INSAIT-Institute/GRPO-Instruct-1.5B

TEXT GENERATIONPricing:Input $0.04 / Cached $0.008 / Output $0.08Concurrent Unit Cost:1Model Size:1.5BQuant:BF16Context Size:32kTool Calling:SupportedPublished:Aug 12, 2026License:cc-by-nc-sa-4.0Architecture:Transformer Open Weights Featherless Exclusive Cold

INSAIT-Institute/GRPO-Instruct-1.5B is a 1.5 billion parameter code verifier model developed by INSAIT-Institute. Fine-tuned from Qwen2.5-1.5B-Instruct, it utilizes Reinforcement Learning with Verifiable Rewards (RLVR) to judge and rank candidate solutions for competitive programming problems. This model is specifically trained without intermediate thinking traces, directly emitting a verdict, making it efficient for deploying robust code verifiers in post-training pipelines.

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Aletheia: GRPO-Instruct-1.5B Code Verifier

This model, GRPO-Instruct-1.5B, is a 1.5 billion parameter code verifier developed by INSAIT-Institute as part of the Aletheia project. It is fine-tuned from Qwen/Qwen2.5-1.5B-Instruct using Reinforcement Learning with Verifiable Rewards (RLVR). A key differentiator of this specific verifier is its training approach: it operates without intermediate thinking traces, directly providing a verdict on candidate code solutions. This design choice aims to balance performance and computational cost, particularly for smaller verifiers.

Key Capabilities

  • Code Verification: Judges and ranks candidate solutions for competitive programming problems.
  • RLVR Training: Utilizes on-policy learning with negative samples for robust verification.
  • Efficiency: Designed to directly emit a verdict without generating intermediate thought processes, offering a compute-efficient strategy at lower budgets.
  • Scalability Insights: Part of a broader research effort to understand how different RLVR training recipes (thinking traces, negative samples, on-policy training) impact verifier performance across various model scales.

Good For

  • RLHF / RLAIF: Serving as a plug-and-play reward function for optimizing code generation policies.
  • Automated Evaluation: Acting as an LLM-as-a-judge for diverse code-related tasks.
  • Research: Studying the impact of specific training components (like the absence of thinking traces) on code verifier efficacy and efficiency.