LegionvsSim
Generated from the two spec rows. Green marks the better value where a spec has a clear direction. Everything else is just different.
Legion
Software Mansion · Agent framework
OSS
Panel
6.53 spec wins
- Reliability
- 6.0
- Usefulness
- 6.2
- Cost
- 8.0
- Longevity
- 5.8
“It writes Lua to get work done in Elixir, which is two functional languages agreeing that a third one should take the blame.”
Sim
Sim · Agent framework
OSSMCP
Panel
6.54 spec wins
- Reliability
- 6.2
- Usefulness
- 6.7
- Cost
- 7.0
- Longevity
- 6.2
“Formerly Sim Studio, now Sim, saving you six characters and creating no confusion whatsoever.”
Spec by spec
| Spec | Legion | Sim |
|---|---|---|
| Architecture | ||
| Category | Agent framework | Agent framework |
| Runs | local | cloud, local |
| Platforms | macos, linux | macos, linux, windows, web |
| Context window | not documented | not documented |
| Protocols | ||
| MCP client | No | Yes |
| MCP server | No | No |
| Capabilities | ||
| Runs terminal commands | No | No |
| Multi-file edits | Yes | No |
| Git operations | No | No |
| Browser control | No | No |
| Sandboxed execution | YesLegion runs generated Lua or Elixir in its own sandbox; the README does not describe a container runtime. | No |
| Multi-agent orchestration | No | Yes |
| Headless / CI mode | No | No |
| Models | ||
| Backbone | multiple providers | any |
| Bring your own model | Yes | Yes |
| Local models | No | Yes |
| Cost | ||
| Pricing model | byok | mixed |
| Starts at | $0/mo | $25/mo |
| Free tier | Yes | Yes |
| Bring your own key | Yes | Yes |
| Openness | ||
| Open source | Yes | Yes |
| License | MIT | Apache-2.0 |
| GitHub stars | 220 | 29,765 |
Which one would each critic pick
| Critic | Legion | Sim | Pick |
|---|---|---|---|
| El Juez | — | — | not enough reviews |
| El Amigo | 6.8 | 6.5 | Legion — Pick Legion if you write Elixir and want the agent inside the application rather than beside it; pick a framework in Python if the rest of your stack already lives there. |
| El Crítico | 6.0 | 5.8 | Legion — The generated snippet runs in the project's own sandbox, and the README does not describe a container runtime, so the isolation boundary is whatever the host process could already reach. |
| El Profesor | 7.8 | 6.8 | Legion — One evaluation can filter, branch and loop, so a sequence that costs a tool-calling agent a model round trip per step collapses into a single call. The claim is structural and checkable. |
| La Inversora | 6.3 | 6.5 | Sim — A thousand integrations plus self-hosting bundled into custom enterprise terms is the standard open-core ladder, and the enterprise tier is where this actually gets sold. |
| La Jefa | 5.5 | 5.8 | Sim — Twenty-five dollars per user is $1,500 a month for sixty, and support is a community repository, with directory integration only appearing in negotiated terms. |
| El Hacker | 6.8 | 7.8 | Sim — Apache-2.0, npx sim-setup puts it on my own box with Docker, local model endpoints work, and it speaks MCP as a client, which is the whole checklist. |
Picks are derived from each critic's own scores. Humans vote on matchups on the duels page.