UPDATE operations timeout on isolated nodes without returning UpdateResponse

[sanity]

Problem Description

UPDATE operations sent to isolated nodes (nodes with no network peers) fail to return an UpdateResponse, causing the operation to timeout. This is a distinct issue from update propagation problems (#1848) and delta transmission optimization (#1450).

Test Evidence

Using the test isolated_node_regression.rs:

1. Single isolated node (no network peers)
2. Contract successfully PUT with initial state
3. UPDATE operation sent with new state
4. Contract executor successfully updates the contract state
5. UpdateResponse is never sent back to the client
6. Operation times out after 10 seconds

Logs from Test

UPDATE operation started
Contract executor updating contract (full state)
Delta updates are not yet supported (runtime.rs:304)
Contract state successfully updated in storage
[10 second timeout - no UpdateResponse received]
Test failed: timeout waiting for UpdateResponse

Root Cause Analysis

The contract executor logs a warning at runtime.rs:304:

tracing::warn!("Delta updates are not yet supported");

Despite this warning, the executor IS sending full state updates (not deltas), but the UpdateResponse appears to never be generated or routed back to the client.

Distinction from Related Issues

• Issue Fix Update Propagation Architecture: Implement Proximity-Based Forwarding and Repair Subscription Topology #1848: Focuses on update propagation between multiple network peers and subscription topology
• Issue Add support for update deltas through the network #1450: Focuses on optimizing network transmission using deltas instead of full state
• This issue: UPDATE operations fail to complete at all on isolated nodes, even when sending full state

Expected Behavior

1. Client sends UPDATE operation
2. Contract executor receives update, processes it (with full state)
3. Contract state is updated in storage
4. UpdateResponse is generated and sent back to client (THIS IS MISSING)
5. Client receives UpdateResponse confirming the update

Actual Behavior

Steps 1-3 succeed, but step 4 never happens, causing step 5 to timeout.

Impact

• Testing single-node configurations fails
• Local development workflows broken
• Cannot verify UPDATE functionality in isolation
• Discovered while testing PR Fix: WebSocket SubscribeResponse not being delivered to clients #1844 (Subscribe fix)

Environment

• Freenet version: Latest main branch
• Test: crates/core/tests/isolated_node_regression.rs
• Node configuration: Single isolated node (no network peers)

Code References

• Warning location: crates/core/src/contract/executor/runtime.rs:304
• Test demonstrating issue: crates/core/tests/isolated_node_regression.rs
• Related to update operation: crates/core/src/operations/update.rs

Related Issues

• Fix Update Propagation Architecture: Implement Proximity-Based Forwarding and Repair Subscription Topology #1848 - Update propagation architecture (multi-peer networks)
• Add support for update deltas through the network #1450 - Delta update transmission optimization
• Fix: WebSocket SubscribeResponse not being delivered to clients #1844 - Subscribe fix that exposed this issue during testing

[AI-assisted debugging and comment]

[iduartgomez]

Fixed in #1887