Unclear Which specific feature (artifact handling, attachments, or something else) consumes this map is not stated.
What
Claude Code's internal map of file extensions to MIME types (labels describing a file's content type) gained entries for .ts and .js/.mjs/.cjs files (mapped to text/plain) and .css files (mapped to text/css), alongside a JavaScript mapping to text/javascript.
Why
This likely improves how these common code file types are handled when attached or used as artifacts, since they can now be correctly identified by type instead of falling back to a generic or missing classification.
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The writer flagged doubt
Which specific feature (artifact handling, attachments, or something else) consumes this map is not stated.