# Best Agent frameworks — Seat model

> Source: https://theagentsindex.com/best/frameworks/seats (curated, quality-gated, re-verified)

4 of 14 agent frameworks have a confirmed yes for “Seat model”. 1 are qualified or tier-scoped, 2 are confirmed no, and 7 remain not established. Only confirmed yes answers appear in this set; an unknown is never treated as a negative.

| # | Name | What it is | Pricing | API |
| --- | --- | --- | --- | --- |
| 1 | [Agno](https://theagentsindex.com/agno.md) | Python SDK, self-hosted AgentOS runtime and hosted control plane for building and running agents | freemium | Yes |
| 2 | [LangChain](https://theagentsindex.com/langchain.md) | Open source agent framework plus LangSmith, its hosted observability, evaluation and deployment platform | freemium | Yes |
| 3 | [LangGraph](https://theagentsindex.com/langgraph.md) | MIT-licensed orchestration framework and runtime for stateful, long-running LLM agents. | paid | Yes |
| 4 | [Letta](https://theagentsindex.com/letta.md) | Stateful agent harness with git-backed memory, run from a CLI, desktop app, web, or SDK | freemium | Yes |

## Methodology

Projected from the live listing datasheets using the tenant’s “Per seat, and is there a floor or a ceiling?” axis. Membership requires a sourced yes; partial and unknown answers are reported above but excluded from the ranking. Entries retain the directory’s paid-tier ordering, visibly labelled on every promoted card.