From c8f44ddd903f270738b7b6bc53d19d60b17bc987 Mon Sep 17 00:00:00 2001
From: ContextVM <contextvm@protonmail.com>
Date: Thu, 30 Apr 2026 10:18:53 +0100
Subject: [PATCH] fix(payments): drop uncorrelated payment_required
 notifications on Nostr transports

---
 .changeset/old-lies-check.md         |  5 +++
 src/payments/client-payments.test.ts | 47 ++++++++++++++++++++++++++++
 src/payments/client-payments.ts      | 41 ++++++++++++++----------
 3 files changed, 77 insertions(+), 16 deletions(-)
 create mode 100644 .changeset/old-lies-check.md

diff --git a/.changeset/old-lies-check.md b/.changeset/old-lies-check.md
new file mode 100644
index 0000000..92ade92
--- /dev/null
+++ b/.changeset/old-lies-check.md
@@ -0,0 +1,5 @@
+---
+'@contextvm/sdk': patch
+---
+
+fix(payments): drop uncorrelated payment_required notifications on Nostr transports
diff --git a/src/payments/client-payments.test.ts b/src/payments/client-payments.test.ts
index 9d21282..d3cab64 100644
--- a/src/payments/client-payments.test.ts
+++ b/src/payments/client-payments.test.ts
@@ -344,6 +344,53 @@ describe('withClientPayments()', () => {
     });
   });
 
+  test('drops uncorrelated payment_required notifications on Nostr transports', async () => {
+    const transport = createMockNostrTransport();
+
+    let canHandleCalls = 0;
+    let handleCalls = 0;
+    const observed: JSONRPCMessage[] = [];
+
+    const paid = withClientPayments(transport, {
+      handlers: [
+        {
+          pmi: 'fake',
+          async canHandle(): Promise<boolean> {
+            canHandleCalls += 1;
+            return true;
+          },
+          async handle(): Promise<void> {
+            handleCalls += 1;
+          },
+        },
+      ],
+    });
+
+    paid.onmessage = (msg) => observed.push(msg);
+
+    await paid.start();
+
+    const paymentRequired: JSONRPCMessage = {
+      jsonrpc: '2.0',
+      method: 'notifications/payment_required',
+      params: { amount: 1, pay_req: 'x', pmi: 'fake' },
+    };
+
+    (transport as unknown as TransportWithContext).onmessageWithContext?.(
+      paymentRequired,
+      {
+        eventId: 'evt',
+        correlatedEventId: undefined,
+      },
+    );
+
+    await new Promise((r) => setTimeout(r, 0));
+
+    expect(observed).toContainEqual(paymentRequired);
+    expect(canHandleCalls).toBe(0);
+    expect(handleCalls).toBe(0);
+  });
+
   test('handler errors call onerror but do not block message delivery', async () => {
     const observed: JSONRPCMessage[] = [];
     const errors: Error[] = [];
diff --git a/src/payments/client-payments.ts b/src/payments/client-payments.ts
index 1ea4bfb..4d53105 100644
--- a/src/payments/client-payments.ts
+++ b/src/payments/client-payments.ts
@@ -209,11 +209,34 @@ export function withClientPayments(
       return;
     }
 
+    const handler = handlersByPmi.get(message.params.pmi);
+    if (!handler) {
+      logger.debug('no handler for PMI, ignoring payment_required', {
+        pmi: message.params.pmi,
+        requestEventId,
+      });
+      return;
+    }
+
+    const isNostrTransport = transport instanceof NostrClientTransport;
+
+    const pending = isNostrTransport
+      ? transport.getPendingRequestForEventId(requestEventId)
+      : undefined;
+
+    if (isNostrTransport && !pending) {
+      logger.warn('dropping uncorrelated payment_required notification', {
+        requestEventId,
+        pmi: message.params.pmi,
+        amount: message.params.amount,
+      });
+      return;
+    }
+
     // If the transport can provide the original request's progressToken, emit synthetic
     // progress notifications locally to keep the upstream MCP request alive while the
     // payment settles (CEP-8 TTL can exceed the default MCP timeout).
-    if (transport instanceof NostrClientTransport) {
-      const pending = transport.getPendingRequestForEventId(requestEventId);
+    if (isNostrTransport) {
       const token = pending?.progressToken;
       // Fall back to defaultPaymentTtlMs when the server omits ttl so the client
       // keeps the MCP request alive for the same duration the server will wait.
@@ -256,15 +279,6 @@ export function withClientPayments(
       }
     }
 
-    const handler = handlersByPmi.get(message.params.pmi);
-    if (!handler) {
-      logger.debug('no handler for PMI, ignoring payment_required', {
-        pmi: message.params.pmi,
-        requestEventId,
-      });
-      return;
-    }
-
     // Best-effort client-side dedupe keyed by pay_req.
     // IMPORTANT: claim synchronously before any await to avoid double-pay races.
     if (inFlightPayReqs.has(message.params.pay_req)) {
@@ -287,11 +301,6 @@ export function withClientPayments(
         requestEventId,
       };
 
-      const pending =
-        transport instanceof NostrClientTransport
-          ? transport.getPendingRequestForEventId(requestEventId)
-          : undefined;
-
       const synthesizeClientDeclineError = (params: {
         message: string;
       }): void => {