feat(payments): grant runtime role payment data-plane perms + system prompt update

The deployed agent runtime role was missing every Get/List/Create payment
instrument+session action and ProcessPayment. The L3 stack only granted
sts:AssumeRole on the ProcessPaymentRole, which carries only
ProcessPayment — and the SDK plugin's auto-pay path calls
GetPaymentInstrument on the runtime's own credentials before any role
assumption. Without this grant the plugin fails with AccessDeniedException
on the very first 402 it tries to settle.

Add the seven required actions to the runtime role's inline policy in
the vended CDK stack template (src/assets/cdk/lib/cdk-stack.ts). Scoped
to the manager ARN.

Also update PAYMENT_SYSTEM_PROMPT in the Strands payments capability to
mention the http_request tool, which the AgentCorePaymentsPlugin now
provides automatically (see SDK PR
aws/bedrock-agentcore-sdk-python#493). The other prompt lines for
get_payment_session / get_payment_instrument_balance /
list_payment_instruments are unchanged — those tools were already
provided by the plugin.

Snapshot updated to reflect the cdk-stack.ts addition.

Author: aidandaly24

src/assets/__tests__/__snapshots__/assets.snapshot.test.ts.snap

@@ -409,6 +409,32 @@ export class AgentCoreStack extends Stack {
             })
           );
 
+          // Grant payment data-plane actions directly to the runtime role.
+          //
+          // NOTE: This deviates from the canonical role model in the AgentCore Payments
+          // beta guide, which assigns Get/List/Create instrument+session actions to a
+          // separate ManagementRole and limits the agent's role to ProcessPayment only.
+          // The current SDK plugin (AgentCorePaymentsPlugin.generate_payment_header)
+          // calls GetPaymentInstrument internally during the 402 auto-pay path, so the
+          // runtime role needs read access. CreatePaymentSession is included so
+          // \`agentcore invoke --auto-session\` works without a separate ManagementRole
+          // call. Tighten this if the SDK is updated to accept pre-fetched instrument
+          // details and split create-session into a backend-only flow.
+          env.runtime.role.addToPrincipalPolicy(
+            new iam.PolicyStatement({
+              actions: [
+                'bedrock-agentcore:GetPaymentInstrument',
+                'bedrock-agentcore:ListPaymentInstruments',
+                'bedrock-agentcore:GetPaymentInstrumentBalance',
+                'bedrock-agentcore:GetPaymentSession',
+                'bedrock-agentcore:ListPaymentSessions',
+                'bedrock-agentcore:CreatePaymentSession',
+                'bedrock-agentcore:ProcessPayment',
+              ],
+              resources: [manager.paymentManagerArn, \`\${manager.paymentManagerArn}/*\`],
+            })
+          );
+
           if (payment.autoPayment !== undefined) {
             env.runtime.addEnvironmentVariable(\`\${prefix}_AUTO_PAYMENT\`, String(payment.autoPayment));
           }
@@ -5399,7 +5425,7 @@ logger = logging.getLogger(__name__)
 
 PAYMENT_SYSTEM_PROMPT = """
 You have payment capabilities via the x402 protocol:
-- Payments are processed automatically when you access paid endpoints (HTTP 402 responses)
+- Use http_request to call HTTP endpoints. 402 Payment Required responses are settled automatically by the plugin and the call is retried.
 - Use get_payment_session to check your remaining budget before expensive operations
 - Use get_payment_instrument_balance to check wallet USDC balance
 - Use list_payment_instruments to see available payment instruments

src/assets/cdk/lib/cdk-stack.ts

@@ -134,6 +134,32 @@ export class AgentCoreStack extends Stack {
             })
           );
 
+          // Grant payment data-plane actions directly to the runtime role.
+          //
+          // NOTE: This deviates from the canonical role model in the AgentCore Payments
+          // beta guide, which assigns Get/List/Create instrument+session actions to a
+          // separate ManagementRole and limits the agent's role to ProcessPayment only.
+          // The current SDK plugin (AgentCorePaymentsPlugin.generate_payment_header)
+          // calls GetPaymentInstrument internally during the 402 auto-pay path, so the
+          // runtime role needs read access. CreatePaymentSession is included so
+          // `agentcore invoke --auto-session` works without a separate ManagementRole
+          // call. Tighten this if the SDK is updated to accept pre-fetched instrument
+          // details and split create-session into a backend-only flow.
+          env.runtime.role.addToPrincipalPolicy(
+            new iam.PolicyStatement({
+              actions: [
+                'bedrock-agentcore:GetPaymentInstrument',
+                'bedrock-agentcore:ListPaymentInstruments',
+                'bedrock-agentcore:GetPaymentInstrumentBalance',
+                'bedrock-agentcore:GetPaymentSession',
+                'bedrock-agentcore:ListPaymentSessions',
+                'bedrock-agentcore:CreatePaymentSession',
+                'bedrock-agentcore:ProcessPayment',
+              ],
+              resources: [manager.paymentManagerArn, `${manager.paymentManagerArn}/*`],
+            })
+          );
+
           if (payment.autoPayment !== undefined) {
             env.runtime.addEnvironmentVariable(`${prefix}_AUTO_PAYMENT`, String(payment.autoPayment));
           }

src/assets/python/http/strands/capabilities/payments/payments.py

@@ -26,7 +26,7 @@
 
 PAYMENT_SYSTEM_PROMPT = """
 You have payment capabilities via the x402 protocol:
-- Payments are processed automatically when you access paid endpoints (HTTP 402 responses)
+- Use http_request to call HTTP endpoints. 402 Payment Required responses are settled automatically by the plugin and the call is retried.
 - Use get_payment_session to check your remaining budget before expensive operations
 - Use get_payment_instrument_balance to check wallet USDC balance
 - Use list_payment_instruments to see available payment instruments