sequenceDiagram
    participant User
    participant UI as UI Component
    participant Hook as useWorkflowExecution
    participant Core as execution-core.ts
    participant Engine as ExecutionEngine
    participant Session as LoggingSession
    participant DB as Database

    User->>UI: Clicks Run or Cancel
    
    alt Start Execution
        UI->>Hook: handleRunWorkflow()
        Hook->>Session: safeStart()
        Session->>DB: INSERT with status='running'
        Hook->>Core: executeWorkflowCore()
        Core->>Engine: execute()
        
        loop While hasWork()
            Engine->>Engine: Check isCancelled flag
            alt Not Cancelled
                Engine->>Engine: processQueue()
                Engine->>Engine: executeNodeAsync()
            else Cancelled and executing.size === 0
                Engine-->>Engine: Break loop
            end
        end
        
        Engine-->>Core: ExecutionResult with status
        
        alt Status: cancelled
            Core->>Session: safeCompleteWithCancellation()
            Session->>DB: UPDATE status='cancelled'
        else Status: paused
            Core->>Session: (Skip completion, keep running)
            Session->>DB: UPDATE status='pending'
        else Status: completed/failed
            Core->>Session: safeComplete/safeCompleteWithError()
            Session->>DB: UPDATE status='completed/failed'
        end
        
        Core-->>Hook: result
        Hook-->>UI: Update execution state
    else Cancel Execution
        UI->>Hook: handleCancelExecution()
        Hook->>Hook: Set context.isCancelled = true
        Hook->>Hook: Cancel stream reader
        Hook->>Hook: Reset execution state
        Note over Engine: Currently executing block<br/>continues to finish
        Engine->>Engine: Check isCancelled on next iteration
        Engine-->>Core: status='cancelled'
        Core->>Session: completeWithCancellation()
        Session->>DB: UPDATE status='cancelled'
    end
    
    alt Resume from Pause
        User->>UI: Provides input for paused execution
        UI->>Hook: Resume execution
        Hook->>DB: UPDATE status='running'
        Hook->>Core: executeWorkflowCore (resume mode)
        Core->>Engine: execute()
        Note over Engine: Continues from snapshot
        Engine-->>Core: ExecutionResult
        Core->>Session: Update parent execution log
        Session->>DB: UPDATE status based on result
    end