Execution Context

• ID: mediator.execution-context
• Name: Execution context
• Maturity: GA
• Summary: Shares per-call state across handlers through an ambient context scope.

What It Does

IExecutionContext carries mediation-scoped state:

• CancellationToken
• Items key-value data
• Tags
• MessageResult
• Abort(...)

AmbientExecutionContext stores the current context via AsyncLocal<IExecutionContext?>. Handlers access it statically inside mediation flow. CreateScope sets and restores ambient context for nested and async flows.

Public Surface

public sealed class ContextAwarePreHandler : ICommandPreHandler<CreateOrderCommand>
{
    public Task PreHandleAsync(CreateOrderCommand message, CancellationToken cancellationToken = default)
    {
        AmbientExecutionContext.Current.Items["tenant"] = "tenant-a";
        return Task.CompletedTask;
    }
}

Packages

• LiteBus.Messaging.Abstractions
• LiteBus.Messaging

Requires

• mediator.handler-pipeline
• mediator.mediation-settings

Invariants

• Context is scoped to one mediation call.
• Current throws NoExecutionContextException when accessed outside scope.
• Result commands and queries aborted in pre-stage require a result object.
• MessageResult write in void command flow is ignored by strategy return path.

Non-Goals

• Cross-request ambient data persistence.
• Distributed context propagation across processes.
• Replacing explicit message fields for business data.

Observability

No context-specific meter or trace source is emitted.

Operational alternatives:

• Use Items to carry timing markers and emit logs in handlers.
• Validate context isolation with unit tests.

Test Coverage

Covered

Untested

• High-concurrency nested scopes across large fan-out event handlers.
• Very large Items payload memory pressure.

Out-of-Scope

• Async local diagnostics outside LiteBus mediation.
• External tracing propagation protocol implementation.

Deep Docs

• Execution context
• The handler pipeline