agurung/cobalt-seeded-rl-base-ramp25-stoppen-gen4k-ep2-ncp10-bgroot16

TEXT GENERATIONPricing:Input $0.4 / Cached $0.08 / Output $0.8Concurrent Unit Cost:1Model Size:4BQuant:BF16Context Size:32kTool Calling:SupportedPublished:Sep 1, 2026Architecture:Transformer Featherless Exclusive Cold

agurung/cobalt-seeded-rl-base-ramp25-stoppen-gen4k-ep2-ncp10-bgroot16 is a 4 billion parameter reinforcement learning (RL) checkpoint based on Qwen3-4B-Instruct-2507, developed by agurung. This model is specifically fine-tuned using OpenRLHF GRPO with binary code-correctness as the reward signal, making it highly optimized for code generation tasks. It excels at solving programming problems, particularly those on the cobalt-train frontier, by generating correct code solutions.

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Model Overview

This model, agurung/cobalt-seeded-rl-base-ramp25-stoppen-gen4k-ep2-ncp10-bgroot16, is a 4 billion parameter reinforcement learning (RL) checkpoint derived from the Qwen/Qwen3-4B-Instruct-2507 base model. Developed by agurung, it was trained using the OpenRLHF GRPO algorithm, which applies RL directly to the base model without an initial Supervised Fine-Tuning (SFT) seed.

Key Capabilities

  • Code Generation: Optimized for generating correct code solutions, validated on the cobalt-train frontier of programming problems.
  • Reinforcement Learning: Utilizes a binary code-correctness reward signal (1.0 for passing tests, 0.0 otherwise) to enhance performance in coding tasks.
  • GRPO Algorithm: Employs Group-Normalized Advantages (GRPO) without a KL penalty for efficient learning.
  • Anti-Truncation Shaping: Incorporates a stop-properly penalty for truncated samples and an overlong penalty for responses nearing the token cap, ensuring more complete and relevant outputs.

What Makes This Model Different?

Unlike many general-purpose LLMs, this model is highly specialized for code generation and problem-solving through a unique RL fine-tuning approach. It directly optimizes for code correctness using a specific reward signal, rather than relying solely on instruction following or broad language understanding. This targeted training makes it particularly effective for use cases where the primary goal is to produce functional and verifiable code. It represents the "best checkpoint by pass@8" in its development run, indicating strong performance in its specialized domain.

When to Use This Model

This model is ideal for applications requiring robust and accurate code generation, especially for competitive programming, automated code completion, or solving specific algorithmic challenges. Its optimization for binary code-correctness makes it a strong candidate for tasks where the output's functional correctness is paramount.