sidepad

A read-only pane beside the transcript. /sidepad opens it and closes it again, and it opens by itself on the file Claude last wrote or edited, at the end of the turn. It shows one page at a time: a file, a directory's listing, or the files Claude edited this session. Code is drawn with the engine's own highlighter, a formatted Markdown page row by row by the hooks themselves, and a passage selected with the mouse reaches Claude through a command of the bar or the next prompt typed.

Nothing in the pane edits a file: every change is Claude's, made from what the person selected.

What it does

Each feature with its rules and its limits is in docs/features.md. In one line each:

| Part | In one line | |---|---| | Opening | /sidepad opens the pane on the page it last showed, holding the keyboard, and closes it again, and /sidepad auto [on\|off] governs its opening on Claude's edits | | Following Claude | At the end of the main loop's turn the pane shows the turn's last edited file, or marks Edited N when the person is reading something else | | Frame | The top row ends on the page's name in bold; a status line names the mode of a Markdown file or a table and the lines or entries shown | | Themes | /sidepad theme auto\|classic\|contrast sets the colours of the pane's own parts, kept across sessions | | Navigation | .., the path's directories, the listing's rows and Edited N, one page at a time, by pointer or by the arrows and Enter | | Viewer | Code with the engine's highlighting and line numbers, Markdown formatted or under Source, a .diff with its hunk headers marked, a .csv or .tsv as a table or under Source, a PNG as a picture | | Selection | A drag takes lines, a click takes the block under it, and a second click clears it | | Asking | The bar sends the selection with Explain, Find issues or Rewrite, and Ask… points at the prompt | | Files changed elsewhere | After a shell call the page is checked against the disk and follows what it finds |

Requirements

Claude Code 2.1.280 with CLAUDE_CODE_ENABLE_FUNCTION_HOOKS=1. Mods are early access and their API changes between releases, so the pane is verified against one Claude Code version at a time, and until mods are released it carries no code for an earlier one.

A hooks module may import only its own files and claude-code, so the one library the pane uses travels with it: markdown-it (MIT), the bundled ESM build under hooks/vendor/, with its license and its type declarations beside it. It reads a Markdown file into the blocks a click selects and into the inline tokens each drawn row is composed from; its own HTML renderer is never called.

The pane draws where the layout docks it beside the transcript, from 110 terminal columns when /sidepad asks for it. An edit opens it unasked, and Claude Code draws it from 144 columns (110 for a pane the person opened before); narrower, it waits undrawn until the terminal is widened or /sidepad asks for it. On the main screen a pane lands inline and two rows tall, so nothing opens there by itself.

What it hooks

| Event | What the hook does | |---|---| | session.start | Binds the engine's calls once and registers /sidepad. It runs again on a plugin reload, which starts from an empty state; a pane the engine still holds shows the session directory's listing | | command.run of sidepad | Opens or closes the pane, or reads and sets the auto-open switch or the theme | | command.run, any | Reads the terminal's width from the command's presentation | | ui.render of PromptHint | Reads the terminal's width and layout from the line the engine draws under the prompt, on the terminal only, which is how both are known before a pane exists | | ui.render of Pane | Draws the pane: the top row, the page, and the command bar over a selection | | ui.scroll of the pane | Moves the page's own window (three lines or rows a wheel tick, a page key the lines or rows the page shows) and leaves the engine's window still | | ui.message of the pane | The presses, drags and scrolls its Client surfaces post | | ui.press of the pane | The top row's Buttons, the list's rows and the bar's commands | | ui.close of the pane | Remembers a close the person made with the pane's mark | | prompt.submit | Attaches the selection to the prompt's context and clears it | | tool.call of Edit, Write, NotebookEdit | Records an edit that landed and reads the open file again | | tool.call of Bash, PowerShell | Checks the page against the disk after a command that ran | | turn.complete | The main loop's turn end reads Claude Code's theme again and decides which file the pane shows; a subagent's turn carries agentId and waits for its parent | | session.end of reason clear, resume | Closes the pane and forgets the session's edits, selection and close |

What it calls on $

command.register, config.list (Claude Code's theme setting), fs.list, fs.read, fs.stat, process.run (a window of a file too large to read whole), prompt.submit, store.get, store.set, ui.close, ui.invalidate, ui.open, ui.panes, ui.resolve, ui.status.

Limits

Every feature's limits are stated with it in docs/features.md, and the code carries each one as a // LIMIT: comment at its site. docs/limits.md lists them all, split by whether Claude Code or sidepad sets them, written from those comments by bun run limits.

Reading it from source

CLAUDE_CODE_ENABLE_FUNCTION_HOOKS=1 claude --plugin-dir plugins/sidepad

Its tests run with claude plugin test plugins/sidepad, and claude plugin validate plugins/sidepad --strict checks the manifest.