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name: bitcoin-l2-rgb description: | RGB protocol: client-side validated smart contracts on Bitcoin + Lightning. v0.12 consensus (zk-AluVM, issuers), the diverging v0.11.1 line, rgb-lightning-node for LN integration. USDT-on-RGB rollout. USE WHEN: building RGB contracts, integrating RGB Lightning, comparing with TAP. allowed-tools: Read, Grep, Glob

RGB Protocol

RGB is a system of client-side validated smart contracts on Bitcoin and Lightning. Maintained by LNP/BP Standards Association

• RGB Consortium.

Repos:

• github.com/RGB-WG — main RGB working group (v0.12 line).
• github.com/rgb-protocol — diverging v0.11.1 line (see below).
• github.com/RGB-Tools/rgb-lightning-node — LN integration.

Two diverging lines (as of September 2026)

Read this before anything else — the ecosystem forked in mid-2025 and "RGB" now names two incompatible protocols.

Aspect	RGB-WG v0.12	v0.11.1 line
Org	RGB-WG (LNP/BP)	rgb-protocol
Site	rgb.tech	rgb.info
Newest	rgb-core v0.12.0, 10 Jul 2025	0.11.1-rc.11, 15 Jul 2026
VM	zk-AluVM (40 instructions)	classic AluVM (rgb-aluvm)
Contract defs	issuers + contract API	schemata (rgb-schemas)
Fungible state	finite-field elements	revealed u64 amounts
Used by	rgb CLI, rgb-std	rgb-lib, rgb-lightning-node

• RGB-WG shipped the final v0.12 consensus layer on 10 July 2025 (rgb-core 0.12.0). Consensus is frozen; contracts issued against it are forward-compatible. The standard library and CLI above it are still at v0.12.0-rc.3 (15 July 2025) — no final tag as of September 2026.
• RGB-WG published a security notice on 18 July 2025 stating that v0.11.1 is a fork of unreleased v0.11 code with "nearly absent" unit test coverage and removed smart-contracting capability, and that "the only version recommended by us for the production is v0.12".
• The v0.11.1 line is nevertheless the one actually shipping in Lightning: rgb-lib 0.3.0-beta.7 (17 July 2026) pins rgb-ops, rgb-invoicing and rgb-schemas at =0.11.1-rc.11, and rgb-lightning-node builds on that rgb-lib. Its repos (rgb-consensus, rgb-aluvm, rgb-tests) were still being pushed in September 2026.
• Contracts issued with pre-v0.12 RGB-WG releases are not compatible with v0.12; RGB-WG recommends re-issuing them.

Concepts

Client-side validation

RGB contracts don't put state on Bitcoin's chain. Instead:

• Contracts publish a contract definition + state transitions (a schema on the v0.11.1 line; an issuer in v0.12).
• Owners hold cryptographic proofs of their balances.
• Bitcoin txs commit to RGB state via single-use seals. v0.12 unified the previously separate tapret (Taproot-tweak) and opret (OP_RETURN) seal types into one, keeping an OP_RETURN fallback for wallets that cannot use Taproot.
• Verification: walk the proof chain back to issuance. In v0.12 consignments are streamed and validated on the go instead of being loaded into memory.

Contract definitions: schemata (v0.11.1) vs issuers (v0.12)

The v0.11.1 line keeps the classic schema model. rgb-schemas ships, as of 0.11.1-rc.11 (July 2026):

• NIA — non-inflatable fungible asset.
• UDA — unique digital asset (single-token NFT with attachment).
• CFA — collectible fungible asset.
• PFA / IFA — permissioned and inflatable fungible assets, both marked not production-ready in the repo.
• Custom schemas (e.g. medical records, supply chain) written against AluVM by the issuer.

RGB v0.12 removed schemata from the wallet-facing model. Per the 10 July 2025 release post, instead of importing schemata, interfaces and other components, wallets consume issuers published by contract developers plus a contract API — "a simple non-generic object explaining to a wallet how to operate with a contract". Interfaces survive only inside the Contractum language, whose compiler emits those contract APIs.

AluVM / zk-AluVM

v0.11.1 line — classic AluVM (rgb-protocol/rgb-aluvm):

• Register-machine with strict resource limits.
• Smart contract code runs client-side during validation.

v0.12 — zk-AluVM, introduced in the 10 July 2025 consensus release:

• Turing-complete zk-VM built for client-side validation.
• Non-von-Neumann architecture, 40 instructions.
• Read-once memory, matching single-use seal semantics.
• Contract state unified into finite-field elements; the three state variants of RGB-WG's pre-v0.12 design (fungible via Pedersen commitments + Bulletproofs, structured non-fungible, binary attachments) are gone. The v0.11.1 fork's shipping code never had them: its FungibleState is a revealed u64 (Bits64).
• Pedersen commitments and Bulletproofs removed — zk-STARKs replace them (Bulletproofs were never implemented for secp256k1).
• Consensus validation reduced to a few hundred lines expressible as an arithmetic circuit, which is what enables recursive history compression by a zk prover.

RGB Lightning Network (RLN)

rgb-lightning-node (RLN node) is an RGB-enabled LN node:

• Lightning channels can carry RGB assets.
• Each commitment tx has an extra output anchoring the RGB state transition.
• Asset transfers via standard Lightning HTLCs with RGB-asset metadata.

Recent (2025–2026)

• RGB v0.12 consensus release, 10 July 2025 — see above. No newer RGB-WG consensus release as of September 2026.
• Fork security notice, 18 July 2025 — RGB-WG disavows v0.11.1.
• rgb-lightning-node has no tagged releases; development happens on master (head commit 26 August 2026). It vendors rust-lightning 0.2.x and declares rgb-lib =0.3.0-beta.7, but a [patch.crates-io] entry redirects it to rgb-lib git master, so the build is not actually pinned to that version.
• RLN work that landed in 2026: zero-amount RGB payments, payment preimages exposed in the payment APIs, push_asset_amount on channel open, and IFA support (all March 2026); BOLT11 description / description_hash on the invoice APIs and an optional-bitcoind chain backend via lightning-transaction-sync (August 2026). No BOLT12 / offers support has landed.
• Desktop wallet: RGB-Tools/iris-wallet-desktop, newest tagged release 0.2.0 (17 April 2025); repo last pushed 3 March 2026.

Bitlight Labs

Major contributor; runs testing infrastructure for RGB Lightning.

USDT on RGB

Tether announced on 28 August 2025 its intent to launch USDT on RGB, citing the v0.11.1 mainnet release. UTEXO leads the commercial rollout, on that same v0.11.1 line. Public milestones since:

• UTEXO shipped an on-chain RGB module for Tether's Wallet Development Kit (February 2026) and an RGB Lightning module for the same WDK (28 August 2026); the Lightning module is still beta.
• UniSat named as the next USDT-on-Bitcoin wallet partner (4 September 2026) — send / receive / swap described as "coming", no release date.

No public mainnet USDT-on-RGB launch announcement had appeared as of mid-September 2026.

Compared to Taproot Assets

Aspect	RGB	Taproot Assets
Backing	LNP/BP Association	Lightning Labs
Smart contracts	Yes (zk-AluVM in v0.12)	Limited
LN integration	rgb-lightning-node	tapd + LND
Contract types	Schemata (NIA/UDA/CFA) or v0.12 issuers	Single asset model
Maturity	v0.12 consensus frozen Jul 2025, std lib still rc	v0.8.3 production (Sept 2026)
Wallets	Limited	Wider (LN Terminal, etc.)

Use cases

• Stablecoins (USDT on RGB).
• Custom smart contracts for regulated assets, NFTs, supply chain tokens.
• Programmable money with privacy by default (validation is client-side; on-chain only sees Taproot commitments).

Architecture

[User wallet]
  - Holds RGB state proofs locally.
  - Commits state to Bitcoin via Taproot anchor.
[Counterparty wallet]
  - Receives state transition + proof.
  - Validates client-side back to genesis.

Privacy: chain analyst sees only Taproot outputs, not asset amounts or recipients.

Implementations

• rgb-core — RGB-WG consensus layer (v0.12.0, 10 Jul 2025).
• rgb-std / rgb — RGB-WG standard library and CLI (v0.12.0-rc.3, 15 Jul 2025).
• rgb-consensus / rgb-ops / rgb-schemas — the rgb-protocol v0.11.1 line (0.11.1-rc.11, 15 Jul 2026).
• rgb-lib — RGB-Tools wallet library on the v0.11.1 line (0.3.0-beta.7, 17 Jul 2026).
• rgb-lightning-node — modified LDK with RGB anchor support.
• rgb-lightning-sample — example apps.

Common bugs

• Lost state proof = lost assets (unrecoverable, no on-chain history).
• LN state desync between channel updates → RGB commitment mismatch.
• AluVM / zk-AluVM contract bugs → logic errors hard to detect post-issuance.
• Wallet incompatibilities: a v0.12 wallet cannot read contracts issued on the v0.11.1 line, or with pre-v0.12 RGB-WG releases.

Status (September 2026)

• Two incompatible lines in parallel: RGB-WG v0.12 (consensus final since 10 July 2025, std lib and CLI still at rc.3) and the rgb-protocol v0.11.1 line (0.11.1-rc.11, July 2026).
• RGB Lightning (rgb-lightning-node) ships on the v0.11.1 line and has no tagged release; master's head commit is 26 August 2026.
• USDT-on-RGB (announced August 2025, UTEXO-led): still pre-launch — no mainnet launch announcement as of September 2026.
• Wallet ecosystem expanding (RGB Tools, BitMask, others).

See also

• taproot-assets/SKILL.md
• liquid/SKILL.md
• ../../lightning/ldk/SKILL.md
• ../../protocol/taproot/SKILL.md