Contract (Instance)

On Concordium, a contract refers to a deployed instance of a module. Each instance has its own address <index,subindex> and can maintain state independent of other deployments of the same module.

Representation

• gRPC: CCD_ContractAddress and CCD_InstanceInfo.
• MongoDB: MongoTypeInstance documents stored in the instances collection.
• Canonical ID: <index,subindex> string that is also used when composing token addresses (<index,subindex>-token_id).

Each instance records: - Source module reference (with versioning between v0/v1 structures). - Named entrypoints (receive functions) and current state hash. - Optional links to recognized projects (set by ms_instances).

Lifecycle

1. A user submits an account transaction with effect contract_initialized, referencing a module hash.
2. The ms_block_analyser service detects the effect and publishes a contract task.
3. ms_instances consumes the task, resolves full instance info via gRPC, persists it to MongoDB, and tries to associate it with a recognized project/module.
4. Subsequent contract_update_issued transactions trigger upgrades; ms_instances records the new module linkage and emits notifications.

Where contracts are used

• The Explorer UI links instances to their parent modules and displays their receive methods.
• Token accounting (ms_token_accounting) uses contract addresses to derive CIS-2 token addresses and track holders.
• Alias-aware lookups collapse contract references via the canonical <index,subindex> format, aligning with how we process account aliases.***