diff --git a/scripts/run-tests.cjs b/scripts/run-tests.cjs
index 83f715ccb..2828dc205 100644
--- a/scripts/run-tests.cjs
+++ b/scripts/run-tests.cjs
@@ -35,9 +35,9 @@
 // See docs/TESTING-SUITES.md for full grouping policy.
 'use strict';
 
-const { readdirSync, readFileSync, mkdtempSync, rmSync, unlinkSync } = require('fs');
+const { readdirSync, readFileSync, mkdtempSync, rmSync, unlinkSync, writeFileSync } = require('fs');
 const { join, basename } = require('path');
-const { tmpdir, devNull } = require('os');
+const { tmpdir } = require('os');
 const { execFileSync } = require('child_process');
 const { ExitError, runMain } = require('./lib/cli-exit.cjs');
 const {
@@ -1079,11 +1079,24 @@ function main() {
   // (GSD_RUN_TESTS_EVENTS_FILE, set per-chunk below in execFileSync's `env`),
   // which does NOT count toward the Windows 32,767-char argv ceiling — only
   // this fixed sink destination does.
+  //
+  // The ndjson reporter yields nothing and ignores its own destination — the
+  // durable write path is GSD_RUN_TESTS_EVENTS_FILE above — but Node still
+  // opens this destination as a real fs.WriteStream and fsyncs it on close,
+  // so it MUST be a regular file. os.devNull (a character device on every
+  // platform) fails that fsync with EINVAL, crashing every chunk, not just
+  // the timeout path (confirmed live: 43/43 chunk failures, "EINVAL: invalid
+  // argument, fsync" on WriteStream close). Do not re-point this at devNull —
+  // it is the ONE destination flavor this feature cannot use. Pre-created
+  // once, alongside eventsDir, so it stays empty and its path length is
+  // identical across every chunk (see FIXED_OVERHEAD below).
+  const reporterSinkPath = join(eventsDir, 'reporter-sink.txt');
+  writeFileSync(reporterSinkPath, '');
   const reporterArgs = [
     `--test-reporter=${humanReporter}`,
     '--test-reporter-destination=stdout',
     `--test-reporter=${reporterModulePath}`,
-    `--test-reporter-destination=${devNull}`,
+    `--test-reporter-destination=${reporterSinkPath}`,
   ];
   const reporterOverhead = reporterArgs.reduce((sum, a) => sum + a.length + 1, 0);
 
diff --git a/tests/run-tests-harness.test.cjs b/tests/run-tests-harness.test.cjs
index 37a34417c..68d856bfc 100644
--- a/tests/run-tests-harness.test.cjs
+++ b/tests/run-tests-harness.test.cjs
@@ -852,6 +852,31 @@ test('noop', () => {});
       );
     });
 
+    // T5 (regression): the human reporter's --test-reporter-destination
+    // pairing must be a regular file, not os.devNull. devNull is a character
+    // device; Node opens the reporter destination as an fs.WriteStream and
+    // fsyncs it on close, and fsync on a character device fails with EINVAL
+    // — surfaced as "Emitted 'error' event on WriteStream instance" /
+    // "EINVAL: invalid argument, fsync", which crashed EVERY chunk on the
+    // real remote run this regresses (43/43 failures), not only the timeout
+    // path. The argv construction lives entirely inside main() with no
+    // exported seam to unit-test directly (see NOTES), so this asserts the
+    // closest real, externally-observable consequence: a normal successful
+    // run must not surface that error text, and must still complete and
+    // exit 0 — both of which a reintroduced devNull destination would break
+    // on any platform where fsync(devNull) actually returns EINVAL (this
+    // suite's own bench platform, historically).
+    test('a successful run never surfaces the devNull fsync/EINVAL reporter crash', () => {
+      seed(tmpDir, ['a.test.cjs']);
+      const r = runHarness(tmpDir, []);
+      assert.strictEqual(r.status, 0, `expected a clean pass; STDERR:\n${r.stderr}`);
+      assert.doesNotMatch(
+        r.stderr,
+        /EINVAL|invalid argument, fsync|WriteStream instance/i,
+        `expected no reporter-destination fsync crash; STDERR:\n${r.stderr}`,
+      );
+    });
+
     // T1: on a chunk timeout, the diagnostic must NAME the file that was
     // still executing — not merely list every file the chunk contained (the
     // pre-instrumentation behavior). A test that hangs INSIDE its own body