Chat templates and tokenizer customization

JINJA chat templates (recommended method)

Some models do not come with support for tool calling or other features, and as such it might be necessary to specify your own chat template.

We provide some chat templates here, and it is easy to modify or create others to customize chat template behavior.

To use this, add the jinja-explicit parameter to the various APIs

./mistralrs-server --port 1234 --isq 4 --jinja-explicit chat_templates/mistral_small_tool_call.jinja vision-plain -m mistralai/Mistral-Small-3.1-24B-Instruct-2503

Chat template overrides

Mistral.rs attempts to automatically load a chat template from the tokenizer_config.json file. This enables high flexibility across instruction-tuned models and ensures accurate chat templating. However, if the chat_template field is missing, then a JINJA chat template should be provided. The JINJA chat template may use messages, add_generation_prompt, bos_token, eos_token, and unk_token as inputs.

We provide some chat templates here, and it is easy to modify or create others to customize chat template behavior.

For example, to use the chatml template, --chat-template is specified before the model architecture. For example:

./mistralrs-server --port 1234 --log output.log --chat-template ./chat_templates/chatml.json plain -m meta-llama/Llama-3.2-3B-Instruct

Note: For GGUF models, the chat template may be loaded directly from the GGUF file by omitting any other chat template sources.

Tokenizer

Some models do not provide a tokenizer.json file although mistral.rs expects one. To solve this, please run this script. It will output the tokenizer.json file for your specific model. This may be used by passing the --tokenizer-json flag after the model architecture. For example:

$ python3 scripts/get_tokenizers_json.py
Enter model ID: microsoft/Orca-2-13b
$ ./mistralrs-server --port 1234 --log output.log plain -m microsoft/Orca-2-13b --tokenizer-json tokenizer.json

Putting it all together, to run, for example, an Orca model (which does not come with a tokenizer.json or chat template):

Generate the tokenizer.json by running the script at scripts/get_tokenizers_json.py. This will output some files including tokenizer.json in the working directory.
Find and copy the correct chat template from chat-templates to the working directory (eg., cp chat_templates/chatml.json .)
Run mistralrs-server, specifying the tokenizer and chat template: cargo run --release --features cuda -- --port 1234 --log output.txt --chat-template chatml.json plain -m microsoft/Orca-2-13b -t tokenizer.json

Note: For GGUF models, the tokenizer may be loaded directly from the GGUF file by omitting the tokenizer model ID.

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