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Preview panel

The Preview panel is Headmaster’s multi-format file viewer. When the agent writes a file or you click a file in the File Manager, the preview panel opens next to the chat showing the file rendered in the appropriate format.

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Supported formats

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Panel layout

The Preview panel is a tabbed interface:
  • Multiple tabs — open multiple files at once and switch between them.
  • Split view — drag a tab to split the panel into two side-by-side views. Useful for comparing two files.
  • Pop out — click the pop-out button to open the preview in a separate window.
The panel can be:
  • Docked right (default) — preview on the right, chat on the left.
  • Docked bottom — preview on the bottom, chat on top.
  • Hidden — click the toggle to give the chat full width.

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Automatic previews

The preview panel opens automatically when:
  • The agent writes a new file
  • The agent creates a new Office document
  • The agent edits an existing file (shows a diff)
Disable auto-open in Settings → My Headmaster → Look → Auto-open previews.

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Editing in the preview

  • Edit tab — write markdown with syntax highlighting.
  • Preview tab — see the rendered markdown in real time.
  • Save with Cmd/Ctrl + S — writes the file to disk.

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Diff viewer

When the agent edits an existing file, the preview panel shows a diff:
  • Side-by-side — original on the left, modified on the right. Added lines in green, removed lines in red.
  • Inline — changes shown in a single view. Added lines prefixed with +, removed with -.
Toggle between views with the toolbar button. The diff viewer supports syntax highlighting, word-level diffs, and a minimap for navigating large diffs.

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Office document previews

For Office documents, the preview is read-only:
  • PowerPoint — slide navigator on the left, current slide on the right.
  • Excel — sheet tabs at the bottom, cell grid in the main area. Formulas shown as calculated values.
  • Word — rendered document with headings, paragraphs, tables, and images.
Click Open externally to edit in PowerPoint, Excel, or Word.

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PDF viewer

The PDF viewer includes:
  • Page navigator (jump to any page)
  • Zoom in / out
  • Fit to width / fit to page
  • Text selection (copy text from the PDF)
  • Search within the PDF

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Context menu

Right-click in the preview panel for:
  • Copy — copy selected text or content
  • Save / Save as — save changes or save a copy
  • Reveal in folder — open the file’s location in your OS file manager
  • Open externally — open in the default OS application (e.g., .pptx in PowerPoint)
  • Close tab / Close all tabs

File management

Open files in the preview from the File Manager.

Documents

Office documents preview automatically when generated.