# Transport Contracts

## Context
- Tenant: HTTP x-tenant-id; NATS tenant-id
- Correlation: HTTP x-correlation-id; NATS x-correlation-id + correlation-id
- Trace: HTTP traceparent; NATS traceparent + trace-id

## Internal RPC (gRPC)
- Aggregate: CommandService (submit commands)
- Projection: QueryService (execute queries)
- Runner: RunnerAdmin (drain, status, reload)
- All calls set deadlines and propagate context metadata

## NATS JetStream
- Streams:
  - AGGREGATE_EVENTS: tenant.*.aggregate.*.*
  - WORKFLOW_COMMANDS, WORKFLOW_EVENTS
- Producers set headers: tenant-id, Nats-Msg-Id, correlation, traceparent/trace-id
- Consumers use AckPolicy::Explicit, bounded ack_wait, max_deliver, max_ack_pending

## Routing
- Gateway routes per-tenant to shards for Aggregate/Projection/Runner
- Routing tables hot-reload atomically