Signet Guardian — Payment Guard Middleware

Overview

Signet Guardian is a policy firewall for money actions. It does not intercept payments at runtime by itself; payment-capable skills must route through it by contract:

1. Before any payment: call signet-preflight (amount, currency, payee, purpose).
2. If result is ALLOW or CONFIRM_REQUIRED (and user has confirmed): the skill may proceed.
3. If result is DENY: do not proceed; tell the user the reason.
4. After a successful payment: call signet-record to append to the ledger.

This gives one place to enforce: master switch (payments on/off), max per transaction (e.g. £20), max per month (e.g. £500), and optional confirmation above a threshold (e.g. £5).

Concurrency: Preflight is advisory (no lock). Record enforces the monthly cap under a file lock ({baseDir}/references/.ledger.lock): it re-checks the cap before appending and refuses to record if the month would be exceeded. So the monthly limit is enforced at record time; idempotency and cap are both safe under concurrent calls. Preflight can still be used to fail fast; the definitive check is in record.

Currency: No FX conversion. The request currency must match the policy currency; otherwise preflight returns DENY. Conversion source/rules are not defined.

Policy (user configuration)

Source of truth: OpenClaw config first (signet.policy in the main config, e.g. editable in the Control UI if the extension is installed), then fallback to {baseDir}/references/policy.json. OpenClaw sets {baseDir} via OPENCLAW_SKILL_DIR or OPENCLAW_BASE_DIR.

Field	Meaning
paymentsEnabled	Master switch. If false, all payments are denied.
maxPerTransaction	Max amount allowed for a single transaction (e.g. 20).
maxPerMonth	Max total spend in the current calendar month (e.g. 500).
currency	ISO currency code (e.g. GBP, USD). Request currency must match.
requireConfirmationAbove	Above this amount, return CONFIRM_REQUIRED so the user must explicitly confirm (e.g. 5).
blockedMerchants	Optional list of substrings; payee matching any is denied.
allowedMerchants	Optional; if non-empty, only payees matching one of these are allowed.
version	Optional number for future policy migrations.

Default behaviour: If the policy file is missing or invalid, preflight returns DENY (default-deny).

Commands

signet-preflight

Run before initiating any payment. Validates: payments enabled, currency match, amount > 0 and ≤ max per transaction, (current month spend + amount) ≤ max per month, and optional merchant rules. Optionally requires explicit confirmation above a threshold. Amount must be greater than zero.

signet-preflight --amount 15 --currency GBP --payee "shop.example.com" --purpose "Subscription"

Optional:

• --idempotency-key "unique-key" — Used when recording later to avoid duplicate ledger entries.
• --caller-skill "skill-name" — Name of the skill invoking the guard (for audit).

Output (JSON):

• { "result": "ALLOW", "reason": "Within policy" } — Proceed with the payment.
• { "result": "CONFIRM_REQUIRED", "reason": "..." } — Ask the user for explicit confirmation; if they agree, proceed then call signet-record. (Confirmation is the caller’s responsibility.)
• { "result": "DENY", "reason": "..." } — Do not proceed. Notify the user.

Every DENY is logged to the audit trail.

Exit code: 0 for ALLOW or CONFIRM_REQUIRED, 1 for DENY.

signet-record

Call after a payment has successfully been made. Appends one line to the ledger (append-only). If an idempotency key was used in preflight, pass the same key here to avoid double-counting.

Record validation scope: signet-record re-checks only currency and monthly cap (under lock). It does not re-check paymentsEnabled or merchant allow/block lists. Policy enforcement (switch, merchants, per-tx limit) is done at preflight (and in an optional future authorize phase). Record is the post-success log; the cap check at record time prevents double-counting when concurrent preflights both allowed.

signet-record --amount 15 --currency GBP --payee "shop.example.com" --purpose "Subscription" --idempotency-key "sub-123"

Optional: --caller-skill "skill-name" for audit.

If the same idempotency-key was already recorded, the command is a no-op (idempotent).

signet-report

Shows spending and transaction history for the user.

signet-report --period today
signet-report --period month

signet-policy

Show, edit, or configure policy via wizard.

signet-policy --show    # Print current policy (config, then file)
signet-policy --edit    # Open policy.json in $EDITOR
signet-policy --wizard  # Interactive step-by-step setup (no JSON)
signet-policy --migrate-file-to-config  # One-time: copy file policy into OpenClaw config

Audit (ledger and deny log)

Ledger file: {baseDir}/references/ledger.jsonl. Format is strict JSONL: one JSON object per line, newline-separated (no space between entries). Each line contains:

• ts — Timestamp UTC (ISO 8601).
• callerSkill — Optional; skill that invoked preflight/record.
• idempotencyKey — Optional; dedupe key for record.
• status — completed or denied.
• reason — Decision reason (especially for denials).
• Plus: amount, currency, payee, purpose.

All preflight denials are appended to the same ledger with status: "denied" and a reason.

Critical Rules (for the agent)

1. Never skip preflight — Any payment from any skill must go through signet-preflight first. No exceptions.
2. Respect DENY — If preflight returns DENY, do not attempt the payment. Tell the user the reason.
3. CONFIRM_REQUIRED — If preflight returns CONFIRM_REQUIRED, ask the user explicitly (“Allow this payment of £X to Y?”). Only proceed if they confirm, then call signet-record.
4. Always record success — After a successful payment, call signet-record with the same amount, currency, payee, purpose, and idempotency key (if used).
5. Idempotency — For critical flows, use a stable --idempotency-key (e.g. order ID or request ID) so retries do not double-count in the monthly total.
6. Default-deny — If the policy file is missing or corrupt, the skill denies by default.
7. Record is authoritative for cap only — The monthly cap is enforced when recording (under lock). If signet-record fails with a cap error, the payment already happened; do not retry without user confirmation. For cap-safe flows before payment, a future authorize (reservation under lock) then settle (convert reservation to completed) pattern can reserve budget before the payment is made.

First Run

On first use, the user must have a valid {baseDir}/references/policy.json. Run signet-policy --show to see current policy; if missing, create it (e.g. via signet-policy --edit) with at least:

• paymentsEnabled: true/false
• maxPerTransaction: number
• maxPerMonth: number
• currency: e.g. "GBP"
• requireConfirmationAbove: number (e.g. 5)

Ledger lives at {baseDir}/references/ledger.jsonl; no extra setup required.