Fable Mode MCP Server

Agents that think before they write. Fable Mode is an open-source control plane for AI coding agents. It runs locally over stdio via the published package.

People who work with ai safety, coding agents and developer tools and want it reachable from Claude, Cursor, VS Code, or another MCP client. The project is written in Python.

VERIFIED ACTIVE

LAST COMMIT 2026-09-18 · ★ 24 · #52 OF 229 MAINTAINED CODING AGENT · VERIFIED 2026-09-18

MIT · Python servers · how we verify → /methodology

01 · Install Fable Mode

Claude Code

claude mcp add rex-codebase-fable-mode -- uvx fable-engine

Claude Desktop / Cursor / VS Code - add to config

{
  "mcpServers": {
    "rex-codebase-fable-mode": {
      "command": "uvx",
      "args": [
        "fable-engine"
      ]
    }
  }
}

Same JSON for Cursor. For VS Code, rename the top-level key from `mcpServers` to `servers`.

Using another client? Same JSON, different key

Claude Desktop · mcpServers

Cursor · mcpServers

VS Code · servers

Windsurf · mcpServers

Zed · context_servers

Cline · mcpServers

Roo Code · mcpServers

Continue · mcpServers

LibreChat · mcpServers

Gemini CLI · mcpServers

Codex CLI · mcp_servers

Full setup guides: every client.

02 · Evidence

Security posture

What to check before giving this server access to your agent - from the registry, GitHub, and our own probes. We don't score safety; we show what's verifiable.

runs as local process (stdio) - runs on your machine with your user's permissions

repo age created 2026-08-27 - young repo, little track record yet

license MIT - declared in the repository

pypi package fable-engine - check the name against the project README before installing (PyPI has no namespace ownership)

registry namespace io.github.REX-codebase is GitHub-verified and matches the repo owner

03 · What Fable Mode can do

Prose above is summarized from the project's README and registry record - no invented capabilities.

Latest releases

v1.3.9 · 2026-09-18

v1.3.9 - Deeper measured evolution, safe web research, and auto-updater idempotence · Evidence-fed evolution loops are bounded and externally gated: evolve_until_stable stops within max generations or stagnation…

v1.3.8 · 2026-09-18

v1.3.8 - Unified MCP and sandbox agent installation · fable-mode setup installs the full 40-file skill and prints both usage routes. · Native MCP agents run the normal stdio MCP server; shell-only agents use fable-mode…

v1.3.7 · 2026-09-17

Fable Engine v1.3.7 · Fix Windows support for the sandboxed red-team executor: Windows select() rejects pipe handles (WinError 10038); the reader now falls back to a thread on OSError, so sandboxed code review…

04 · Who maintains Fable Mode

Fable Mode is maintained by rex-codebase. It's the only MCP server we track from this author; the repo dates to Aug 2026.

05 · Facts

repository: github.com/rex-codebase/fable-mode
category: coding agent - ranked #52 of 229 actively-maintained coding agent servers as of 2026-09-18.
release cadence: 10+ releases in the last 90 days (latest 2026-09-18)
registry: io.github.REX-codebase/fable-mode (active, first published 2026-09-15 · 4 versions)
packages: pypi:fable-engine

06 · Fable Mode FAQ

What is Fable Mode?

Agents that think before they write. Fable Mode is an open-source control plane for AI coding agents. It runs locally over stdio via the published package.

Is Fable Mode still maintained?

Yes - as of 2026-09-18, its last commit was 2026-09-18 and it shipped 10+ releases in the last 90 days. We re-verify nightly.

How do I install Fable Mode?

Run `uvx fable-engine`. You can also paste the ready-made client config above.

Does Fable Mode run locally?

Yes - it's a stdio server: it runs on your machine (via uvx) with your user's permissions. Your data stays local unless the server itself calls external APIs.

07 · Alternatives to Fable Mode

Alternatives to Fable Mode

Maintained coding agent servers if Fable Mode isn't the fit.

Pairs well with

Servers that cover what Fable Mode doesn't - only shown when the pairing reason fits the companion.

More coding agent MCP servers · Raven · Tyrekick · SimConnect MCP · Filesift · Agent Harnesses

More Python MCP servers · Linux MCP Server · Prolog Reasoner · TractorBeeam365 MCP · Projectmem · Audio Sonic MCP · see all