This page summarizes the on-chain responsibilities of the EVM settlement hub lane.

UntronV3 hub: shared state + facet entrypoints

The hub is a single deployed contract that owns all state.

To keep runtime bytecode under size limits, heavy entrypoints live in separate facet contracts that are invoked via delegatecall.

Important property:

• facet addresses are set as constructor immutables (a “static facet split”), not a governance-upgrade mechanism.

Hub index (event emission + hub-local hash chain)

The hub’s eventing is typically routed through an index helper:

• events are emitted through internal helpers rather than being emitted directly from the hub logic,
• events may also be appended into a hub-local SHA-256 event hash-chain for integrity/indexing.

Key facets / entrypoints (conceptual)

• Admin: privileged configuration (proof reader, allowlists, swap rates, bridgers, pauses, chain deprecations, etc.)
• Lease: create leases; update payout configs
• Entitle: preEntitle (fast path) and optional subjectivePreEntitle
• Controller: slow path relay (relayControllerEventChain) and processing (processControllerEvents)
• LP vault: deposit/withdraw principal
• Fill: fill claim settlement

Tron proof reader (tronReader)

The hub relies on a configured tronReader to:

• verify Tron tx inclusion/finality, and
• decode tx call data and timestamps.

The tronReader is a trust boundary because it is configurable by the hub owner.

See: Admin & trust model.

SwapExecutor

Swaps are executed via a per-hub SwapExecutor:

• only callable by the hub
• executes a filler-provided call sequence
• enforces a minimum output for a specific token
• returns output to the hub

This isolates swap execution from core accounting.

Bridgers (adapter interface)

Bridgers implement a simple adapter interface used during fill:

• if targetChainId != block.chainid, the hub transfers tokens to a bridger and calls it to deliver cross-chain.

The hub does not verify destination delivery; bridgers are trusted configuration.