VSCode extension: slash commands (/fast, /model) sent to terminal instead of interpreted

Description

When typing slash commands like /fast, /model, /compact in the Claude Code chat input panel in VSCode, they are routed to the PowerShell terminal as claude /fast instead of being interpreted as internal slash commands by the extension.

Steps to Reproduce

1. Open VSCode with Claude Code extension installed
2. Open the Claude Code chat panel (right-side panel)
3. Type /fast in the chat input and press Enter
4. Observe: the command is sent to the PowerShell terminal as claude /fast instead of toggling fast mode

Expected Behavior

Slash commands typed in the chat input should be processed by the Claude Code extension internally (e.g., /fast should toggle fast mode, /model should allow model selection).

Actual Behavior

The slash command is forwarded to the integrated terminal as a shell command (claude /fast), which fails with:

claude : The term 'claude' is not recognized as the name of a cmdlet, function, script file, or operable program.

Environment

• OS: Windows 11 (build 26100)
• VSCode: Latest stable
• Shell: PowerShell (default integrated terminal)
• Claude Code extension: Latest from marketplace

Workaround

Settings can be configured directly in ~/.claude/settings.local.json instead of using slash commands:

{
  "model": "opus",
  "fastMode": true
}

Screenshot

The screenshot below shows /fast typed in the Claude Code chat input, with the terminal showing it was routed to PowerShell as claude /fast:

!slash-command-bug

(Unable to attach screenshot via CLI — see description above for reproduction steps)

<img width="3837" height="2359" alt="Image" src="https://github.com/user-attachments/assets/daf02079-254c-4b97-8b83-cdbc055c4f0c" />