# Harness contract `claude-spt` is glue: it maps Claude Code **hook events** to the `spt` binary's harness-contract inbound surface (`spt api --adapter claude-spt `). The binary is harness-agnostic; this adapter is the Claude-Code-shaped edge of it. The authoritative contract lives on `spt-core`'s published surface — the [harness-contract + CLI reference](https://sabermage.github.io/spt-releases). This page documents the **adapter's** wiring: which Claude Code hook drives which `spt api` verb. ## Hook → `spt api` mapping | Claude Code hook | sptc wrapper | `spt api` verb | Purpose | | ------------------ | --------------------------- | ------------------------ | --------------------------------------------------- | | `SessionStart` | `hooks/session-start.sh` | `seed` / `bind` / `boundary` | Bootstrap spt-core, register the perch (`bind` spt-hosted · `seed` harness-hosted · `boundary` on clear/compact), then relay an agent-facing brief (see below); non-blocking — never `listen`. | | `UserPromptSubmit` | `hooks/user-prompt-submit.sh` | `poll` | Drain delivered messages and surface them to the prompt as `additionalContext`. | | `Stop` | `hooks/stop.sh` | `state` (idle) | Mark the agent idle when a turn ends. | | `SessionEnd` | `hooks/session-end.sh` | `session-end` | Tear down session state cleanly. | | `SubagentStart` | `hooks/subagent-start.sh` | `worker-*` | Track a spawned subagent. | | `SubagentStop` | `hooks/subagent-stop.sh` | `worker-*` | Track subagent completion. | ## Two invariants the wrappers hold - **Payload comes from stdin, never from a `/`-leading argument.** On Windows under Git Bash / MSYS, any argument beginning with `/` is silently rewritten to a Windows path. The wrappers read the Claude Code hook payload as JSON from **stdin**, so a `/sptc:…` token is never corrupted. - **Messages are self-delimiting `` envelopes.** `poll` output is rendered by splitting on the canonical `body` envelope, so a multi-message drain parses cleanly and each message keeps its sender for reply-correlation. ## Identity Every session resolves its own perch id via `spt whoami`, off `$OWL_SESSION_ID` / `$SPT_AGENT_ID`. A session with no perch (never made reachable) simply delivers nothing — the per-prompt drain no-ops rather than erroring. ## SessionStart briefs `SessionStart` also relays an **agent-facing brief** as `additionalContext`, composed from the adapter's `[strings.briefs]` (same file-backed/inline machinery as `[strings.skills]`). The hook only selects + composes + `{id}`-substitutes — it never authors the prose. | session state | trigger | brief | | --- | --- | --- | | has a perch | `bind` (`$SPT_ENDPOINT_ID`) or `boundary` (clear/compact) | **identity brief** — who it is (`{id}`), that its perch is already live (don't re-arm → `COLLISION`), and how to message (`spt send` + reply + the `spt endpoint list` roster). | | no perch, node has subnet peers | `seed` / fresh startup | **ring brief** — how to reach other agents without a perch (`spt ring --timeout 60`) + the roster. | | no perch and no peers · subagent (`agent_type` set) | — | nothing. | The brief is **liveness-agnostic** (no live-vs-ready distinction) pending a published machine-readable liveness query on the spt surface. The peer gate is a line-count presence check on `spt subnet status` — it never parses the human-formatted column values. > The operative skill instructions are **not** in this plugin. They are delivered by the adapter > manifest (conducted by spt-core) at invocation time; the `/sptc:*` `SKILL.md` files are > deliberately thin skeletons. This split keeps the marketplace artifact low-churn while logic and > instructions update through spt-core's signed adapter-update channel.