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fix(core): keep resumption options off cancellation notifications #2649

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63408d4
fix legacy cancellation resumption options
LizunovSergey Aug 11, 2026
3445994
Merge branch 'main' into fix/v2-2646-cancel-resumption
LizunovSergey Aug 15, 2026
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5 changes: 5 additions & 0 deletions .changeset/calm-taxis-cancel.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
'@modelcontextprotocol/core': patch
---

Prevent legacy cancellation notifications from inheriting request resumption options.
2 changes: 1 addition & 1 deletion packages/core-internal/src/shared/protocol.ts
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Expand Up @@ -1461,7 +1461,7 @@ export abstract class Protocol<ContextT extends BaseContext> {
reason: String(reason)
}
}),
{ relatedRequestId, resumptionToken, onresumptiontoken }
{ relatedRequestId }
)
.catch(error => this._onerror(new Error(`Failed to send cancellation: ${error}`)));
} else {
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25 changes: 25 additions & 0 deletions packages/core-internal/test/shared/protocol.test.ts
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Expand Up @@ -830,9 +830,11 @@ describe('protocol tests', () => {
class PerRequestStreamTransport extends MockTransport {
readonly hasPerRequestStream = true;
sent: JSONRPCMessage[] = [];
sentCalls: { message: JSONRPCMessage; options?: TransportSendOptions }[] = [];
lastRequestSignal: AbortSignal | undefined;
override async send(message: JSONRPCMessage, options?: TransportSendOptions): Promise<void> {
this.sent.push(message);
this.sentCalls.push({ message, options });
this.lastRequestSignal = options?.requestSignal;
}
}
Expand Down Expand Up @@ -899,6 +901,29 @@ describe('protocol tests', () => {
expect(cancelledSent(tx.sent)).toHaveLength(1);
});

test('legacy era: cancellation does not inherit request resumption options', async () => {
const tx = new PerRequestStreamTransport();
const proto = createTestProtocol();
await proto.connect(tx);
setNegotiatedProtocolVersion(proto, '2025-11-25');

const ac = new AbortController();
const pending = testRequest(proto, { method: 'example', params: {} }, z.object({}), {
signal: ac.signal,
relatedRequestId: 'parent-request',
resumptionToken: 'resume-token',
onresumptiontoken: vi.fn()
});

ac.abort('user cancel');
await expect(pending).rejects.toThrow();

const cancellationCall = tx.sentCalls.find(
({ message }) => 'method' in message && message.method === 'notifications/cancelled'
);
expect(cancellationCall?.options).toEqual({ relatedRequestId: 'parent-request' });
});

test('modern era + per-request-stream transport: timeout aborts the stream, NO notifications/cancelled', async () => {
const tx = new PerRequestStreamTransport();
const proto = createTestProtocol();
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