Runtime Behavioral Contracts

Authority: Navigation (non-normative)
Purpose: Index and layer boundary for runtime behavioral contracts.

The runtime/ layer defines externally observable behavioral contracts for @sideband/runtime — the session lifecycle, message routing, and RPC correlation semantics that peer and application layers depend on.

These contracts sit above wire encoding. Wire-level rules remain in docs/protocols/. Runtime docs may reference protocol docs; they MUST NOT restate or redefine wire-level invariants.

Documents

Document	Scope	Authority
session.md	Session states, negotiators, retry, termination	Primary
router.md	Handler registration, dispatch ordering, error propagation	Primary

Key Invariants

• A Peer owns zero or more Session instances; at most one may be Active per peer in v1.
• Session retry is opt-in and per-session; it uses exponential backoff.
• Router dispatch is deterministic: exact match before prefix, registration order within each bucket.
• cid (correlation ID) is set by the request and echoed unchanged by the response; the runtime matches on cid, never on frameId.

ADRs

• ADR-009 — Session lifecycle design and negotiator interface
• ADR-010 — RPC correlation via cid
• ADR-011 — Message routing and dispatch rules