diff --git a/.gitignore b/.gitignore
index c55eccad..8519e410 100644
--- a/.gitignore
+++ b/.gitignore
@@ -91,6 +91,9 @@ simulator/SDL2/
 # Python
 .venv/
 
+# Serial tool - runtime state (logs, machine-specific)
+tools/serial_tool/state/
+
 # Binary / large files
 *.bin
 *.pyc