# Shellstream Boundary

Shellstream is the attested stream protocol for inter-cluster communication. Kedge DaemonSet terminates Shellstream handshakes at the cluster boundary.

## 3-Way Handshake
1. **ATTEST-INIT**: Remote peer sends SAT token with capability request
2. **ATTEST-VERIFY**: Local Kedge validates SAT, evaluates capabilities against accord policy, sends attenuated grant
3. **ATTEST-CONFIRM**: Session established with granted capabilities

## Mode Selection
The capability token determines overlay vs. underlay access, governed by MSP trust tier mappings in the local accord policy.