diff --git a/models/Google/gemma-4-31B-it.yaml b/models/Google/gemma-4-31B-it.yaml
index b9325120..c8dca77b 100644
--- a/models/Google/gemma-4-31B-it.yaml
+++ b/models/Google/gemma-4-31B-it.yaml
@@ -3,7 +3,7 @@ meta:
   slug: "gemma-4-31b-it"
   provider: "Google"
   description: "Google's unified multimodal Gemma 4 dense model (31B) with native text, image, and audio, plus thinking mode and tool-use protocol."
-  date_updated: 2026-05-11
+  date_updated: 2026-07-24
   difficulty: intermediate
   tasks:
     - multimodal
@@ -288,6 +288,12 @@ guide: |
   ### Structured Outputs
   vLLM guided decoding constrains output to a JSON schema. Include semantic instructions in the system prompt — the model does not see schema descriptions.
 
+  Gemma 4 31B can enter a grammar-valid whitespace loop after producing a valid JSON prefix, eventually reaching `max_tokens` with `finish_reason="length"`. If you observe this failure mode, add the following option to your existing server launch command to enable compact xgrammar JSON:
+  ```bash
+  --structured-outputs-config '{"backend":"xgrammar","disable_any_whitespace":true}'
+  ```
+  This disables optional whitespace between JSON tokens; it does not remove whitespace inside string values. See [vLLM #40080](https://github.com/vllm-project/vllm/issues/40080) for background.
+
   ## Configuration Tips
 
   - Set `--max-model-len` to match your workload.