feat(plugins): ProofKiosk — pay-to-actuate + attested kiosk suite (Track C)

[Sushant6095]

ProofKiosk — the machine that earns, acts, and proves it

Track C (DePIN & the physical edge) with Track A payment rails inside. A Raspberry Pi
running ZeroClaw becomes a self-service kiosk: a customer pays USDC via Solana Pay in
chat, a cron SOP verifies the payment on-chain and fires a GPIO relay (lock /
dispenser / charger), and the machine keeps a tamper-evident, hash-chained,
Merkle-batched record of its sensor readings and sale receipts. The agent sells;
deterministic SOPs deliver; the chain proves. No component ever holds a spendable key.

This is not another attestation builder — it is the closed physical loop: money in,
actuation out, proof forever. Every plugin is also useful standalone from a laptop
(no hardware needed to start), and works on any ZeroClaw channel (demoed on Telegram).

What's in it

Component	Track	Tier	Role
crates/kiosk-core	E	—	Wasm-friendly Solana substrate: base58, shortvec, Solana Pay, mockable JSON-RPC, memo, durable-nonce, unsigned legacy-message encode, seq/prev chain recovery, output shaping. No solana-sdk.
plugins/kiosk-charge	A	T1	Solana Pay charge URL + QR payload + unique reference. permissions = ["config_read"] only — zero network, zero secrets; the component imports no wasi:http at all.
plugins/kiosk-watch	A	T0	Verifies a payment on-chain (recipient + mint + amount + reference + finality) in ONE getSignaturesForAddress + ≤1 getTransaction; single-use reference = replay guard. Its structured verdict — not model text — is what the SOP gates the relay on. Also a device heartbeat.
plugins/kiosk-attest	C	T1	Hash-chained, durable-nonce, memo-only attestation of readings and receipts (a transfer is not expressible in its output); seq/prev recovered from the chain in ONE call.

Verified (all host-run, no live network)

• 107 host tests green across the suite (incl. property tests + untrusted-input fuzz hardening), cargo clippy --all-targets -D warnings clean, cargo fmt clean.
• cargo build --target wasm32-wasip2 --release clean for all three plugins (209 / 347 / 383 KB).
• Permissions == imports, verified: kiosk-charge imports 0 wasi:http (config_read only); watch/attest import wasi:http exactly matching their http_client grant. Script: scripts/verify-no-network.sh.
• Layout matches plugins/redact-text exactly: pure core / thin #[cfg(target_family="wasm")] shim, cdylib+rlib, standalone [workspace], structured logging via log-record, wit-bindgen 0.46 against the vendored wit/v0.
• CI workflow (.github/workflows/proofkiosk-ci.yml): test + clippy + wasm build + no-network proof.

Safety posture

The LLM is untrusted wherever money or actuation is concerned — it sells; deterministic
SOP rules deliver; the chain proves. Recipient, prices, caps, metric bounds all live in
operator config, unreachable from the prompt. Fail-closed injection drills ship as
executable tests + README transcripts per plugin. Third-party trust is declared in
SECURITY.md: the only trusted external system is the operator's own chosen RPC
endpoint — no facilitator, no MCP server, no oracle. Custody is strictly T0/T1; no
shipped component can sign or submit.

Hardware (the Track C part)

Pi 4 + BME280 (I2C) + relay (GPIO). Host built with
plugins-wasm,plugins-wasm-cranelift,hardware,peripheral-rpi. The plugins are
hardware-independent by design (readings/events arrive as tool args from the host's
hardware tools via SOP), so all logic is host-tested today. Wiring diagram + the
on-camera pay→relay→attest demo land this week; SOP examples for the payment loop,
sensor loop, and heartbeat are in sops/.

Reproducibility

PROOFKIOSK.md has a 3-rung ladder (laptop / +sensor / +relay), a 3-line minimal config,
and a 5-minute rung-1 quickstart. scripts/devnet-setup.sh creates a test SPL mint on
devnet/localnet so a reviewer can run the full loop without hardware.

Questions for maintainers

1. Preferred home for the shared crate: top-level crates/kiosk-core (as here) or publish to crates.io and depend on the registry version?
2. For a cron SOP step gating relay actuation on kiosk-watch's structured output (when: $.steps.N.paid == "true") — is engine-side condition evaluation the intended pattern, or is there a better host-native gate?

Happy to split into per-plugin PRs if preferred. Building in public on X; active in #solana-bounty.

— Superteam Earn "Build Solana-native plugins for ZeroClaw" submission (Track C ⭐)