JetBrains/PyCharm: Messages appear multiple times in chat UI, causing double token charges

Bug Report

Summary

When using Claude Code inside PyCharm (JetBrains extension), each user message appears multiple times in the chat UI. The duplication results in the query being processed more than once, which doubles token usage and cost.

Environment

| Field | Value |
|-------|-------|
| Claude Code version | 2.1.107 |
| IDE | PyCharm 2025.3.3 |
| OS | macOS 26.3 (Build 25D125) |
| Custom keybindings | None (~/.claude/keybindings.json does not exist) |
| Hooks configured | None |

Steps to Reproduce

1. Open Claude Code inside PyCharm (JetBrains extension)
2. Type any message and submit it
3. Observe the chat UI

Expected Behavior

Each submitted message appears once and is processed once.

Actual Behavior

The same message appears multiple times in the chat UI. This causes the query to be processed multiple times, resulting in approximately 2x the expected token consumption and cost.

Additional Context

• No custom keybindings or submit hooks are configured, ruling out accidental double-submit via keybinding conflict
• Issue appears specific to the PyCharm/JetBrains integration — not reproduced when running Claude Code from a plain terminal
• No workaround currently known

Impact

Double billing on every query when using the JetBrains extension.