WIT ABI Reference¶

The contract host ABI is defined in config/wit/contract.wit as chain:contract@1.0.0. All host functions are imported through the host interface.

Storage¶

Function	Signature	Description
`kv-get`	`func(key: string) -> option<list<u8>>`	Read a value from the contract's KV namespace. Returns `None` if the key does not exist.
`kv-set`	`func(key: string, value: list<u8>)`	Write a value. Traps if called during a query.
`kv-delete`	`func(key: string)`	Delete a key. Traps if called during a query.
`kv-has`	`func(key: string) -> bool`	Check whether a key exists without reading the value.

Events¶

Function	Signature	Description
`emit-event`	`func(kind: string, data: list<u8>)`	Emit an event with a type tag and arbitrary data. Traps during queries.

Context¶

Function	Signature	Description
`get-sender`	`func() -> list<u8>`	Address of the immediate caller. For top-level transactions this is the signer. For sub-messages this is the dispatching contract.
`get-origin`	`func() -> list<u8>`	Address of the original transaction signer. Unchanged across sub-message depth.
`get-self-address`	`func() -> list<u8>`	Address of the currently executing contract.
`get-block-height`	`func() -> u64`	Current block height.

Logging¶

Function	Signature	Description
`log`	`func(msg: string)`	Write a debug log line. Available in dev mode; may be no-op in production.

Cross-contract communication¶

Function	Signature	Description
`dispatch`	`func(target: list<u8>, msg: list<u8>, reply-on: reply-on, funds: u64) -> result<u64, string>`	Queue a sub-message for deferred execution. Returns a locally-unique message ID used for routing replies. See Cross-Contract Calls.
`query-contract`	`func(target: list<u8>, msg: list<u8>) -> result<list<u8>, string>`	Synchronously query another contract (read-only, no state changes).

ReplyOn enum¶

The reply-on parameter on dispatch controls when the reply export is invoked:

Variant	Behavior
`never`	Fire and forget. Sub-message failure reverts the entire transaction.
`success`	Reply only on success. Failure reverts the entire transaction.
`error`	Reply only on error. Success does not trigger a reply.
`always`	Reply on both success and error.