Sim

Sim (formerly Sim Studio, now at sim.ai) is an open-source agent-building platform that gives technical teams a unified workspace to compose, deploy, and monitor AI agents. The core experience is a visual drag-and-drop builder that connects to 1,000+ apps (Slack, GitHub, Jira, Salesforce, Notion), stitches in semantic knowledge bases for RAG, and pipes runs through real-time traces, logs, and cost tracking. Agents can be authored visually, conversationally, or in code, and they can call every major LLM including Claude, OpenAI, and Google models.

It targets engineering teams that want the ergonomics of a Zapier-style canvas without giving up the depth of a real agent framework. The Free tier is genuinely usable (1,000 credits/mo, 1 workspace, 5 GB storage); Pro is $25/user/mo, Max is $100/user/mo, and Enterprise unlocks SSO, SOC2 attestations, self-hosting support, and dedicated help. With ~29k GitHub stars and a permissive self-host path, it is a credible alternative to closed platforms like Relevance AI or n8n's AI workflows.

The API and MCP-friendly integration surface make it viable as either the orchestration layer for internal automations or the runtime for customer-facing agents. Caveat: like most agent canvases, non-trivial workflows quickly want code, and the credit-based pricing can bite once you hook up expensive frontier models on high-volume triggers.