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What is GPT-5.3-Codex-Spark? How to Use it?

In February 2026, OpenAI introduced GPT-5.3-Codex-Spark, a research-preview variant of its Codex family that is explicitly optimized for real-time coding. Codex-Spark trades model size for extremely low latency and very high token throughput — OpenAI reports >1,000 tokens/sec generation and a 128k token context window for the model when served on a low-latency hardware path provided in partnership with Cerebras. The release targets interactive developer workflows: live coding, instant edits, tight edit–compile–run loops inside IDEs, and agentic coding workflows where responsiveness is crucial.

Mar 19, 2026

Exciting Innovations in GPT-5.3 Chat released( Comet Support): What’s New?

OpenAI’s latest update to ChatGPT—marketed as GPT-5.3 Chat (often referred to in the product UI as GPT-5.3 Instant)—is a targeted evolution of the company’s most widely used conversational model. Rather than promising a step-change in raw reasoning capability, the release focuses on polishing the day-to-day experience: fewer unhelpful refusals, fewer “hallucinations” (fabricated or incorrect facts), smoother conversational tone, better web-context integration, and reduced friction in sustained dialogues. The rollout began as an update to ChatGPT’s default/instant model and is being positioned as an improvement to the large body of everyday interactions users have with the assistant.

GPT‑5.3 Codex Spark vs GPT‑5.3 Codex: Comprehensive analysis

In February 2026, OpenAI released two closely related—but strategically different—members of the “Codex” family: GPT-5.3-Codex (a high-capability agentic coding model) and GPT-5.3-Codex-Spark (a smaller, ultra-low-latency variant optimized for interactive coding). Together they represent OpenAI’s dual approach to serving both “deep thinking” and “fast doing” in software engineering workflows: one model that pushes the ceiling of coding intelligence and tool-driven agentic behavior, and one that prioritizes real-time interactivity for developer-facing UI.

Claude Opus 4.6 vs GPT-5.3 Codex: Which is Better for Developers

Both launches (Anthropic’s Claude Opus 4.6 and OpenAI’s GPT-5.3-Codex) advance agentic coding and long-context reasoning, but they pull in slightly different directions. Opus 4.6 leans into very large context windows, safety/analysis workflows, and a new “fast” mode; GPT-5.3-Codex doubles down on agentic software engineering benchmarks and tighter IDE/CLI integrations. The “better” model depends on what you need: huge-context, safety-first code review and long-running agents (Opus 4.6) — or marginally stronger raw coding benchmark performance, speed and immediate Codex integrations (GPT-5.3-Codex). See the deep dive below.

GPT-5.3 Codex: Features, Benchmarks, and how to get it

On February 5, 2026, OpenAI announced GPT-5.3 Codex, a focused upgrade to its Codex family that merges advanced coding ability with broader professional reasoning, faster inference, and deeper “agentic” workflows. The release brings a new Codex desktop app and extends access across the Codex ecosystem (CLI, IDE extensions, web), with API access (promised “soon").