feat: add Gemma 4 multimodal chat support (abetlen#2241)

Author: abetlen

CHANGELOG.md

@@ -7,6 +7,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+- feat: add Gemma 4 multimodal chat support by @abetlen in #2241
 - feat(ci): add CUDA 13.0 and 13.2 wheel builds by @abetlen in #2239
 - feat(ci): add CUDA 11.8 wheel builds by @abetlen in #2238
 - fix(ci): add Pascal compute capability targets to CUDA wheel builds by @abetlen in #2237

README.md

@@ -510,6 +510,7 @@ Below are the supported multi-modal models and their respective chat handlers (P
 | [llama-3-vision-alpha](https://huggingface.co/abetlen/llama-3-vision-alpha-gguf) | `Llama3VisionAlphaChatHandler` | `llama-3-vision-alpha` |
 | [minicpm-v-2.6](https://huggingface.co/openbmb/MiniCPM-V-2_6-gguf) | `MiniCPMv26ChatHandler` | `minicpm-v-2.6` |
 | [qwen2.5-vl](https://huggingface.co/unsloth/Qwen2.5-VL-3B-Instruct-GGUF) | `Qwen25VLChatHandler` | `qwen2.5-vl` |
+| [gemma-4](https://huggingface.co/unsloth/gemma-4-E4B-it-GGUF) | `Gemma4ChatHandler` | `gemma4` |
 
 Then you'll need to use a custom chat handler to load the clip model and process the chat messages and images.
 

llama_cpp/llama_chat_format.py

@@ -3265,6 +3265,50 @@ def from_pretrained(
         )
 
 
+class Gemma4ChatHandler(Llava15ChatHandler):
+    DEFAULT_SYSTEM_MESSAGE = None
+
+    CHAT_FORMAT = (
+        "{% if messages and messages[0]['role'] == 'system' %}"
+        "{% if messages[0]['content'] is string %}"
+        "{% set first_user_prefix = messages[0]['content'] + '\n\n' %}"
+        "{% else %}"
+        "{% set first_user_prefix = messages[0]['content'][0]['text'] + '\n\n' %}"
+        "{% endif %}"
+        "{% set loop_messages = messages[1:] %}"
+        "{% else %}"
+        "{% set first_user_prefix = '' %}"
+        "{% set loop_messages = messages %}"
+        "{% endif %}"
+        "{% for message in loop_messages %}"
+        "{% if (message['role'] == 'user') != (loop.index0 % 2 == 0) %}"
+        "{{ raise_exception('Conversation roles must alternate user/assistant/user/assistant/...') }}"
+        "{% endif %}"
+        "{% set role = 'model' if message['role'] == 'assistant' else message['role'] %}"
+        "{{ '<start_of_turn>' + role + '\n' + (first_user_prefix if loop.first else '') }}"
+        "{% if message['content'] is string %}"
+        "{{ message['content'] | trim }}"
+        "{% elif message['content'] is iterable %}"
+        "{% for item in message['content'] %}"
+        "{% if item['type'] == 'image_url' and item['image_url'] is string %}"
+        "{{ '\n\n' + item['image_url'] + '\n\n' }}"
+        "{% elif item['type'] == 'image_url' and item['image_url'] is mapping %}"
+        "{{ '\n\n' + item['image_url']['url'] + '\n\n' }}"
+        "{% elif item['type'] == 'text' %}"
+        "{{ item['text'] | trim }}"
+        "{% endif %}"
+        "{% endfor %}"
+        "{% else %}"
+        "{{ raise_exception('Invalid content type') }}"
+        "{% endif %}"
+        "{{ '<end_of_turn>\n' }}"
+        "{% endfor %}"
+        "{% if add_generation_prompt %}"
+        "{{ '<start_of_turn>model\n' }}"
+        "{% endif %}"
+    )
+
+
 class ObsidianChatHandler(Llava15ChatHandler):
     # Prompt Format
     # The model followed ChatML format. However, with ### as the separator

llama_cpp/server/model.py

@@ -115,6 +115,20 @@ def load_llama_from_model_settings(settings: ModelSettings) -> llama_cpp.Llama:
                 chat_handler = llama_cpp.llama_chat_format.Llava16ChatHandler(
                     clip_model_path=settings.clip_model_path, verbose=settings.verbose
                 )
+        elif settings.chat_format == "gemma4":
+            assert settings.clip_model_path is not None, "clip model not found"
+            if settings.hf_model_repo_id is not None:
+                chat_handler = (
+                    llama_cpp.llama_chat_format.Gemma4ChatHandler.from_pretrained(
+                        repo_id=settings.hf_model_repo_id,
+                        filename=settings.clip_model_path,
+                        verbose=settings.verbose,
+                    )
+                )
+            else:
+                chat_handler = llama_cpp.llama_chat_format.Gemma4ChatHandler(
+                    clip_model_path=settings.clip_model_path, verbose=settings.verbose
+                )
         elif settings.chat_format == "moondream":
             assert settings.clip_model_path is not None, "clip model not found"
             if settings.hf_model_repo_id is not None: