Agent systems are increasingly decomposed into specialized services: a planning agent delegates research, a research agent invokes retrieval and synthesis, and a compliance agent validates the result before an action is allowed. Open standards such as A2A formalize communication between independent agents, but transport interoperability is only part of the production problem. Requests can be lost after acceptance, retries can duplicate expensive work, callers can disappear while remote tasks continue, and multi-agent chains can become difficult to reconstruct. Temporal Nexus addresses a different layer. It connects Temporal applications through durable service contracts, allowing an agent capability to behave less like a fragile HTTP handoff and more like a reliable distributed operation.