GPT-5.1 Codex vs GPT-4.1 Nano

1. Purpose-Built for Agentic Coding

• Designed specifically for environments where the model acts as an autonomous or semi-autonomous coding agent.
• Optimized for multi-step reasoning in code tasks such as planning, refactoring, debugging, file generation, and tool coordination.

2. Enhanced Coding Intelligence

• Extends GPT-5.1's advanced reasoning capabilities to handle complex software architecture decisions.
• Better accuracy in code generation across languages (JavaScript, Python, TypeScript, Go, Rust, etc.).
• Produces cleaner, more idiomatic code aligned with modern frameworks and best practices.

3. Superior Tool Use & Code Navigation

• Excels at reading, understanding, and transforming multi-file codebases.
• Works well with Codex workflows that simulate real developer tooling.
• Strong at following function signatures, constraints, and code patterns within an existing project.

4. Long-Range Context Awareness

• 400,000-token context window enables the model to ingest large repositories or multiple files simultaneously.
• Supports deep analysis of project structures, dependencies, and cross-file logic.

5. Multi-Modal Development Capabilities

• Accepts text + image input and output — suitable for tasks like:
  • Reading UI mockups or screenshots to generate code
  • Understanding architectural diagrams
  • Reviewing images of whiteboard sessions

6. Agentic Workflow Optimization

• Built to manage longer chains of thought and execution typically required in:
  • Automated code repair
  • Project bootstrapping
  • Linting and migration tasks
  • Long-running coding agents using planning + execution loops

7. Continually Updated Model Snapshot

• Codex-specific version receives regular upgrades behind the scenes.
• Ensures the latest coding improvements without requiring developers to update model names.

8. Reliable Instruction Following

• Highly consistent in honoring explicit constraints:
  • Code styles
  • Folder structures
  • API contracts
  • Framework conventions

9. Broad API Support

• Works across Chat Completions, Responses API, Realtime, Assistants, and more.
• Ideal for apps that need live, reasoning-heavy coding agents or generative dev environments.

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.