GPT-5 Codex vs GPT-4.1 Nano

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.

1. Ultra-Fast, Low-Latency Performance

• The fastest model in the GPT-4.1 family, ideal for real-time interactions and high-throughput applications.
• Designed for scenarios where speed matters more than complex reasoning.

2. Most Cost-Efficient GPT-4.1 Variant

• Lowest price point among GPT-4.1 models.
• Enables large-scale deployments such as support bots, routing systems, and lightweight assistants without high compute costs.

3. Solid Instruction Following

• Consistent and reliable at following clear instructions.
• Well-suited for:
  • Classification
  • Simple reasoning
  • Data extraction
  • Content rewriting
  • Chat-style responses

4. Strong Tool Calling Capabilities

• Built with robust support for:
  • Function calling
  • Structured outputs (e.g., JSON)
  • Lightweight automation tasks
• Works well within multi-step agent workflows that rely on simple tools.

5. Basic Multimodal Input

• Supports text and image input.
• Useful for:
  • Simple visual recognition
  • Alt-text generation
  • Reading graphics or screenshots

6. Text-Only Output

• Produces text only, ensuring:
  • Clean structured outputs
  • High reliability for downstream processing
  • Ease of integration into backend systems

7. 1M-Token Context Window

• Supports up to 1,047,576 tokens, allowing:
  • Long documents
  • Multiple files
  • Large prompt memory
• Reduces or eliminates the need for chunking and retrieval in many simple workflows.

8. Ideal Use Cases

• Customer support bots
• Routing and intent detection
• Simple agents and workflow automation
• Content cleanup and rewriting
• Basic Q&A, summaries, and extraction

9. Broad API Integration

• Available across major API endpoints:
  • Chat Completions
  • Responses
  • Realtime
  • Assistants
  • Fine-tuning
• Supports predicted outputs for reliability and determinism.