GPT-5 Codex vs Claude 3 Opus
Compare pricing, context windows, and strengths for GPT-5 Codex by OpenAI and Claude 3 Opus by Anthropic - and see how to put either to work in Appaca.
GPT-5 Codex
Version of GPT-5 optimized for agentic coding tasks in Codex, offering strong reasoning, reliable code generation, and long-context project understanding.
View GPT-5 CodexClaude 3 Opus
The most intelligent Claude 3 model, built for highly complex reasoning, analysis, and open-ended problem solving across any domain.
View Claude 3 OpusGPT-5 Codex vs Claude 3 Opus at a glance
Specs and pricing side by side, from the Appaca AI models directory.
| Spec | GPT-5 Codex | Claude 3 Opus |
|---|---|---|
| Provider | OpenAI | Anthropic |
| Model type | Text | Text |
| Context window | 400K tokens | 200K tokens |
| Input price | $1.25 / 1M tokens | $15 / 1M tokens |
| Output price | $10 / 1M tokens | $75 / 1M tokens |
| Status | Superseded by GPT-5.1 Codex | Superseded by Claude 4.1 Opus |
How GPT-5 Codex and Claude 3 Opus differ
What the numbers mean in practice when choosing between GPT-5 Codex and Claude 3 Opus.
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GPT-5 Codex is 92% cheaper on input tokens ($1.25 vs $15 per million), which adds up quickly in document-heavy workloads.
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GPT-5 Codex is 87% cheaper on output tokens ($10 vs $75 per million) - the bigger factor for tools that generate long documents.
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GPT-5 Codex's 400K tokens context window is roughly 2x larger than Claude 3 Opus's 200K tokens, so it can work across bigger codebases, contracts, or archives in one pass.
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GPT-5 Codex has been superseded by GPT-5.1 Codex - for new builds, consider the newer model first.
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Claude 3 Opus has been superseded by Claude 4.1 Opus - for new builds, consider the newer model first.
Strengths side by side
Where each model shines, according to benchmarks and provider positioning.
GPT-5 Codex
1. Purpose-Built for Agentic Coding
- Optimized specifically for scenarios where the model must act as an autonomous or semi-autonomous coding agent.
- Tailored for Codex workflows such as planning, editing, debugging, and multi-step tool-driven code tasks.
2. Advanced Coding Reasoning
- Extends GPT-5's higher reasoning mode to better handle complex software logic and multi-file dependencies.
- Produces more accurate, structured, and maintainable code across modern programming languages.
3. Strong Tool Use in Developer-Like Environments
- Designed for Codex's agent environment, enabling the model to:
- Read and modify files
- Follow function signatures and API contracts
- Navigate codebases with awareness of context and structure
4. Large Context Window for Full-Project Understanding
- 400,000-token context allows ingestion of:
- Entire repositories
- Multiple files at once
- Architectural descriptions
- Enables long-range reasoning across codebases rather than isolated snippets.
5. Multimodal Capability for Development Tasks
- Accepts text and image as input (great for screenshots of error logs, UI mocks, whiteboards).
- Outputs text only, focusing its output precision on code, reasoning, and documentation.
6. Continuous Snapshot Updates
- The underlying model version is regularly upgraded behind the scenes.
- Ensures developers always use the best coding-enhanced GPT-5 variant without changing model names.
7. Reliable Instruction Following
- Very strong adherence to constraints like:
- File/folder structure requirements
- Framework conventions
- Naming patterns
- Linting rules
- Makes it suitable for production coding agents.
8. Broad API Integration
- Available only in the Responses API, giving you:
- Streaming
- Structured outputs
- Function calling
- Allows creation of interactive coding tools and agent workflows with tight model control.
Claude 3 Opus
1. Intelligence & Reasoning
- Highest capability in the Claude 3 family
- Near-human comprehension and fluency
- Excels at MMLU, GPQA, GSM8K, advanced reasoning tasks
2. Complex Problem Solving
- Best for research, strategy, multi-step planning
- Handles ambiguous, open-ended tasks with ease
3. Vision & Multimodal Capabilities
- Strong chart/graph understanding
- Processes documents, technical diagrams, and dense visual data
4. Recall & Long-Context Reasoning
- Near-perfect recall (>99% on NIAH benchmark)
- Handles very large documents and multi-file workflows
5. Enterprise-Grade Accuracy
- Significantly reduced hallucinations
- High correctness rate for factual queries
Use GPT-5 Codex or Claude 3 Opus - or both
Appaca is the AI workspace for operators. Build internal tools and AI co-workers powered by GPT-5 Codex or Claude 3 Opus - connected to your real data and ready for your whole team. No code, no deployment.
Describe it, and it's built
Tell the Appaca agent the internal tool you need and it builds a working app powered by GPT-5 Codex or Claude 3 Opus. No code, no API keys, no deployment.
Switch models without rebuilding
Start on GPT-5 Codex, test the same tool on Claude 3 Opus, and keep whichever performs better - the rest of your app stays exactly as it is.
Automated for the whole team
Schedule tools to run on autopilot - daily digests, weekly reports, real-time triggers - and share them with your whole team from one workspace.
Describe it, and it's built
Tell the Appaca agent what your team needs and it builds a working app powered by GPT-5 Codex or Claude 3 Opus - connected to the tools you already use.
Related comparisons
See how GPT-5 Codex and Claude 3 Opus stack up against other models in the directory.
FAQs
GPT-5 Codex is generally cheaper: $1.25 input / $10 output per million tokens, versus $15 / $75 for Claude 3 Opus. Actual cost depends on how many tokens your workload reads and writes.
GPT-5 Codex has the larger context window at 400K tokens, compared to 200K tokens for Claude 3 Opus. A larger window means the model can consider more text at once - useful for long contracts, codebases, or months of records.
It depends on the job. Compare the pricing, context window, and strengths above against your workload - and remember the choice isn't permanent. In Appaca you can build a tool on GPT-5 Codex, test the same tool on Claude 3 Opus, and switch at any time without rebuilding anything.
Yes. Appaca is a no-code AI workspace: describe the internal tool your team needs and the Appaca agent builds it as a working app powered by GPT-5 Codex, Claude 3 Opus, or any other model in the directory - with a built-in database, team access, and integrations. No API keys to wire up and nothing to deploy.
Build AI tools with GPT-5 Codex or Claude 3 Opus
Describe the tool your team needs and get a working app powered by the model you choose - with a built-in database, team access, and integrations. No code, no deployment.