GPT-5.2 Codex vs Gemini 2.5 Pro Experimental

1. Optimized for Long-Horizon Coding Tasks

• OpenAI describes GPT-5.2 Codex as a highly intelligent coding model built for long-horizon, agentic coding work.
• Well suited to planning, refactoring, debugging, and multi-step implementation flows inside real codebases.

2. Adjustable Reasoning for Coding Work

• Supports configurable reasoning effort from low to xhigh depending on speed and quality needs.
• Accepts both text and image inputs while producing text output.

3. Large Context + Long Output

• 400 k token context window supports broad repository understanding and larger working sets.
• Allows up to 128 k output tokens for longer patches, code generation, and technical explanations.

4. Up-to-Date Model Snapshot

• Knowledge cut-off of Aug 31 2025 keeps it current with newer tools and frameworks.
• Supports streaming, function calling, and structured outputs for tool-driven coding workflows.

1. State-of-the-art reasoning performance

• #1 on LMArena human preference leaderboard.
• Excels at advanced reasoning benchmarks like GPQA and AIME 2025.
• Achieves 18.8% on Humanity's Last Exam (no tools), representing frontier human-level reasoning.

2. New “thinking model” architecture

• Built with explicit reasoning steps internally before responding.
• Handles complex, multi-stage logic with higher accuracy and fewer hallucinations.

3. Elite science and mathematics capabilities

• Leads in math and science tasks across industry benchmarks.
• High performance without costly inference tricks like majority voting.

4. Exceptional coding abilities

• Major leap over Gemini 2.0 in coding performance.
• 63.8% on SWE-Bench Verified with custom agent setup.
• Strong at code transformation, debugging, and building agentic apps.
• Capable of generating full applications (e.g., a playable video game) from a single-line prompt.

5. Massive multimodal context

• Ships with a 1,000,000 token window (2M coming soon).
• Handles entire documents, datasets, video sequences, audio files, and large codebases.
• Maintains strong performance even at extreme context lengths.

6. Native multimodality across all inputs

• Understands and reasons over text, images, audio, video, and code.
• Designed for real-world, multi-source problem-solving and agent workflows.

7. Consistent high-quality outputs

• Improved post-training results in more accurate, coherent, and stylistically strong responses.
• Higher reliability across complex workloads.

8. Early availability for developers

• Available today in Google AI Studio for experimentation.
• Coming soon to Vertex AI with higher rate limits and production-ready access.