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

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

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,

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,

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,

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' },

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(),
 }
 

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) {

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,
  }),
  },

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,
  }),
  },

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
 }