Mullion

Windows Terminal, with more in it. A personal fork of microsoft/terminal that evolves on its own terms: features land here because they belong in this terminal, whether or not upstream would ever take them. Named for the upright bar between window panes.

 ·  mullion.aylith.com: the feature tour, with screenshots

What it adds

Links that do something

• Paths are links. Windows, UNC and POSIX paths in the output are detected, ~/... included, and resolved in the right WSL distribution. That includes file:// links with fragments and /mnt/<drive>/ paths. A path that exists in two distributions is shown as ambiguous rather than guessed.
• Click without Ctrl, if you like, even inside tmux and other mouse-mode apps. The primary and alternative click gestures, modifiers and actions are all configurable, and detection is separate from clickability.
• A link card instead of a tooltip. It has a show/hide delay and action buttons: Open, Copy link, Copy path, Show in Explorer and Show in pane. It renders Markdown and stays inside the pane on both axes.
• File previews for text, Markdown (rendered or raw), syntax-highlighted source and Office documents, plus images and media fitted to the card or to a dedicated preview pane.
• Integrations for GitHub, Jira, Slack, Stith, shefrd and Unblocked Code. An issue key, PR link or Slack permalink turns into a live preview, and Jira tables, callouts and comments survive the trip.
• Tooltip rules written as ICU regexes, with presets, per-rule actions and plain-text matching, so any token in the output can become a link.

Path policy, file types and integration manifests are shared with a sibling Tabby fork through Lintel, so both terminals resolve the same text the same way.

Tabs, windows and panes

• Tab strip on any edge, with the new-tab button where you want it, tab numbers, and window-level overrides for tab icons and close buttons.
• Dock the window to a screen edge at a fixed size, and remember window geometry, so each window reopens where it was.
• Pane title bars with draggable dividers, and a configurable pane resize step.
• Safer closing. Warn only above a tab threshold, and never ask a lone window whether to "close all windows".
• Motion follows Windows or overrides it in either direction.
• Colour schemes in light/dark pairs that follow the OS theme, with per-scheme control of how indistinguishable text is adjusted.

Coming back to where you were

• Session restore that resumes work. Coding agents and multiplexers (tmux, screen, zellij, herdr, shefrd) are recognised, and restored panes attach or resume instead of starting a bare shell.
• Pane contents saved periodically, on a clock, not only at exit.

Scriptable from outside

• Control pipe. A per-process named pipe, restricted to the current user, that can list panes, capture their text, send input and focus a pane. See doc/control-pipe.md.
• Activity log. A record of what the Terminal started and what was handed to it, readable in a pane and on its own Settings page.

A Settings UI that knows what changed

• New pages: Link Tooltip, Integrations, Session Restore, Activity, and in-app Documentation.
• Search that is always a box and remembers what you chose. The shortcut list is searchable and lets you type a chord to find it.
• Hover Save or Discard to see exactly what would change.
• Fork marks, if you want them: a filled mark on every setting this fork adds, and a hollow ◇ on settings upstream supports but only exposes in JSON. The ones still without a UI are listed in doc/json-only-settings.md.

Getting a build

Builds happen in CI, never locally. A warm local tree runs to about 40 GB per checkout. Every push to main runs build.yml, which builds and tests both slots, packages them, and uploads one artifact for both.

This machine runs two Terminals built from this repo, side by side:

Slot	Alias	What it is
Dev	muld	The one I live in. It changes only when I press promote inside it.
Test	mult	Disposable. Refreshed on demand to verify a build in a window of its own.

• tools/Fetch-CIBuild.ps1 stages the newest successful build for both slots.
• tools/Install-CIBuildPoller.ps1 does that on a timer. The interval is a Settings option.
• muld notices a staged build and offers to promote it.
• tools/Refresh-TestSlot.ps1 puts the staged Test build into mult.

When a build will not start, read doc/troubleshooting.md first. For crashes and silent XAML failures, use the terminal-fork-diagnostics skill in .claude/skills/.

The process is mullion.exe. Package identities, the window class and credential keys keep their Windows Terminal names on purpose, so existing settings and saved tokens survive the rename.

Working on it

AGENTS.md is the rulebook, for people and agents alike: the two slots, what may and may not be restarted, line endings, CI etiquette, and the traps that each cost a 40-minute CI round to learn.

After cloning, enable the hook that refuses commits which flip a file's line endings wholesale:

git config core.hooksPath tools/githooks

Relationship to upstream

Upstream is merged in, never rebased onto, for its bug and security fixes. Its issues and pull requests are read before anything here is built. Nothing goes back: no pull requests to microsoft/terminal, and the upstream remote cannot push. Conflicts resolve in favour of this fork's behaviour, and divergence is the point.

For the Terminal itself, its documentation and its history, see microsoft/terminal.

License

MIT, as upstream. See LICENSE. Windows Terminal is © Microsoft Corporation; this fork's changes are © their author.