Gamunu-4B-Instruct-Alpha: A Sinhala-Centric Bilingual LLM

Gamunu-4B-Instruct-Alpha is an experimental 4.3 billion parameter language model developed by Manthila Mallawa as part of The Gamunu Project. It is the first checkpoint in a series of Sinhala-centric bilingual LLMs, built upon Google's Gemma 3 4B base model. The model underwent continued pre-training to enhance Sinhala linguistic coverage and then supervised fine-tuning on a custom Sinhala instruction dataset, focusing on reasoning, roleplay, and assistant-style behavior.

Key Capabilities

• Bilingual Fluency: Generates fluent, idiomatic Sinhala and demonstrates robust Sinhala ↔ English understanding.
• Reasoning: Exhibits solid mathematical reasoning (percentages, word problems) and logical, step-by-step reasoning in QA tasks.
• Instruction Following: Accurately adheres to single-turn instructions and can simulate expert personas (teacher, scientist, analyst).
• NLP Tasks: Supports text generation, summarization, translation (Sinhala ↔ English), paraphrasing, question answering, and instruction-based classification.

Limitations

As an alpha experimental model, it currently lacks conversational memory, is single-turn only, and has not undergone RLHF or safety tuning. Users may encounter occasional factual drift.

Intended Use Cases

• Research and evaluation of Sinhala LLMs.
• Educational assistants and analytical Q&A.
• Cultural, marketing, and academic content generation.
• Benchmarking instruction following in low-resource languages.