improvement(copilot): only ask for a preview derivative on image thumbnails

A video has no derivative path, so preview=1 there only spent a brand sniff
per request. Adds the missing test coverage for the helper.

Author: waleedlatif1

apps/sim/lib/copilot/chat/attachment-preview.test.ts

@@ -0,0 +1,35 @@
+/**
+ * @vitest-environment node
+ */
+import { describe, expect, it } from 'vitest'
+import { getMothershipAttachmentPreviewUrl } from './attachment-preview'
+
+describe('getMothershipAttachmentPreviewUrl', () => {
+  it('asks for a preview derivative on images', () => {
+    const url = getMothershipAttachmentPreviewUrl({
+      key: 'copilot/a.heic',
+      media_type: 'image/heic',
+    })
+    expect(url).toContain('preview=1')
+  })
+
+  it('omits preview on videos, which have no derivative path', () => {
+    const url = getMothershipAttachmentPreviewUrl({ key: 'copilot/a.mp4', media_type: 'video/mp4' })
+    expect(url).not.toContain('preview')
+    expect(url).toContain('context=mothership')
+  })
+
+  it('returns undefined for a non-renderable attachment', () => {
+    expect(
+      getMothershipAttachmentPreviewUrl({ key: 'copilot/a.pdf', media_type: 'application/pdf' })
+    ).toBeUndefined()
+  })
+
+  it('encodes the key so a slashed storage key stays one path segment', () => {
+    const url = getMothershipAttachmentPreviewUrl({
+      key: 'copilot/nested/a b.png',
+      media_type: 'image/png',
+    })
+    expect(url).toContain(encodeURIComponent('copilot/nested/a b.png'))
+  })
+})

apps/sim/lib/copilot/chat/attachment-preview.ts

@@ -2,10 +2,13 @@ export function getMothershipAttachmentPreviewUrl(file: {
   key: string
   media_type: string
 }): string | undefined {
-  if (!file.media_type.startsWith('image/') && !file.media_type.startsWith('video/')) {
+  const isImage = file.media_type.startsWith('image/')
+  if (!isImage && !file.media_type.startsWith('video/')) {
     return undefined
   }
-  // `preview=1`: this URL only ever backs a rendered thumbnail, so the serve route may
-  // substitute a browser-renderable derivative for a format no browser decodes (HEIC).
-  return `/api/files/serve/${encodeURIComponent(file.key)}?context=mothership&preview=1`
+  // `preview=1` only for images: this URL backs a rendered thumbnail, so the serve route
+  // may substitute a browser-renderable derivative for a format no browser decodes (HEIC).
+  // A video has no derivative path, so asking would only spend a brand sniff per request.
+  const preview = isImage ? '&preview=1' : ''
+  return `/api/files/serve/${encodeURIComponent(file.key)}?context=mothership${preview}`
 }