GPT-5.3-Codex-Spark

GPT-5.3-Codex-Spark — explained in more detail

OpenAI released GPT-5.3-Codex-Spark on February 12, 2026 as the first model designed for real-time coding. It is a lightweight variant of the larger GPT-5.3-Codex and delivers more than 1000 tokens per second on ultra-low-latency hardware — while staying highly capable for real-world coding tasks. Codex-Spark marks the first milestone in the OpenAI–Cerebras partnership announced in January 2026.

Example / Practical use

On SWE-Bench Pro and Terminal-Bench 2.0, Codex-Spark posts results comparable to GPT-5.3-Codex but finishes the tasks in a fraction of the time. The enabler is a persistent WebSocket connection with targeted optimizations: 80% less overhead per client/server roundtrip, 30% less per-token overhead, 50% faster time-to-first-token. At launch it shipped as a research preview on Cerebras for ChatGPT Pro users. The WebSocket path is the default for Codex-Spark and is expected to roll out to all models over time.

How it differs from similar concepts

Unlike the larger GPT-5.3-Codex (February 2026), the focus is not on peak coding quality but on speed for interactive tools such as IDE autocomplete or live coding pair-programming. Comparable to Anthropic’s Haiku line as the “fast, cheap variant” of a large model family.

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