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Design systems covered the parts of a video that should never change per render — the brand. This page covers the parts that should. A card per customer. A stat per quarter. A name per recipient. When you know a composition will be reused, say so in the prompt. Name the parts that change. The agent turns them into declared variables — typed, labeled slots filled at render time instead of hardcoded into the HTML. The trigger phrase is simple. Call out the slots:
Build a 6-second title card. Make the name, the logo, and the accent color variables; everything else stays fixed.
Default variable values. The same composition re-rendered with --variables overrides — different name, logo, and accent, zero re-prompting. The agent declares data-composition-variables on the composition root, with the right type for each slot. The name is a string. The accent is a color. The logo is an image, and a plain URL is a valid value for it. A plain <img> logo needs no timing attributes. Only <video> and <audio> variables involve the media wiring described in variables. One composition, many fills.

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Say what type each slot is

There are seven variable types: string, number, color, boolean, enum, font, and image. Each one validates differently at render time. In Studio, boolean, enum, color, and number each get their own control, while string, font, and image use a plain text input. You don’t write the JSON yourself. But naming the type in the prompt removes a guess:
Variables: plan (enum: Free / Pro / Enterprise), price (number, shown as $), featured (boolean — toggles the ribbon), headline (text).
  • ❌ make the plan and price editable
  • ✅ plan is an enum (Free / Pro / Enterprise); price is a number in dollars
The engine rationale: an enum with declared options is checked against that list at render time, so enum-out-of-range gets caught. A number can carry min, max, step, and a unit label, which is what gives Studio a real slider instead of a bare text box. Say “editable” and you leave the agent to pick a type. A mistyped value then surfaces much later.

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Template, then render one per record

Once the varying parts are variables, the same source renders once per data row. This is a real batch mode, not a copy-paste-per-video loop. You author the composition once and feed it a list of value sets:
Build this as a template with name and title variables, then render one video per row of my data — output to renders/{name}.mp4.
The agent authors the composition, then runs a batch render. The batch input is a JSON array. Each row is one set of variable values, and each row produces one output file. {key} placeholders in the output path get filled from that row. If your source is a CSV, say so. The agent converts it to the row array the batch expects. Add “fail on any undeclared or mistyped value” and it renders with --strict-variables. A typo in a column name then stops the run instead of silently rendering the default. Everything shares one composition. So a design fix propagates to every output on the next render. You are not editing a hundred near-duplicate files.

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Personalization asks

Personalized-at-scale videos are the same pattern, with the value set coming from your data:
A 10-second welcome clip that greets each new signup by first name and shows their company logo. I’ll supply a list of { firstName, logoUrl } records.
firstName is a string. logoUrl is the image slot your composition binds to an <img src>. Pass assets as URL references, not inlined data. URL-shaped values travel cleanly through both the local renderer and distributed Lambda renders. Wiring this behind your own product UI or an agent instead of the CLI? The @hyperframes/sdk opens a base template and layers a sparse override set per instance. The host then stores only each record’s delta.

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Declare up front — don’t bake values in

The most common miss is describing the finished video with the values already fixed, then asking to “make it reusable” afterward:
  • ❌ Make a card that says "Acme — Pro plan — $49". Later I'll want other companies too.
  • ✅ Make a plan card. Variables: company (text), plan (enum), price (number, $). Show "Acme / Pro / 49" as the default.
The engine rationale: variables are runtime values a script applies to the live DOM. They resolve from declared defaults first, then per-instance overrides, then the CLI. Declare them up front and the reusable structure exists from the first render. The default is then just one more value set. Bake "Acme — Pro — $49" into the markup and you get a composition with no slots. Reuse then means an edit pass over hardcoded text for every variant. That is exactly what variables exist to avoid.

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Prove the template actually re-skins

A template that never re-skins can pass every gate you have. lint and check verify structure. --strict-variables catches an undeclared or mistyped key. Neither can tell you whether the values you passed ever reached the DOM. The failure looks like success. The render completes, exits clean, and is pixel-identical to the default. So test it differentially. Render twice and compare:
Two identical files mean the override never reached the property you expected. Check three things. Is the variable ID declared? Does the render command use that exact ID? Is the visible property actually bound to its CSS custom property or variable value? Render-time --variables overrides are global by variable ID. The compiler applies a matching override to CSS custom properties on the root and on sub-compositions pulled in with data-composition-src. data-variable-values is still the per-instance way to give two mounts different values. Scoped JavaScript inside a sub-composition reads its own per-instance variable table. So forward values at the mount point when that script calls getVariables() instead of reading CSS. The capstone keeps its variables on one root file for simplicity, not because templates require one file. Sub-compositions work as long as shared CSS-bound IDs are declared consistently. Use mount-point values for instance-specific or JavaScript-read inputs. Its exact variable clause is quoted at the bottom of this page.

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What can’t be a variable

A few inputs are read once at compile time, and no variable can move them:
  • composition dimensions (data-width / data-height)
  • the root composition’s total duration
  • frame rate
  • output format, codec, or quality
So this doesn’t do what it reads like:
  • ❌ make the video length a variable so each render can be a different duration
  • ✅ author one composition per target length — or vary a clip’s duration, which is re-read from the live DOM
If total length must differ per output, that is a different root data-duration per render, not a variable. See what can’t be a variable for the full list and the compile-time-vs-live-DOM rule behind it.
An authored CSS custom property always wins over a same-named variable. Say your composition already defines its own :root { --accent: ... } as a hand-written theme token. A variable called accent never overwrites it — the authored value stands. A render-time --variables override still wins over both. So when you need to override an authored value per render, use --variables, not a same-named declared variable.

Variables (concept)

The mechanics: declaring types, per-instance overrides, batch renders, precedence.

@hyperframes/sdk

Template + sparse-override editing behind your own product UI or agent.

The specification dial

How much to specify — and why naming the type is cheap precision.

Design systems and brand

Brand tokens as variables that re-skin every reuse from one value.
Capstone thread — the Level 7 film is a working template. One single-file composition, one variable scope. Its second render is nothing but one --variables flag: navy ground, acid-green ink, every region re-skinned including the generated mural. Both full renders are embedded on the capstone page.
This is the clause in the full capstone prompt that buys the piece — prompt language you can lift for your own video:
Variables: expose ground (default #0a0a0a) and ink (default #3CE6AC) as composition variables on the single root file, bound via CSS custom properties everywhere (including the duotoned mural), so one --variables call re-skins the entire journey. It will be rendered twice: the default brand palette, and a second full render with {"ground":"#0d1420","ink":"#c8ff3d"}. Architecture constraint (technical): single composition file — one index.html, one variable scope. […] No data-composition-src sub-files.
Next: Storyboards — for multi-scene work, prompt the plan a frame-by-frame build fills in, not the scenes one by one.