Terminal decision

The Shell tab needs a real TTY (colors, cursor keys, resize, vi/top/less). The shell is wslc exec --interactive --tty, run under a Windows pseudoconsole (ConPTY). The output is parsed by a managed VT engine and drawn natively in the XAML tree with Win2D. There is no WebView2 and no child window, so nothing can overlay other content (no airspace problems).

Options considered

Option	Verdict
Managed VT parser and screen buffer (VtScreen) drawn on a Win2D CanvasControl	Chosen. Pure XAML: clips, themes, scales and layers like any control. The VT logic is UI-free and unit tested.
Native HwndTerminal child HWND (Microsoft.Terminal.Control.dll)	Dropped. Airspace overlay bugs and a repackaged DLL with no license metadata. Kept on branch seiggy-wt-control-shell.
xterm.js in WebView2 (PR #20)	Worked, but an embedded WebView2 was rejected. Kept on seiggy-conpty-terminal-shell.
WinUI 3 TermControl (WinRT)	No maintained package.
XAML Island	Wrong direction: islands host XAML inside Win32/WPF.

How it works

• ConPtySession owns the pseudoconsole: pipe pairs, STARTUPINFOEX with PROC_THREAD_ATTRIBUTE_PSEUDOCONSOLE, a reader thread, a dedicated writer thread (UI input never blocks on the pipe), ResizePseudoConsole, and a non-blocking ClosePseudoConsole shutdown.
• VtScreen handles SGR (16, 256 and truecolor), cursor movement, erase, insert/delete, scroll regions, scrollback, the alternate screen, wide characters, line drawing, OSC titles, and answers DSR/DA queries that ConPTY sends. It tracks application cursor keys, bracketed paste and mouse modes.
• VtInput encodes keys, paste and mouse reports. TerminalView draws the grid and handles selection, copy/paste (Ctrl+C copies only with a selection, otherwise it is SIGINT; Ctrl+V, Ctrl+Shift+V, Shift+Insert paste; right-click copies or pastes), wheel and Shift+PageUp/Down scrollback, and resizing.
• Font family and size come from Settings > Terminal. Colors follow the app theme.
• If the Win2D surface can't initialise, the old piped shell is used.

ConPTY audit against MiniTerm and the pseudoconsole blog

Matches: pipe pairs, attribute list, thread-handle close, resize, reader thread, UTF-8 decoding across chunks. Deviations fixed: input was written on the UI thread (now a writer thread); shutdown ordering and handle ownership were tightened. The temporary clearing of the parent's standard handles is kept because a console-app parent (such as a test host) otherwise passes its redirected handles to the child; a GUI app has none, so it is a no-op there.

Risks

• Win2D (Microsoft.Graphics.Win2D, MIT) restores through the single repo feed; x64 and ARM64 packaging still needs a check.
• The VT engine is deliberately minimal (no sixel, no hyperlinks, no IME composition UI).
• Raw VT output bypasses secret redaction. ConPTY needs Windows 10 1809 or later.

Tests

VtScreenTests, VtInputTests and TerminalTests (command line, palettes, ConPTY output, exit code, input and resize). Interactive rendering validation (ls --color, vi, top, Ctrl+C, resize, copy/paste) is pending until UI automation is allowed.