Markdown is the handshake format between you and your agent.
That's the file type worth supporting well. Not all files. This one. ## What does the viewer actually do? *PonyMux interface view: files.* It's a read-only Markdown renderer that lives in the Side Panel, next to Sessions. Press `⌥⌘F` or click the toolbar button. It renders `.md` files with styled headings, code blocks, tables, task lists, and inline images. There are three ways to open a file: - **Click a `file://` link** in terminal output — if it points to a `.md` file, PonyMux opens it in the viewer instead of Finder. - **`pony open## Can agents open files for you? This is the part I'm most interested in. The viewer isn't just something you open manually — agents can push files into it. When an agent finishes writing a plan, it can run `pony open plan.md` and the file appears in your Side Panel. A small toast shows who sent it — "Opened by Claude Code" or "Opened by Codex" — so you know why the panel popped up. The same thing happens with `file://` links. If an agent prints a path to a markdown file in its output and you click it, the viewer catches it. No Finder window. No editor launch. Just the rendered file, right there beside the terminal. This flips the usual direction. Instead of you going to find the file, the file comes to you. The agent produces a document, and it shows up where you're already looking. It's a small workflow change. But after using it for a few days, going back to `cat DECISIONS.md` feels like a step backwards. ## How does it stay light? The viewer borrows a few ideas from a browser without trying to become one. Back and forward navigation works within the panel. Click a relative `.md` link inside a rendered file and it navigates in place — no new window, no stack of tabs. The chevrons in the header track where you've been. You can pin up to ten files for quick access. Pinned files and recent files show up in the empty state when nothing is open. Each terminal maintains its own browsing history, so switching terminals swaps the context. The history is deliberately ephemeral. Quit PonyMux and it clears. The viewer doesn't track what you've read across sessions or build a project model out of your file visits. It's browsing state, not persistent data. One detail I like: the viewer renders through the terminal's own surface. Same font, same theme, same copy behavior. If you change your terminal theme, the viewer changes with it. It doesn't look like a different app was embedded beside your terminal — because it wasn't. File watching keeps it current: edit the file in your editor, the viewer refreshes automatically. ## Just enough, not everything There's a version of this feature that supports every file type, has syntax highlighting for source code, and lets you edit inline. That version would be genuinely useful. It would also mean PonyMux is now competing with the editor you already have. I'd rather keep the boundary. Agents are getting better at reading and writing code. The part where humans still need to look carefully is the coordination layer — the plans, the decisions, the context documents that tell the agent what to do and tell you what it did. A read-only markdown viewer is a small, specific answer to that. It doesn't try to replace your editor. It doesn't try to show you everything. It shows you the one format that matters most for the way agents and humans work together right now. For the full details — keyboard shortcuts, pinning, and how `pony open` works from scripts — see the [Files section in the docs](/docs/workspace-navigation#files).Agents are doing more of the writing. What you need more of is a place to read.