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fix(mcp-gateway): stop killing slow-starting owners during session handover #141

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Merged
jayleaton merged 1 commit into from
Oct 25, 2026
Merged

fix(mcp-gateway): stop killing slow-starting owners during session handover #141

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7 changes: 7 additions & 0 deletions packages/mcp-gateway/src/sharedGateway.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -672,10 +672,17 @@ describe("shared MCP gateway", () => {
T3_MCP_GRANTS: "{}",
},
});
let stderr = "";
transport.stderr?.on("data", (chunk: Buffer) => {
stderr += chunk.toString();
});
cleanup.push(() => client.close());
await client.connect(transport);
const changed = Promise.withResolvers<void>();
client.setNotificationHandler(ToolListChangedNotificationSchema, () => changed.resolve());
// A launcher that cannot move the session exits; fail with its reason instead of waiting.
// oxlint-disable-next-line unicorn/prefer-add-event-listener -- MCP Client exposes an onclose callback rather than a DOM event API.
client.onclose = () => changed.reject(new Error(`Launcher exited: ${stderr.trim()}`));
expect((await client.listTools()).tools.length).toBeGreaterThan(0);

await first!.close();
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6 changes: 2 additions & 4 deletions packages/mcp-gateway/src/sharedLauncher.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -39,9 +39,9 @@ export function launchSharedOwner(
},
},
);
const timeout = AbortSignal.timeout(15_000);
// Startup waits on no peer, so it always ends in ready, an error, or an exit. A deadline would
// only kill a healthy owner a loaded machine starts slowly; a stuck launcher is its host's to end.
const cleanup = () => {
timeout.removeEventListener("abort", onTimeout);
child.off("error", fail);
child.off("exit", onExit);
child.off("message", onMessage);
Expand All @@ -52,7 +52,6 @@ export function launchSharedOwner(
if (child.connected) child.disconnect();
reject(error);
};
const onTimeout = () => fail(new Error("Timed out starting the shared MCP gateway owner."));
const onExit = (code: number | null) =>
fail(new Error(`Shared MCP gateway owner exited before startup (code ${code}).`));
const onMessage = (value: unknown) => {
Expand All @@ -66,7 +65,6 @@ export function launchSharedOwner(
resolve(child);
}
};
timeout.addEventListener("abort", onTimeout, { once: true });
child.once("error", fail);
child.once("exit", onExit);
child.on("message", onMessage);
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