Opus 4.5 vs Codex CLI
A comprehensive 2026 comparison to help you choose the right AI tool for your needs. We tested both extensively.
Quick Verdict: Opus 4.5 vs Codex CLI
After extensive testing, **Claude Opus 4.5** comes out ahead with a 4.9/5 rating. It's the better choice for most users, especially those focused on Professional developers, complex codebases, autonomous agents. However, Codex CLI remains competitive and may be preferable if you prioritize Rapid prototyping, open-source flexibility, ChatGPT users.
Claude Opus 4.5 edges out Codex CLI with superior overall performance and features that make it the better choice for most users in 2026. With a 4.9/5 rating, it excels particularly in Professional developers, complex codebases, autonomous agents.
Try Opus 4.5 FreeFeature Comparison Table
Side-by-side comparison of key features and capabilities
When to Use Opus 4.5 vs Codex CLI
Choose Opus 4.5 When You Need:
- Professional developers, complex codebases, autonomous agents
- Superior coding assistance and code generation
- Better quality content writing and creative tasks
- Processing longer documents with 200K context
Choose Codex CLI When You Need:
- Rapid prototyping, open-source flexibility, ChatGPT users
- Faster response times for time-sensitive work
- Testing capabilities with a free tier before committing
In-Depth Analysis: Opus 4.5 vs Codex CLI
Performance & Capabilities
In our comprehensive testing for 2026, we evaluated both Claude Opus 4.5 and Codex CLI across multiple dimensions including coding tasks, creative writing, reasoning problems, and general conversation quality. Claude Opus 4.5 emerged as our top pick with an overall rating of 4.9/5.
Claude Opus 4.5 scored 5.0/5 on coding tasks, making it an excellent choice for developers. In comparison, Codex CLI achieved 4.7/5 in this category.
Pricing & Value
When it comes to pricing, Codex CLI offers a free tier for testing. For paid plans, Codex CLI is more affordable at $20/month compared to $20/month.
Use Cases & Target Audience
Claude Opus 4.5 is particularly well-suited for Professional developers, complex codebases, autonomous agents. Its strengths make it ideal for professionals who need advanced coding help, quality content creation, and reliable AI assistance.
Codex CLI, on the other hand, excels at Rapid prototyping, open-source flexibility, ChatGPT users. Users who prioritize fast response times, complex reasoning, will find it particularly valuable.
Claude Opus 4.5 Pros & Cons
Pros
- Best coding model available (80.9% SWE-bench)
- Excellent for autonomous agents
- Effort parameter allows speed/quality tradeoff
- 76% fewer tokens than Sonnet at same quality
- Strong at long-horizon tasks
Cons
- More expensive than Sonnet
- Slower on simple tasks
- Requires Claude Pro/Max subscription for full access
Codex CLI Pros & Cons
Pros
- Open source (Apache 2.0)
- Multimodal input support
- Local-first privacy
- Rich approvals workflow
- Included with ChatGPT subscription
Cons
- Newer tool with evolving features
- Less mature than Claude Code
Best For: Opus 4.5
Professional developers, complex codebases, autonomous agents
Best For: Codex CLI
Rapid prototyping, open-source flexibility, ChatGPT users
Frequently Asked Questions
Common questions about Opus 4.5 vs Codex CLI
Is Claude Opus 4.5 better than Codex CLI in 2026?
Based on our benchmarks and analysis, Claude Opus 4.5 performs better overall with a rating of 4.9/5. However, the best choice depends on your specific needs - Claude Opus 4.5 excels at Professional developers, complex codebases, autonomous agents, while Codex CLI is better for Rapid prototyping, open-source flexibility, ChatGPT users.
What is the price difference between Opus 4.5 and Codex CLI?
Claude Opus 4.5 costs $20/month for paid plans. Codex CLI offers a free tier and costs $20/month for paid plans.
Which is better for coding: Opus 4.5 or Codex CLI?
For coding tasks, Claude Opus 4.5 scores higher with a 5.0/5 coding rating compared to 4.7/5.
Can I use Opus 4.5 and Codex CLI for free?
Claude Opus 4.5 requires a paid subscription. Codex CLI does offer a free tier with limited features. Both tools offer trial periods or limited free access for new users.
Which AI has a larger context window: Opus 4.5 or Codex CLI?
Claude Opus 4.5 has a larger context window at 200,000 tokens, compared to 128,000 tokens. Larger context windows allow processing more text in a single conversation.
Is Opus 4.5 faster than Codex CLI?
In our speed tests, Codex CLI is faster with a speed rating of 4.6/5. Response times can vary based on server load and query complexity.
Which is better for writing content: Opus 4.5 or Codex CLI?
For content writing, Claude Opus 4.5 excels with a writing rating of 4.8/5 versus 4.3/5. Consider your specific writing needs when choosing.
Do Opus 4.5 and Codex CLI support image generation?
Claude Opus 4.5 supports image understanding and analysis. Codex CLI supports image understanding and analysis. For dedicated image generation, consider specialized tools like DALL-E or Midjourney.
Which AI should beginners choose: Opus 4.5 or Codex CLI?
For beginners, we recommend Codex CLI since it offers a free tier. Claude Opus 4.5 has a slightly better overall user experience based on our testing.
Can I switch from Opus 4.5 to Codex CLI easily?
Yes, switching between AI tools is straightforward since they use similar prompting interfaces. Your conversation history won't transfer, but you can export important outputs. Many professionals use both tools depending on the task - Claude Opus 4.5 for Professional developers, complex codebases, autonomous agents and Codex CLI for Rapid prototyping, open-source flexibility, ChatGPT users.
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Ready to Get Started?
Both tools offer free tiers or trials. Try them out and see which one works best for your workflow in 2026.