Markdown links with custom URL schemes (e.g. obsidian://) not rendered as OSC 8 hyperlinks

Description

Claude Code's markdown renderer generates OSC 8 terminal hyperlinks for http:// and https:// URLs, but not for custom URL schemes like obsidian://, vscode://, etc.

Environment

• Claude Code: latest (via claude CLI)
• Terminal: Ghostty (xterm-ghostty)
• tmux: 3.6a with terminal-features 'xterm*:hyperlinks'
• OS: macOS (Darwin 24.6.0)
• FORCE_HYPERLINK=1 set in settings.json env

Steps to Reproduce

1. In Claude Code running inside tmux + Ghostty, output a markdown link with a custom scheme:

``
[Open in Obsidian](obsidian://open?vault=MyVault&file=test)
``

1. The link text is displayed, but it is not clickable (no OSC 8 hyperlink generated).
2. An https:// link in the same output is clickable.

Verification that the terminal supports custom scheme OSC 8

Running this directly in the same terminal session produces a clickable link that opens Obsidian:

echo -e '\033]8;;obsidian://open?vault=Obsidian&file=test\033\\Click to open Obsidian\033]8;;\033\\'

Similarly, vscode:// links also work via raw OSC 8:

printf '\033]8;;vscode://file//home/user/project/main.go\033\\Open in VS Code\033]8;;\033\\'

This confirms the terminal stack (Ghostty + tmux) fully supports OSC 8 hyperlinks with custom URL schemes. The issue is that Claude Code's renderer does not generate them.

Expected Behavior

Markdown links with any valid URL scheme should be rendered as OSC 8 hyperlinks, not just http(s)://.

Workaround

Using the open command via Bash tool to open custom-scheme URLs, but this loses the inline clickable link UX.