History

101 lines · 6.7 KBPreview CodeRaw

1	# diff
2
3	The diff pane as a plugin: `/diff` opens the session's uncommitted changes
4	beside the transcript, one row per changed file and every file's hunks
5	beneath, and closes it again; each toggle leaves `Diff panel shown` or
6	`Diff panel hidden` in the transcript. The header, the file list and its
7	toggles stay put while the wheel moves the hunks under them three rows a
8	tick, or the list a file a tick while the wheel is over a list longer than
9	its eight rows (the plugin answers the pane's `ui.scroll` itself); a row's
10	click puts that file's hunks at the top; the list also scrolls under the
11	built-in's list keys (`ctrl+up`/`ctrl+down`, `opt+up`/`opt+down`), and
12	`ctrl+x b` moves the comparison base on, as the built-in's chord does: both
13	through Buttons that declare the engine's own actions. The pane refreshes
14	as Claude edits and runs shell commands, and while it is open it polls
15	the repository's HEAD so a commit or checkout made elsewhere shows too.
16	The main loop's first successful edit of a session opens the pane by
17	itself, as the built-in panel opens on its first checkpoint: where the
18	layout docks it beside the transcript (the fullscreen layout, which each
19	drawing's `viewport` says), the terminal is wide enough (144 columns when
20	the person never chose, 110 when they kept it open before; a person who
21	closed it is left alone) and file checkpointing is on; a subagent's edit
22	opens nothing, and where the surface does not say, nothing opens by
23	itself. A docked pane fetches before it opens, as the built-in panel
24	primes its data, so it never lands on `Loading diff…`; an open the engine
25	leaves waiting undrawn is withdrawn, so no later resize seats it, and the
26	next edit asks again. A session resumed or continued whose transcript
27	already holds such an edit opens the pane on the same terms as soon as the
28	width is known, as the built-in opens on the history it restores.
29
30	Under the fullscreen layout a terminal under 110 columns gets the
31	built-in's line asking for a wider one and nothing opens. Without that
32	layout (`CLAUDE_CODE_NO_FLICKER=0`, which `/diff` learns from the command's
33	`presentation`) the pane opens inline at any width, focused and as tall
34	as its content (the open's `rows`), in the built-in dialog's shape: the
35	title, the count, five file rows at a time round the selected one (`❯`,
36	where the focus ring starts; the plugin follows the ring's walk through
37	`ui.focus` and re-centres the rows as the built-in does), the key hints;
38	Enter shows that file's hunks alone,
39	Escape backs out to the list and then closes, leaving `Diff dialog
40	dismissed`; toasts are held while it is up. A file's ask button arms that
41	file: its hunks ride the next prompt as context, once.
42
43	The pane compares the working tree against HEAD, split at the session's
44	start (the default; the start the engine gives in `$.session.usage()`, so a
45	resumed session keeps its first and `/clear` begins anew), against HEAD
46	plainly, or against the merge-base with
47	the default branch; the base line under the header names a base other than
48	the session's, and the choice is kept per repository in the plugin's store.
49	A picker shows one earlier turn's edits instead of the working tree, read
50	from the session's messages. Files that changed before the session started
51	(by their timestamp, among the paths already dirty when the pane first
52	read the repository), and noise (lockfiles, generated and test files), are
53	listed apart and folded until asked for; a rename lists as git prints it.
54	Outside a git repository `/diff` says so and does nothing else.
55
56	Git runs when the built-in panel's would: nothing at the session's start;
57	one `git rev-parse`, in the directory the session started in, when `/diff`
58	or the first edit a pane has room to open on first needs the repository
59	(an answer of no repository is kept too, until `/clear` or `/resume`
60	forgets it); and the working tree is read only by a fetch for a pane that
61	is open, after an edit that landed or a shell command that ran. The one
62	read the built-in has no counterpart for is a `git status` at a pane's
63	first fetch, which stands in for the change time the built-in dates a
64	moved file by.
65
66	`hooks/register.ts` is the module; everything under `hooks/` is its parts.
67
68	## What it hooks
69
70	\| event \| what the hook does \|
71	\| --- \| --- \|
72	\| `session.start` \| Binds the engine once and registers `/diff` (a session where another `/diff` is listed leaves the plugin idle); asks nothing of the repository, which `/diff` or the first edit pins when it comes; off its dispatch, reads the transcript, and for a resumed session whose turns edited opens the pane as the first edit would. \|
73	\| `ui.render` of `PromptHint` \| Reads the terminal's width and whether its layout docks a pane, which decide whether the first edit opens the pane. \|
74	\| `ui.render` of `Pane` \| Draws the pane: docked, the header, base line, source picker, file list and toggles over the window of hunks; inline, the dialog. \|
75	\| `command.run` of `diff` \| Pins the repository when none is, opens or closes the pane (focused and closing on Escape without the fullscreen layout), says which, and remembers the choice. \|
76	\| `ui.close` of the pane \| Backs out of the dialog's detail view instead of closing; else remembers the person's close as `/diff`'s. \|
77	\| `ui.scroll` of the pane \| Docked, moves the hunks under the pinned header and list (three rows a wheel tick, a page a page key), or the list when the wheel is over it, and keeps the engine's window still. \|
78	\| `ui.focus` in the pane \| In the dialog's list, selects the file the ring lands on, re-centres the five rows on it, and lands the ring where that row now sits. \|
79	\| `command.run` of `clear`, `resume` \| Closes the pane and forgets the session's state, the pinned repository with it. \|
80	\| `tool.call` of `Edit`, `Write`, `NotebookEdit` \| After an edit that landed (not refused, not failed), refreshes an open pane; the main loop's first such edit opens it, pinning the repository then if the terminal has the room and checkpointing is on. \|
81	\| `tool.call` of `Bash`, `PowerShell` \| After a command that was not refused, failed and interrupted ones too, refreshes an open pane. \|
82	\| `prompt.submit` \| Adds the armed file's hunks to the prompt's context and disarms. \|
83
84	## What it calls on `$`
85
86	`clock.after`, `clock.every`, `clock.now`, `command.register`, `env.get`
87	(`CLAUDE_CODE_DISABLE_FILE_CHECKPOINTING`), `fs.list`, `fs.read`, `fs.stat`,
88	`process.run` (git, read-only), `session.id`, `session.messages`,
89	`settings.read`, `store.get`, `store.set`, `telemetry.log`, `telemetry.mark`,
90	`ui.close`, `ui.invalidate`, `ui.log`, `ui.open`, `ui.resolve`, `ui.status`.
91
92	`$.telemetry` is the telemetry plugin's noun; where it is absent the rows
93	are dropped and nothing else changes.
94
95	## Try it
96
97	```sh
98	claude --plugin-dir /path/to/diff
99	```
100
101	then `/diff` inside a git repository with a modified file.