ContrabassvsSandbox Agent
Generated from the two spec rows. Green marks the better value where a spec has a clear direction. Everything else is just different.
Contrabass
junhoyeo · Agent harness
OSSMCP
Panel
7.14 spec wins
- Reliability
- 6.8
- Usefulness
- 7.3
- Cost
- 8.2
- Longevity
- 6.0
“Every issue gets a worktree under workspaces/ named after the ticket, so your filesystem is now a faithful copy of your backlog.”
Sandbox Agent
Rivet · Agent harness
OSS
Panel
7.22 spec wins
- Reliability
- 7.2
- Usefulness
- 7.0
- Cost
- 8.0
- Longevity
- 6.5
“It ships an Inspector UI, because the only way to trust an agent in a box is to watch it through the glass.”
Spec by spec
| Spec | Contrabass | Sandbox Agent |
|---|---|---|
| Architecture | ||
| Category | Agent harness | Agent harness |
| Runs | local | local, sandbox, cloud |
| Platforms | macos, linux | macos, linux, windows |
| Context window | not documented | agent-dependent |
| Protocols | ||
| MCP client | No | No |
| MCP server | Yes | No |
| Capabilities | ||
| Runs terminal commands | Yes | Yes |
| Multi-file edits | YesFiles are changed by the agent runner Contrabass launches in each issue's worktree. | Yes |
| Git operations | Yes | No |
| Browser control | No | No |
| Sandboxed execution | No | YesThe server is designed to run inside the sandbox; deployment guides cover E2B, Daytona, Modal, Cloudflare Containers, Vercel Sandboxes and Docker. |
| Multi-agent orchestration | Yes | No |
| Headless / CI mode | YesA --no-tui flag runs the orchestrator headless with events logged to stdout. | Yes |
| Models | ||
| Backbone | Codex app-server, OpenCode, oh-my-opencode, OMX, OMC | via managed agents (Claude Code, Codex, OpenCode, Cursor, Amp, Pi) |
| Bring your own model | Yes | No |
| Local models | No | No |
| Cost | ||
| Pricing model | byok | byok |
| Starts at | $0/mo | $0/mo |
| Free tier | Yes | Yes |
| Bring your own key | Yes | Yes |
| Openness | ||
| Open source | Yes | Yes |
| License | Apache-2.0 | Apache-2.0 |
| GitHub stars | 223 | 1,582 |
Which one would each critic pick
| Critic | Contrabass | Sandbox Agent | Pick |
|---|---|---|---|
| El Juez | — | — | not enough reviews |
| El Amigo | 7.5 | 7.8 | Sandbox Agent — Pick it when you want to change which coding agent runs without changing your product; pick Warren if you want the run managed rather than merely exposed. |
| El Crítico | 6.8 | 6.8 | no preference |
| El Profesor | 7.5 | 7.5 | no preference |
| La Inversora | 6.5 | 6.5 | no preference |
| La Jefa | 6.3 | 6.8 | Sandbox Agent — This is the first thing in the category that answers my audit question, and its cost across sixty engineers is sandbox compute rather than a licence. |
| El Hacker | 8.0 | 7.8 | Contrabass — Apache-2.0, `nix profile install` if you want it, and WORKFLOW.md with Liquid templating means the prompts are a file in my repository. |
Picks are derived from each critic's own scores. Humans vote on matchups on the duels page.