Arabic/RTL text renders broken in the terminal (xterm.js limitation)

[omaralbeik]

Arabic (and other RTL/complex scripts) renders incorrectly in the session terminal: letters appear in isolated, unjoined forms and in the wrong visual order.

Root cause: xterm.js has no contextual shaping or BiDi/RTL support. It renders one glyph per grid cell, which structurally can't join Arabic letters or reorder RTL runs. This affects all renderers (WebGL/Canvas/DOM) and isn't specific to our code.

Scope: Display only — typed input bytes reach the agent intact (UTF-8 correct). It's purely cosmetic.

Upstream / prior art:

• Support RTL languages xtermjs/xterm.js#701 (open for years, not on roadmap)
• Arabic text appears disjointed (not connected) in VS Code integrated terminal — missing RTL and Arabic shaping support microsoft/vscode#271615, Arabic (RTL) Rendering Issues in Integrated Terminal on macOS microsoft/vscode#296495 (same bug in VS Code's terminal)
• "Arabic/RTL Text Support with BiDi Rendering" ghostty-org/ghostty#9774 (FriBidi + HarfBuzz approach — the only known fix, requires replacing the renderer)

Options: accept as a known upstream limitation, or replace xterm.js with a shaping-capable renderer (large effort). No config flag or addon fixes it.