[FEATURE] Desktop app: support HEIC/HEIF photos as attachments

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

iPhone photos are HEIC by default, so most photos on a Mac are HEIC. When I drop a HEIC photo into the Claude desktop app on macOS, it says it can't read the file. I have to convert each photo to JPEG by hand first.

Proposed Solution

Accept HEIC and HEIF files in the desktop app, at the least. The app can convert them to JPEG on the user's machine before it sends them. On macOS, the built-in sips tool or the ImageIO framework can do this with no new dependency. Keep the photo's orientation during the conversion (see #22598).

Alternative Solutions

Today I convert each photo to JPEG first, in Preview or with sips, and then attach the JPEG. That works, but it is an extra step for every photo, and dropping the original is the natural action.

Priority

Medium - Would be very helpful

Feature Category

File operations

Use Case Example

1. I take a photo on my iPhone. It syncs to my Mac as a .HEIC file.
2. I drag it into the Claude desktop app.
3. Today: the app says it can't read the file. Expected: Claude sees the photo.

Additional Context

#76492 asked for the same thing in the VS Code extension. A bot closed it as inactive on 2026-09-19 and asked for a new issue if it is still relevant. It is.