GPT-5 Codex vs GPT-5 Mini

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. High reasoning performance

• Retains strong reasoning capabilities despite being a smaller, faster model.
• Suitable for tasks requiring accurate logic and structured thinking.

2. Fast and cost-efficient

• Optimized for speed, making it ideal for real-time or high-volume workloads.
• Far cheaper than GPT-5 while maintaining solid capability.

3. Great for well-defined tasks

• Excels when prompts are precise and objectives are clearly specified.
• More predictable and stable for deterministic workflows.

4. Multimodal input

• Accepts text + image as input.
• Outputs text only.

5. Tool support

• Works with Web Search, File Search, Code Interpreter, MCP.
• (Does not support Image Generation as a tool and does not support Computer Use.)