StartupEst. 2024 · Y Combinator (W26)
1code (21st)
An orchestration layer for coding agents such as Claude Code and Codex, from YC-backed 21st.
1code is an open-source orchestration layer for coding agents, built by 21st, a Y Combinator W26 company that YC lists as making "UI building blocks for the agentic internet". The 1code repository describes itself as an orchestration layer for Claude Code and Codex, so several agents can be run and supervised together.
Neighbours in the directory
San Francisco, CA · Est. 2022
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.
~$75M raised
San Francisco, CA · Est. 2023
Devin, the AI software engineer, and the Windsurf IDE.
Cognition builds Devin, an autonomous AI software engineer that plans and executes engineering tasks end-to-end, and acquired the Windsurf agentic IDE in 2025. One of the defining startups of the coding-agent wave.
~$10.2B valuation (Sep 2025)
San Francisco, CA · Est. 2023
Conversational AI agents for customer experience.
Sierra, co-founded by Bret Taylor and Clay Bavor, builds production conversational agents that resolve real customer issues with guardrails, evaluation and human escalation — a template for deploying vertical agents at the enterprise edge.
~$10B valuation (Oct 2025)
Connections
Relations from the Harness Hub knowledge graph, as charted in the State of Harness reports.
Built on · 2
- Claude CodeProject
- CodexProject
Sources
Verified Oct 29, 2026