How do I combine Runway-generated B-roll with a HeyGen talking-head avatar into one finished video?

the agent that answers this

Cinematic B-Roll Generator with Avatar Presenter. Build a simple generator that accepts either a short prompt or a basic prompt markdown file, expands it into a detailed cinematic b-roll prompt, generates fresh high quality b-roll clips with Runway ML, creates a talking-head avatar presenter with HeyGen, and assembles the final video.

• Step 1decision

  Collect the run input by accepting either source_prompt or prompt_md_file, require at least one, and normalize it into a single plain-language creative brief.

  Decision step
• Step 2

  Rewrite the creative brief into a high quality cinematic b-roll generation prompt with visual subject, setting, camera movement, lens language, lighting, color grade, motion details, composition, duration, aspect ratio, negative constraints, and a short presenter narration script.

  Seedance2 Video Generation Prompt Engineering — multimodal reference system, cinematic camera language, audio-video sync, and scene-by-scene prompt patterns...

  --- name: seedance-2-prompt description: Seedance2 Video Generation Prompt Engineering — multimodal reference system, cinematic camera language, audio-video sync, and scene-by-scene prompt patterns for ByteDance's Seedance2 model. license:…

  Full skill: Seedance2 Prompt Engineering
• Step 3decision

  Hold for approval before generating paid or time-consuming media; show the cinematic prompt, presenter script, duration, aspect ratio, and planned clip list, then wait for Approve & continue or user edits.

  Decision step
• Step 4tool

  Preflight: immediately before the first dependency-using step, make sure the remaining work has what it needs, so the run never fails halfway on a missing tool or an unconfigured account. Command-line tools (free, auto-install only if missing; idempotent, later runs find them present): Remotion - npx remotion versions (auto-fetches), or `npm i remotion` in the project; ffmpeg - `ffmpeg -version` || install (`brew install ffmpeg` on macOS, `apt-get install -y ffmpeg` on Linux). Services and accounts (these need a key, login, or subscription, NOT auto-installed): Runway ML (usage-based (credits); get it at https://dev.runwayml.com; alternative: Seedance (via HeyGen)); HeyGen (free trial, then paid; get it at https://heygen.com). Before the FIRST step that calls a paid service, verify its API key or login is configured. If one is missing, STOP and tell the user exactly what to sign up for, the link, and any cheaper alternative, instead of failing partway through a paid run.

  Your model fills this step
• Step 5tool

  Generate fresh high quality cinematic b-roll clips from the approved prompt pack using Runway ML text-to-video or image-to-video API, poll until each render completes, download the generated media, and save the clip files into the output folder.

  Your model fills this step

  • No integration? If the Runway API key is unavailable, stop with Needs You asking the user to connect a Runway API key or provide already-generated b-roll files.
  • No integration? If the Runway API is unavailable but a signed-in browser session is available, reroute to browser for Runway web generation and require a verified downloaded file before continuing.
• Step 6tool

  Create a talking-head avatar presenter clip in HeyGen from the approved presenter script, using the configured avatar/presenter style, then wait for the render to finish, download the MP4, and verify the local file exists before continuing.

  Your model fills this step

  • No integration? If HeyGen requires login or browser-only controls, reroute to browser rather than failing the run.
  • No integration? If the HeyGen render is submitted but not downloadable before the session ends, record a partial Needs You item with the exact render URL, expected destination path, and download instructions.
• Step 7tool

  Assemble the Runway b-roll clips and HeyGen presenter clip into a clean final video with basic pacing, cuts, audio levels, optional captions, and a manifest, using local Remotion or ffmpeg rendering.

  Produce programmable videos with Remotion using scene planning, asset orchestration, and validation gates for automated, brand-consistent video content.

  Remotion Video Production A skill for producing programmable videos using Remotion. Generate automated videos from text instructions and produce brand-consistent videos at scale. When to use this skill Automated video generation: Create…

  Full skill: remotion-video-production

  • No integration? If Remotion is not installed, use ffmpeg for a simple assembled MP4 when possible.
  • No integration? If neither local render path is available, stop with Needs You naming the missing local render dependency.
• Step 8decision

  Quality gate: adversarially critique the deliverable produced by the prior steps, from three lenses (a domain expert, a hard skeptic, and the end user). Check it actually accomplishes the job, is accurate and on-brand, and is genuinely high quality. Fix clear problems in place; if something should block or materially change it, say so before it reaches the user.

  Decision step
• Step 9decision

  Voice Pass: before showing any user-facing text, rewrite the final draft so it sounds natural, platform-native, and non-generic. Preserve the meaning, facts, links, citations, decisions, and concrete details. Remove obvious AI tells: generic praise, inflated significance, rule-of-three padding, em/en dash overuse, chatbot artifacts, fake-candid openers, promotional filler, vague hedging, and formulaic conclusions. Match any provided voice samples, agent memory, prior feedback, and platform norms (Reddit/HN/social/email); if none exist, use a concise natural voice. Do not add unsupported claims. For factual, technical, legal, or reference outputs, keep the voice plain and neutral rather than adding personality.

  Decision step
• Step 10decision

  Verify that the final video file and manifest exist inside the workspace output folder, declare the final video artifact, and summarize the generation settings, source prompt, and output path for review.

  Decision step

common questions

1. v3Aug 20generated

   reconciled active outcome capability input authority

2. v2Aug 20generated

   added immutable outcome-search identity

3. v1Jul 28generated

   auto-generated from "Build a simple generator that accepts either a short prompt or a basic prompt ma"

Agents are alive: every change is a version, and a run can propose improvements that get reviewed and applied.

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