Claude Code surfaced a hallucinated tip suggesting a non-existent /plugin install command

Description

During a Claude Code session, a tip appeared in the UI (during model processing/thinking) that suggested running the following command:

/plugin install frontend-design@claude-plugins-official

The tip read something like: "Tip: Working with HTML/CSS? Install the frontend-design plugin: /plugin install frontend-design@claude-plugins-official"

Problem

This command does not exist. When the user attempted to run it:

• In the terminal: zsh: no such file or directory: /plugin
• Via the ! prefix inside Claude Code: same error

After investigation, frontend-design does not appear to be a real plugin in any official registry, and the /plugin install command itself does not appear to be a valid Claude Code command.

Concern

Tips that appear to come from the Claude Code interface itself carry implicit trust. A hallucinated tip suggesting a shell command is a meaningful security/trust concern — users are likely to act on tips that appear to originate from the tool rather than from model output.

Steps to Reproduce

The tip appeared spontaneously during a session involving HTML/CSS work (generating PDFs from markdown via pandoc and weasyprint). The exact trigger is unknown.

Environment

• Claude Code version: current (April 2026)
• OS: macOS (Darwin 25.3.0, Apple Silicon)
• Model: claude-sonnet-4-6