OpenAI launches Codex MacOS app with GPT-5.3 model to challenge Claude Code dominance

Reviewed byNidhi Govil

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OpenAI released a new MacOS app for Codex, its AI coding tool, alongside the GPT-5.3-Codex model that runs 25% faster than previous versions. The launch marks OpenAI's push to catch up with Anthropic's Claude Code, which has dominated the agentic coding market and reached $1 billion in annualized revenue within six months of public release.

OpenAI Launches MacOS App for Codex to Compete in AI Coding Market

OpenAI unveiled a new MacOS app for Codex on Monday, marking a significant step in the company's effort to catch up with competitors in the rapidly evolving AI coding landscape

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. The launch comes as agentic coding—where AI agents work independently on programming tasks—has become the dominant trend in software development

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. OpenAI faces stiff competition from Anthropic, whose Claude Code tool has captured significant market share and reportedly reached $1 billion in annualized revenue within six months of public availability

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Source: Inc.

Source: Inc.

The new Codex app provides developers with a centralized workspace to manage multiple AI coding agents across projects without losing task context

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. According to OpenAI, agents run in separate threads organized by projects, allowing developers to switch between tasks seamlessly. Sam Altman, OpenAI's CEO, emphasized the app's ability to accelerate development: "You can use this from a clean sheet of paper, brand new, to make a really quite sophisticated piece of software in a few hours"

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GPT-5.3-Codex Model Delivers 25% Speed Boost and Self-Improvement Capabilities

Days after the MacOS app launch, OpenAI announced GPT-5.3-Codex, describing it as the most capable agentic coding model yet released

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. The new model runs 25% faster than previous versions while using fewer resources, enabling longer-running tasks that can span more than one day

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. The model sets new industry benchmarks on SWE-Bench Pro and TerminalBench, though competitors from Gemini 3 and Claude Opus have logged roughly equivalent scores within the margin of error

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Source: Analytics Insight

Source: Analytics Insight

Remarkably, GPT-5.3-Codex was instrumental in creating itself, with the Codex team using early versions to debug its own training, manage deployment, and diagnose test results

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. Alexander Embiricos, OpenAI's product lead for Codex, stated in December that "the vast majority of Codex is built by Codex, so it's almost entirely just being used to improve itself"

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. This self-improvement capability aligns with Sam Altman's stated goal of building an AI research intern by September 2026 and a fully automated AI researcher by March 2028

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Codex Expands Beyond Programming to Cover Full Software Development Lifecycle

GPT-5.3-Codex represents a shift from code-generation to comprehensive workflow support, handling debugging, deployment, monitoring, writing PRDs, editing copy, user research, tests, and metrics

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. OpenAI describes it as moving "from an agent that can write and review code to an agent that can do nearly anything developers and professionals can do on a computer"

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. The model can build slide decks and spreadsheets, extending its utility beyond traditional programming tasks

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Source: ET

Source: ET

The new app includes features designed to improve user experience, including background automations that run on automatic schedules with results queued for review

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. Users can select different agent personalities—from pragmatic to empathetic—depending on their working style

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. The model also better understands intent, with simple or underspecified prompts now defaulting to sites with more functionality and sensible defaults

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Market Competition Intensifies as Enterprises Evaluate Autonomous AI Coding Tools

The launch positions OpenAI to compete more directly with Anthropic, which recently introduced Cowork, extending Claude Code beyond programming into broader enterprise workflows

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. Sam Altman acknowledged the competitive pressure, stating that GPT-5.2 "is the strongest model by far" for sophisticated work, though "it's been harder to use"

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. The new interface aims to make that power more accessible to attract Claude Code users.

While many observers note that autonomous AI coding tools aren't yet good enough to entirely replace human tech workers, they significantly accelerate development work

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. Altman highlighted this endurance advantage: "The models just don't run out of dopamine. They keep trying, they don't run out of motivation"

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. As enterprises weigh the impact of these autonomous AI coding tools on development workflows and governance, the competition between OpenAI and Anthropic will likely shape how organizations approach the software development lifecycle in the coming months.

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