The AI field has advanced rapidly, with Claude Sonnet 4.5 and GPT-5 Codex emerging as top options for coding. Both models, released in September 2025, offer unique strengths for developers. This look at their key features highlights differences to help you pick the right one.
Why Compare These AI Models?
Claude Sonnet 4.5 and GPT-5 Codex represent different paths in AI coding tools. Claude Sonnet 4.5 excels at long, complex tasks with strong benchmark results and extended runtime. GPT-5 Codex focuses on speed and affordability, ideal for quick development cycles. Developers must consider these aspects based on project needs.
Key differences include performance metrics and cost, which can impact daily work. For instance, Claude Sonnet 4.5 handles detailed tasks over 30 hours, while GPT-5 Codex manages short bursts efficiently.
Performance Highlights
When evaluating coding abilities, Claude Sonnet 4.5 leads in benchmarks like SWE-bench Verified, especially with parallel processing. It also performs better in terminal tasks, making it suitable for advanced programming.
In math and reasoning, both models are capable. Claude Sonnet 4.5 achieves perfect scores on high school math tests, while GPT-5 Codex shows strength in graduate-level reasoning. For computer use, Claude Sonnet 4.5 sets new standards in benchmarks, allowing seamless automation of tasks.
- Performance summary:
- * Claude Sonnet 4.5: Higher scores in complex benchmarks
- * GPT-5 Codex: Strong in adaptive reasoning for simpler tasks
Autonomous Operation Features
Claude Sonnet 4.5 is built for endurance, maintaining focus for over 30 hours on projects like building apps from scratch. This helps with large-scale development where context matters.
GPT-5 Codex uses a flexible approach, scaling resources per task. It works well for fast iterations, such as quick fixes or refactoring, without needing much oversight.
- Use case examples:
- * Claude Sonnet 4.5: Best for extended projects with deep analysis
- * GPT-5 Codex: Ideal for rapid code changes and daily tweaks
Pricing and Integration Details
Cost is a major factor. Claude Sonnet 4.5 charges $3/$15 per million tokens, which may add up for big projects. GPT-5 Codex is cheaper at $1.25/$10 per million tokens, offering variants for various budgets.
For integration, Claude Sonnet 4.5 connects with platforms like Amazon Bedrock and GitHub. GPT-5 Codex fits smoothly into IDEs like VS Code and supports real-time suggestions.
| Feature | Claude Sonnet 4.5 | GPT-5 Codex |
|---|---|---|
| Context Window | 1000K tokens | 400K tokens |
| Pricing (per M) | $3 input, $15 output | $1.25 input, $10 output |
| Speed | Faster for complex tasks | Efficient for quick ones |
Safety and Recommendations
Both models prioritize reliability. Claude Sonnet 4.5 includes better prompt defenses, while GPT-5 Codex has strong content filters.
For developers, choose Claude Sonnet 4.5 if you deal with intricate projects needing stamina. Opt for GPT-5 Codex for cost savings and ease in routine work.
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