Delegate capability: Contract UPDATE

[sanity]

Parent: #2827

Summary

Allow delegates to send updates to contracts, modifying their state.

Proposed Implementation

1. Add to OutboundDelegateMsg (freenet-stdlib)

UpdateContractRequest {
    contract_id: ContractInstanceId,
    delta: StateDelta,
},

2. Add to InboundDelegateMsg (freenet-stdlib)

UpdateContractResponse {
    contract_id: ContractInstanceId,
    result: Result<UpdateResult, UpdateError>,
},

Where UpdateResult might include:

• New state summary
• Whether update was accepted
• Any feedback from the contract

3. Handle in delegate runtime (freenet-core)

In delegate.rs, when processing OutboundDelegateMsg::UpdateContractRequest:

1. Call executor.perform_contract_update()
2. Package result as InboundDelegateMsg::UpdateContractResponse
3. Call delegate again with the response

Design Questions

1. Authorization: How does the contract know the update is authorized?

   • The delegate signs the update with a private key
   • The contract verifies against a known public key
   • This is entirely the contract's responsibility
   • Should we provide helper utilities for common auth patterns?

2. Sender attestation in the update flow:

   • When a delegate sends an update, should the contract see who sent it?
   • Currently updates go through the network layer which may anonymize
   • For delegate-initiated updates, should there be an option to include sender identity?

3. Conflict handling: What if the contract rejects the update?

   • Return error to delegate
   • Include reason/details if contract provides them

4. Batching: Should delegates be able to send multiple updates atomically?

   • Single update at a time (simpler)
   • Batch updates (more efficient but complex)

5. Optimistic vs confirmed updates:

   • Should the delegate be notified when update is locally computed?
   • Or only when it's confirmed/propagated in network mode?
   • Different use cases may need different guarantees

Testing

• Unit test for new message types
• Integration test: delegate updates contract state via freenet local
• Test rejected update (contract validation fails)
• Test authorized update (delegate signs, contract verifies)
• Verify update triggers notifications to subscribed delegates (Delegate capability: Contract SUBSCRIBE #2830)

Acceptance Criteria

• OutboundDelegateMsg::UpdateContractRequest added to stdlib
• InboundDelegateMsg::UpdateContractResponse added to stdlib
• Runtime handles the request and applies update
• Works in both freenet local and freenet network modes
• Example/test delegate demonstrates update flow

[github-actions]

🤖 Auto-labeled

Applied labels:

• T-feature (95% confidence)
• P-medium (85% confidence)
• E-medium (80% confidence)
• A-contracts (95% confidence)
• S-needs-design (90% confidence)

Reasoning: This is a request to add new delegate-initiated contract update functionality (new messages, runtime handling, tests), which is a new feature. It impacts the contract runtime and stdlib (A-contracts) and touches developer-facing APIs/tests (A-developer-xp) and authorization/signature concerns (A-crypto). The scope appears moderate complexity (stdlib + runtime + auth + tests), so E-medium. The issue raises multiple open design questions (authorization, sender attestation, conflict handling, batching), so it should be marked as needing design. Priority set to medium as it introduces new capability but is not described as blocking or critical.

Previous labels: none

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