Module chat_template 

Chat Template Engine

Implements APR Chat Template Specification v1.1.0

This module provides a generic, model-agnostic chat template system supporting:

• ChatML (Qwen2, OpenHermes, Yi)
• LLaMA2 (TinyLlama, Vicuna)
• Mistral/Mixtral
• Alpaca
• Phi-2/Phi-3
• Custom Jinja2 templates

Toyota Way Principles

• Jidoka: Auto-detect template format; stop on invalid template
• Standardized Work: Unified ChatTemplateEngine API
• Poka-Yoke: Validate templates before application
• Muda Elimination: Use minijinja instead of custom parsing

Example

use aprender::text::chat_template::{ChatMessage, ChatMLTemplate, ChatTemplateEngine};

let template = ChatMLTemplate::new();
let messages = vec![
    ChatMessage::new("user", "Hello!"),
];
let formatted = template.format_conversation(&messages).expect("format conversation should succeed");
assert!(formatted.contains("<|im_start|>user"));

References

• Touvron et al. (2023) - “Llama 2” (arXiv:2307.09288)
• Bai et al. (2023) - “Qwen Technical Report” (arXiv:2309.16609)
• docs/specifications/chat-template-improvement-spec.md

Structs

AlpacaTemplate

Alpaca Template

ChatMLTemplate

ChatML Template (Qwen2, OpenHermes, Yi)

ChatMessage

Chat message structure

HuggingFaceTemplate

Jinja2-based Chat Template Engine

Llama2Template

LLaMA 2 Template (TinyLlama, Vicuna, LLaMA 2)

MistralTemplate

Mistral Template (Mistral, Mixtral)

PhiTemplate

Phi Template (Phi-2, Phi-3)

RawTemplate

Raw Template (Fallback - no formatting)

SpecialTokens

Special tokens used in chat templates

Enums

TemplateFormat

Template format enumeration

Constants

MAX_LOOP_ITERATIONS

Maximum loop iterations (CTC-05)

MAX_RECURSION_DEPTH

Maximum recursion depth for templates (CTC-04)

MAX_TEMPLATE_SIZE

Maximum template size in bytes (100KB per spec CTC-03)

Traits

ChatTemplateEngine

Chat template engine trait

Functions

auto_detect_template

Auto-detect and create template from model name

contains_injection_patterns

Check if content contains potential injection patterns.

create_template

Create a template engine for a given format

detect_format_from_name

Auto-detect template format from model name or path

detect_format_from_tokens

Auto-detect template format from special tokens

sanitize_user_content

Sanitize user content to prevent prompt injection attacks.