fx

fx

Vercel
+
+

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About

GPT-5.1-Codex is a specialized version of the GPT-5.1 model built for software engineering and agentic coding workflows. It is optimized for both interactive development sessions and long-horizon, autonomous execution of complex engineering tasks, such as building projects from scratch, developing features, debugging, performing large-scale refactoring, and code review. It supports tool-use, integrates naturally with developer environments, and adapts reasoning effort dynamically, moving quickly on simple tasks while spending more time on deep ones. The model is described as producing cleaner and higher-quality code outputs compared to general models, with closer adherence to developer instructions and fewer hallucinations. GPT-5.1-Codex is available via the Responses API route (rather than a standard chat API) and comes in variants including “mini” for cost-sensitive usage and “max” for the highest capability.

About

fx is a tiny, open, native coding agent harness and CLI written in Zig, optimized for research, performance, and embeddability as part of larger systems. Its design focuses on minimalism across the system prompt, tools, feature set, memory use, and a 6 MB binary, with an interface intended to feel closer to a Unix shell than a heavy terminal IDE. fx cold starts in microseconds and performs no unnecessary work or I/O before accepting input, making it suitable for programmatic use, resource-constrained environments, and agent sandboxes. Developers can start it inside a project and ask it to read files, search code, run commands, make changes, execute tests, and stream tool calls as they happen. The core is model- and provider-agnostic, supporting local models, gateways, direct provider access, and cloud inference. It is context-efficient by design, using a minimal system prompt and toolset to reduce token overhead and improve time to first token.

Platforms Supported

Windows
Mac
Linux
Cloud
On-Premises
iPhone
iPad
Android
Chromebook

Platforms Supported

Windows
Mac
Linux
Cloud
On-Premises
iPhone
iPad
Android
Chromebook

Audience

Software engineers and engineering organizations wanting a tool to generate, refactor and maintain code at scale, integrated into their existing development toolchain

Audience

Developers and AI infrastructure builders in need of a solution to run or embed a lightweight, extensible, model-agnostic coding agent in terminals, applications, and automated systems

Support

Phone Support
24/7 Live Support
Online

Support

Phone Support
24/7 Live Support
Online

API

Offers API

API

Offers API

Screenshots and Videos

Screenshots and Videos

Pricing

$1.25 per input
Free Version
Free Trial

Pricing

Free
Free Version
Free Trial

Reviews/Ratings

Overall 0.0 / 5
ease 0.0 / 5
features 0.0 / 5
design 0.0 / 5
support 0.0 / 5

This software hasn't been reviewed yet. Be the first to provide a review:

Review this Software

Reviews/Ratings

Overall 0.0 / 5
ease 0.0 / 5
features 0.0 / 5
design 0.0 / 5
support 0.0 / 5

This software hasn't been reviewed yet. Be the first to provide a review:

Review this Software

Training

Documentation
Webinars
Live Online
In Person

Training

Documentation
Webinars
Live Online
In Person

Company Information

OpenAI
Founded: 2015
United States
platform.openai.com/docs/models/gpt-5.1-codex

Company Information

Vercel
Founded: 2015
United States
fx.sh/

Alternatives

Claude Opus 4.5

Claude Opus 4.5

Anthropic

Alternatives

Categories

Categories

Integrations

C
C#
C++
ChatGPT
ChatGPT Pro
Codex CLI
Cursor
F#
GPT-5.6 Luna
GPT-5.6 Terra
GPT-6
GitHub Copilot
HTML
Laravel
Microsoft Foundry
OpenAI Codex
PHP
R
SQL
TypeScript

Integrations

C
C#
C++
ChatGPT
ChatGPT Pro
Codex CLI
Cursor
F#
GPT-5.6 Luna
GPT-5.6 Terra
GPT-6
GitHub Copilot
HTML
Laravel
Microsoft Foundry
OpenAI Codex
PHP
R
SQL
TypeScript
Claim GPT-5.1-Codex and update features and information
Claim GPT-5.1-Codex and update features and information
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