[Doc] Add Gemma 4 to supported models list (#39607)

Signed-off-by: z1ying <tzzying@outlook.com>
Signed-off-by: Ziying Tao <tzzying@outlook.com>

docs/models/supported_models.md

@@ -400,6 +400,7 @@ th {
 | `Gemma2ForCausalLM` | Gemma 2 | `google/gemma-2-9b`, `google/gemma-2-27b`, etc. | ✅︎ | ✅︎ |
 | `Gemma3ForCausalLM` | Gemma 3 | `google/gemma-3-1b-it`, etc. | ✅︎ | ✅︎ |
 | `Gemma3nForCausalLM` | Gemma 3n | `google/gemma-3n-E2B-it`, `google/gemma-3n-E4B-it`, etc. | | |
+| `Gemma4ForCausalLM` | Gemma 4 | `google/gemma-4-E2B-it`, etc. | ✅︎ | ✅︎ |
 | `GlmForCausalLM` | GLM-4 | `zai-org/glm-4-9b-chat-hf`, etc. | ✅︎ | ✅︎ |
 | `Glm4ForCausalLM` | GLM-4-0414 | `zai-org/GLM-4-32B-0414`, etc. | ✅︎ | ✅︎ |
 | `Glm4MoeForCausalLM` | GLM-4.5, GLM-4.6, GLM-4.7 | `zai-org/GLM-4.5`, etc. | ✅︎ | ✅︎ |
@@ -554,6 +555,7 @@ These models primarily accept the [`LLM.generate`](./generative_models.md#llmgen
 | `FuyuForCausalLM` | Fuyu | T + I | `adept/fuyu-8b`, etc. | | ✅︎ |
 | `Gemma3ForConditionalGeneration` | Gemma 3 | T + I<sup>E+</sup> | `google/gemma-3-4b-it`, `google/gemma-3-27b-it`, etc. | ✅︎ | ✅︎ |
 | `Gemma3nForConditionalGeneration` | Gemma 3n | T + I + A | `google/gemma-3n-E2B-it`, `google/gemma-3n-E4B-it`, etc. | | |
+| `Gemma4ForConditionalGeneration` | Gemma 4 | T + I<sup>+</sup> + V + A<sup>*</sup> | `google/gemma-4-E2B-it`, etc. | | ✅︎ |
 | `GLM4VForCausalLM`<sup>^</sup> | GLM-4V | T + I | `zai-org/glm-4v-9b`, `zai-org/cogagent-9b-20241220`, etc. | ✅︎ | ✅︎ |
 | `Glm4vForConditionalGeneration` | GLM-4.1V-Thinking | T + I<sup>E+</sup> + V<sup>E+</sup> | `zai-org/GLM-4.1V-9B-Thinking`, etc. | ✅︎ | ✅︎ |
 | `Glm4vMoeForConditionalGeneration` | GLM-4.5V | T + I<sup>E+</sup> + V<sup>E+</sup> | `zai-org/GLM-4.5V`, etc. | ✅︎ | ✅︎ |
@@ -633,6 +635,7 @@ Some models are supported only via the [Transformers modeling backend](#transfor
 <sup>^</sup> You need to set the architecture name via `--hf-overrides` to match the one in vLLM.</br>
 <sup>E</sup> Pre-computed embeddings can be inputted for this modality.</br>
 <sup>+</sup> Multiple items can be inputted per text prompt for this modality.
+<sup>*</sup> Only specific variants of the model support this modality (see notes below).</br>
 
 !!! note
     `Gemma3nForConditionalGeneration` is only supported on V1 due to shared KV caching and it depends on `timm>=1.0.17` to make use of its
@@ -643,6 +646,11 @@ Some models are supported only via the [Transformers modeling backend](#transfor
     - Both audio and vision MM encoders use `transformers.AutoModel` implementation.  
     - There's no PLE caching or out-of-memory swapping support, as described in [Google's blog](https://developers.googleblog.com/en/introducing-gemma-3n/). These features might be too model-specific for vLLM, and swapping in particular may be better suited for constrained setups.
 
+!!! note
+    For `Gemma4ForConditionalGeneration`:
+    - audio input is only supported by the `gemma-4-E2B` and `gemma-4-E4B` variants.
+    - The model does not ingest videos directly. However, vLLM’s Gemma 4 implementation supports video inputs by handling video processing internally. Users can send videos directly in the message structure to vLLM, where they are converted into text and image frames before being passed to the model.
+
 !!! note
     For `InternVLChatModel`, only InternVL2.5 with Qwen2.5 text backbone (`OpenGVLab/InternVL2.5-1B` etc.), InternVL3 and InternVL3.5 have video inputs support currently.