SDK MCP connection session ignores connect AbortSignal

[AdamsukS]

Summary

MCPConnectionSession.connect(signal?: AbortSignal) accepts cancellation, but the session returned
by SDKMCPConnectionSessionFactory.create() ignores the signal. Both an already-aborted signal and
an abort during initialization still result in a successful connection.

Version

• @codesoul-co/hypha-mcp: 1.0.1
• Hypha source/current main checked: ac80a8f7d1fbc8136b3bd85d94c48cf6e18dedf5
• Transitive @modelcontextprotocol/sdk: 1.30.0
• Transport: Streamable HTTP, isolated loopback fixture; no external service or credentials required.

Expected / actual

Case	Expected	Actual
Signal already aborted before connect	Reject without sending initialize	Sends initialize, then resolves
Abort while initialize response is pending	Reject and clean up initialization	Resolves after the server responds

The public interface declares connect(signal?: AbortSignal), while the SDK-backed implementation
declares async connect() and calls this.client.connect(this.transport) without request options.
The pinned MCP SDK accepts request options, including the signal, in its second connect argument.
The tool-adapter guide also asks implementations to preserve AbortSignal.

This report is specifically about the SDK connection-session contract. It does not claim that
MCPConnectionManager's initialization timeout or tool-call cancellation is absent.

Minimal reproduction

In a Node project with @codesoul-co/hypha-mcp@1.0.1, save as repro.cjs and run node repro.cjs.
Only the fixture profile below allows loopback HTTP; no production security settings are changed.

const { createServer } = require('node:http');
const { once } = require('node:events');
const { SDKMCPConnectionSessionFactory } = require('@codesoul-co/hypha-mcp');

async function probe(preAborted) {
  let initializeRequests = 0;
  const server = createServer(async (req, res) => {
    if (req.method !== 'POST') { res.writeHead(405).end(); return; }
    const chunks = [];
    for await (const chunk of req) chunks.push(chunk);
    const message = JSON.parse(Buffer.concat(chunks).toString());
    if (message.method !== 'initialize') { res.writeHead(202).end(); return; }
    initializeRequests++;
    setTimeout(() => {
      res.writeHead(200, { 'Content-Type': 'application/json' });
      res.end(JSON.stringify({ jsonrpc: '2.0', id: message.id, result: {
        protocolVersion: '2025-11-25', capabilities: {},
        serverInfo: { name: 'abort-repro', version: '1.0.0' },
      } }));
    }, 150);
  });
  server.listen(0, '127.0.0.1');
  await once(server, 'listening');
  const session = new SDKMCPConnectionSessionFactory().create({
    id: 'abort-repro', mode: 'fixture',
    transport: { type: 'streamable_http', endpoint: `http://127.0.0.1:${server.address().port}/mcp` },
    egressPolicy: { allowedHosts: ['127.0.0.1'], denyPrivateNetworks: false, requireTls: false },
  });
  const controller = new AbortController();
  if (preAborted) controller.abort(new Error('cancelled before connect'));
  const timer = preAborted ? undefined : setTimeout(() => controller.abort(new Error('cancelled during connect')), 20);
  let outcome;
  try { await session.connect(controller.signal); outcome = 'resolved'; }
  catch { outcome = 'rejected'; }
  finally {
    clearTimeout(timer);
    await session.close();
    server.closeAllConnections();
    await new Promise((resolve) => server.close(resolve));
  }
  return { preAborted, aborted: controller.signal.aborted, initializeRequests, outcome };
}
(async () => {
  const results = [await probe(true), await probe(false)];
  console.log(JSON.stringify(results, null, 2));
  if (results.some((r) => r.outcome !== 'rejected')) process.exitCode = 1;
})().catch((error) => { console.error(error); process.exitCode = 1; });

Observed (exit 1):

[
  { "preAborted": true, "aborted": true, "initializeRequests": 1, "outcome": "resolved" },
  { "preAborted": false, "aborted": true, "initializeRequests": 1, "outcome": "resolved" }
]

Suggested acceptance checks: reject an already-aborted signal before initialization, propagate
in-flight cancellation to the MCP SDK, clean up the transport, and preserve successful connection
behavior when no signal is supplied.

[erwinmsmith]

Thanks for the detailed report and the minimal reproduction.\n\nI confirmed the contract mismatch: MCPConnectionSession.connect() accepts an AbortSignal, while the SDK-backed session currently does not forward it to Client.connect().\n\nWe will treat this as a bug. The fix will cover:\n\n- rejecting an already-aborted signal before initialization starts;\n- forwarding in-flight cancellation to the MCP SDK;\n- cleaning up a partially initialized client/transport after cancellation or connection failure; and\n- adding regression coverage while preserving normal connection behavior when no signal is provided.\n\nThanks again for the clear reproduction and acceptance checks.