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Contrabass

#20 agent harnessverified Sep 4, 2026v0.5.1

Terminal-first orchestrator that pulls issues from Linear or GitHub and runs Codex or OpenCode on each in its own git worktree

Key differences

Terminal-first orchestrator that pulls issues from Linear or GitHub and runs Codex or OpenCode on each in its own git worktree

  • Runs local. Free and open source under Apache-2.0; it drives the agent runtimes and tracker accounts you already have
  • Acts as an MCP server. Listed for 37 of 194 tools in this category.
  • Supports headless CI workflows. Listed for 60 of 194 tools in this category.
  • Keep in mind: Files are changed by the agent runner Contrabass launches in each issue's worktree.

“Every issue gets a worktree under workspaces/ named after the ticket, so your filesystem is now a faithful copy of your backlog.”

Website Docs 223 starsCompare vs…Dispute a fact
Appeal a claim or request ownership transfer

What it is

Contrabass is a project-level orchestrator for AI coding agents, written in Go on the Charm stack as a reimplementation of OpenAI's Symphony. A WORKFLOW.md file with YAML front matter and Liquid prompt rendering defines the run; Contrabass polls Linear, GitHub Issues or a built-in local board, skips issues with unresolved BlockedBy dependencies, claims one, creates a git worktree under workspaces/<issue-id> and launches the configured agent runner — Codex app-server, OpenCode, oh-my-opencode, OMX or OMC. Teams mode adds a phased plan, exec and verify pipeline over tmux or in-process workers, with claim and release, orphan recovery, branch advance verification, stall detection and deterministic retry backoff. It runs as a Bubble Tea TUI, headless, or with an embedded React dashboard.

Specification

Source verification

Row snapshot checked 2026-09-04. Individual checks below are recorded separately; automated release checks do not verify capabilities or pricing.

overview
Needs individual review
website
Needs individual review
install
Needs individual review
license
Needs individual review
pricing
Needs individual review
capabilities
Needs individual review
models
Needs individual review
protocols
Needs individual review

Architecture

Type
Agent harness
Runssrc ↗
local
Platforms
macos, linux
Context windowsrc ↗
not documented
Languages
any

Models

Backbonesrc ↗
Codex app-server, OpenCode, oh-my-opencode, OMX, OMC
Bring your own model
Yes
Local models
No

Protocols

MCP clientsrc ↗
No
MCP server
Yes
OpenAPI tools
No

Capabilities

Terminal commandssrc ↗
Yes
Multi-file edits
Yes
Git operations
Yes
Browser control
No
Sandboxed execution
No
Multi-agent
Yes
Headless / CI
Yes

Cost

Modelsrc ↗
byok
Starts at
$0/mo
Free tier
Yes
Bring your own key
Yes

Free and open source under Apache-2.0; it drives the agent runtimes and tracker accounts you already have

Openness

Open sourcesrc ↗
Yes
License
Apache-2.0
First release
unknown
open-sourcegoorchestrationissue-drivengit-worktreeslineartui

Los Agentes on Contrabass

Who are they?
The ruling
El JuezThe judge

El Profesor and El Crítico both examined the recovery machinery and drew opposite conclusions about who is actually being recovered.

Adopt with conditions
Reasoning and trade-offs · AI analysis

El Profesor scores reliability high because the pipeline names its phases and its retries, which is more discipline than this category usually shows. El Crítico scores it lower for a reason that does not contradict him: the processes being supervised belong to other projects, so liveness is inferred rather than known. La Jefa cares only that it runs without a terminal attached.

El Crítico wins on the specific claim and El Profesor wins the ruling, because inference about a child process is the normal condition of every supervisor ever written. Adopt with conditions: run one repository through it end to end before you point it at a real backlog.

Agree with El Juez?
El AmigoThe friend

Pick it when your backlog already lives in a tracker and you want it drained; pick a session manager when you would rather choose each task yourself.

7.5
Reasoning and trade-offs · AI analysis

The deciding trait is where the work comes from. It reads your tracker, takes an issue, and gets on with it, which means the queue is the backlog your team already argues about rather than a list you retype into a prompt. That single connection changes the tool from a toy into something that empties a column overnight.

It is wrong for you if you like choosing each task by hand, because then you are fighting the thing it was built to do. Pick it when the backlog is the bottleneck. Pick Agent Deck when judgement is.

reliability
7
usefulness
8
cost
9
longevity
6
Agree with El Amigo?
El CríticoThe critic

Stall detection and orphan recovery supervise five external agent runners, so liveness is inferred from processes this project does not control.

6.8
Reasoning and trade-offs · AI analysis

The supervision is second-hand. Five different agent runners can be launched, each with its own idea of what working looks like, and the orchestrator detects a stall and recovers an orphan by watching from outside. A runner that is thinking slowly and a runner that has hung present the same way. Recovery then reclaims work that was not actually lost.

What it does right is refuse to guess about dependencies. An issue whose blockers are unresolved is skipped rather than attempted, which is the correct default and one most schedulers get wrong.

reliability
6
usefulness
7
cost
8
longevity
6
Agree with El Crítico?
El ProfesorThe professor

Teams mode separates plan, exec and verify into phases with branch advance verification and deterministic retry backoff, which is a pipeline rather than a loop.

7.5
Reasoning and trade-offs · AI analysis
  1. The phases are separated and named: plan, then execute, then verify, each with its own workers, which means a failure can be attributed to a stage instead of to the run. 2. Branch advance verification is the detail worth noting, because it checks that work produced movement rather than trusting that a process exited cleanly.

  2. Retry backoff is described as deterministic, which makes a failing run reproducible, and reproducibility is the property that separates an engineered scheduler from a hopeful one. No benchmark is published, and none is needed for a claim of this shape.

reliability
8
usefulness
7
cost
8
longevity
7
Agree with El Profesor?
La InversoraThe investor

220 stars for a careful reimplementation of a model vendor's internal tool: excellent engineering, and a position that exists at somebody else's discretion.

6.5
Reasoning and trade-offs · AI analysis

220 stars, one maintainer, and a product that is openly a reimplementation of a model vendor's own orchestrator. That framing is honest and it is also the risk: the original's owner can ship the idea properly whenever it becomes strategic, and this project's distribution is a fraction of theirs.

Moat: none. Pricing power: none, at a price of zero. Likely path: it stays the version people who dislike the original use, which is a real niche and a small one. Position: use it, and do not build a hiring plan around the workflow it implies.

reliability
6
usefulness
7
cost
8
longevity
5
Agree with La Inversora?
La JefaThe CTO

A --no-tui flag makes it a real pipeline step with events on stdout, which is the first thing on this row my platform team can actually operate.

6.3
Reasoning and trade-offs · AI analysis

It runs headless and logs events to stdout, which is the sentence that separates a tool from a demo. That means it can sit in our infrastructure, be scheduled by something we already run, and produce output a log pipeline can read without anyone screen-scraping a terminal.

Against that: it holds tracker credentials, and there is no SSO, no audit log and no retention policy describing what it keeps. Sixty engineers' worth of agent runs against one tracker account is an attribution problem. Approved with conditions: a service account per repository, and logs shipped somewhere we retain.

reliability
6
usefulness
7
cost
7
longevity
5
Agree with La Jefa?
El HackerThe tinkerer

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.

8.0
Reasoning and trade-offs · AI analysis

The file that matters is WORKFLOW.md. YAML front matter plus Liquid rendering means the run definition and the prompts live in my repository, under review, in the diff, rather than inside a settings screen. That is the difference between configuring a tool and programming one.

Apache-2.0 keeps the fork clean, and there is a Nix install for people who take that seriously. It exposes a token-protected endpoint so another agent can drive it, and consumes none itself, which is an unusual direction to point the protocol and a defensible one.

reliability
8
usefulness
8
cost
9
longevity
7
Agree with El Hacker?