seam-craft

A HyperFrames rule set for making scene-to-scene transitions render correctly in the master timeline, the page that assembles all scenes into one video. It covers the wrappers around scenes and guards against unwanted white flashes.

In plain words
What is it for?
Use it while assembling the master timeline or investigating a white flash at a cut or crossfade. It supports transitions built from scene movement, opacity, or filters.
Why use it?
Transitions can briefly reveal the page background when scene opacity drops, causing visible flashes. These rules ensure the underlying composition and scene wrappers are prepared for such transitions.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/heygen-com/hyperframes/seam-craft
Any agent
npx skills add heygen-com/hyperframes --skill seam-craft
Clone the repo
git clone --depth 1 https://github.com/heygen-com/hyperframes

Made for: Claude Code, Codex.

Per session 144 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,066 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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.

ModelPer sessionOnce invoked
Fable 5 $0.00144 $0.01066
Opus 5 $0.00072 $0.00533
Sonnet 5 $0.00029 $0.00213
Haiku 4.5 $0.00014 $0.00107

Measured 2d ago against content hash e86400c1fba3, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

seam-craft 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 2d ago.

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.

.agents/skills/seam-craft/SKILL.md · 69 lines

How it starts

The opening of the file, as written. The whole thing — 69 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Seam Craft — render prerequisites for scene-to-scene transitions

This is the render-correctness doctrine for PLV scene-to-scene seams: the prerequisites and master-timeline mechanics that make any transition composite correctly, independent of which specific transition is chosen. The per-transition catalog (crossfade, push-slide, zoom-through, cut-the-curve, …) lives in the transition registry — this page is the doctrine that sits underneath all of them.

The transitions this doctrine governs are Tier-B-ready: pure transform / opacity / filter on the two scene clip wrappers (#el-<sid>), no injected overlay DOM, no per-scene cooperation. Overlay families (staggered blocks, blinds, light leak, grid dissolve, page burn) and shader transitions are deferred to later phases.

Stage ground prerequisite (white-flash guard)

Several templates open a window where the two wrappers' summed opacity < 1 (the cut-the-curve mid-window cut, zoom-through's 0.15 floor, plain crossfade's power-curve dip). Whatever is BEHIND the wrappers shows through during that window. If the assembled index.html #root has no opaque background, the renderer composites the dip over its default white page → a white flash at every seam, glaring on dark films (observed on two Spotify runs before the fix). The assembler must paint the stage: #root { background: var(--canvas-deep, var(--canvas, #000)) }assemble-index.mjs now emits this; any other consumer of these templates owns the same guarantee.

How the injector applies a transition

At a break boundary between scene i (from) and scene i+1 (to), the injector:

  1. Extends #el-<from> wrapper data-duration by duration_s (holds its final frame — verified: core/src/runtime/init.ts:1393-1410 external-slot branch).
  2. Pulls #el-<to> wrapper data-start earlier by duration_s (creates the overlap window).
  3. Reassigns all clip data-track-index as a 0/1 ping-pong so the two overlapping wrappers never share a track (same-track overlap is illegal — core/src/lint/rules/composition.ts). Higher track composites on top.
  4. Stamps the gsap_template into window.__timelines["main"] at T = overlap-start.

Read the full file on GitHub · 69 lines

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.

  1. 2d ago First seen · 69 lines · 144 tokens per session scan A e86400c1fba3

Subscribe to this mod's changes

seam-craft is a skill published in the GitHub repository heygen-com/hyperframes (43,593 stars, last pushed today), licensed Apache-2.0. It adds 144 tokens to every session and 1,066 once invoked, about $0.0007 per session on Opus 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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