Strands Agents
strands-agents/harness-sdk
AWS's open-source SDK for building production agent harnesses.
Strands is a model-driven agent SDK where the loop is directed by the model with typed tools, and batteries included for AWS. Its Python repo was renamed to harness-sdk in 2026 — AWS now talks the harness language natively.
In the news
DeepSeek ships Harness Desktop; the 'everything is a plugin' harness passes 240k stars
DeepSeek releases a macOS and Windows Desktop app for DeepSeek Harness, its open-source agent harness where everything — tools, sub-agents, even the loop — is a plugin. The repo passed 240k stars within three months of its August launch, making it the fastest-growing harness in the field's history.
HarnessTax: harness choice swings agent cost more than model choice
Arena.ai's HarnessTax study tests 21 model–harness combinations across Claude Code, Codex CLI and Pi, finding harness choice can significantly change cost even at similar task success rates. Weeks earlier, SWE-bench Pro analysis showed swapping harnesses moved pass@1 more than model upgrades (23%→52% on GLM-5.2) — and that harness rankings barely transfer across models.
Anthropic launches the Claude Agent SDK
Anthropic open-sources the SDK behind Claude Code — the agent loop, tool use, subagents, memory and hooks — letting developers build their own Claude-powered agents on production rails.
OpenAI ships the Agents SDK and upgraded Responses API
OpenAI releases an open-source Agents SDK (successor to the Swarm experiments) with handoffs, guardrails and tracing, plus a Responses API purpose-built for agentic workflows.
Related projects
OpenClaw
openclaw/openclaw
The viral open-source personal AI assistant that really does things.
OpenClaw (born as Clawdbot in late 2025) is a self-hosted personal agent that connects your chats, email, browser and terminal into one always-on assistant. Its explosive growth — hundreds of thousands of stars within months — made 'personal agent harness' a mainstream category.
Hermes Agent
NousResearch/hermes-agent
The agent that grows with you.
Nous Research's self-improving personal agent: a learning loop turns experience into reusable skills, builds a persistent user model across sessions, and checkpoints state to disk with rollback — lean enough for a $5 VPS and driven from the chat apps you already use.
DeepSeek Harness
deepseek-ai/deepseek-harness
Everything is a Plugin — DeepSeek's open agent harness.
DeepSeek Harness is the breakout open-source harness of 2026: an architecture where everything — tools, subagents, even the loop itself — is a plugin. A Desktop app for macOS and Windows followed in October 2026, and the project passed 240k stars in under three months.