What is embedded-captions?

A workflow for adding captions or subtitles to an existing single-person talking-head video without changing the footage. Captions can appear as ordinary subtitles, behind the speaker, or as stylized visual effects.

Use it for verbatim subtitles, cinematic behind-the-speaker captions, visual-effects captions, and themed caption treatments in HyperFrames.

It lets developers choose how text should appear based on the desired visual identity instead of treating every caption as the same kind of subtitle.

embedded-captions — Skill for Claude Code by heygen-com/hyperframes

About the project

HyperFrames is an open-source framework that turns HTML, CSS, media, and timed animations into deterministic MP4 videos. It is used locally, by coding agents, and in hosted authoring workflows to create rendered videos from web-based designs. Its catalogue add-ons provide skills, agents, instructions, hooks, settings, and a plugin for agent-driven video production.

heygen-com/hyperframes · 65,314 stars · on GitHub · hyperframes.dev

Install

Getting it into your agent

It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.

Clone the repo

git clone --depth 1 https://github.com/heygen-com/hyperframes

agentmods

npx agentmods add skills/heygen-com/hyperframes/embedded-captions

Made for: Claude Code.

Or install hyperframes, the plugin that ships this one along with the rest of its 34 skills, 1 hook.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/heygen-com/hyperframes/embedded-captions/github.svg)](https://agentmods.dev/skills/heygen-com/hyperframes/embedded-captions)

Your own site

<a href="https://agentmods.dev/skills/heygen-com/hyperframes/embedded-captions"><img src="https://agentmods.dev/badge/skills/heygen-com/hyperframes/embedded-captions/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/heygen-com/hyperframes/embedded-captions"><img src="https://agentmods.dev/badge/skills/heygen-com/hyperframes/embedded-captions.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 120 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 7,669 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits

Socket pass 2 Oct 2026
Snyk pass 2 Oct 2026
NVIDIA SkillSpector warn 7 Sept 2026

SkillSpector: 13 findings, up to medium

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

medium MCP Rug Pull · line 12
npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.

Fix: Pin the version: npx @scope/[email protected]
medium Prompt Injection · line 44
Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.

Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
medium Prompt Injection · line 46
Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.

Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
medium Prompt Injection · line 160
Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.

Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
medium Prompt Injection · line 207
Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.

Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
medium Prompt Injection · line 214
Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.

Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
medium Prompt Injection · line 217
Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.

Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
medium Prompt Injection · line 219
Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.

Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
medium Prompt Injection · line 221
Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.

Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
medium Prompt Injection · line 222
Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.

Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
medium Rogue Agent · line 242
Skill establishes unauthorized persistence across sessions via cron jobs, startup scripts, or state files. Session persistence allows an attacker to maintain access beyond the current interaction.

Fix: Remove any persistence mechanisms (cron jobs, startup scripts, state files). Skills should not maintain state across sessions without explicit user consent.
medium MCP Rug Pull · line 253
uvx/uv tool run commands without ==version create a rug-pull risk.

Fix: Pin the version: uvx package-name==1.2.3
medium Prompt Injection · line 220
Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.

Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be

How audits are shown

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00120	$0.07669
Opus 5.5	$0.00048	$0.03068
Sonnet 5.5	$0.00024	$0.01534
Haiku 4.5	$0.00012	$0.00767

Measured 12d ago against content hash 983a4e61310d, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

embedded-captions scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 12d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (modes/standard/fonts/build-fonts-css.cjs), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

Copies of this mod

3 near-identical copies found in the catalogue:

embedded-captions — 98% identical, 45 lines differ
embedded-captions — 94% identical, 127 lines differ
embedded-captions — 94% identical, 127 lines differ

skills/embedded-captions/SKILL.md · 284 lines

How it starts

The opening of the file, as written. The whole thing — 284 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Plugin installs: Before setup or freshness commands, follow plugin execution rules when this skill is inside a HyperFrames plugin. Standalone installs keep the update instructions below.

First, keep this skill fresh — confirm with the user before running: npx hyperframes skills update embedded-captions. A fast no-op when everything is current; otherwise it refreshes this skill plus the core domain skills it depends on before you rely on them.

Embedded Captions

One catalog, picked up front (CATALOG.md — 35 identities; the engines behind it are backend detail). Standard (default) builds a clean verbatim rail (lower-third subtitle carrying most text) + an embed climax composited into the scene behind the subject at the peak. Cinematic is pure embed — no rail, every caption composited behind the subject (hero typography, accumulation, occlusion as the effect). Theme is a complete themed constitution — body paradigm × hero setpiece × front fx × plate reaction, composed from registries (themes/README.md): ordnance terminal neonsign stardust stomp. Most explainer / voiceover is Standard; embed is the scarce, earned peak — embedding every word is the common mistake; Theme is for VFX-grade asks ("炸", "特效", "像 AE 做的").

Runtime prerequisites

Plugin installs use the bundled, manifest-pinned CLI for matting, transcription, and rendering; no source checkout is required. The local preview and caption measurement helpers also need Sharp, Puppeteer (with its Chromium browser), and GSAP. Install these in the caption project, not inside the read-only plugin:

npm install --prefix <project> --save-dev --save-exact [email protected] [email protected] [email protected]

Keep the project's lockfile. If these dependencies already exist, use its locked versions instead of overwriting them. Bash and FFmpeg/ffprobe must be on PATH. Matting and transcription may download their own models on first use.

Read the full file on GitHub · 284 lines

Files

What ships with it

60 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

12d ago Changed 983a4e61310d
19d ago Changed · +23 lines 761d9cd5e03f
1mo ago Changed a966ebd548e6
1mo ago Changed · +2 lines 019e382b13a3
1mo ago First seen · 259 lines · 120 tokens per session scan A 5a7cb108c414

Subscribe to this mod's changes

embedded-captions is a skill published in the GitHub repository heygen-com/hyperframes (65,314 stars, last pushed today), licensed Apache-2.0. It adds 120 tokens to every session and 7,669 once invoked, about $0.0005 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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