PreToolUse Hook Fixes Claude Code Image Crash Problem

A developer has shared a PreToolUse hook that addresses Claude Code's image processing crashes, specifically API Error 400: "Could not process image." The hook intercepts problematic images before they enter the main context, preventing session failures.

Problem Description

The source identifies specific image types that cause Claude Code sessions to crash: PNG files with transparency, large screenshots, and multiple images. Once a problematic image enters the context, every subsequent message errors out. Users can sometimes recover by double-escaping back, but this results in lost context and tokens.

Solution Implementation

The solution is a PreToolUse hook that:

• Intercepts Read calls on images
• Converts images safely before processing
• Proxies them through a Haiku subprocess
• Ensures zero image data enters the main context

This approach prevents the API Error 400 crashes by handling image processing externally before Claude Code attempts to read them.

Technical Details

The hook specifically targets the Read tool use calls that involve images. By using a Haiku subprocess for image conversion and proxying, it isolates potentially problematic image data from the main Claude Code session context. This prevents the cascade of errors that occurs once a bad image enters the context.

The developer notes this solution eliminates the need to double-escape back to recover from crashes, preserving both context and tokens during sessions involving images.