Agent skill

Helios Renderer

by BintzGavin in BintzGavin/helios

Renderer API for generating video/image output from Helios compositions.

Apache-2.0Auto-check passedMedia & Creative

Install Helios Renderer

skills CLI
$ npx skills add BintzGavin/helios --skill helios-renderer -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install BintzGavin/helios helios-renderer --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/BintzGavin/helios.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/renderer .claude/skills/helios-renderer && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
helios-renderer
GitHub stars
118
Token cost
~1.8k tokens
SKILL.md length
307 words
Files
1
Skills in repo
16
Repo updated
First seen
Licence
Apache-2.0

At a glance

Renderer API for generating video/image output from Helios compositions.

  • You need to programmatically render a composition to a file using Node.js
  • SKILL.md covers Quick Start, API Reference, Rendering Modes and Utilities, plus 2 more sections
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Helios Renderer is an agent skill from BintzGavin/helios. Renderer API for generating video/image output from Helios compositions. Use when you need to programmatically render a composition to a file using Node.js.

Its SKILL.md is about 1.8k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Media & Creative. It works with Node.js. The repository describes itself as: Programmatic video creation with web technologies you already know. CSS animations just work. The licence is Apache-2.0.

When your agent uses it

  • You need to programmatically render a composition to a file using Node.js

Example prompts

  • “/helios-renderer”

Requirements

  • Node.js

What it can do on your machine

Read from SKILL.md and the folder at commit c6b0c13. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md (its code samples are typescript).

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Helios Renderer loads about 1.8k tokens when it runs. Until then it costs about 43 tokens; SKILL.md has 307 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~43
When it runs · the whole SKILL.md, loaded when a task matches
~1.8k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from BintzGavin/helios at commit c6b0c13, republished under its Apache-2.0 licence (© BintzGavin). 307 words, ~1,792 tokens.

Download SKILL.mdSave it as .claude/skills/helios-renderer/SKILL.md (or your agent's skills folder).
name
helios-renderer
description
Renderer API for generating video/image output from Helios compositions. Use when you need to programmatically render a composition to a file using Node.js.

Helios Renderer API

The Renderer class enables headless rendering of Helios compositions using Playwright and FFmpeg. It supports both DOM-based and Canvas-based rendering strategies.

Quick Start

typescript
import { Renderer } from '@helios-project/renderer';

const renderer = new Renderer({
  width: 1920,
  height: 1080,
  fps: 30,
  durationInSeconds: 10,
  mode: 'canvas', // or 'dom'
  inputProps: { title: "Render Job 1" }
});

await renderer.render(
  'http://localhost:3000/composition.html',
  './output.mp4',
  {
    onProgress: (progress) => console.log(`Rendering: ${(progress * 100).toFixed(1)}%`)
  }
);

API Reference

Constructor
typescript
new Renderer(options: RendererOptions)

interface RendererOptions {
  width: number;           // Output width
  height: number;          // Output height
  fps: number;             // Frames per second
  durationInSeconds: number; // Duration of the clip
  frameCount?: number;     // Exact total frames (overrides durationInSeconds)
  startFrame?: number;     // Frame to start rendering from (default: 0)
  mode?: 'dom' | 'canvas'; // Rendering strategy (default: 'canvas')
  inputProps?: Record<string, any>; // Inject props into window.__HELIOS_PROPS__

  // Audio Configuration
  audioFilePath?: string;        // Path to single audio file
  audioTracks?: (string | AudioTrackConfig)[]; // List of audio tracks
  audioCodec?: string;           // e.g., 'aac', 'libvorbis'
  audioBitrate?: string;         // e.g., '128k', '192k'

  // Video Encoding
  videoCodec?: string;           // e.g., 'libx264' (default, prioritized), 'libvpx'
  pixelFormat?: string;          // e.g., 'yuv420p' (default)
  crf?: number;                  // Constant Rate Factor (quality control)
  preset?: string;               // Encoding preset (e.g., 'fast')
  videoBitrate?: string;         // e.g., '5M', '1000k'
  subtitles?: boolean;           // Burn subtitles into video (requires libx264)

  // Intermediate Capture (Canvas Mode)
  intermediateVideoCodec?: string; // 'vp8' (default), 'vp9', 'av1'

  // Intermediate Capture (DOM Mode)
  intermediateImageFormat?: 'png' | 'jpeg'; // Default: 'png'
  intermediateImageQuality?: number;        // 0-100 (only for jpeg)

  // System
  ffmpegPath?: string;           // Custom FFmpeg binary path
  browserConfig?: {              // Playwright Launch Options
    headless?: boolean;
    executablePath?: string;
    args?: string[];
  };
}

interface AudioTrackConfig {
  path: string;
  volume?: number; // 0.0 to 1.0
  offset?: number; // Start time in composition (seconds)
  seek?: number;   // Start time in source file (seconds)
  playbackRate?: number; // Speed multiplier (default: 1.0)
}
Methods
Render

Renders the composition at the given URL to a video file.

typescript
async render(
  compositionUrl: string,
  outputPath: string,
  jobOptions?: RenderJobOptions
): Promise<void>

interface RenderJobOptions {
  onProgress?: (progress: number) => void; // Callback 0.0 to 1.0
  signal?: AbortSignal;                    // For cancellation
  tracePath?: string;                      // Path to save Playwright trace (for debugging)
}
Diagnose

Check the rendering environment (Playwright, WebCodecs support, FFmpeg).

typescript
// Returns a comprehensive diagnostic report
const diagnostics = await renderer.diagnose();

/*
{
  browser: {
    waapi: boolean,
    webCodecs: boolean,
    offscreenCanvas: boolean,
    userAgent: string
  },
  ffmpeg: {
    version: string,
    encoders: string[],
    filters: string[]
  }
}
*/

Rendering Modes

Canvas Mode (mode: 'canvas')
  • Best for: WebGL, Three.js, Pixi.js, 2D Canvas.
  • Mechanism: Uses CdpTimeDriver to control time and CanvasStrategy to capture the canvas context directly.
  • Performance: High. Fast capture via CDP.
  • Sync: Uses TreeWalker to recursively discover and sync media in Shadow DOMs.
DOM Mode (mode: 'dom')
  • Best for: CSS Animations, HTML/DOM elements, complex video/audio compositions.
  • Mechanism: Uses SeekTimeDriver (seek & screenshot) to ensure DOM layouts settle.
  • Performance: Slower than Canvas mode due to full-page screenshots.
  • Implicit Audio: Automatically discovers <audio> and <video> tags in the DOM and includes their audio in the render.
  • Media Synchronization: Supports precise control over nested media elements using attributes:
    • data-helios-offset="2.5": Delay playback start by 2.5 seconds.
    • data-helios-seek="10": Start playing from 10s into the source file.
    • muted: Respects the HTML muted attribute.
  • Recursive Sync: Traverses Shadow DOMs (open and closed) to find and synchronize animations and media elements.
  • Stability: Waits for seeked events on all media elements (Multi-Frame Seek) to ensure frames are perfectly aligned before capturing.

Utilities

Distributed Rendering

Split a render job into multiple chunks to run concurrently (e.g., on multiple cores).

typescript
import { RenderOrchestrator, DistributedRenderOptions } from '@helios-project/renderer';

const options: DistributedRenderOptions = {
  // ...standard Renderer options...
  concurrency: 4 // Number of parallel workers (default: CPU cores - 1)
};

await RenderOrchestrator.render(
  'http://localhost:3000/composition.html',
  'output.mp4',
  options,
  { onProgress: (p) => console.log(`Total Progress: ${p}`) }
);
Concatenate Videos

Combine multiple video files into one.

typescript
import { concatenateVideos } from '@helios-project/renderer';

await concatenateVideos(['part1.mp4', 'part2.mp4'], 'full-video.mp4');

Common Patterns

Caption Burning

Burn subtitles (e.g. from the player) into the video output. Requires videoCodec: 'libx264'.

typescript
const renderer = new Renderer({
  // ...
  videoCodec: 'libx264',
  subtitles: './captions.srt' // path to an SRT file
});
Range Rendering

Render only a specific section of the composition (e.g., for distributed rendering).

typescript
const renderer = new Renderer({
  // ...
  startFrame: 0,
  durationInSeconds: 5 // Render only first 5 seconds
});
// To render the next 5 seconds:
// startFrame: 150, durationInSeconds: 5
Fast Draft Renders (DOM Mode)

Use JPEG instead of PNG for faster intermediate screenshots during DOM rendering.

typescript
const renderer = new Renderer({
  mode: 'dom',
  intermediateImageFormat: 'jpeg',
  intermediateImageQuality: 80
});
Audio Mixing

Mix multiple audio tracks with offsets and volume control.

typescript
const renderer = new Renderer({
  // ...
  audioTracks: [
    { path: 'music.mp3', volume: 0.5 },
    { path: 'voiceover.wav', volume: 1.0, offset: 2 } // Start voice at 2s
  ]
});

Source Files

  • Main class: packages/renderer/src/index.ts
  • Strategies: packages/renderer/src/strategies/
  • Types: packages/renderer/src/types.ts

© BintzGavin, Apache-2.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in skills/renderer of BintzGavin/helios.

Open the folder on GitHubat commit c6b0c13

Compare with similar skills

Helios Renderer next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Helios Renderer compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Helios Renderer this skillBintzGavin/helios118—~1.8kAutomated safety check: PassApache-2.0
Qiaomu Cutjoeseesun/qiaomu-cut-skill372—~6.8kAutomated safety check: NotesMIT
Script To Shootable Storyboardzyz254009-crypto/script-to-shootable-storyboard117—~1.9kAutomated safety check: PassMIT
Image Context Runtimeshixinnt/codex-image-context-runtime100—~723Automated safety check: PassApache-2.0
Bilibili Page ReaderMisaka-Mikoto-Tech/agent-skills278—~3.6kAutomated safety check: PassMIT
Seedancefreestylefly/wesight944—~2.2kAutomated safety check: PassMIT

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Works with

Questions about Helios Renderer

What does Helios Renderer do?

Renderer API for generating video/image output from Helios compositions. Helios Renderer is an agent skill from BintzGavin/helios. Renderer API for generating video/image output from Helios compositions.

When should I use Helios Renderer?

Helios Renderer fits situations like: you need to programmatically render a composition to a file using Node.js.

How do I install Helios Renderer in Claude Code?

Run `npx skills add BintzGavin/helios --skill helios-renderer -a claude-code`. Or copy the skill folder (skills/renderer in BintzGavin/helios) into .claude/skills/helios-renderer in your project. Claude Code loads it when a task matches its description.

How do I install Helios Renderer in Codex?

Run `npx skills add BintzGavin/helios --skill helios-renderer -a codex`. Or copy the skill folder (skills/renderer in BintzGavin/helios) into .agents/skills/helios-renderer in your project. Codex loads it when a task matches its description.

Can I use Helios Renderer in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add BintzGavin/helios --skill helios-renderer -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/helios-renderer, .gemini/skills/helios-renderer, .github/skills/helios-renderer and .opencode/skills/helios-renderer in your project.

What does Helios Renderer need to run?

SKILL.md names no scripts, command-line tools or credentials: Helios Renderer is instructions for the agent only. Our summary lists: Node.js.

Does Helios Renderer access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Helios Renderer safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Helios Renderer use?

Helios Renderer is published under the Apache-2.0 licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Helios Renderer use?

About 1.8k tokens (SKILL.md is roughly 7.2k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Helios Renderer?

Skills that share tags, products or a category with Helios Renderer: Qiaomu Cut (joeseesun/qiaomu-cut-skill, 372 stars), Script To Shootable Storyboard (zyz254009-crypto/script-to-shootable-storyboard, 117 stars), Image Context Runtime (shixinnt/codex-image-context-runtime, 100 stars) and Bilibili Page Reader (Misaka-Mikoto-Tech/agent-skills, 278 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Helios Renderer?

BintzGavin (a GitHub user) maintains it in BintzGavin/helios, which has 118 GitHub stars. The repository holds 16 skills in this directory. The repository was last updated on October 9, 2026.

Source: BintzGavin/helios on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.