improvement(buffer): explicit mediaType override instead of guessing on ambiguous media (#5642)

waleedlatif1 · web-flow · commit e7afe45b2df8 · 2026-07-13T14:48:16.000-07:00
* improvement(buffer): explicit mediaType override; error instead of guessing on ambiguous media

* fix(buffer): forward validated mediaType from routes into the media resolver

* fix(buffer): presign uploaded media for 7 days — Buffer fetches assets at publish time

* docs(buffer): document presign lifetime bound by signing credentials

* fix(buffer): always mint fresh presigned URLs from verified storage keys for media
diff --git a/apps/docs/content/docs/en/integrations/buffer.mdx b/apps/docs/content/docs/en/integrations/buffer.mdx
@@ -33,7 +33,8 @@ Create a post in Buffer for a channel — add it to the queue, share it immediat
 | `schedulingType` | string | No | How the post publishes: automatic \(Buffer publishes it, default\) or notification \(you get a mobile reminder\) |
 | `dueAt` | string | No | Publish time as an ISO 8601 timestamp \(required when mode is customScheduled\) |
 | `saveToDraft` | boolean | No | Save the post as a draft instead of scheduling it |
-| `media` | file | No | Image or video to attach — an uploaded file, a file reference from a previous block, or a publicly accessible URL |
+| `media` | file | No | Image or video to attach — an uploaded file, a file reference from a previous block, or a publicly accessible URL. Buffer downloads the media at publish time; uploaded files are shared via a link valid for 7 days, so use a public URL for posts scheduled further out |
+| `mediaType` | string | No | Force the attachment type when it cannot be detected from the file or URL: image or video \(default auto\) |
 | `mediaAltText` | string | No | Alt text for an attached image |
 
 #### Output
@@ -82,7 +83,8 @@ Edit an existing Buffer post — update its text, schedule, or media. Attaching
 | `schedulingType` | string | No | How the post publishes: automatic \(Buffer publishes it, default\) or notification \(you get a mobile reminder\) |
 | `dueAt` | string | No | Publish time as an ISO 8601 timestamp \(required when mode is customScheduled\) |
 | `saveToDraft` | boolean | No | Save the post as a draft instead of scheduling it |
-| `media` | file | No | Image or video to attach — an uploaded file, a file reference from a previous block, or a publicly accessible URL. Replaces existing attachments |
+| `media` | file | No | Image or video to attach — an uploaded file, a file reference from a previous block, or a publicly accessible URL. Buffer downloads the media at publish time; uploaded files are shared via a link valid for 7 days, so use a public URL for posts scheduled further out. Replaces existing attachments |
+| `mediaType` | string | No | Force the attachment type when it cannot be detected from the file or URL: image or video \(default auto\) |
 | `mediaAltText` | string | No | Alt text for an attached image |
 
 #### Output
diff --git a/apps/sim/app/api/tools/buffer/create-post/route.ts b/apps/sim/app/api/tools/buffer/create-post/route.ts
@@ -56,6 +56,7 @@ export const POST = withRouteHandler(async (request: NextRequest) => {
       dueAt: body.dueAt,
       saveToDraft: body.saveToDraft,
       media: body.media,
+      mediaType: body.mediaType,
       mediaAltText: body.mediaAltText,
       userId: authResult.userId,
       requestId,
diff --git a/apps/sim/app/api/tools/buffer/edit-post/route.ts b/apps/sim/app/api/tools/buffer/edit-post/route.ts
@@ -56,6 +56,7 @@ export const POST = withRouteHandler(async (request: NextRequest) => {
       dueAt: body.dueAt,
       saveToDraft: body.saveToDraft,
       media: body.media,
+      mediaType: body.mediaType,
       mediaAltText: body.mediaAltText,
       userId: authResult.userId,
       requestId,
diff --git a/apps/sim/app/api/tools/buffer/server-utils.ts b/apps/sim/app/api/tools/buffer/server-utils.ts
@@ -18,6 +18,17 @@ import {
 const VIDEO_EXTENSIONS = ['.mp4', '.mov', '.m4v', '.webm', '.avi']
 const IMAGE_EXTENSIONS = ['.png', '.jpg', '.jpeg', '.gif', '.webp']
 const MEDIA_PROBE_TIMEOUT_MS = 5000
+/**
+ * Buffer fetches asset URLs at publish time, which for queued or scheduled
+ * posts can be days after createPost. Presign stored files for the S3 maximum
+ * of 7 days so scheduled posts within that window can still be published.
+ * The effective lifetime is additionally bounded by the signing credentials:
+ * Sim's storage clients sign with static keys (AWS_ACCESS_KEY_ID /
+ * AWS_SECRET_ACCESS_KEY), which support the full 7 days; deployments signing
+ * with temporary session credentials cap every presigned URL at the session
+ * lifetime platform-wide.
+ */
+const MEDIA_PRESIGN_EXPIRY_SECONDS = 7 * 24 * 60 * 60
 
 const CREATE_POST_MUTATION = `
   mutation CreatePost($input: CreatePostInput!) {
@@ -53,6 +64,7 @@ const EDIT_POST_MUTATION = `
 
 interface ResolveMediaAssetOptions {
   media: RawFileInput | string
+  mediaType?: 'auto' | 'image' | 'video' | null
   mediaAltText?: string | null
   userId: string
   requestId: string
@@ -79,15 +91,16 @@ function mediaKindFromExtension(pathOrName: string): 'image' | 'video' | null {
  * Determines whether media should be attached as a video or image asset.
  * Prefers the file's MIME type, then the path/URL extension, and for
  * extensionless URLs falls back to a DNS-pinned HEAD probe of the resolved
- * URL's Content-Type. Defaults to image when nothing is conclusive.
+ * URL's Content-Type. Returns null when nothing is conclusive so the caller
+ * can ask for an explicit media type instead of guessing.
  */
 async function resolveMediaKind(
   mimeType: string | undefined,
   pathOrName: string,
   fileUrl: string,
   requestId: string,
   logger: Logger
-): Promise<'image' | 'video'> {
+): Promise<'image' | 'video' | null> {
   if (mimeType?.startsWith('video/')) return 'video'
   if (mimeType?.startsWith('image/')) return 'image'
 
@@ -106,11 +119,11 @@ async function resolveMediaKind(
       if (contentType.startsWith('image/')) return 'image'
     }
   } catch (error) {
-    logger.warn(`[${requestId}] Media content-type probe failed, defaulting to image`, {
+    logger.warn(`[${requestId}] Media content-type probe was inconclusive`, {
       error: getErrorMessage(error, 'probe failed'),
     })
   }
-  return 'image'
+  return null
 }
 
 /**
@@ -122,7 +135,7 @@ async function resolveMediaKind(
 export async function resolveMediaAsset(
   options: ResolveMediaAssetOptions
 ): Promise<ResolvedMediaAsset> {
-  const { media, mediaAltText, userId, requestId, logger } = options
+  const { media, mediaType, mediaAltText, userId, requestId, logger } = options
 
   const isFileInput = typeof media === 'object'
   const resolution = await resolveFileInputToUrl({
@@ -131,6 +144,7 @@ export async function resolveMediaAsset(
     userId,
     requestId,
     logger,
+    presignExpirySeconds: MEDIA_PRESIGN_EXPIRY_SECONDS,
   })
   if (resolution.error || !resolution.fileUrl) {
     return {
@@ -143,7 +157,22 @@ export async function resolveMediaAsset(
 
   const mimeType = isFileInput ? media.type : undefined
   const pathOrName = isFileInput ? media.name || '' : media
-  const kind = await resolveMediaKind(mimeType, pathOrName, resolution.fileUrl, requestId, logger)
+  const kind =
+    mediaType === 'image' || mediaType === 'video'
+      ? mediaType
+      : await resolveMediaKind(mimeType, pathOrName, resolution.fileUrl, requestId, logger)
+  if (!kind) {
+    return {
+      errorResponse: NextResponse.json(
+        {
+          success: false,
+          error:
+            'Could not determine whether the media is an image or a video. Set mediaType to "image" or "video".',
+        },
+        { status: 400 }
+      ),
+    }
+  }
   if (kind === 'video') {
     return { asset: { video: { url: resolution.fileUrl } } }
   }
@@ -210,6 +239,7 @@ interface ForwardPostMutationOptions {
   dueAt?: string | null
   saveToDraft?: boolean | null
   media?: RawFileInput | string | null
+  mediaType?: 'auto' | 'image' | 'video' | null
   mediaAltText?: string | null
   userId: string
   requestId: string
@@ -224,7 +254,8 @@ interface ForwardPostMutationOptions {
 export async function forwardPostMutation(
   options: ForwardPostMutationOptions
 ): Promise<NextResponse> {
-  const { apiKey, postId, channelId, media, mediaAltText, userId, requestId, logger } = options
+  const { apiKey, postId, channelId, media, mediaType, mediaAltText, userId, requestId, logger } =
+    options
 
   const input: Record<string, unknown> = {
     mode: options.mode,
@@ -243,6 +274,7 @@ export async function forwardPostMutation(
   if (media) {
     const { asset, errorResponse } = await resolveMediaAsset({
       media,
+      mediaType,
       mediaAltText,
       userId,
       requestId,
diff --git a/apps/sim/blocks/blocks/buffer.ts b/apps/sim/blocks/blocks/buffer.ts
@@ -140,6 +140,19 @@ export const BufferBlock: BlockConfig<BufferPostResponse> = {
       mode: 'advanced',
       condition: { field: 'operation', value: POST_EDIT_OPS },
     },
+    {
+      id: 'mediaType',
+      title: 'Media Type',
+      type: 'dropdown',
+      options: [
+        { label: 'Auto-detect', id: 'auto' },
+        { label: 'Image', id: 'image' },
+        { label: 'Video', id: 'video' },
+      ],
+      value: () => 'auto',
+      mode: 'advanced',
+      condition: { field: 'operation', value: POST_EDIT_OPS },
+    },
     {
       id: 'mediaAltText',
       title: 'Media Alt Text',
@@ -321,6 +334,10 @@ export const BufferBlock: BlockConfig<BufferPostResponse> = {
     dueAt: { type: 'string', description: 'Publish time (ISO 8601)' },
     saveToDraft: { type: 'boolean', description: 'Save the post as a draft' },
     media: { type: 'string', description: 'Image or video attachment (file or public URL)' },
+    mediaType: {
+      type: 'string',
+      description: 'Attachment type override: auto, image, or video',
+    },
     mediaAltText: { type: 'string', description: 'Alt text for an attached image' },
     channelIds: { type: 'string', description: 'Comma-separated channel IDs filter' },
     status: { type: 'string', description: 'Comma-separated post status filter' },
diff --git a/apps/sim/lib/api/contracts/tools/buffer.ts b/apps/sim/lib/api/contracts/tools/buffer.ts
@@ -62,6 +62,7 @@ const postSharedFields = {
     .nullable(),
   saveToDraft: z.boolean().optional().nullable(),
   media: FileInputSchema.optional().nullable(),
+  mediaType: z.enum(['auto', 'image', 'video']).default('auto'),
   mediaAltText: z.string().max(1000, 'mediaAltText is too long').optional().nullable(),
 }
 
diff --git a/apps/sim/lib/uploads/utils/file-utils.server.ts b/apps/sim/lib/uploads/utils/file-utils.server.ts
@@ -49,6 +49,12 @@ export interface ResolveFileInputOptions {
   userId: string
   requestId: string
   logger: Logger
+  /**
+   * Expiry for presigned URLs minted for stored files, in seconds.
+   * Defaults to 5 minutes; raise it only when the external service fetches
+   * the URL later than the current request (e.g. scheduled publishing).
+   */
+  presignExpirySeconds?: number
 }
 
 /**
@@ -62,7 +68,7 @@ export interface ResolveFileInputOptions {
 export async function resolveFileInputToUrl(
   options: ResolveFileInputOptions
 ): Promise<FileResolutionResult> {
-  const { file, filePath, userId, requestId, logger } = options
+  const { file, filePath, userId, requestId, logger, presignExpirySeconds = 5 * 60 } = options
 
   if (file) {
     let userFile: UserFile
@@ -77,19 +83,11 @@ export async function resolveFileInputToUrl(
       }
     }
 
-    let fileUrl = userFile.url || ''
-
-    // Handle internal URLs
-    if (fileUrl && isInternalFileUrl(fileUrl)) {
-      const resolution = await resolveInternalFileUrl(fileUrl, userId, requestId, logger)
-      if (resolution.error) {
-        return { error: resolution.error }
-      }
-      fileUrl = resolution.fileUrl || ''
-    }
-
-    // Generate presigned URL if we have a key but no URL
-    if (!fileUrl && userFile.key) {
+    // A stored file always gets a freshly minted presigned URL scoped to the
+    // requested expiry — an embedded url (internal serve path or a previously
+    // minted presigned link) may be stale, shorter-lived than required, or
+    // point at a different object than the verified key.
+    if (userFile.key) {
       const context = resolveTrustedFileContext(userFile.key, userFile.context)
       const hasAccess = await verifyFileAccess(userFile.key, userId, undefined, context, false)
 
@@ -102,7 +100,30 @@ export async function resolveFileInputToUrl(
         return { error: { status: 404, message: 'File not found' } }
       }
 
-      fileUrl = await StorageService.generatePresignedDownloadUrl(userFile.key, context, 5 * 60)
+      const fileUrl = await StorageService.generatePresignedDownloadUrl(
+        userFile.key,
+        context,
+        presignExpirySeconds
+      )
+      return { fileUrl }
+    }
+
+    let fileUrl = userFile.url || ''
+
+    // Without a key, the schema guarantees the url references an uploaded
+    // file, so resolve the internal serve path to a presigned URL.
+    if (fileUrl && isInternalFileUrl(fileUrl)) {
+      const resolution = await resolveInternalFileUrl(
+        fileUrl,
+        userId,
+        requestId,
+        logger,
+        presignExpirySeconds
+      )
+      if (resolution.error) {
+        return { error: resolution.error }
+      }
+      fileUrl = resolution.fileUrl || ''
     }
 
     return { fileUrl }
@@ -112,7 +133,13 @@ export async function resolveFileInputToUrl(
     let fileUrl = filePath
 
     if (isInternalFileUrl(filePath)) {
-      const resolution = await resolveInternalFileUrl(filePath, userId, requestId, logger)
+      const resolution = await resolveInternalFileUrl(
+        filePath,
+        userId,
+        requestId,
+        logger,
+        presignExpirySeconds
+      )
       if (resolution.error) {
         return { error: resolution.error }
       }
@@ -227,7 +254,8 @@ export async function resolveInternalFileUrl(
   filePath: string,
   userId: string,
   requestId: string,
-  logger: Logger
+  logger: Logger,
+  presignExpirySeconds = 5 * 60
 ): Promise<{ fileUrl?: string; error?: { status: number; message: string } }> {
   if (!isInternalFileUrl(filePath)) {
     return { fileUrl: filePath }
@@ -247,7 +275,11 @@ export async function resolveInternalFileUrl(
       return { error: { status: 404, message: 'File not found' } }
     }
 
-    const fileUrl = await StorageService.generatePresignedDownloadUrl(storageKey, context, 5 * 60)
+    const fileUrl = await StorageService.generatePresignedDownloadUrl(
+      storageKey,
+      context,
+      presignExpirySeconds
+    )
     logger.info(`[${requestId}] Generated presigned URL for ${context} file`)
     return { fileUrl }
   } catch (error) {
diff --git a/apps/sim/tools/buffer/create_post.ts b/apps/sim/tools/buffer/create_post.ts
@@ -62,7 +62,14 @@ export const bufferCreatePostTool: ToolConfig<BufferCreatePostParams, BufferPost
       required: false,
       visibility: 'user-or-llm',
       description:
-        'Image or video to attach — an uploaded file, a file reference from a previous block, or a publicly accessible URL',
+        'Image or video to attach — an uploaded file, a file reference from a previous block, or a publicly accessible URL. Buffer downloads the media at publish time; uploaded files are shared via a link valid for 7 days, so use a public URL for posts scheduled further out',
+    },
+    mediaType: {
+      type: 'string',
+      required: false,
+      visibility: 'user-or-llm',
+      description:
+        'Force the attachment type when it cannot be detected from the file or URL: image or video (default auto)',
     },
     mediaAltText: {
       type: 'string',
@@ -85,6 +92,7 @@ export const bufferCreatePostTool: ToolConfig<BufferCreatePostParams, BufferPost
       dueAt: params.dueAt,
       saveToDraft: params.saveToDraft,
       media: params.media,
+      mediaType: params.mediaType,
       mediaAltText: params.mediaAltText,
     }),
   },
diff --git a/apps/sim/tools/buffer/edit_post.ts b/apps/sim/tools/buffer/edit_post.ts
@@ -62,7 +62,14 @@ export const bufferEditPostTool: ToolConfig<BufferEditPostParams, BufferPostResp
       required: false,
       visibility: 'user-or-llm',
       description:
-        'Image or video to attach — an uploaded file, a file reference from a previous block, or a publicly accessible URL. Replaces existing attachments',
+        'Image or video to attach — an uploaded file, a file reference from a previous block, or a publicly accessible URL. Buffer downloads the media at publish time; uploaded files are shared via a link valid for 7 days, so use a public URL for posts scheduled further out. Replaces existing attachments',
+    },
+    mediaType: {
+      type: 'string',
+      required: false,
+      visibility: 'user-or-llm',
+      description:
+        'Force the attachment type when it cannot be detected from the file or URL: image or video (default auto)',
     },
     mediaAltText: {
       type: 'string',
@@ -85,6 +92,7 @@ export const bufferEditPostTool: ToolConfig<BufferEditPostParams, BufferPostResp
       dueAt: params.dueAt,
       saveToDraft: params.saveToDraft,
       media: params.media,
+      mediaType: params.mediaType,
       mediaAltText: params.mediaAltText,
     }),
   },
diff --git a/apps/sim/tools/buffer/types.ts b/apps/sim/tools/buffer/types.ts
@@ -389,6 +389,7 @@ export interface BufferCreatePostParams extends BufferBaseParams {
   dueAt?: string
   saveToDraft?: boolean
   media?: unknown
+  mediaType?: 'auto' | 'image' | 'video'
   mediaAltText?: string
 }
 
@@ -400,6 +401,7 @@ export interface BufferEditPostParams extends BufferBaseParams {
   dueAt?: string
   saveToDraft?: boolean
   media?: unknown
+  mediaType?: 'auto' | 'image' | 'video'
   mediaAltText?: string
 }
 

Original file line number	Diff line number	Diff line change
`@@ -62,6 +62,7 @@ const postSharedFields = {`
`62`	`62`	`.nullable(),`
`63`	`63`	`saveToDraft: z.boolean().optional().nullable(),`
`64`	`64`	`media: FileInputSchema.optional().nullable(),`
	`65`	`+ mediaType: z.enum(['auto', 'image', 'video']).default('auto'),`
`65`	`66`	`mediaAltText: z.string().max(1000, 'mediaAltText is too long').optional().nullable(),`
`66`	`67`	`}`
`67`	`68`
Original file line number	Diff line number	Diff line change
`@@ -389,6 +389,7 @@ export interface BufferCreatePostParams extends BufferBaseParams {`
`389`	`389`	`dueAt?: string`
`390`	`390`	`saveToDraft?: boolean`
`391`	`391`	`media?: unknown`
	`392`	`+ mediaType?: 'auto' \| 'image' \| 'video'`
`392`	`393`	`mediaAltText?: string`
`393`	`394`	`}`
`394`	`395`
`@@ -400,6 +401,7 @@ export interface BufferEditPostParams extends BufferBaseParams {`
`400`	`401`	`dueAt?: string`
`401`	`402`	`saveToDraft?: boolean`
`402`	`403`	`media?: unknown`
	`404`	`+ mediaType?: 'auto' \| 'image' \| 'video'`
`403`	`405`	`mediaAltText?: string`
`404`	`406`	`}`
`405`	`407`