Allow new attachments for previous messages in a chat

[Slava-256]

What's happening?

If you have an attachment in a previous message in a chat, I am not able to find a way to update the attached file.

I can click on a file attached to a previous message, and it gives me "Delete" and "Edit" buttons.

If I delete the file, I can no longer attach a new one to a previous message.

I can only attach a file to a new message by clicking "Attach" next to the edit box for the new message. I cannot seem to find an equivalent functionality for previous messages in the chat.

Even if I click the Edit option for a previous message text, it does not give me an option to attach a file.

Where does this happen?

Big-AGI Pro (big-agi.com)

Impact on your workflow

None

Environment (if applicable)

No response

Additional context

No response

[github-actions]

Thanks for the detailed report!

Assessment: This is a valid feature request. You've identified a gap in the current UX - while the data model and backend operations fully support attachments on existing messages, the UI to add new attachments to previous messages doesn't exist yet.

Current behavior:

• Attachments can be deleted or edited (content only) on previous messages ✓
• New attachments can only be added via the Composer (for new messages)
• The message edit mode only exposes text editing, not attachment addition

Technical details:

• The infrastructure is in place: messageFragmentAppend() can accept attachment fragments
• Attachment creation utilities exist (createDocAttachmentFragment(), etc.)
• The gap is purely UI - no "Add Attachment" button exists in the message edit context

Workaround for now: Copy the previous message content to a new message where you can add attachments, then delete the old message if needed.

Implementation path (for contributors/maintainers):

1. Add attachment UI to ChatMessage.tsx edit mode (similar to Composer's attachment buttons)
2. Create a reusable attachment drafts hook or extract from Composer
3. Wire the attachment fragment creation to the existing onMessageFragmentAppend callback

Key files: src/apps/chat/components/message/ChatMessage.tsx, src/apps/chat/components/composer/Composer.tsx

No duplicates found.

[enricoros]

This would be a great feature. I think I'd need to unify the input methods or the authoring/editing of messages. There's the bottom "Composer", then the quick inputs used in floating windows, the inline message editing (e.g. we fixed on #934), the inline 'attachments' editing (e.g. editing a doc in a message), etc.. needs a cleanup.
Would love to be able to work on it.