[FEATURE REQUEST] Allow filtering @ mentions autocomplete to show only agents (hide folders)

Problem

When typing @ in Claude Code CLI, the autocomplete shows everything: folders, files, and agents. For users who primarily use @ to invoke agents (e.g., @agent-name), the folder/file suggestions create noise and slow down agent selection.

There is currently no way to configure what types of items appear in the @ mentions autocomplete.

Proposed Solution

Add a settings.json option to control what appears in @ autocomplete. For example:

{
  "mentions": {
    "showFolders": false,
    "showFiles": false,
    "showAgents": true
  }
}

Or a simpler approach:

{
  "mentionTypes": ["agents"]
}

Use Case

Power users who have many custom agents in .claude/agents/ use @ exclusively for agent invocation. Seeing dozens of folders in the autocomplete makes it harder to quickly find the right agent.

Alternatives Considered

• Using @agent: prefix to filter — doesn't exist
• Moving folders to reduce noise — impractical
• permissions.deny — only blocks Read access, doesn't filter autocomplete

Related Issues

• #20087 — Agents not appearing in @agent autocomplete
• #21587 — @.claude/ shows global instead of project-local
• #23287 — Autocomplete disappears in subdirectories
• #8543 — Custom Symbol Autocomplete Providers

Environment

• Claude Code on Windows 11
• Many custom agents in ~/.claude/agents/
• Working directory has multiple project folders