Best tools for training and fine-tuning agents (2026)

LayerFS

Newagent infraOpen source

LayerFS is a filesystem built for running many coding agents in parallel. Each agent mounts a complete, writable workspace on top of shared committed history, does its work, commits what it changed and goes away, so compute only exists while a command runs. Every tool call becomes a commit on a branch, same-file clashes between agents are refused rather than silently merged, each line records the step that wrote it, and any commit can be forked at no cost for recursive exploration or RL training. Agents on different computers share one serverless store with chunk-level deduplication.

Added Oct 21, 2026

AgentEnv Framework

Newevals & observabilityOpen source

AgentEnv Framework is Scale AI's open-source Python SDK and CLI for building RL environments for agents: containerized worlds with realistic apps and data behind an MCP gateway, plus tasks (as DAGs) that grade any agent in any sandbox.

Added Oct 20, 2026

Kiln

Newevals & observabilitySource-available

Free desktop app and open-source library for building AI systems with evals, RAG, agents, fine-tuning and synthetic data in one workbench.

Added Oct 18, 2026

Agent Lightning

NewframeworksOpen source

Microsoft's lightweight trainer that improves existing agents with reinforcement learning through a model proxy, without rewriting the agent's tools or control flow.

Added Oct 17, 2026

NVIDIA TAO Agent Skills

NewvisionOpen source

NVIDIA's vision-model post-training toolkit, now packaged as agent skills so Claude Code or Codex can fine-tune, optimize and export vision foundation models from plain-English prompts.

Added Oct 17, 2026

OpenPipe

frameworksOpen source + cloud

Reinforcement learning tooling, including the ART library, to train better agents.

Added Oct 16, 2026

Oumi

models & local runtimesOpen source

Open platform for fine-tuning, evaluating and deploying open agentic LLMs and VLMs.

Added Oct 16, 2026

AReaL

frameworksOpen source

Reinforcement learning system for training LLM-based agents.

Added Oct 16, 2026

Prime Intellect

frameworksOpen source + cloud

Decentralized compute and open RL environment hub for training agentic models.

Added Oct 16, 2026

RAGEN

frameworksOpen source

Reinforcement learning framework for multi-turn LLM agents.

Added Oct 16, 2026

CoreWeave Forge

evals & observabilityFreemium

One product to run, observe, evaluate and post-train agents (W&B, OpenPipe, sandboxes).

Added Oct 14, 2026

Together AI

agent infraUsage-based

AI cloud for running, fine-tuning and serving open models.

Added Oct 16, 2026