4. Activity Execution Snapshots

Date: 2025-08-04
Status: Accepted

Context

Today the ActivityExecutionContext is persisted only at commit points.
If an activity references a workflow variable that changes after it has run—but before the next commit—the value saved is the later value, not the one that existed when the activity executed.
As a result, the Workflow Instance Viewer shows misleading data: users expect to see the variable values at execution time, not at commit time.

Decision

Capture a snapshot of the ActivityExecutionContext immediately when an activity executes.
The snapshot must include:

• All workflow variables and their values at that moment.
• Any other execution-specific metadata required for replay or inspection.

The snapshot is created by serializing the ActivityExecutionRecord to JSON and storing it in the database. The persistence layer will be updated to handle this new snapshot field, ensuring it is stored alongside the activity execution record.

Consequences

• The Workflow Instance Viewer will now display the exact state that the activity saw, eliminating confusion during debugging and auditing.
• Additional storage will be consumed for each snapshot. We accept this overhead in exchange for correctness and developer experience.
• Existing persistence schemas will require a non-breaking migration to store the snapshot payload.
• Workflow instances before this change will not have snapshots, but they will still be replayable even if the variable values are not accurate at execution time.