Helicone
Open-source LLM observability and AI gateway.
Helicone is an open-source LLM observability platform — logging, caching, rate limits and evals behind a one-line proxy — with an AI gateway for routing and cost control. A YC company that became the self-hostable counterweight to LangSmith.
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.
xAI open-sources Grok Build, its coding agent harness
xAI open-sources Grok Build — a Rust coding agent harness and fullscreen TUI around Grok models — unusually early for a first-party tool. It joins Claude Code, Codex and Gemini CLI as the fourth major first-party harness, now with a fourth open one.
ClickHouse acquires Langfuse
ClickHouse acquires the open-source LLM observability platform Langfuse as part of its $400M Series D at a $15B valuation — the first big consolidation in agent observability. The open-source core remains maintained; the deal signals that agent tracing is becoming a database-scale problem.
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.
Related startups
LangChain
The de-facto standard toolkit for building LLM applications and agents.
LangChain makes the LangChain framework and LangGraph, the low-level orchestration standard for stateful, controllable agents, plus the LangSmith platform for tracing, evaluating and monitoring them in production.
Modal
Serverless cloud built for AI and agentic compute.
Modal lets teams run inference, fine-tuning and arbitrary agent workloads as serverless Python without managing infrastructure — a common substrate for harness backends at scale.
Temporal
Durable execution for long-running agent workflows.
Temporal's durable execution engine is widely adopted to make agent pipelines reliable: state survives crashes, retries are automatic, and workflows run for minutes or months. A key piece of serious harness infrastructure.