Stop external callers from killing runs via the public API

app.py

@@ -1,7 +1,12 @@
 """Unitree G1 rough-terrain locomotion training, on the Space's GPU.
 
 Training runs in a background thread so the Gradio server stays responsive; the
-UI is a log tail plus start/stop. Brax PPO cannot be interrupted from outside,
+UI is a log tail plus start/stop.
+
+Start/stop are deliberately NOT exposed as named API endpoints (api_name=False).
+On a public Space, auto-named endpoints get probed -- a caller sent the string
+"ping" to /start and then hit /stop, which killed a run mid-flight. The read-only
+log and status endpoints stay exposed so the run can be monitored remotely. Brax PPO cannot be interrupted from outside,
 so the stop button sets a flag that the progress callback checks and raises on.
 """
 
@@ -225,8 +230,11 @@ def start(timesteps=None):
     t = STATE["thread"]
     if t is not None and t.is_alive():
         return status_md()
-    if timesteps:
-        STATE["target"] = int(timesteps)
+    try:
+        if timesteps is not None:
+            STATE["target"] = max(100_000, int(float(timesteps)))
+    except (TypeError, ValueError):
+        log(f"ignoring non-numeric timesteps input: {timesteps!r}")
     STATE["step"] = 0
     STATE["stop"] = False
     STATE["thread"] = threading.Thread(target=train_worker, daemon=True)
@@ -260,10 +268,10 @@ with gr.Blocks(title="G1 rough-terrain training") as demo:
     gr.Markdown("# Unitree G1 — rough-terrain locomotion training")
     st = gr.Markdown(status_md())
     with gr.Row():
-        steps_in = gr.Number(value=NUM_TIMESTEPS, precision=0, label="timesteps",
-                             minimum=100_000, maximum=2_000_000_000)
-        gr.Button("Start", variant="primary").click(start, inputs=steps_in, outputs=st)
-        gr.Button("Stop", variant="stop").click(stop, outputs=st)
+        steps_in = gr.Number(value=NUM_TIMESTEPS, precision=0, label="timesteps")
+        gr.Button("Start", variant="primary").click(
+            start, inputs=steps_in, outputs=st, api_name=False)
+        gr.Button("Stop", variant="stop").click(stop, outputs=st, api_name=False)
     out = gr.Textbox(label="training log", lines=26, max_lines=26,
                      autoscroll=True, value=logs())
     timer = gr.Timer(3.0)