lagent vs harness-sdk
Python agent framework compared with a Python and TypeScript SDK
lagent and harness-sdk help developers build LLM-powered agents with tools, memory, and multi-agent workflows. lagent is a Python framework centered on composable agent components, while harness-sdk combines ready-made Python and TypeScript harnesses with lower-level SDKs for controlling agent execution.
lagent: Build LLM Agents with a PyTorch-Inspired Framework
InternLM’s Lagent is a lightweight Python framework for building LLM-based agents, using a PyTorch-inspired design for composing agents and message passing. It supports synchronous and asynchronous workflows, tools, memory, and multi-agent applications.
harness-sdk: Build and Run AI Agents in Python and TypeScript
Strands Agents provides Python and TypeScript tools for building AI agents, from a ready-made harness to a customizable agent SDK. It suits teams that want model flexibility and control over agent execution without a hosted control plane.
| lagent | harness-sdk | |
|---|---|---|
| Language | Python | Python |
| License | Apache-2.0 | Apache-2.0 |
| Stars | 2.3k | 8.6k |
| Forks | 248 | 1.3k |
| Last analyzed | Oct 15, 2026 | Oct 3, 2026 |
Key differences
- lagent is Python-only, while harness-sdk supports Python and TypeScript.
- lagent emphasizes components such as message handling, aggregators, parsers, and action executors; harness-sdk offers an assembled harness as well as lower-level SDKs for configuring the agent loop.
- harness-sdk documents support for Amazon Bedrock, Anthropic, OpenAI, Gemini, and custom providers; lagent's examples illustrate backends including vLLM and LMDeploy.
- harness-sdk lists execution controls, tracing, hooks, guardrails, and evaluation support; lagent highlights session memory, message conversion, and synchronous and asynchronous components.
- Both projects use the Apache-2.0 license and are not archived. The supplied figures list 8.6k stars and 1.3k forks for harness-sdk, compared with 2.3k stars and 245 forks for lagent.
Choose lagent if you…
- need a Python framework built around composable agent components and structured messages.
- want synchronous and asynchronous options for tool-using or collaborative agent workflows.
- plan to build workflows such as code execution, browsing, or iterative writing with session memory.
Choose harness-sdk if you…
- want a ready-made harness or a lower-level SDK for Python or TypeScript.
- need provider options, including Bedrock, Anthropic, OpenAI, or Gemini, alongside tool integrations such as MCP.
- need controls and visibility such as turn limits, token budgets, cancellation, hooks, tracing, or evaluation support.
Compare the numbers side by side, or add more projects
This comparison is generated with AI from the OSRepos analyses of both projects. Always check each project's repository and documentation before choosing.