GPT-5 Codex vs Claude 4.5 Sonnet

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. Best-in-class coding performance

• #1 on SWE-bench Verified (77.2% standard, 82.0% high-compute).
• Excels at debugging, architecture, and multi-file code generation.
• Maintains coherence for extremely long tasks (30+ hours).

2. State-of-the-art computer use & agents

• Leads OSWorld at 61.4%.
• Strongest model for agentic workflows, multi-step tool use, and real computer control.
• Powering Claude Code, the new Claude Agent SDK, and Chrome agent actions.

3. Advanced reasoning & math

• Large improvements across reasoning-heavy benchmarks (AIME, MMMLU, τ2-bench, Terminal-Bench).
• Deep multi-step reasoning with extended or interleaved thinking.

4. High alignment & safety

• Most aligned Claude model to date with reduced deception, hallucinations, sycophancy, and harmful compliance.
• Strong protections against prompt injection for agentic tasks (ASL-3 safeguards).

5. Domain-expert performance

• Notable gains in finance, law, medicine, and STEM tasks.
• Trusted by early customers for long-context legal analysis, multi-file engineering, security research, and red-teaming.