> ## Documentation Index
> Fetch the complete documentation index at: https://docs.train.tech/llms.txt
> Use this file to discover all available pages before exploring further.

# Protocol Updates

> Protocol updates and improvements

<Update label="2026-07-31" description="v0.6">
  * Released contracts **v3**: all deployment addresses rotated (deterministic CreateX deploys, salt `train.protocol.v3`) — see the updated [Deployments](/deployments) page.
  * Solver locks are now keyed by **(hashlock, solver address)** instead of an incremental index. Each solver gets exactly one slot per hashlock (the double-lock guard), so a blind retry can never double-fund a swap and no one can squat another solver's slot. The [Core spec](/protocol-spec/core) and [implementation guides](/protocol-spec/implementation-solver) are updated to the v3 interface.
  * Recorded mainnet deployments for Starknet, Fuel Ignition, and Tempo alongside the 7 EVM mainnets.
  * Aztec upgraded to v5.0.1 with solver-keyed locks on testnet; Solana devnet now covers the full SOL/SPL reward matrix with three gasless rails.
</Update>

<Update label="2026-07-29" description="v0.5">
  * EVM contracts rewritten on Foundry with deterministic CREATE2 deployment, and relaunched on mainnet with one shared address across Ethereum, Arbitrum One, OP Mainnet, Base, Polygon PoS, BSC, and Robinhood.
  * Updated the Starknet and Fuel mainnet contracts to the current version.
  * Launched on [Tempo](https://tempo.xyz) mainnet, TRAIN's first deployment to a chain with no native gas token.
  * See the new [Deployments](/deployments) page for the full, current list of mainnet, testnet, and in-progress network addresses — it replaces the old Contracts page.
</Update>

<Update label="2025-11-16" description="v0.4">
  * Introduced [Wallet HTLC](/protocol/atomic-swaps-secret_gen), secret generation from the wallet mechanism.
  * Added [HKDF specification](/protocol-spec/HKDF) describing HKDF usage in TRAIN.
</Update>

<Update label="2025-11-11" description="v0.3">
  * Updated the [Auction Mechanism](/protocol-spec/auction) to enable solver competition and ensure users receive the best possible swap price.
</Update>

<Update label="2025-04-29" description="v0.2">
  * Added research about [cross-chain trading dynamics](/research/cross-chain-trading) with TRAIN protocol.
</Update>

<Update label="2025-02-10" description="v0.2">
  * Released TRAIN to mainnet.
  * Mainnet contracts are available [here](/deployments).
  * Added Bridge Deployment API documentation (later retired).
</Update>

<Update label="2025-02-10" description="v0.1.6-testnets">
  * Updated the [Edge Cases](/protocol-spec/edge-cases) specification with more detailed explanations.
  * Rebranded to TRAIN from Layerswap V8. All repositories have been migrated to the new [TrainProtocol](https://github.com/trainProtocol) organization.
</Update>

<Update label="2024-12-26" description="v0.1.6-testnets">
  * Removed the Atomic Pool concept.
  * Introduced the new [Reward & Slash mechanism](/protocol/slashing) embedded in Atomic Swaps themselves, eliminating the need for Atomic Pools.
</Update>

<Update label="2024-12-14" description="v0.1.5-testnets">
  * Added introduction to the [Auction system](/protocol/auction) and the [technical details](/protocol-spec/auction).
</Update>

<Update label="2024-12-12" description="v0.1.5-testnets">
  * Released TRAIN [Bridge dApp](https://app.train.tech) to use [Signature flow](/protocol-spec/core) instead of requiring two transactions; users now complete one transaction and one signature.
</Update>

<Update label="2024-12-11" description="v0.1-testnets">
  * Updated [dApp Implementation](/protocol-spec/implementation-dApp) and [dApp](/protocol/dApp) pages to include details for verifying the state of destination chains via Light Clients and/or multiple providers.
  * Replaced 'LP' terminology with 'Solver' to avoid confusion with passive liquidity providing and to better explain the concept.
</Update>

<Update label="2024-11-29" description="v0.1.1-testnets">
  * Prepared branch for EVM security audit
  * EVM Gas Optimization

  | Function       | Optimization | Gas (new) | Gas (old) |
  | -------------- | ------------ | --------- | --------- |
  | `commit()`     | 52.7%        | 146,300   | 309,608   |
  | `addLock()`    | 56.6%        | 34,250    | 78,961    |
  | `addLockSig()` | 48.9%        | 42,103    | 82,447    |
  | `refund()`     | 35.5%        | 39,460    | 61,262    |
  | `redeem()`     | 45.5%        | 45,835    | 84,110    |
</Update>

<Update label="2024-11-27" description="v0.1-testnets">
  * Released the first version of the TRAIN protocol on EVM, Fuel, Starknet, Solana, and TON testnets.
  * Released the first version of the Bridge Deployment API (later retired).
  * Released the documentation page.
</Update>