Tool call fails with 'Invalid tool parameters' after assistant text output

Description

During a refactoring session, Claude outputs assistant text (e.g. "Начинаю рефакторинг. Сначала нужно найти точные сигнатуры методов в api.ts и все места их использования.") and then immediately attempts a tool call that fails with:

Invalid tool parameters

Steps to reproduce

1. Ask Claude to perform a refactoring task
2. Claude writes a text message about its plan
3. Claude attempts to call a tool (e.g. Grep or Read) with invalid parameters
4. Error appears inline in the conversation

Expected behavior

Tool calls should be made with valid parameters, or Claude should detect invalid parameters before attempting the call.

Actual behavior

The tool call is attempted with invalid parameters and fails visibly in the conversation.

Environment

• Claude Code CLI
• Model: claude-sonnet-4-6
• Platform: macOS (darwin 24.6.0)