Feature Request: Multimodal Image Support via @ File Search

What feature would you like to see?

Multimodal Image Support via @ File Search

Problem: Codex CLI has full backend infrastructure for OpenAI Vision API but no way for users to send images in interactive mode.

Solution: Extend the existing @ file search system to detect image files and display them as [Image #1] placeholders while sending actual image data to the Vision API.

Usage Example:
user> @screenshot.png explain this UI
[TAB to select image]
user> [Image #1] explain this UI

codex> This interface shows a terminal with...

Benefits:

• Unlocks existing unused multimodal capabilities
• Uses familiar @ syntax with TAB completion
• Clean visual feedback with numbered placeholders
• Zero breaking changes to existing functionality
• Maintains chat history readability

Are you interested in implementing this feature?

Yes, I have a working prototype that extends the existing file search system. I will wait for acknowledgement before opening a PR.

Additional information

The implementation builds on existing infrastructure:

• InputItem::LocalImage already exists in protocol
• OpenAI Vision API integration already works
• @ file search popup system already exists
• Only missing piece is image detection in file search UI

Implementation preserves all existing functionality while adding seamless image support.

Technical Details:

• Supports jpg, jpeg, png, gif, webp, bmp formats
• Extends ChatComposer::insert_selected_path() to detect images
• Creates numbered placeholders [Image #1], [Image #2] for display
• Sends cleaned text + actual image data to AI processing
• Maintains backward compatibility with existing @ file search