diff --git a/join-use-case/model-optimization.mdx b/join-use-case/model-optimization.mdx
index c05cccd..dc5469e 100644
--- a/join-use-case/model-optimization.mdx
+++ b/join-use-case/model-optimization.mdx
@@ -23,6 +23,34 @@ model/
     - model_weights.pkl
 ```
 
+## Models build locally (no external hubs)
+
+Your model file must build its architecture from local code. tracebloc does not
+fetch models, weights, tokenizers, or configs from an external hub (such as
+HuggingFace) while training — a training pod has no such egress. In practice your
+model file must **not**:
+
+- call `*.from_pretrained("<hub-id>")` for a model, tokenizer, or config, or
+- call `torch.hub.load(...)`, or reach the same functions indirectly via
+  `getattr(X, "from_pretrained")`.
+
+These are refused at upload by the model-validation check, not merely
+discouraged. Setting `model_id`, `tokenizer_id` or `hf_token` is a separate
+matter — see the note under [Additional variables](#additional-variables).
+
+To start from a pretrained model, download its weights once, build the same
+architecture in your model file, and upload the weights alongside it (see
+[Use pre-trained weights](#use-pre-trained-weights)). For text and other NLP
+tasks, also ship a `tokenizer.json` — pass it with
+`user.upload_model(..., tokenizer="tokenizer.json")` or place it next to your
+model file.
+
+<Note>
+The uploaded weights file is loaded into the architecture your model file builds,
+matching parameter names and shapes exactly. Build the same architecture you
+produced the weights from, or the load will fail.
+</Note>
+
 ## Model Code Formats
 
 Model code can be:
@@ -75,8 +103,16 @@ Each format must contain these variables on the main file:
 
 Some additional variables are required for specific categories
 * **num_feature_points** : number of keypoints or feature points for which this model file is created. This variable is used only for keypoint_detection and generic_classification category.
-* **model_id** : model id using which this model file is created. This variable is used only for text_classification category.
-* **hf_token** : hf token using which this model file is created. This variable is used only for text_classification category.
+
+<Note>
+`model_id`, `tokenizer_id` and `hf_token` are **still accepted** by the SDK and
+the API — they are not rejected at upload. What changed is that they can no
+longer achieve a hub fetch: a training pod has no egress to an external hub, and
+the hub-fetching calls themselves are refused (see
+[Models build locally (no external hubs)](#models-build-locally-no-external-hubs)).
+So supplying them has no effect on where your architecture or tokenizer comes
+from — build locally and upload weights instead.
+</Note>
 
 <Warning>
 * The framework variable is compulsory and should always be placed at the top of your code just after the imports, before any other variable.