URL: https://sabermage.github.io/spt-releases/messaging/overview.md Content-Type: text/markdown Method: text --- # Messaging The substrate everything else rides on: durable, addressed, reply-routable messages between endpoints — live when the target listens, spooled when it doesn't, across machines once nodes are paired. You've probably already run the [quickstart](../quickstart/messaging.md); this page is the model. ## Semantics - **Live-first, spool-fallback.** `spt send ` connects directly to a listening target (`SENT`); if the perch exists but nothing is listening, the message lands in the target's durable spool (`QUEUED`) and drains on its next `ready`. A target with *no* perch is an error (`NO_PERCH`) — identity is never invented on someone else's behalf. - **Reply routing.** Every message carries its sender id structurally; the arriving `` envelope surfaces it, and `spt send ` answers without knowing anything else. - **The blocking ask.** `spt ring ` sends and waits for the reply (with a timeout) — the synchronous question between agents. - **Per-message send control (three orthogonal axes).** Each `spt send` carries one value per axis; every axis defaults to unrestricted: - **Delivery window** (*when*) — `--active-only` spools for the agent's own poll without waking a live listener (it reaches the agent at its next natural boundary instead of interrupting now; also held for resting dormant/suspended instances and released exactly once on wake). This **renames the older `--deferred`**, which still parses as a hidden alias. `--idle-only` holds until the target is idle, then delivers (the wake). Default delivers in whichever window fires first. - **Channel** (*through what*) — `--prefer-native` routes through the target's translation binary when one is running, else falls back to the standard delivery; `--force-native` uses the binary only (no fallback, no reroute — if no binary is live it reports non-delivery rather than spooling to another method). Default is unrestricted. The translation binary is the adapter's idle-delivery filter; an adapter declares it with a `[message-idle-translation-binary].command` (a program token plus args, new in v0.16.0 — the bare `path` form is deprecated) and spt-core lifecycle-manages it. - **Persistence** (*how long*) — `--ephemeral` drops the message if it can't be delivered in its accepted window instead of spooling; it is the one path allowed to drop silently (everything else spools and reports non-delivery). *In this release ephemeral evaporation applies to translation-binary delivery and TTL expiry; the harness-relay carrier-absence case is not yet wired.* - **Opaque metadata.** `--json-payload ''` attaches a JSON metadata block alongside the body. spt-core carries it verbatim across every rail and never interprets it — the **receiving adapter** parses it. It can't forge spt-core's own envelope attributes (it rides inside a single `json` value), and any sender may attach it. - **Typed payloads.** Message bodies carry typed operations and file blobs, not just text — file transfers are addressable and progress-queryable mid-flight. ## Send outcomes — the closed set Every `spt send` reports exactly one outcome line. The line goes to **stderr** (stdout is reserved for message payloads); classify success by the **exit code** — `0` for every delivered/spooled outcome, non-zero for every failure. The token before the first `:` is stable; this set is complete as of v0.26.0. **Success (exit 0):** | Line | Meaning | |---|---| | `SENT:` | Delivered live to a listening target on this node. | | `SENT(WAN):@` | Delivered cross-node, **receiver-confirmed** — printed only when the remote daemon acknowledged. A suffix annotates the confirmed disposition: ` (spooled)` — the remote daemon accepted it into the target's durable spool; ` (duplicate)` — the receiver had already processed this message (a safe dedup'd replay). No suffix = delivered live. | | `QUEUED:` | The perch exists but nothing is listening — spooled durably, drains on the target's next `ready`. Success, not an error. | | `QUEUED(idle-only):` | An `--idle-only` send holding for the target's idle window. | | `DEFERRED:` | An `--active-only` send spooled for the target's own next poll (never interrupts a live listener). | **Failure (non-zero exit, stderr):** | Line | Meaning | |---|---| | `NO_PERCH: is not listening` | No perch for that id — identity is never invented on someone else's behalf. An `--active-only` send reports this with `(active-only stays local-only)`: the hook channel does not take the cross-node leg. | | `WAN_NO_PERCH: — no perch on ` | The route resolved to a node, but no perch lives there (a stale route — the endpoint may have moved or stopped). | | `WAN_REFUSED:@` | The receiver denied the message (access gate). | | `WAN_UNCONFIRMED:@` | No receiver acknowledgment — the peer may be offline or on an old version. The message may or may not have landed; only `SENT(WAN)` means confirmed. | | `WAN_FAIL: — ` | Cross-node transport failure. | | `AMBIGUOUS: — ` | Several nodes host that id — qualify (`@`). | | `EMPTY_MSG` | Refused: empty body. | ## The `` wire contract Every arriving message on an **agent** surface (`spt ready`, `api listen`, `api poll`, `api worker-poll`) is one `body` envelope — never a bare body: ```text hello check the build ``` A body that is already a fully-formed typed envelope (`echo_commune`, `notify`, `user-msg`, …) passes through **verbatim** — one envelope, never re-wrapped, and the body's own `from` wins. On the listener stream an oversized line splits into `` chunks the receiver reassembles; `api poll` / `api worker-poll` always emit one whole envelope per message, never chunked. **Escaping — the closed entity set.** Exactly four entities, plus the newline token; there is no `'`/`'` (single quotes ride literal): - **Encode (body):** `&` → `&` **first**, then `<` → `<`, `>` → `>`, `"` → `"`; then CRLF and lone CR normalize to LF, and LF → `
`. - **Decode (body):** split/replace `
` → newline **first**, then `<` → `<`, `>` → `>`, `"` → `"`, and `&` → `&` **last**. Amp-last is the invariant that keeps an embedded `&lt;` from double-decoding into `<`. - **Attribute values:** the same four entities in the same order, with no `
` step (attribute values are line-safe by construction). - Decode only the **extracted body substring** after parsing the envelope framing — never run the entity decode over the full line, or the framing tokens themselves unescape. **MAC-stamped frames are a different surface.** The shell relay drain (`api poll --link `) emits raw stamped frames of the form ` ` — a 64-hex-char HMAC-SHA256 over the frame bytes, one space, then the frame — and is deliberately **not** ``-wrapped (the shell child verifies the MAC and parses its own vocabulary). Agent-perch surfaces never emit stamped frames; a parser of agent traffic only ever sees `` / `` lines. ## Addressing Bare ids (`sergey`) resolve locally first, then across the subnet; when the same id is live on several nodes, resolution **refuses and asks you to qualify** (`sergey@desktop` — node labels and key prefixes both work) rather than guessing. The full form is `[subnet:]id[@node]`. ## Commands `send` · `ring` · `ready` (blocks; `--once` drains and exits) · `list` · `stop` · `whoami` — every flag in the [CLI reference](../cli/reference.md). Agents get the task-oriented version from the binary itself: `spt how-to ready` / `spt how-to send`.