> ## 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

**2026-07-31**

v0.6

* Released contracts **v3**: all deployment addresses rotated (deterministic CreateX deploys, salt `train.protocol.v3`) — see the updated [Deployments](https://docs.train.tech/deployments.md) 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](https://docs.train.tech/protocol-spec/core.md) and [implementation guides](https://docs.train.tech/protocol-spec/implementation-solver.md) 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.

**2026-07-29**

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](https://docs.train.tech/deployments.md) page for the full, current list of mainnet, testnet, and in-progress network addresses — it replaces the old Contracts page.

**2025-11-16**

v0.4

* Introduced [Wallet HTLC](https://docs.train.tech/protocol/atomic-swaps-secret_gen.md), secret generation from the wallet mechanism.
* Added [HKDF specification](https://docs.train.tech/protocol-spec/HKDF.md) describing HKDF usage in TRAIN.

**2025-11-11**

v0.3

* Updated the [Auction Mechanism](https://docs.train.tech/protocol-spec/auction) to enable solver competition and ensure users receive the best possible swap price.

**2025-04-29**

v0.2

* Added research about [cross-chain trading dynamics](https://docs.train.tech/research/cross-chain-trading.md) with TRAIN protocol.

**2025-02-10**

v0.2

* Released TRAIN to mainnet.
* Mainnet contracts are available [here](https://docs.train.tech/deployments.md).
* Added Bridge Deployment API documentation (later retired).

**2025-02-10**

v0.1.6-testnets

* Updated the [Edge Cases](https://docs.train.tech/protocol-spec/edge-cases.md) 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.

**2024-12-26**

v0.1.6-testnets

* Removed the Atomic Pool concept.
* Introduced the new [Reward & Slash mechanism](https://docs.train.tech/protocol/slashing.md) embedded in Atomic Swaps themselves, eliminating the need for Atomic Pools.

**2024-12-14**

v0.1.5-testnets

* Added introduction to the [Auction system](https://docs.train.tech/protocol/auction) and the [technical details](https://docs.train.tech/protocol-spec/auction).

**2024-12-12**

v0.1.5-testnets

* Released TRAIN [Bridge dApp](https://app.train.tech) to use [Signature flow](https://docs.train.tech/protocol-spec/core.md) instead of requiring two transactions; users now complete one transaction and one signature.

**2024-12-11**

v0.1-testnets

* Updated [dApp Implementation](https://docs.train.tech/protocol-spec/implementation-dApp.md) and [dApp](https://docs.train.tech/protocol/dApp.md) 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.

**2024-11-29**

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 |

**2024-11-27**

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.


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