yikart/AiToEarn · error · BadRequestException

last_frame requires first_frame

Error message

last_frame requires first_frame

What it means

Volcengine frame-interpolation generation requires a first frame when a last frame is provided. validateContent throws this BadRequestException when last_frame images exist but no first_frame image was supplied, because a last frame alone is not a valid generation mode.

Source

Thrown at project/aitoearn-backend/apps/aitoearn-ai/src/core/ai/video/volcengine/volcengine.service.ts:171

    const firstFrameImages = imageContents.filter(item => !item.role || item.role === ImageRole.FirstFrame)
    const lastFrameImages = imageContents.filter(item => item.role === ImageRole.LastFrame)
    const referenceImages = imageContents.filter(item => item.role === ImageRole.ReferenceImage)
    const referenceVideos = videoContents.filter(item => item.role === VideoRole.ReferenceVideo)
    const referenceAudios = audioContents.filter(item => item.role === AudioRole.ReferenceAudio)

    const hasFrameScene = firstFrameImages.length > 0 || lastFrameImages.length > 0
    const hasReferenceScene = referenceImages.length > 0 || referenceVideos.length > 0 || referenceAudios.length > 0

    if (firstFrameImages.length > 1) {
      throw new BadRequestException('Only one first frame image is allowed')
    }

    if (lastFrameImages.length > 1) {
      throw new BadRequestException('Only one last frame image is allowed')
    }

    if (lastFrameImages.length > 0 && firstFrameImages.length === 0) {
      throw new BadRequestException('last_frame requires first_frame')
    }

    if (hasFrameScene && hasReferenceScene) {
      throw new BadRequestException('first_frame/last_frame and reference media cannot be mixed')
    }

    if (referenceAudios.length > 0 && referenceImages.length === 0 && referenceVideos.length === 0) {
      throw new BadRequestException('reference_audio requires at least one reference image or reference video')
    }
  }

  private normalizeRequest(request: UserVolcengineGenerationRequestDto) {
    let prompt = ''
    let inlineResolution: string | undefined
    let inlineRatio: string | undefined
    let inlineDuration: number | undefined
    let inlineSeed: number | undefined
    let inlineWatermark: boolean | undefined

View on GitHub (pinned to d3aa8bea5b)

Solutions

1. Add a first_frame image content item alongside the last_frame
2. If only one image is intended, assign it role first_frame instead
3. Validate the pair client-side: last_frame implies first_frame

Example fix

// before
content: [{ type:'image_url', role:'last_frame', url: img }]
// after
content: [{ type:'image_url', role:'first_frame', url: start }, { type:'image_url', role:'last_frame', url: img }]

const hasLast = content.some(c => c.role === 'last_frame'); const hasFirst = content.some(c => c.role === 'first_frame'); if (hasLast && !hasFirst) throw new Error('last_frame requires first_frame')

const isValidFramePair = (c: Content[]) => !c.some(i => i.role === 'last_frame') || c.some(i => i.role === 'first_frame')

try { await generate(req) } catch (e) { if (e instanceof BadRequestException && e.message === 'last_frame requires first_frame') { /* add a first_frame or change role */ } else throw e }

When it happens

Trigger: Sending content with exactly one last_frame image and zero first_frame images.

Common situations: Client mixes up role assignment (marking the start image as last_frame); UI only collects an end frame; refactor swapped role values.

Related errors

• Only one first frame image is allowed
• Only one last frame image is allowed
• reference_audio requires at least one reference image or ref
• image_tail requires a single first frame image
• content is required

AI-assisted analysis of yikart/AiToEarn@d3aa8bea5b (2026-08-31). Data as JSON: /api/errors/8aed9e090d1e023c. Report an issue: GitHub.