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what is fastctx fr?

yc-duan/fastctx — explained in plain English

Analysis updated 2026-05-18

318RustAudience · developerComplexity · 2/5Setup · easy

tl;dr

A local Rust tool runtime that gives AI coding agents fast, structured file reading, search, and command execution through MCP instead of raw shell commands.

vibe map

mindmap
  root((repo))
    What it does
      Structured repo tools
      Reduces tool-call overhead
      Runs via MCP
    Tech stack
      Rust
      MCP
      Node.js
    Use cases
      File read and search
      Background job management
      Batch text replacement
    Audience
      Developers
      AI agent builders

Code map

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filefunction / class

what do people make with this?

VIBE 1

Give a ChatGPT App or Codex CLI session structured file read, search, and glob tools instead of raw shell commands.

VIBE 2

Run and manage long-running background Bash jobs from an AI coding session.

VIBE 3

Perform mechanical batch text replacements across a repository through a single MCP tool call.

VIBE 4

Register fastctx serve with any MCP-compatible client to reduce tool-call overhead.

what's the stack?

RustMCPNode.js

how it stacks up fr

yc-duan/fastctxthatmagicalcat/txmjeff141/meatshell
Stars318307339
LanguageRustRustRust
Setup difficultyeasyeasyeasy
Complexity2/52/52/5
Audiencedeveloperdeveloperdeveloper

Figures from each repo's GitHub metadata at analysis time.

how do i run it?

Difficulty · easy time til it works · 5min

Requires Node.js 18 or later for the npm install path, cargo and GitHub Release binaries are also available.

in plain english

FastCtx is a local tool runtime, written in Rust, that gives AI coding agents like ChatGPT or Codex a faster and cleaner way to work with a code repository. Instead of having the AI construct raw shell commands to read files, search text, or list files, which forces it to worry about quoting, escaping, and platform differences, FastCtx exposes those repository operations as structured tools that take simple parameters such as a path, a pattern, or a range. The problem it addresses is that coding agents spend a lot of their limited attention on tool mechanics rather than the actual code. Building and checking a shell command correctly can take several back and forth tool calls before useful information comes back, and that overhead eats into the context and reasoning the model has available for the real task. FastCtx moves that work into a persistent Rust process with stable input and output formats, so the model can gather what it needs in fewer steps. It ships nine tools through the Model Context Protocol: read for text, images, PDFs, and raw bytes, grep for searching file contents, glob for finding files by pattern, replace for mechanical batch text replacement, and a set of run tools for executing Bash commands in the foreground or as tracked background jobs that can be listed, followed, or killed. Installation is through npm, requiring Node.js 18 or later, and running the fastctx command opens a full screen control terminal supporting seventeen languages where you review and apply configuration changes before restarting your ChatGPT or Codex session. The tool can also be installed with cargo or downloaded directly from GitHub Releases for Windows, Linux, and macOS. FastCtx checks for updates in the background, verifies downloaded release archives against published checksums, and can roll back an update automatically if a restart fails. A command line mode supports non interactive setup, status checks, and background job management for scripting.

prompts (copy fr)

prompt 1
Help me install fastctx globally with npm and run the control terminal for the first time.
prompt 2
Explain the difference between the read, grep, and glob tools in fastctx.
prompt 3
Show me how to start and monitor a background job using fastctx's run_background and job_output tools.
prompt 4
Walk me through using fastctx in non-interactive mode with apply, status, and jobs commands.

Frequently asked questions

what is fastctx fr?

A local Rust tool runtime that gives AI coding agents fast, structured file reading, search, and command execution through MCP instead of raw shell commands.

What language is fastctx written in?

Mainly Rust. The stack also includes Rust, MCP, Node.js.

How hard is fastctx to set up?

Setup difficulty is rated easy, with roughly 5min to a first successful run.

Who is fastctx for?

Mainly developer.

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