creative_template storyboard: add audio variant (TTS / mix / master pattern)

[bokelley]

Gap

The creative_template storyboard's build_creative step is hardcoded to display assets:

sample_request:
  creative_manifest:
    format_id: { agent_url: ..., id: 'display_300x250' }
    assets:
      image: { asset_type: 'image', url: '...hero-300x250.jpg', width: 300, height: 250 }
      headline: { asset_type: 'text', content: 'Summer Sale — 40% Off' }
      click_url: { asset_type: 'url', url: '...' }

This means audio creative-template platforms (AudioStack, ElevenLabs, Resemble, Speechmatics) cannot pass the storyboard — they don't accept image inputs or produce display tags. Audio adopters today validate via manual round-trip + the SDK's three-gate test contract, but lack the same compliance signal display/video adopters get from the storyboard grader.

Proposal

Add an audio variant phase to creative_template/index.yaml — same shape as the existing build_creative step, different assets:

- id: build_audio_creative
  task: build_creative
  sample_request:
    creative_manifest:
      format_id: { agent_url: ..., id: 'audio_30s' }
      assets:
        script: { asset_type: 'text', content: 'Built for the trail. Acme Outdoor — premium gear for every adventure.' }
        voice: { asset_type: 'text', content: 'narrator-warm' }
        click_through: { asset_type: 'url', url: '...' }

Test-kit additions (acme-outdoor.yaml):

assets:
  audio_script:
    content: \"Built for the trail. Acme Outdoor — premium gear for every adventure.\"
  audio_voice:
    content: \"narrator-warm\"

The audio variant should:

1. Be optional (skip when the agent doesn't declare audio support in list_creative_formats)
2. Accept either sync return (small platforms render fast) OR task-envelope return (TTS pipelines run minutes — exercise the polling path)
3. Validate that the response carries an audio asset in creative_manifest.assets with asset_type: 'audio' and a resolvable url

Why now

@adcp/sdk shipped a worked audio-template path in PR #1496 follow-up (audio template seeded in mock-server/creative-template, audio_url output projected via audioAsset() in hello_creative_adapter_template.ts). The pattern is in production-ready code; the storyboard is the last gap.

Reference implementation

• Mock-server: src/lib/mock-server/creative-template/seed-data.ts — tpl_audiostack_spot_30s_v1 with TTS / mix / master shape
• Adapter: examples/hello_creative_adapter_template.ts — projects audio_url to creative_manifest.assets.serving_audio via audioAsset({ url })
• Skill prose: skills/build-creative-agent/SKILL.md § creative-template archetype

Adopter audience

Major audio-creative platforms in scope:

• AudioStack
• ElevenLabs (voice generation)
• Resemble.ai (voice cloning)
• Speechmatics (transcription + voice)
• Adobe Podcast (audio enhancement + voice)
• WellSaid Labs

All would benefit from a storyboard signal aligned with display/video.

[bokelley]

Triage

Classification: Feature request
Bucket(s): compliance-suite, creative
Status: drafting-pr
Milestone: (omitted — conformance harness change, no protocol version bump)

What the experts said:

• ad-tech-protocol-expert: Sound as proposed with minor fixes — asset_type: "audio" already in the registry, skip_if / optional: true mechanism exists, async path covered by existing comply_scenario: creative_flow; flagged click_through → click_url key name fix (addressed) and noted text_type omission is consistent with existing headline pattern in the same storyboard
• adtech-product-expert: Ship with modifications — optional phase pattern is correct, audio-only preview not needed (no audio preview render surface exists yet), use skip_if on test-kit flag rather than runtime response; adopter friction is zero for display-only agents
• code-reviewer: Added optional: true to pair with skip_if (blocker, fixed); idempotency key suffix and step structure are consistent with existing build steps; restricted files untouched

My take: All three experts converge. Change is non-breaking (additive scenario, existing steps unchanged), the SDK already ships a worked audio-template path, and the storyboard is the last gap. Draft PR at #4019.

Drafting PR: adds optional audio_build phase to creative_template/index.yaml with a build_audio_creative step (task: build_creative, audio text inputs, comply_scenario: creative_flow), plus supports_audio_formats flag and assets.audio reference block in acme-outdoor.yaml. Display-only agents grade the phase not_applicable with no behavior change.

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Triaged by Claude Code. Session: https://claude.ai/code/session_013KNxYsZtapmfcVndMGx1Tw

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Generated by Claude Code