cedrus-mcp

CEDRUS

Reasoning scaffolding that supercharges your small AI.

CEDRUS gives a local model an argument map to think in: the model lays out claims and the reasons for and against them, and the map keeps everything in place.

• A scaffold, not a scratchpad. The map records which reason answers which claim, so the model doesn't have to hold it in its head, and a small model can work through a debate that would otherwise swamp it.
• Structure is checked for the model. IDs, sides and placement are worked out by the server. A move that doesn't fit is refused with an explanation, so mistakes get fixed instead of piling up.
• You see the reasoning. Every step lands in a map you can read, question and extend: "add an objection to A3", "what supports A7?".
• Local and private. Made for small models on your own machine, with maps saved as plain text and JSON.

What a map looks like

- C1 Legalisation of Soft Drugs
  - A1 Minimize destructive activity [con] — attacks C1
  - A2 No harm, no ban [pro] — supports C1
    - A3 Law must protect [con] — attacks A2
      - A4 Soft drugs are harmful [con] — supports A3 (also attacks A2, supports A1)
  - A5 Lifestyle decision [pro] — supports C1
    - A6 Moral leadership [con] — attacks A5
  - A7 Alcohol and tobacco analogy [pro] — supports C1
    - A8 Tobacco and alcohol more dangerous [pro] — supports A7
    - A9 Major differences [con] — attacks A7
    - A10 Poor reason [con] — undercuts A7
  - A11 Listen to society [pro] — supports C1
  - A12 Argument from addiction [con] — attacks C1
    - A13 Soft drugs are addictive [con] — supports A12
    - A14 Addiction no reason to ban [pro] — undercuts A12
  - A15 Slippery slope [con] — attacks C1
    - A16 Coffee houses [pro] — attacks A15
  - A19 Tax revenue [pro] — supports C1

This is the outline. The full view the model reads also has every claim and argument in full, and notes which ones nothing has challenged yet.

Quick start

1. Install uv

CEDRUS is started by uv, which downloads and runs it for you.

# macOS and Linux
curl -LsSf https://astral.sh/uv/install.sh | sh

# Windows
powershell -ExecutionPolicy ByPass -c "irm https://astral.sh/uv/install.ps1 | iex"

2. Add CEDRUS to your app

Each setup below saves your maps to ~/cedrus-maps, a folder in your home directory. Use any folder you like, or leave out --save-dir and its path if you don't want files.

Whichever app you use, the model has to support tool calling.

LM Studio

In the right sidebar, open the Program tab and choose Install → Edit mcp.json. Add CEDRUS under mcpServers:

{
  "mcpServers": {
    "cedrus": {
      "command": "uvx",
      "args": ["cedrus-mcp", "--save-dir", "~/cedrus-maps"]
    }
  }
}

Jan

Go to Settings → MCP Servers, click +, and fill in:

Field	Value
Server Name	cedrus
Command	uvx
Arguments	cedrus-mcp --save-dir ~/cedrus-maps

For a local model, turn on tool calling in the model's settings (the edit button under Model Capabilities).

Goose

Run goose configure, choose Add Extension → Command-line Extension, name it cedrus, and give the command uvx cedrus-mcp --save-dir ~/cedrus-maps. In Goose Desktop, the same is under Extensions → Add custom extension.

Or add it to ~/.config/goose/config.yaml (%APPDATA%\Block\goose\config\config.yaml on Windows) yourself:

extensions:
  cedrus:
    name: cedrus
    type: stdio
    cmd: uvx
    args: [cedrus-mcp, --save-dir, ~/cedrus-maps]
    enabled: true
    timeout: 300

Goose can run local models through Ollama, so this is also the way to use CEDRUS with Ollama.

Other MCP clients

Any client that can start a local (stdio) MCP server works: the command is uvx, the arguments are cedrus-mcp and any options below.

Try it

Map the debate on whether cities should ban cars from their centres. Start with the main claim, then add the strongest arguments on both sides.

Now add an objection to the weakest pro argument.

Which arguments has nobody challenged yet? Add a reply to one of them.

Whenever you want to see the whole map, ask the model to show it.

Saving your maps

With --save-dir DIR, CEDRUS writes the map after every change to DIR/<id>.txt, the readable view, and DIR/<id>.json. Each time your app starts CEDRUS, it gets a new <id>, so earlier maps are kept. --save-file PATH writes to one fixed file instead, and a new session overwrites it.

When the model starts a new map, the old one is kept beside the live file as .1, then .2, and so on.

What the model can do

Tool	What it does
show	Print the whole map.
add_claim	Add a claim: the statement being debated, or a principle.
add_argument	Add an argument for or against something already in the map.
link	Relate two items already in the map, or change how they relate.
unlink	Remove one relation.
edit	Change a label or a text.
delete	Delete an item, optionally with the arguments that respond only to it.
new_map	Start over with an empty map, for another question.

An argument can support or attack what it responds to, or undercut another argument: grant its premises, but deny that they lead to its conclusion.

Options

Option	What it does
--save-dir DIR	Save each session's map in DIR. Also CEDRUS_SAVE_DIR.
--save-file PATH	Save the map to one file, PATH and PATH with .txt. Also CEDRUS_SAVE_FILE.
--max-chars N	Size limit for the map view, default 24000 (roughly 6k tokens). Larger maps are shown shortened.
--hints	Add a short hint to each tool result.

Running over HTTP, from a checkout, or under the MCP inspector is covered in docs/ADVANCED.md.

More

• docs/ADVANCED.md: running from source, HTTP, the file format, context pruning, development.
• docs/PLAN.md: the design.
• Version 1 is a separate code base, tagged v1-final.

Licence

GNU Affero General Public License v3.0 or later. See LICENSE.