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Ouroboros

#27 agent harnessverified Sep 4, 20260.55.3

Spec-first orchestration layer that gates agent work behind an interview, an immutable seed spec and a three-stage evaluation

Key differences

Spec-first orchestration layer that gates agent work behind an interview, an immutable seed spec and a three-stage evaluation

  • Runs local. Free and open source under MIT, funded by GitHub Sponsors; you supply the host agent's credentials
  • Acts as an MCP server. Listed for 37 of 194 tools in this category.
  • Runs local models. Listed for 65 of 194 tools in this category.
  • Keep in mind: Through the LiteLLM adapter with per-stage model pinning, which reaches any endpoint LiteLLM supports including local servers.

“It installs into fourteen different agent runtimes, so whichever agent you chose, it will still ask you what you actually meant.”

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What it is

Ouroboros is a local-first Python runtime, CLI and MCP server that turns agent work into a replayable, ledger-recorded execution contract. Work is gated behind a Socratic interview with an ambiguity score, crystallised into an immutable seed spec, executed through a pluggable runtime adapter, then verified by a mechanical, semantic and multi-model consensus gate and evolved until an ontology similarity threshold is met. It registers as an MCP server inside 14 agent runtimes including Claude Code, Codex CLI, Copilot, OpenCode, Gemini CLI, Kiro, Goose and Grok Build.

Specification

Source verification

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

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

Architecture

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

Models

Backbonesrc ↗
via host agent runtime, LiteLLM, DeepSeek
Bring your own model
Yes
Local models
Yes
Through the LiteLLM adapter with per-stage model pinning, which reaches any endpoint LiteLLM supports including local servers.

Protocols

MCP clientsrc ↗
Yes
MCP server
Yes
OpenAPI tools
No

Capabilities

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

Cost

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

Free and open source under MIT, funded by GitHub Sponsors; you supply the host agent's credentials

Openness

Open sourcesrc ↗
Yes
License
MIT
First release
2026-01
orchestrationspec-drivenevaluationmcpmulti-agentopen-source

Los Agentes on Ouroboros

Who are they?
The ruling
El JuezThe judge

El Profesor wants the thresholds defined before he believes the gate; El Crítico wants to know what the gate costs per task. Neither doubts that the gate is the product.

Adopt with conditions
Reasoning and trade-offs · AI analysis

El Profesor's complaint is that the quantities driving every decision here are named and never specified, so a reader cannot tell what a passing score means. El Crítico's is that the machinery runs several models over every task, turning a small change into an expensive one. Both point at the same design from opposite directions.

El Profesor wins on rigour and El Crítico on economics, and neither is overruled: the tool asks to be trusted about correctness while declining to publish its units. La Inversora's reading of who funds it explains why. Adopt with conditions: route the gate to cheap models first, and measure the extra spend for a fortnight.

Agree with El Juez?
El AmigoThe friend

Pick it if your agent failures come from vague requests rather than weak models; pick Kiro if you want that discipline inside an editor instead of in front of one.

5.8
Reasoning and trade-offs · AI analysis

You will either love this or bounce off it in ten minutes. The deciding trait in daily use is friction, deliberately applied: nothing starts until you have answered an interview about what you actually want, so the tool slows down the exact moment where most agent work quietly goes wrong. If your last three failures were the model misunderstanding the task, that friction is the feature.

Pick it when specification is your bottleneck. Pick Kiro if you want spec-driven work with an editor around it, or skip both if your tasks are small enough to describe in a sentence.

reliability
6
usefulness
6
cost
6
longevity
5
Agree with El Amigo?
El CríticoThe critic

Every task passes a multi-model consensus gate, so the cost and latency of a small change are multiplied by however many models must agree about it.

5.5
Reasoning and trade-offs · AI analysis

The economics are the failure mode here. Work is verified by several models voting, and each vote is a full inference over the same material, so the price of a two-line fix scales with the size of the panel rather than the size of the change. Worse, a consensus of models that share a training lineage can be confidently and unanimously wrong, which is the failure that looks most like success.

What it does right: everything is written to a ledger, so a disputed run can be replayed and examined instead of reconstructed from memory.

reliability
6
usefulness
6
cost
5
longevity
5
Agree with El Crítico?
El ProfesorThe professor

An ambiguity score and an ontology similarity threshold govern every decision, and neither has a published scale, validation or worked example.

6.0
Reasoning and trade-offs · AI analysis

The vocabulary is quantitative and the definitions are absent. 1. Work is gated on a numeric ambiguity measure with no stated range and no evidence that it correlates with downstream failure. 2. Iteration stops when a similarity threshold is met, with no account of how similarity is computed or how the threshold was chosen. 3. Verification is split into mechanical, semantic and consensus stages, and only the mechanical stage is reproducible by a reader.

Naming a number does not make a thing measured. The structure is thoughtful and the calibration is undocumented, which are separable problems and only one of them is hard.

reliability
6
usefulness
6
cost
6
longevity
6
Agree with El Profesor?
La InversoraThe investor

Sponsorship is the funding model and one named individual is the vendor, which prices the roadmap at whatever the maintainer's enthusiasm is worth this year.

5.8
Reasoning and trade-offs · AI analysis

The revenue line is donations. That is honest and it is also the entire commercial thesis, so there is no pricing power, no enterprise tier and no incentive structure beyond the maintainer's own interest. Five thousand stars indicates the idea travelled further than the funding did.

The asset, if there is one, is the methodology rather than the code, and methodologies are not acquirable; a larger vendor that liked this would implement the pattern rather than buy the Python. Likely outcome is continued sponsored maintenance or absorption of the idea by an agent vendor. Position: adopt the workflow, keep the specs portable, expect no support contract.

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

Free for sixty and no headless mode, so the tool that exists to gate work cannot itself be a gate in our pipeline, and Windows support is marked experimental.

5.8
Reasoning and trade-offs · AI analysis

The irony is hard to miss. This is a verification layer, and there is no headless mode, so it cannot run as a required check on a pull request where a verification layer belongs. It sits on an engineer's machine instead, needing Python 3.12 or newer, with native Windows marked experimental, which for my fleet means a supported path for some engineers and a caveat for the rest.

No SSO, no SCIM, no audit trail attached to a person. Onboarding is a day because the workflow is the product. Approved with conditions: volunteer teams only, and not on the release path.

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

MIT, `pip install 'ouroboros-ai[litellm]'`, `ouroboros mcp serve`, and per-stage model pinning through LiteLLM so each stage can hit a different endpoint of mine.

7.5
Reasoning and trade-offs · AI analysis

MIT and installable with pip and an extras marker, which tells you the shape of it: Python I can read, patch and vendor. The part I actually want is per-stage model pinning through LiteLLM, because it means the interview, the execution and the verification can each point at a different endpoint, including servers running on my own machine, rather than one provider for the whole pipeline.

It registers as an MCP server with a single serve command, so whichever agent I am using this month picks it up as a tool. Nothing here holds my keys and a fork would compile the first time.

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