fx

fx

Vercel
+
+

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About

GPT-5.3-Codex-Spark is an ultra-fast coding model designed for real-time collaboration inside Codex. Built as a smaller version of GPT-5.3-Codex, it delivers over 1000 tokens per second when served on low-latency Cerebras hardware. The model is optimized for interactive coding tasks, enabling developers to make targeted edits and see results almost instantly. With a 128k context window, Codex-Spark supports substantial project context while maintaining speed. It focuses on lightweight, precise edits and does not automatically run tests unless prompted. Infrastructure upgrades such as persistent WebSocket connections significantly reduce latency across the full request-response pipeline. Released as a research preview for ChatGPT Pro users, Codex-Spark marks the first milestone in OpenAI’s partnership with Cerebras.

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 developers, engineering teams, and AI-powered coding tool builders seeking ultra-low-latency, real-time code generation and iterative collaboration within the Codex ecosystem

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

No information available.
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
openai.com

Company Information

Vercel
Founded: 2015
United States
fx.sh/

Alternatives

Claude Opus 4.5

Claude Opus 4.5

Anthropic

Alternatives

Claude Opus 4.6

Claude Opus 4.6

Anthropic

Categories

Categories

Integrations

Codex CLI
Codex Security
Microsoft Foundry
OpenAI
OpenAI Codex
OpenClaw

Integrations

Codex CLI
Codex Security
Microsoft Foundry
OpenAI
OpenAI Codex
OpenClaw
Claim GPT‑5.3‑Codex‑Spark and update features and information
Claim GPT‑5.3‑Codex‑Spark and update features and information
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Claim fx and update features and information