diff --git a/server/operators/comfyui_sd/run.py b/server/operators/comfyui_sd/run.py
index b66da80..4635d3f 100644
--- a/server/operators/comfyui_sd/run.py
+++ b/server/operators/comfyui_sd/run.py
@@ -108,6 +108,30 @@ if LORA and ("xl" in CKPT.lower() or "biglust" in CKPT.lower() or "v2-1" in CKPT
     print(f"WARNING: {LORA} is SD1.5 but {CKPT} is not — the LoRA will silently do nothing. "
           f"Use Hyper_Realism_1.2_fp16.safetensors (see localmodels/README.md)", flush=True)
 
+# Checkpoints are NOT identical across nodes (the M3 keeps only the LoRA-compatible
+# SD1.5 model; the M1 holds the full SDXL archive). Ask this node's ComfyUI what it
+# actually has and fail fast with a useful message rather than a cryptic 400.
+try:
+    info = json.load(urllib.request.urlopen(f"{API}/object_info/CheckpointLoaderSimple"))
+    have = info["CheckpointLoaderSimple"]["input"]["required"]["ckpt_name"][0]
+    if CKPT not in have:
+        print(f"ERROR: '{CKPT}' is not on this node.\n"
+              f"  available here: {', '.join(have) or '(none)'}\n"
+              f"  The full SDXL set lives on the m1 node; every node has "
+              f"Hyper_Realism_1.2_fp16.safetensors (the only LoRA-compatible checkpoint).\n"
+              f"  Fix: use a checkpoint listed above, or rsync it from m1.", flush=True)
+        sys.exit(1)
+    if LORA:
+        have_l = json.load(urllib.request.urlopen(f"{API}/object_info/LoraLoader"))
+        have_l = have_l["LoraLoader"]["input"]["required"]["lora_name"][0]
+        if LORA not in have_l:
+            print(f"ERROR: LoRA '{LORA}' is not on this node. available: {', '.join(have_l) or '(none)'}", flush=True)
+            sys.exit(1)
+except SystemExit:
+    raise
+except Exception as e:
+    print(f"(could not pre-check model availability: {e}) — continuing", flush=True)
+
 body = json.dumps({"prompt": build(seed)}).encode()
 req = urllib.request.Request(f"{API}/prompt", data=body, headers={"Content-Type": "application/json"})
 try: