OpenAI Codex vs JetBrains AI Assistant
Detailed comparison of features, performance, and use cases
96/100
OpenAI Codex
OpenAI's flagship agentic coding platform combining Codex Web (autonomous cloud agent powered by o3) and Codex CLI (open-source local tool using GPT-5), delivering end-to-end software development with PR automation and multimodal input support.
Quick Verdict
OpenAI Codex excels at autonomous development and pr automation with a score of 96/100. OpenAI Codex has emerged as a legitimate Claude Code challenger, with GPT-5.
90/100
JetBrains AI Assistant
Integrated AI coding assistant built into JetBrains IDEs, offering context-aware suggestions and explanations.
Quick Verdict
JetBrains AI Assistant excels at jetbrains ide users and enterprise development with a score of 90/100. JetBrains AI Assistant leverages the deep IDE integration and powerful static analysis capabilities of JetBrains tools.
📊 Visual Score Comparison
Side-by-side comparison of key performance metrics across six evaluation criteria
Technical Specifications
| Feature | OpenAI Codex | JetBrains AI Assistant |
|---|---|---|
| Core AI Model(s) | Codex Web uses specialized o3 optimized for coding. Codex CLI uses GPT-5 by default with support for GPT-5.1-Codex-Mini for extended local usage. | JetBrains AI Assistant uses a combination of models. It leverages its own proprietary LLM, Mellum, which is optimized for coding. It also provides access to third-party cloud models from providers like OpenAI, Google (Gemini 2.5 Pro), and Anthropic (Claude 3.7 Sonnet). |
| Context Window | Large context via o3/GPT-5. Repository preloading enables full codebase understanding without manual file selection. | The assistant is deeply integrated into the IDE and is context-aware, using information from the current project, including language versions, libraries, and related files, to generate more accurate prompts and suggestions. |
| Deployment Options | Codex Web runs in OpenAI's cloud sandboxes. Codex CLI is open-source and runs locally. Enterprise deployment options available. | The AI Assistant is available as a plugin within JetBrains' commercial IDEs. For enterprise customers with strict data privacy needs, an on-premises solution is available through IDE Services, which can run in an air-gapped environment using local models like Llama 3.1 via Hugging Face. |
| Offline Mode | Codex CLI supports local execution. Codex Web requires internet for cloud sandbox operation. | Yes, JetBrains AI Assistant supports an offline mode. Users can connect to locally hosted models through tools like Ollama or LM Studio, allowing most AI features to function without an internet connection. However, some advanced features like multi-file edits are not available in offline mode. |
Core Features Comparison
OpenAI Codex Features
- Dual-mode operation: Codex Web (cloud sandbox) and Codex CLI (local execution)
- Autonomous task execution running 1-30 minutes independently in cloud sandboxes
- Auto-review PRs with semantic understanding beyond static analysis
- Multimodal inputs: screenshots, diagrams, and images for context
- MCP (Model Context Protocol) integration for external tools
- Open-source CLI under permissive license
- Repository preloading for full codebase understanding
JetBrains AI Assistant Features
- Context-aware code completion within JetBrains IDEs
- Code explanation and documentation generation
- Refactoring suggestions based on best practices
- Integration with JetBrains' powerful development tools
Pricing & Value Analysis
| Aspect | OpenAI Codex | JetBrains AI Assistant |
|---|---|---|
| Pricing URL | View OpenAI Codex Pricing | View JetBrains AI Assistant Pricing |
| Overall Score | 96/100 | 90/100 |
| Best For | Autonomous Development, PR Automation, ChatGPT Ecosystem, Multimodal Coding, Enterprise Teams | JetBrains IDE Users, Enterprise Development, Code Refactoring |
Best Use Cases
OpenAI Codex Excels At
- Autonomous feature implementation: describe the task, Codex works independently in a cloud sandbox for up to 30 minutes, then returns completed code with PR
- Automated PR review: tag Codex on any PR for semantic review that understands intent, runs tests, and catches bugs beyond static analysis
- Multimodal debugging: share screenshots of UI bugs or architecture diagrams—Codex interprets visual context to understand and fix issues
- Codebase exploration: ask questions about unfamiliar repositories, Codex navigates and explains code structure with full context
JetBrains AI Assistant Excels At
- Automated commit message generation based on code changes and project context
- Complex refactoring operations with AI understanding of code dependencies and design patterns
- Code explanation and documentation for team knowledge sharing and onboarding new developers
Performance & Integration
| Category | OpenAI Codex | JetBrains AI Assistant | Winner |
|---|---|---|---|
| IDE Support | IDE-agnostic via CLI. Integrates with GitHub for PR workflows. ChatGPT desktop and web interfaces. | Fully integrated with the suite of JetBrains IDEs, including IntelliJ IDEA, PyCharm, WebStorm, CLion, ReSharper, and others. | Tie |
| Community | Active community | Active community | Tie |
| Data Richness | Comprehensive | Comprehensive | Tie |
| Overall Score | 96/100 | 90/100 | OpenAI Codex |
The Bottom Line
Both OpenAI Codex and JetBrains AI Assistant are capable AI coding tools, but they serve different needs. OpenAI Codex scores higher (96/100 vs 90/100) and excels in autonomous development and pr automation. The choice depends on your specific workflow, team size, and technical requirements.
Choose OpenAI Codex if: you prioritize autonomous development and pr automation and want the higher-rated option (96/100).
Choose JetBrains AI Assistant if: you prioritize jetbrains ide users and enterprise development and don't mind a slightly lower score for specialized features.