fix(memory-host-sdk): handle stdout/stderr stream errors in runCliCommand (#101402)

* fix(memory-host-sdk): handle stdout/stderr stream errors in runCliCommand

Register error handlers on stdout and stderr streams in
runCliCommand() to prevent uncaught exceptions when a pipe
breaks (e.g. EPIPE after child process exit).

Without these listeners, Node.js throws an uncaught exception
that crashes the process.

Co-Authored-By: Claude <noreply@anthropic.com>

* fix(memory-host-sdk): extract listenForChildOutputErrors helper

Refactor the inline stream error handling into a reusable
listenForChildOutputErrors helper, matching the pattern
established in the merged #101370 (agent-core).

The helper registers error listeners on stdout/stderr via a
shared loop, keeping the pattern consistent across the codebase.

Co-Authored-By: Claude <noreply@anthropic.com>

* fix(memory-host-sdk): harden qmd stream failures

* fix(memory-host-sdk): harden qmd stream failures

* docs(changelog): note qmd stream hardening

* chore: keep release changelog out of contributor PR

---------

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Peter Steinberger <steipete@gmail.com>

packages/memory-host-sdk/src/host/qmd-process.test.ts

@@ -524,4 +524,52 @@ describe("runCliCommand", () => {
     });
     expect(child.kill).not.toHaveBeenCalledWith("SIGKILL");
   });
+
+  it.each(["stdout", "stderr"] as const)(
+    "rejects when %s stream emits an error",
+    async (streamName) => {
+      const child = createMockChild();
+      spawnMock.mockReturnValueOnce(child);
+      const streamError = new Error(`${streamName} EPIPE`);
+
+      const pending = runCliCommand({
+        commandSummary: "qmd query test",
+        spawnInvocation: { command: "qmd", argv: ["query", "test", "--json"] },
+        env: process.env,
+        cwd: tempDir,
+        maxOutputChars: 10_000,
+      });
+
+      child[streamName].emit("error", streamError);
+
+      await expect(pending).rejects.toMatchObject({
+        message: `qmd query test ${streamName} error: ${streamName} EPIPE`,
+        cause: streamError,
+      });
+      expect(child.kill).toHaveBeenCalledOnce();
+      expect(child.kill).toHaveBeenCalledWith("SIGKILL");
+    },
+  );
+
+  it("keeps the other stream guarded after stdout error", async () => {
+    const child = createMockChild();
+    spawnMock.mockReturnValueOnce(child);
+
+    const pending = runCliCommand({
+      commandSummary: "qmd query test",
+      spawnInvocation: { command: "qmd", argv: ["query", "test", "--json"] },
+      env: process.env,
+      cwd: tempDir,
+      maxOutputChars: 10_000,
+    });
+
+    child.stdout.emit("error", new Error("stdout EPIPE"));
+
+    expect(() => {
+      child.stderr.emit("error", new Error("stderr later"));
+    }).not.toThrow();
+
+    await expect(pending).rejects.toThrow("qmd query test stdout error: stdout EPIPE");
+    expect(child.kill).toHaveBeenCalledOnce();
+  });
 });

packages/memory-host-sdk/src/host/qmd-process.ts

@@ -246,6 +246,26 @@ export async function runCliCommand(params: {
       stderr = next.text;
       stderrTruncated = stderrTruncated || next.truncated;
     });
+
+    // Guard stdout/stderr against stream errors (e.g. EPIPE when the
+    // child exits before all pipe data is consumed). Without listeners,
+    // Node.js throws an uncaught exception that crashes the process.
+    for (const streamName of ["stdout", "stderr"] as const) {
+      child[streamName].on("error", (error: Error) => {
+        if (settled) {
+          return;
+        }
+        signalQmdProcessTree(child, "SIGKILL");
+        settle(() =>
+          reject(
+            new Error(`${params.commandSummary} ${streamName} error: ${error.message}`, {
+              cause: error,
+            }),
+          ),
+        );
+      });
+    }
+
     child.on("error", (err) => {
       if (timer) {
         clearTimeout(timer);