ByteDance Researchers Introduce Seed-Coder: A Model-Centric Code LLM Trained on 6 Trillion Tokens

Reframing Code LLM Training through Scalable, Automated Data Pipelines

Code data plays a key role in training LLMs, benefiting not just coding tasks but also broader reasoning abilities. While many open-source models rely on manual filtering and expert-crafted rules to curate code datasets, these approaches are time-consuming, biased, and hard to scale across languages. Proprietary models like Claude 3.7 and OpenAI o3 excel at coding tasks but don’t share details about their data. Even open-source models like DeepSeek and Qwen2.5 still depend heavily on human-designed filters. However, this reliance limits progress, echoing “The Bitter Lesson” that real breakthroughs come from scalable, data-driven methods, not handcrafted heuristics. 

Seed-Coder’s Model-First Pipeline Minimizes Human Dependency in Pretraining

Researchers at ByteDance introduce Seed-Coder, a family of 8B open-source LLMs including base, instruction, and reasoning models, designed to reduce human involvement in code data curation. Instead of relying on manual rules, their model-centric pipeline utilizes LLMs to score and filter large-scale code data from sources such as GitHub and code-related websites, resulting in a 6-trillion-token dataset. The instruction model is fine-tuned using synthetic data and preference optimization, while the reasoning model enhances multi-step code logic via Long-Chain-of-Thought reinforcement learning. Seed-Coder achieves top performance for its size, often surpassing larger models, and is openly shared to encourage further research and development. 

6-Trillion Token Corpus Built with LLM Quality Filters across GitHub and Web Data

Seed-Coder is trained using a model-driven approach that minimizes manual intervention. The pretraining corpus comprises approximately 6 trillion tokens, sourced from various sources, including GitHub code, commit histories, and code-related web data. Initially, basic filtering removes files with syntax issues or inappropriate content. Then, large language models are used to evaluate and score the remaining code, ensuring high-quality data without relying on hand-crafted rules. Pretraining occurs in two stages: first, with core code and web data, and later, with more complex structures, such as full repositories and long-context tasks, like fill-in-the-middle, to enhance the model’s coding capabilities. 

Post-Training via Instruction Tuning and LongCoT Enables Multi-Step Code Understanding

After pretraining, Seed-Coder undergoes further refinement through two post-training stages. First, the instruction model is trained using supervised fine-tuning on a diverse set of synthetic instruction data generated and filtered by LLMs, helping it better understand and follow human prompts. Then, its performance is enhanced using direct preference optimization (DPO), which aligns model responses more closely with human preferences. For complex reasoning tasks, the reasoning model is improved using LongCoT reinforcement learning, which strengthens its ability to handle multi-step coding challenges. These steps significantly boost Seed-Coder’s performance across various code generation and reasoning tasks. 

Seed-Coder Excels in Code Generation, Editing, and Multi-Step Reasoning Benchmarks

The evaluation reveals that the three Seed-Coder models, Base, Instruct, and Reasoning, perform exceptionally well across a range of coding tasks. The Base model outperforms other open-source models of similar size on code generation tasks, achieving strong scores on benchmarks like HumanEval and MultiPL-E. The Instruct model excels in tasks requiring code editing and instruction-following, leading in evaluations such as CodeEditorBench and FullStack. The Reasoning model, trained with long-chain-of-thought techniques, demonstrates outstanding multi-step problem-solving skills, particularly on challenging benchmarks like LiveCodeBench and Codeforces, even surpassing models that are several times larger in size. 

In conclusion, Seed-Coder is a family of efficient and high-performing open-source language models designed specifically for coding tasks. These models stand out by relying largely on LLMs rather than humans to filter and curate training data, significantly reducing manual effort. Despite being trained on fewer tokens compared to some larger models, Seed-Coder exhibits exceptional performance in tasks such as code generation, completion, editing, and reasoning. However, its abilities in general language understanding are still limited due to the absence of broad web data and mathematical content. Future updates aim to expand the model family and improve its capabilities across different model sizes. 

Check out the Paper, Model Series, GitHub Page and Project Page. All credit for this research goes to the researchers of this project. Also, feel free to follow us on Twitter and don’t forget to join our 100k+ ML SubReddit and Subscribe to our Newsletter.

Sana Hassan, a consulting intern at Marktechpost and dual-degree student at IIT Madras, is passionate about applying technology and AI to address real-world challenges. With a keen interest in solving practical problems, he brings a fresh perspective to the intersection of AI and real-life solutions.