[ANN] XChain - A Chain-Agnostic Token, Exchange, and Smart-Contract Metalayer

https://xchain.io/assets/xchain-logo.png

XChain

XChain is an open source token platform for any blockchain, deployed today on Bitcoin, Litecoin, and Dogecoin, with no sidechains and no bridges. It is a metalayer, a meta-protocol in the tradition of Counterparty: a protocol embedded in ordinary transactions on an unmodified base chain, providing tokens, a native decentralized exchange, trustless cross-chain swaps, deterministic JavaScript smart contracts, on-chain data and messaging, and validator-verified external data, all secured directly by the host chain's existing proof-of-work consensus. There is no new chain, no new consensus for transaction ordering, and no bridge anywhere in the system. The public testnets are open to anyone today; mainnet opens for use at launch, which will be announced in this thread.

At a glance

Project: XChain (gas token: XCHAIN)
Category: token, exchange, and smart-contract metalayer on UTXO chains
Chains: Bitcoin, Litecoin, Dogecoin; adding a further UTXO chain is a configuration change, not a rebuild
Consensus: inherited entirely from the host chain; XChain adds none for ordering or settlement
Supply: 100,000,000 XCHAIN, hard-capped at genesis; distribution terms are finalized at protocol freeze and published before the distribution runs
License: AGPL-3.0, source public on GitHub
Status: deployed on mainnet and testnet on all three chains; the public testnets are open today, and mainnet opens for use at launch, which will be announced in this thread
White paper: https://docs.xchain.io/whitepaper
Documentation: https://docs.xchain.io
Source: https://github.com/XChain-Platform
Website: https://xchain.io

The problem

A blockchain like Bitcoin maintains one thing extremely well: a decentralized, tamper-proof, proof-of-work-secured ledger. It does not natively provide tokens, an exchange, programmable contracts, or structured data. For a decade the dominant answer has been to move value off the most secure chains, onto sidechains, bridges, and separate Layer-1s with their own validator sets and their own trust assumptions. That migration is also where the largest losses occur: cross-chain bridges remain among the most exploited constructs in the ecosystem, with losses in the billions. The largest, most liquid, most secure chains were never extended to do this work safely. XChain adds those capabilities on top of them, inheriting their security instead of rebuilding it on something weaker.

How it works

Every XChain operation is a compact, pipe-delimited ACTION string (for example

Code:

ISSUE|0|MYTOKEN|1000000|...

) embedded in a standard transaction using one of five encodings: OP_RETURN, bare multisig, P2SH, P2WSH, or a Taproot envelope carrying up to 390 KB in a single witness on BTC and LTC. To the base chain these are ordinary transactions. Software running the protocol reads each block, extracts and validates embedded ACTIONs against a fixed, deterministic rule set, and derives its own state: balances, order books, contract storage. The base chain is never modified, never forked, and never asked to understand the protocol.

Because the inputs (block data) and the rules (the protocol) are fixed and public, anyone can replay the chain from genesis and confirm every balance independently. State is a strict double-entry ledger (balances are always derived, never stored authoritatively), every block's state is committed to chained SHA-256 consensus hashes, and a node whose hashes diverge from the network halts rather than propagate bad data.

Design principles

Inherited security. No new chain, no new consensus for ordering, no bridge. Finality and double-spend resistance come entirely from the host chain. The validator network exists only for configuration, price data, cross-chain coordination, and attestation, never for ordering or settling token state.
Determinism. Every node processing the same base-chain data computes byte-identical state. No randomness, no wall-clock branching, no un-replayable external input anywhere in state processing.
Constraint over generality. Every state change, including every change produced by a smart contract, flows through one fixed, audited set of ACTION handlers. XChain is deliberately not a general-purpose world computer; in exchange, the state-transition surface is finite, small, and auditable.

Capabilities

The protocol defines 36 ACTIONs. In outline:

Tokens: fixed-supply currencies, permissionless public mints with per-address caps and time windows, non-fungible and edition tokens as locked compositions of the same fields, allow/block lists, issuer callback (redemption) terms, and one-way lock flags that make guarantees permanent and verifiable.
Markets: on-chain limit orders, token-for-token swaps, vending-machine dispensers with oracle-based fiat pricing, and native-coin settlement.
Cross-chain: trustless swaps and contract calls between chains, coordinated (never custodied) by a stake-weighted Byzantine-fault-tolerant validator federation. Tokens stay on their home chains; only ownership changes. No wrapping, no lockboxes.
Smart contracts: deterministic JavaScript executed in isolated V8 with AST-instrumented gas metering. Contracts cannot touch the ledger directly; they emit the same validated ACTIONs a user would, which pass through the same handlers. A contract bug cannot bypass protocol rules.
Outside-world data: a contract can request an HTTPS fetch, or a query to an approved AI model, through the attestation framework: validators fetch the answer independently, agree by consensus, and write it on-chain, so the result is reproducible by anyone replaying the chain.
Content and messaging: encrypted messaging, on-chain file storage, and token-gated encrypted content whose decryption key provably follows the token on every transfer, with no key server.
Betting and governance: parimutuel markets escrowed and paid out by consensus, and token-weighted polls (including quadratic and time-weighted modes) that can bind a contract to execute the outcome.
Staking: validator capability staking, plus contract-targeted staking of any token with programmatic slashing.

What it is not

Deliberate exclusions, each preserving a core guarantee:

No confidentiality. All state is public. The payload obfuscation layer is not encryption; its key derives from public transaction data. Public, replayable state is what makes independent verification possible.
Block-speed, not real-time. Confirmation, matching, and settlement proceed at the cadence of the host chain's blocks. There are no payment channels or rollups.
Not an EVM-style world computer. Contracts orchestrate validated ACTIONs; they cannot mutate ledger state directly, and a contract cannot observe its own emissions mid-execution.
UTXO chains only, today. Account-model ecosystems (Ethereum and similar) are a longer-term research direction, not a current capability. There are no wrapped external assets.
Light-client limits. The implemented light-client path verifies balance and action proofs against quorum-signed, DOGE-anchored checkpoints; its root of trust is the validator federation, not host-chain proof-of-work. Full trustless verification still means running a node.

Token and economics

XCHAIN is the gas token: actions that write state pay fees in it, or in native coin via oracle conversion. What is set in stone is the supply: a hard cap of 100,000,000 XCHAIN (8 decimals), fixed at genesis. Validator rewards are paid from a pre-funded pool and are never minted, and paying fees in XCHAIN can burn them, so the model has no inflationary issuance.

The distribution method is deliberately not published here, because it is not final. It is finalized at protocol freeze and will be published in full, in this thread and in the white paper, before the mainnet distribution runs. Whatever the final terms are, the distribution will be verifiable by replay rather than by announcement: the genesis files carry pinned hashes that every indexer verifies before deriving a single genesis action, and a node whose files do not match halts.

Current status

The protocol is deployed and running on Bitcoin, Litecoin, and Dogecoin, mainnet and testnet, with public explorer, encoder, and hub services.
The testnets are open: anyone can issue, trade, and deploy contracts on them today.
Mainnet is not yet open for use. The protocol is not frozen and the XCHAIN distribution has not run; until launch, treat mainnet as pre-release and build against the testnets.
Cross-chain settlement has executed end-to-end between chains on the test networks.
The source is public: 15 repositories on GitHub under AGPL-3.0, covering the full stack (node manager, encoder, decoder, indexer, explorer, hub, UTXO tracker, VM, replication, SDK, wallet, contract templates, regtest tooling, end-to-end tests, documentation).
Still ahead, in order: protocol freeze (wire format, gas schedule, GAS_PRICE), finalization of the XCHAIN distribution, the remaining consensus flag-day activations, and the mainnet launch and distribution. The mainnet launch date will be announced in this thread when it is set. The gas schedule and distribution are consensus-critical and are explicitly marked not final in the white paper until freeze.

Who we are

XChain is built by Jeremy Johnson and Javier Varona Zavatti (Dankest, LLC), former maintainers of Counterparty. We kept a production metalayer correct and live through real forks, real reorgs, and real user funds. XChain is a clean, modern, multi-chain implementation of what we learned doing that.

Resources

Overview (plain language): https://docs.xchain.io/overview
White paper: https://docs.xchain.io/whitepaper
Documentation: https://docs.xchain.io
Source: https://github.com/XChain-Platform
Explorer: https://explorer.xchain.io
Wallet: https://wallet.xchain.io
Website: https://xchain.io

Community

Telegram: https://t.me/XChainPlatform
X: https://x.com/xchain_io
Development discussion and bug reports: GitHub issues on the relevant repository. Security reports: see SECURITY.md in any repository.

Invitation

We welcome technical review, discussion, criticism, and bug reports. The protocol is not frozen yet, which means review now can still change it: if you think a mechanism described above is unsound, the white paper is the place to check the details and this thread is the place to say so.

Thread notes: this thread is not self-moderated. Please keep discussion technical; there is no token sale and price speculation is off-topic here. The first post will be kept up to date, with changes recorded below.

Changelog: 2026-09-01 initial post.