REFERENCE · PROTOCOL
Versions, capabilities, and compatibility.
The connection version selects framing and authentication; Hello capability negotiation selects the semantic terminal and session features available to that connection.
Version range
The current application protocol is N=2 and supports N-1=1. ALPN astra/1 identifies the framing and authentication family; Hello's version range and capability selection define the actual semantics.
Capability table
| Capability | Version | Status |
|---|---|---|
terminal.semantic_state | v2 | Enabled |
terminal.history_paging | v1 | Enabled |
session.objects | v1 | Enabled |
terminal.input_lease | v1 | Enabled |
terminal.datagram_state | — | Not enabled |
Compatibility boundary
Only N-1 clients without semantic capability negotiation enter the isolated ANSI path. Standalone SSH/SFTP Hosts are a separate product mode, not Astra-over-SSH stdio fallback.
Evolution rules
Capabilities must be negotiated explicitly. UI code must not guess old-field semantics, and migration paths must be versioned and registered. Clients reject unknown or incomplete state and request a reliable baseline.