diff --git a/src/crestodian/probes.stream-errors.test.ts b/src/crestodian/probes.stream-errors.test.ts
new file mode 100644
index 000000000000..8a5e97442a5d
--- /dev/null
+++ b/src/crestodian/probes.stream-errors.test.ts
@@ -0,0 +1,59 @@
+// Crestodian probe stream-error handling tests.
+import type { ChildProcess, SpawnOptions } from "node:child_process";
+import { EventEmitter } from "node:events";
+import { PassThrough } from "node:stream";
+import { beforeEach, describe, expect, it, vi } from "vitest";
+
+const spawnMock = vi.hoisted(() => vi.fn());
+
+type MockChildProcess = EventEmitter & {
+  stdin: PassThrough;
+  stdout: PassThrough;
+  stderr: PassThrough;
+  kill: ReturnType<typeof vi.fn>;
+};
+
+function createMockChildProcess(): MockChildProcess {
+  const child = new EventEmitter() as MockChildProcess;
+  child.stdin = new PassThrough();
+  child.stdout = new PassThrough();
+  child.stderr = new PassThrough();
+  child.kill = vi.fn();
+  return child;
+}
+
+vi.mock("node:child_process", async () => {
+  const actual = await vi.importActual<typeof import("node:child_process")>("node:child_process");
+  return { ...actual, spawn: spawnMock };
+});
+
+describe("probeLocalCommand stream error handling", () => {
+  beforeEach(() => {
+    vi.resetModules();
+    vi.clearAllMocks();
+  });
+
+  it("keeps child close authoritative when stdout and stderr emit errors", async () => {
+    const child = createMockChildProcess();
+
+    spawnMock.mockImplementationOnce(
+      (_cmd: string, _args: readonly string[], _opts: SpawnOptions): ChildProcess => {
+        process.nextTick(() => {
+          child.stdout.emit("error", new Error("stdout closed"));
+          child.stderr.emit("error", new Error("stderr closed"));
+          child.emit("close", 0);
+        });
+        return child as unknown as ChildProcess;
+      },
+    );
+
+    const { probeLocalCommand } = await import("./probes.js");
+
+    await expect(probeLocalCommand("echo", ["test"], { timeoutMs: 1000 })).resolves.toEqual({
+      command: "echo",
+      found: true,
+      version: undefined,
+      error: undefined,
+    });
+  });
+});
diff --git a/src/crestodian/probes.ts b/src/crestodian/probes.ts
index 401e3f98c966..bb8cc739c841 100644
--- a/src/crestodian/probes.ts
+++ b/src/crestodian/probes.ts
@@ -19,6 +19,9 @@ export type LocalCommandProbe = {
 const LOCAL_COMMAND_PROBE_OUTPUT_MAX_CHARS = 16 * 1024;
 const LOCAL_COMMAND_PROBE_KILL_GRACE_MS = 500;
 
+// The child close/error events own the probe result; pipe errors must not escape and crash setup.
+const ignoreOutputStreamError = () => {};
+
 function appendBounded(previous: string, chunk: string, limit: number): string {
   const next = previous + chunk;
   return next.length > limit ? next.slice(-limit) : next;
@@ -79,9 +82,11 @@ export async function probeLocalCommand(
     child.stdout.on("data", (chunk) => {
       stdout = appendBounded(stdout, String(chunk), outputLimit);
     });
+    child.stdout.on("error", ignoreOutputStreamError);
     child.stderr.on("data", (chunk) => {
       stderr = appendBounded(stderr, String(chunk), outputLimit);
     });
+    child.stderr.on("error", ignoreOutputStreamError);
     child.on("error", (err: NodeJS.ErrnoException) => {
       finish({
         command,