Pasted File Editor
Simon Willison · Simon Willison · 2026-06-02
Simon Willison built a Pasted File Editor prototype using Codex desktop that replicates Claude's large-paste detection feature, converting large text pastes into file attachments and supporting file open and drag-and-drop including image thumbnails.
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Extraction
Topics: ai-assisted-programmingdeveloper-toolsclaudecodex
Claims
- Claude.ai and the Claude desktop and mobile apps automatically detect large text pastes and convert them into file attachments.
- Simon Willison used Codex desktop to build a standalone prototype that replicates this paste-to-file behavior.
- The prototype supports opening files directly and dragging files onto the textarea, with images displayed as thumbnails.
Key quotes
I really like how you can paste a large volume of text into claude.ai (or the Claude desktop/mobile apps) and it will detect it as a large paste and turn it into a file attachment instead.