Reference

License and Versioning

The license for each component, the versioning signals used in these docs, and where to find the changelog.

By the end of this page you will know which license covers each component, what the version requirements in these docs mean, and where the changelog lives.

Licenses

Vellar is not one repository. Each component carries its own license, and a reviewer deciding whether to depend on Vellar needs to check the one that covers the piece they are actually taking.

Component	License	Source
`vellar-sdk` (published on npm)	MIT	github.com/Vellar-Wallet/vellar-sdk
The Vellar facilitator	Apache-2.0	github.com/Vellar-Wallet/vellar-facilitator
The Vellar explorer	Apache-2.0	github.com/Vellar-Wallet/vellar-explorer

Note: The identifiers above are what each repository declares. Read the LICENSE file in the repository you are depending on and rely on that rather than on this table, which is a summary and can fall behind.

The explorer is a separate open-source repository rather than a component of the facilitator. It reads ledger data directly and asks the facilitator nothing, so its license and its release cadence are independent. See Explorer.

The upto settlement contract

Contract	License	Origin
`contracts/upto-vellar/`	MIT	Vellar's own implementation, written from the x402 `upto` scheme specification

upto-vellar is the contract Vellar deploys. Its design brief at contracts/upto-vellar/DESIGN.md was committed before the implementation.

The deployed artifact, so the license note can be tied to something verifiable:

Field	Value
Contract id (testnet)	`CCZL7CTRS6GWEYXDYD54DZM3OUHQW2S2A4KSU75SH275P3SFZLL4YQAN`
Wasm sha256	`92365d9e5effe046a1db5b959bd2357672aef3f4b2137653c8095a0764d1f6c8`
Deployed	2026-09-09

upto-vellar is what the hosted facilitator serves in GET /supported.

Version signals in these docs

Where a page says a feature needs a minimum SDK version, it means the API did not exist, or did not behave as described, before that release.

Minimum version	Feature
`>= 0.4.0`	`wallet.x402` payments
`>= 0.5.0`	`wallet.agents` (agent keys)
`>= 0.6.1`	`rpcUrl` validation at construction

⚠️ APIs may change before 1.0. Pin a version rather than tracking the latest release, and read the changelog before upgrading. Breaking changes are noted there.

Changelog

For the SDK, CHANGELOG.md in the vellar-sdk repository is the record of what changed in each release.

For the facilitator there is no single changelog file. Use the git log for the sequence of changes, and docs/decisions.md, which records significant findings and decisions chronologically. The decisions file is the better read of the two if you want to know why something is the way it is rather than when it landed.

When it fails

Symptom	Cause	Fix
`wallet.x402` is missing on the wallet handle	The installed SDK is older than 0.4.0	Upgrade `vellar-sdk` to `>= 0.4.0`
`wallet.agents` is missing	The installed SDK is older than 0.5.0	Upgrade `vellar-sdk` to `>= 0.5.0`
A bad `rpcUrl` is not rejected when the wallet is constructed, and fails later instead	The installed SDK is older than 0.6.1, so the URL is not validated at construction	Upgrade `vellar-sdk` to `>= 0.6.1`