diff --git a/resources/scripts/nap_install.py b/resources/scripts/nap_install.py
index ba35fd2..2726b49 100644
--- a/resources/scripts/nap_install.py
+++ b/resources/scripts/nap_install.py
@@ -682,15 +682,17 @@ def compact_log_file(path, max_bytes=MAX_SERVICE_LOG_BYTES):
     newline_index = chunk.find(b"\n")
     if newline_index >= 0 and newline_index + 1 < len(chunk):
         chunk = chunk[newline_index + 1 :]
-    tmp_path = file_path.with_suffix(file_path.suffix + ".tmp")
     try:
-        tmp_path.write_bytes(chunk)
-        tmp_path.replace(file_path)
+        # Preserve the inode used by a running gateway process. Replacing the
+        # path here would leave its inherited stdout/stderr descriptors
+        # writing to a deleted file.
+        with file_path.open("r+b") as handle:
+            handle.seek(0)
+            handle.write(chunk)
+            handle.truncate()
+            handle.flush()
     except OSError:
-        try:
-            tmp_path.unlink(missing_ok=True)
-        except OSError:
-            pass
+        return
 
 
 def ensure_port_available(kind, port):
diff --git a/tests/test_cli_command_system.py b/tests/test_cli_command_system.py
index d935da0..7eba751 100644
--- a/tests/test_cli_command_system.py
+++ b/tests/test_cli_command_system.py
@@ -313,3 +313,19 @@ def test_manifest_rejects_a_minimum_contract_newer_than_installer():
         assert "newer bootstrap installer" in str(exc)
     else:
         raise AssertionError("incompatible minimum contract must be rejected")
+
+
+def test_cli_log_compaction_preserves_live_writer_inode(tmp_path):
+    module = load_installer()
+    log_path = tmp_path / "gateway.log"
+    log_path.write_bytes((b"old-line\n" * 200) + b"recent-line\n")
+    inode_before = log_path.stat().st_ino
+
+    with log_path.open("ab", buffering=0) as live_writer:
+        module.compact_log_file(log_path, 128)
+        live_writer.write(b"after-cli-compaction\n")
+
+    assert log_path.stat().st_ino == inode_before
+    content = log_path.read_bytes()
+    assert content.endswith(b"after-cli-compaction\n")
+    assert b"recent-line\n" in content