Treat Anthropic's Opus 4.6 as a productive product engineer, excellent for generative, greenfield work. Then, use OpenAI's GPT-5.3 Codex as a principal engineer to review architecture, find edge cases, and harden the code. This mimics a real-world engineering team dynamic for optimal results.
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When choosing between Opus 4.6 and Codex 5.3, consider their failure modes. Opus can get stuck in "analysis paralysis" with ambiguous prompts, hesitating to execute. Conversely, Codex can be overconfident, quickly locking onto a flawed approach, though it can be steered back on course.
The latest models from Anthropic (Opus 4.6) and OpenAI (Codex 5.3) represent two distinct engineering methodologies. Opus is an autonomous agent you delegate to, while Codex is an interactive collaborator you pair-program with. Choosing a model is now a workflow decision, not just a performance one.
The vision for Codex extends beyond a simple coding assistant. It's conceptualized as a "software engineering teammate" that participates in the entire lifecycle—from ideation and planning to validation and maintenance. This framing elevates the product from a utility to a collaborative partner.
For large projects, use a high-level AI (like Claude's Mac app) as a strategic partner to break down the work and write prompts for a code-execution AI (like Conductor). This 'CTO' AI can then evaluate the generated code, creating a powerful, multi-layered workflow for complex development.
The differing capabilities of new AI models align with distinct engineering roles. Anthropic's Opus 4.6 acts like a thoughtful "staff engineer," excelling at code comprehension and architectural refactors. In contrast, OpenAI's Codex 5.3 is the scrappy "founding engineer," optimized for rapid, end-to-end application generation.
Effective prompting requires adapting your language to the AI's core design. For Anthropic's agent-based Opus 4.6, the optimal prompt is to "create an agent team" with defined roles. For OpenAI's monolithic Codex 5.3, the equivalent prompt is to instruct it to "think deeply" about those same roles itself.
The comparison reveals that different AI models excel at specific tasks. Opus 4.5 is a strong front-end designer, while Codex 5.1 might be better for back-end logic. The optimal workflow involves "model switching"—assigning the right AI to the right part of the development process.
Treat different LLMs like colleagues with distinct personalities. Zevi Arnovitz views Claude as a collaborative dev lead, Codex (GPT) as a brilliant but terse bug-fixer, and Gemini as a creative but chaotic designer. This mental model helps in delegating tasks to the most suitable AI, maximizing their strengths and mitigating their weaknesses.
To optimize AI agent costs and avoid usage limits, adopt a “brain vs. muscles” strategy. Use a high-capability model like Claude Opus for strategic thinking and planning. Then, instruct it to delegate execution-heavy tasks, like writing code, to more specialized and cost-effective models like Codex.
In a head-to-head test to build a Polymarket clone, Anthropic's Opus 4.6 produced a visually polished, feature-rich app. OpenAI's Codex 5.3 was faster but delivered a basic MVP that required multiple design revisions. The multi-agent "research first" approach of Opus resulted in a superior initial product.