diff --git a/scripts/win32_input_matrix_probe.cjs b/scripts/win32_input_matrix_probe.cjs
new file mode 100644
index 0000000..9300c9b
--- /dev/null
+++ b/scripts/win32_input_matrix_probe.cjs
@@ -0,0 +1,16 @@
+// Probe side of scripts/win32_input_matrix.ps1 — runs as the PTY child inside
+// Nebula, dumps every stdin chunk as hex. The driver injects a fixed key
+// matrix via PostMessage and asserts the concatenated byte sequence against a
+// recorded baseline. 'q' (0x71) terminates.
+const fs = require('fs');
+const out = process.argv[2] || 'D:\\temp_build\\nebula\\.tmp_win32_matrix.log';
+const t0 = Date.now();
+const log = (s) => fs.appendFileSync(out, `${((Date.now() - t0) / 1000).toFixed(1)}s ${s}\n`);
+fs.writeFileSync(out, `matrix-probe ready node=${process.version} isTTY=${process.stdin.isTTY}\n`);
+process.stdin.setRawMode(true);
+process.stdin.resume();
+process.stdin.on('data', (b) => {
+  log(`rx ${b.toString('hex')}`);
+  if (b.includes(0x71)) { log('end'); process.exit(0); }
+});
+setTimeout(() => { log('timeout'); process.exit(0); }, 90000);