v2026.7.21: SPEC-244 — Native std.utcp (SBI Peer)

v2026.7.21: SPEC-244 — Native std.utcp

SPEC-244 RATIFIED. Janus ships a first-class std.utcp family for agent tool RPC — capability-gated, SBI-only, length-prefixed over TCP.

Implementation tip: origin/unstable @ 82a77dff.

What’s new

In-process substrate

• Tool registry with required capabilities
• Sessions: present caps → invoke (or ERR_CAP_MISMATCH / -1403)
• Intern table for well-known tools and caps (compile, version, JPEN apply)

SBI wire (not JSON)

Frames use the standard SBI preamble (SBI\0) plus a fixed LE header. Kinds: invoke request/response, PRESENT, RESET, STAGE.

TCP unit: u32 LE length + SBI frame.

Persistent peer

• Bind 127.0.0.1 (ephemeral port supported)
• Sequential accept loop or concurrent multi-client accept
• Multi-invoke sessions on one connection
• STAGE + pipeline.envelope.apply → SPEC-236 JPEN apply

Docs

• Reference: std.utcp
• Tutorial: UTCP peer and JPEN tool
• Spec: SPEC-244 in project _COMPLETED/

Follow-through (same day)

Landed after the initial tip above (current unstable @ 402c62e1):

• LEAS STAGE + LRES response bodies; MANL binary manuals (utcp.manual)
• janusd SBI+HTTP dual-stack; --json kept as INTEROP (not retired)
• CHNK multi-chunk STAGE reassembly (16 KiB)
• Schema fingerprint BLAKE3-128 domain-separated KDF

Residual

TLS / non-loopback bind, CAP_NET gates, full Zig lease registry → pure Janus.