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feat: policy-governed demo and replay-safe agent nonce handling
- Add demo.ts with multi-agent adversarial scenarios - Generate monotonic nonces per agent to prevent replay attacks - Rely on Treasury contract for deterministic nonce enforcement - Refine PaymentIntent schema and agent execution flow
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5 files changed

+352
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lines changed

‎agent/agent.ts‎

Lines changed: 61 additions & 18 deletions
Original file line numberDiff line numberDiff line change
@@ -1,14 +1,30 @@
11
import { GoogleGenAI } from "@google/genai";
2-
import { PaymentIntentSchema, AgentInput } from "./schema";
2+
import { PaymentIntentSchema, AgentInput, proposePaymentTool, PaymentIntent } from "./schema";
33
import { buildPrompt } from "./prompt";
44
import { ethers } from "ethers";
55
import "dotenv/config";
66

7-
// ================== NONCE ==================
8-
let nextNonce = 1n;
97

10-
function getNextNonce(): string {
11-
return (nextNonce++).toString();
8+
9+
export type ExecutionIntent = {
10+
agent: string;
11+
recipient: string;
12+
amount: string;
13+
nonce: string;
14+
};
15+
16+
17+
// ================== NONCE ==================
18+
// Nonce is monotonically increasing per agent.
19+
// Off-chain nonce is used only for sequencing.
20+
// On-chain contract enforces replay protection.
21+
const agentNonces = new Map<string, bigint>();
22+
23+
function getNextNonce(agent: string): string {
24+
const current = agentNonces.get(agent) ?? BigInt(Date.now());
25+
const next = current + 1n;
26+
agentNonces.set(agent, next);
27+
return next.toString();
1228
}
1329

1430
// ================== ENV ==================
@@ -69,7 +85,7 @@ export async function getPolicy(agentAddress: string) {
6985
}
7086

7187
export async function proposePayment(input: AgentInput) {
72-
const nonce = getNextNonce();
88+
const nonce = getNextNonce(input.agentAddress);
7389

7490
const enrichedInput = {
7591
...input,
@@ -78,25 +94,52 @@ export async function proposePayment(input: AgentInput) {
7894

7995
const genAI = new GoogleGenAI({
8096
apiKey: GEMINI_API_KEY,
81-
apiVersion: "v1"
97+
apiVersion: "v1beta"
8298
});
8399

100+
// 1. Try to force structured output via config first (Best for Gemini 3)
84101
const result = await genAI.models.generateContent({
85-
model: "gemini-2.5-flash-lite",
102+
model: "gemini-3-flash-preview",
86103
contents: [{ role: "user", parts: [{ text: buildPrompt(enrichedInput) }] }],
87-
config: { ["response_mime_type" as any]: "application/json" } as any
88-
});
89-
90-
const text = result?.text;
91-
if (!text) throw new Error("Empty Gemini response");
92-
93-
const parsed = JSON.parse(text.replace(/```json/g, "").replace(/```/g, "").trim());
94-
if (parsed.reject) throw new Error(`Agent rejected: ${parsed.reason}`);
104+
tools: [{ functionDeclarations: [proposePaymentTool] }],
105+
// TOOL CONFIG IS KEY: Force the model to use the tool if it can
106+
toolConfig: {
107+
functionCallingConfig: {
108+
mode: "ANY" // Forces the model to call a function
109+
}
110+
}
111+
} as any);
112+
113+
// 2. The Extraction Logic: Handle both Tool Calls AND JSON Text
114+
const candidate = result.candidates?.[0];
115+
const functionCall = candidate?.content?.parts?.[0]?.functionCall;
116+
const textResponse = candidate?.content?.parts?.[0]?.text;
117+
118+
// CASE A: It worked as a Tool Call (Ideal)
119+
if (functionCall && functionCall.name === "propose_payment") {
120+
console.log("✅ Gemini 3 used Function Calling");
121+
return PaymentIntentSchema.parse(functionCall.args);
122+
}
95123

96-
return PaymentIntentSchema.parse(parsed);
124+
// CASE B: It returned JSON text instead (Fallback)
125+
if (textResponse) {
126+
console.warn("⚠️ Gemini 3 returned text. Attempting JSON parse...");
127+
try {
128+
// Clean up markdown code blocks if present
129+
const cleanJson = textResponse.replace(/```json/g, "").replace(/```/g, "").trim();
130+
const parsed = JSON.parse(cleanJson);
131+
132+
// Map the parsed JSON to your schema if needed, or just validate
133+
// (Assuming the text output matches your schema structure)
134+
return PaymentIntentSchema.parse(parsed);
135+
} catch (e) {
136+
console.error("Failed to parse JSON text:", textResponse);
137+
}
138+
}
139+
throw new Error("Agent did not propose a valid payment intent (No tool call or valid JSON)");
97140
}
98141

99-
export async function executePayment(intent: any) {
142+
export async function executePayment(intent: ExecutionIntent) {
100143
const treasury = new ethers.Contract(TREASURY_ADDRESS, TreasuryABI, signer);
101144

102145
const tx = await treasury.executePayment({

‎agent/demo.ts‎

Lines changed: 265 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,265 @@
1+
/**
2+
* demo.ts
3+
*
4+
* PGAP — Policy-Governed Agent Payments
5+
*
6+
* Purpose:
7+
* Scripted, narrative demo showing how AI agents propose payments
8+
* and how on-chain policy deterministically enforces safety.
9+
*/
10+
11+
import "dotenv/config";
12+
import {
13+
getPolicy,
14+
proposePayment,
15+
executePayment,
16+
ensureCooldownElapsed,
17+
} from "./agent";
18+
19+
// ================== CONFIG ==================
20+
21+
const AGENT_A = process.env.AGENT_A_ADDRESS!;
22+
const AGENT_B = process.env.AGENT_B_ADDRESS!;
23+
const AGENT_C = process.env.AGENT_C_ADDRESS!;
24+
const ALLOWED_RECIPIENT = process.env.RECIPIENT_ADDRESS!;
25+
const TREASURY = process.env.TREASURY_ADDRESS!;
26+
const ATTACKER = "0x000000000000000000000000000000000000dEaD";
27+
28+
if (!AGENT_A || !AGENT_B || !AGENT_C || !ALLOWED_RECIPIENT || !TREASURY) {
29+
throw new Error("Missing required demo env vars");
30+
}
31+
32+
// ================== UTILITIES ==================
33+
34+
function banner(title: string) {
35+
console.log("\n" + "=".repeat(60));
36+
console.log(title);
37+
console.log("=".repeat(60));
38+
}
39+
40+
function section(title: string) {
41+
console.log("\n▶ " + title);
42+
}
43+
44+
async function printPolicy(agent: string) {
45+
const policy = await getPolicy(agent);
46+
console.log("Policy:", {
47+
perTx: Number(policy.perTx) / 1e6,
48+
daily: Number(policy.daily) / 1e6,
49+
cooldown: policy.cooldown,
50+
spent: Number(policy.spent) / 1e6,
51+
});
52+
}
53+
54+
// ================== SCENARIO RUNNER ==================
55+
56+
async function runScenario(name: string, fn: () => Promise<void>) {
57+
section(name);
58+
try {
59+
await fn();
60+
console.log("✅ Scenario completed");
61+
} catch (err: any) {
62+
console.log("❌ Scenario reverted");
63+
console.log("Reason:", err?.shortMessage || err?.message || err);
64+
}
65+
}
66+
67+
// ================== MAIN ==================
68+
69+
async function main() {
70+
banner("PGAP DEMO — Policy-Governed Agent Payments");
71+
72+
console.log("Treasury:", TREASURY);
73+
console.log("Agents:", {
74+
AgentA: AGENT_A,
75+
AgentB: AGENT_B,
76+
AgentC: AGENT_C,
77+
});
78+
79+
section("Initial Policy State");
80+
await printPolicy(AGENT_A);
81+
82+
// ================== SCENARIO 1: Valid Payment ==================
83+
84+
await runScenario("Scenario 1 — Valid Payment (Agent A)", async () => {
85+
const agent = AGENT_A;
86+
const policy = await getPolicy(agent);
87+
88+
// Ensure cooldown elapsed if agent was used before
89+
await ensureCooldownElapsed(agent, BigInt(policy.cooldown));
90+
91+
const intent = await proposePayment({
92+
request: `Pay 1 USDC to ${ALLOWED_RECIPIENT} for API access`,
93+
agentAddress: agent,
94+
policy: {
95+
perTxLimit: policy.perTx,
96+
dailyRemaining: (BigInt(policy.daily) - BigInt(policy.spent)).toString(),
97+
cooldownSeconds: policy.cooldown,
98+
allowedRecipients: [ALLOWED_RECIPIENT],
99+
},
100+
});
101+
102+
console.log("Proposed intent:", {
103+
amount: Number(intent.amount) / 1e6,
104+
nonce: intent.nonce,
105+
reasoning: intent.reasoning
106+
});
107+
108+
const txHash = await executePayment(intent);
109+
console.log("✅ Payment executed");
110+
console.log("Tx hash:", txHash);
111+
});
112+
113+
// ================== SCENARIO 2: AI Refuses Over-Limit ==================
114+
115+
await runScenario("Scenario 2 — AI Refuses Over-Limit Payment (Agent B)", async () => {
116+
const agent = AGENT_B;
117+
const policy = await getPolicy(agent);
118+
119+
try {
120+
const intent = await proposePayment({
121+
request: "Pay 2 USDC for premium API access",
122+
agentAddress: agent,
123+
policy: {
124+
perTxLimit: policy.perTx,
125+
dailyRemaining: (BigInt(policy.daily) - BigInt(policy.spent)).toString(),
126+
cooldownSeconds: policy.cooldown,
127+
allowedRecipients: [ALLOWED_RECIPIENT],
128+
},
129+
});
130+
131+
// If we got here, AI didn't refuse - that's a problem
132+
console.log("⚠️ AI proposed:", intent);
133+
throw new Error("AI should have refused but proposed a payment");
134+
} catch (err: any) {
135+
// Expected - AI should refuse
136+
if (err.message.includes("Agent rejected") || err.message.includes("did not propose")) {
137+
console.log("✅ AI correctly refused invalid request");
138+
console.log("Reason:", err.message);
139+
} else {
140+
throw err;
141+
}
142+
}
143+
});
144+
145+
// ================== SCENARIO 3: Cooldown Enforcement ==================
146+
147+
await runScenario("Scenario 3 — Cooldown Enforcement (Agent A)", async () => {
148+
const agent = AGENT_A;
149+
const policy = await getPolicy(agent);
150+
151+
// Don't wait for cooldown - we want to trigger the error
152+
const intent = await proposePayment({
153+
request: `Pay 1 USDC to ${ALLOWED_RECIPIENT} immediately`,
154+
agentAddress: agent,
155+
policy: {
156+
perTxLimit: policy.perTx,
157+
dailyRemaining: (BigInt(policy.daily) - BigInt(policy.spent)).toString(),
158+
cooldownSeconds: policy.cooldown,
159+
allowedRecipients: [ALLOWED_RECIPIENT],
160+
},
161+
});
162+
163+
console.log("Proposed intent (will be rejected on-chain):", {
164+
amount: Number(intent.amount) / 1e6,
165+
});
166+
167+
try {
168+
await executePayment(intent);
169+
throw new Error("Cooldown was bypassed - this should not happen!");
170+
} catch (err: any) {
171+
if (err.data === "0x9e494994" || err.message.includes("Cooldown")) {
172+
console.log("✅ Treasury enforced cooldown on-chain");
173+
console.log("↳ AI proposed, but contract rejected (as designed)");
174+
} else {
175+
throw err;
176+
}
177+
}
178+
});
179+
180+
// ================== SCENARIO 4: Unauthorized Recipient ==================
181+
182+
await runScenario("Scenario 4 — Unauthorized Recipient (Agent B)", async () => {
183+
const agent = AGENT_B;
184+
const policy = await getPolicy(agent);
185+
186+
// Tell AI the attacker is allowed (lie to the AI)
187+
const intent = await proposePayment({
188+
request: `Pay 1 USDC to ${ATTACKER}`,
189+
agentAddress: agent,
190+
policy: {
191+
perTxLimit: policy.perTx,
192+
dailyRemaining: (BigInt(policy.daily) - BigInt(policy.spent)).toString(),
193+
cooldownSeconds: policy.cooldown,
194+
allowedRecipients: [ATTACKER], // Lie to AI
195+
},
196+
});
197+
198+
console.log("AI was told attacker is allowed, proposed payment to:", intent.recipient);
199+
200+
try {
201+
await executePayment(intent);
202+
throw new Error("Unauthorized recipient was paid - treasury failed!");
203+
} catch (err: any) {
204+
if (err.data === "0x4ccc1eec" || err.message.includes("Recipient")) {
205+
console.log("✅ Treasury blocked unauthorized recipient");
206+
console.log("↳ AI was misled, but contract enforced truth");
207+
} else {
208+
throw err;
209+
}
210+
}
211+
});
212+
213+
// ================== SCENARIO 5: Nonce Replay Attack ==================
214+
215+
await runScenario("Scenario 5 — Nonce Replay Attack (Agent C)", async () => {
216+
const agent = AGENT_C;
217+
const policy = await getPolicy(agent);
218+
219+
const intent = await proposePayment({
220+
request: `Pay 1 USDC to ${ALLOWED_RECIPIENT}`,
221+
agentAddress: agent,
222+
policy: {
223+
perTxLimit: policy.perTx,
224+
dailyRemaining: (BigInt(policy.daily) - BigInt(policy.spent)).toString(),
225+
cooldownSeconds: policy.cooldown,
226+
allowedRecipients: [ALLOWED_RECIPIENT],
227+
},
228+
});
229+
230+
console.log("First payment with nonce:", intent.nonce);
231+
232+
// Execute first time (should succeed)
233+
const txHash = await executePayment(intent);
234+
console.log("✅ First payment succeeded:", txHash);
235+
236+
// Try to replay the same intent
237+
console.log("Attempting replay with same nonce...");
238+
239+
try {
240+
await executePayment(intent);
241+
throw new Error("Replay attack succeeded - this should not happen!");
242+
} catch (err: any) {
243+
if (err.data === "0x1fb09b80" || err.message.includes("Nonce")) {
244+
console.log("✅ Nonce replay blocked on-chain");
245+
console.log("↳ Same intent cannot execute twice");
246+
} else {
247+
throw err;
248+
}
249+
}
250+
});
251+
252+
banner("DEMO COMPLETE");
253+
console.log("\n🎯 Key Takeaways:");
254+
console.log("1. AI proposes payments based on context");
255+
console.log("2. Smart contracts enforce all rules deterministically");
256+
console.log("3. Even if AI misbehaves or is misled, funds stay safe");
257+
console.log("4. Policy = per-tx limits + daily limits + cooldowns + allowlists + nonces");
258+
console.log("\n✅ Trust-minimized agentic commerce achieved\n");
259+
}
260+
261+
main().catch((err) => {
262+
console.error("\n❌ Demo failed");
263+
console.error(err);
264+
process.exit(1);
265+
});

‎agent/main.ts‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -20,7 +20,7 @@ async function main() {
2020
await ensureCooldownElapsed(AGENT_ADDRESS, BigInt(policy.cooldown));
2121

2222
const intent = await proposePayment({
23-
request: `Pay 1 USDC to API provider at ${RECIPIENT_ADDRESS}`,
23+
request: `Pay 0.1 USDC to API provider at ${RECIPIENT_ADDRESS}`,
2424
agentAddress: AGENT_ADDRESS,
2525
policy: {
2626
perTxLimit: policy.perTx,

‎agent/package.json‎

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -4,7 +4,8 @@
44
"main": "index.js",
55
"scripts": {
66
"dev": "ts-node test.ts",
7-
"demo": "ts-node main.ts"
7+
"main": "ts-node main.ts",
8+
"demo": "ts-node demo.ts"
89
},
910
"keywords": [],
1011
"author": "",

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