## Description
Inbound email attachments are stored with `file_type: 'file'` regardless
of their actual MIME type. As a result, image screenshots shared by
customers via email are not exposed to Captain V2's multimodal pipeline
— `Captain::OpenAiMessageBuilderService#attachment_parts` selects images
via `attachments.where(file_type: :image)` and emits a placeholder
`"User has shared an attachment"` text part instead of an `image_url`
part. The model never gets the image, so Captain keeps asking the
customer to retype information that is already visible in the
screenshot.
This PR makes the email mailbox derive `file_type` from the blob's
`content_type` using the existing shared `FileTypeHelper`, matching how
every other inbound channel (`twilio`, `sms`, `telegram`, `line`,
`tiktok`, `twitter`, `messenger`) and `MessageBuilder` already classify
attachments.
Fixes#14448
## Type of change
- [x] Bug fix (non-breaking change which fixes an issue)
## How Has This Been Tested?
Reproduced and verified on a self-hosted production instance:
1. Real customer reply via email with a PNG screenshot of an in-app
error.
Before:
```ruby
a = Message.find(<id>).attachments.first
a.file_type # => "file"
a.file.blob.content_type # => "image/png"
Captain::OpenAiMessageBuilderService.new(message:
a.message).generate_content
# => [{type: 'text', text: '...'},
# {type: 'text', text: 'User has shared an attachment'}] ❌ no image_url
```
Captain reply: "Please copy and paste the full error text…" (model never
saw the image).
2. After the patch + force-recreate, same conversation:
```ruby
a.file_type # => "image"
Captain::OpenAiMessageBuilderService.new(message:
a.message).generate_content
# => [{type: 'text', text: '...'},
# {type: 'image_url', image_url: {url: 'https://.../<blob>.png'}}] ✅
```
Captain reply now correctly references the on-screen error text from the
screenshot via the multimodal vision path — no more deflection.
3. Regression sanity-check on non-image attachments (PDF / Office docs):
`file_type` falls through to `:file`, behavior unchanged.
## Notes for self-hosted operators
Existing email image attachments in the DB will still have `file_type:
'file'`. A one-shot backfill is straightforward and safe (no data loss,
only metadata):
```ruby
Attachment.joins(message: :conversation)
.where(messages: { content_type: 'incoming_email' })
.where(file_type: 'file')
.find_each do |a|
next unless a.file.attached?
ct = a.file.blob.content_type.to_s
next unless ct.start_with?('image/', 'audio/', 'video/')
new_type = ct.start_with?('image/') ? :image : (ct.start_with?('video/') ? :video : :audio)
a.update_columns(file_type: Attachment.file_types[new_type])
end
```
## Checklist
- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [x] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective — happy to add a
`mailbox_helper_spec` example for `process_regular_attachments` if
maintainers prefer; existing specs in that file focus on inline-image
handling.
---------
Co-authored-by: Aakash Bakhle <48802744+aakashb95@users.noreply.github.com>
