Bitfield Docs

Build the smallest complete package recipe: one package set, one package, one boundary file, one durable record, and one verification point.

Use this recipe when your product needs stable package-owned data before you add files, callable targets, or a React surface.

What you will build

You are building a tiny package called product-copy inside a package set called starter-package-set.The package declares one record:

Field	Value
Package set	`starter-package-set`
Package	`product-copy`
Boundary file	`product-copy/things-to-store-and-run.json`
Record address	`package::product-copy::welcome`
Payload	Welcome copy for a product screen

A record is addressed data. Addressed means the package gives the data a stable name, so the same package can be admitted again without guessing what the data is.

Folder shape

starter-package-set/
  product-copy/
    things-to-store-and-run.json

starter-package-set is the collection. product-copy is one package inside it. The file inside the package is the boundary Bitfield reads.Success check:

The package folder contains exactly one public files and names file:
starter-package-set/product-copy/things-to-store-and-run.json

If the boundary file is missing, there is no package contract to admit.

Boundary file

{
  "package": "product-copy",
  "things": [
    {
      "type": "record",
      "address": "package::product-copy::welcome",
      "payload": {
        "headline": "Welcome back.",
        "body": "Your product can keep moving without every feature importing every other feature."
      }
    }
  ]
}

What each field means

Field	Meaning
`package`	The package name Runtime Kit is admitting.
`things`	The public list of things the package brings.
`type: "record"`	This entry stores durable package-owned data.
`address`	The stable name for this record inside the package.
`payload`	The JSON value the package owns at that address.

The package now has one durable record named package::product-copy::welcome. The address is not a UI label. It is the stable package-owned name that lets Runtime Kit admit the same record predictably.

Verify the recipe

Use this checklist before building on top of the recipe:

Check	Pass condition
Package folder	`starter-package-set/product-copy/` exists.
Boundary filename	The file is named `things-to-store-and-run.json`.
Boundary JSON	The file parses as JSON.
Package field	`package` equals `product-copy`.
Thing type	The only entry uses `type: "record"`.
Address	The address starts with `package::product-copy::`.
Payload	The payload is product data, not a secret.

If any row fails, fix the recipe before adding a React component. React cannot repair a broken package file.

Change the record later

Change the payload, keep the address, and admit the package again. Same address means same piece of package data. New payload means new content for that piece.That gives you a safe edit path:

same address + new payload = update this package-owned record
new address + new payload  = add a separate package-owned record
new package name           = create a different package file

Do not change all three at once while debugging. Change one field, verify it, then move to the next.

Common failures

Symptom	Cause	Fix
The package is not admitted.	The boundary file is missing or invalid JSON.	Fix `things-to-store-and-run.json` first.
The record cannot be found later.	The address changed between package versions.	Keep the address stable when changing payload only.
Another package overwrote the meaning.	Two examples copied the same package/address names into one set.	Rename the package or address intentionally.
A public example contains secrets.	Someone treated package data like a secret store.	Remove the secret and rotate it outside this docs path.

Extend it

After this works, add one capability at a time:

Add a second record for another piece of product copy.
Add a stored_bytes entry when the package owns a file.
Add a slot when app code needs a named target to ask for work.
Add a React surface that reads a data name created from the record.

The shape stays the same: package declares, Runtime Kit admits, app surfaces read named data or call named targets.

Do not put private product secrets in public package examples. Package records are product data. Secrets belong behind your account and deployment controls.

Read Package-owned file when the package needs bytes beside records.Read Package file for exact record field rules, payload choices, and invalid examples.Read Package to screen when you want to turn admitted package data into a React surface.

Use Runtime Kit

Understand Runtime Kit

Build without tangled code

Runtime Kit Cookbook

Reference

Package set with one record

What you will build

Folder shape

Boundary file

What each field means

Verify the recipe

Change the record later

Common failures

Extend it

Next

​What you will build

​Folder shape

​Boundary file

​What each field means

​Verify the recipe

​Change the record later

​Common failures

​Extend it

​Next

What you will build

Folder shape

Boundary file

What each field means

Verify the recipe

Change the record later

Common failures

Extend it

Next