GPT-5.1 vs GPT-4.1

1. Configurable Reasoning for Agentic Tasks

• Built to excel in autonomous or semi-autonomous coding workflows, with adjustable reasoning effort for planning, refactoring and debugging.

2. Fast Multi-Modal Input with Large Output

• Accepts both text and image inputs while producing text outputs.
• Offers up to 128 k output tokens, allowing long responses and code generation across multiple files.

3. Large Context & Knowledge Cut-Off

• 400 k token context window supports processing large codebases or documents.
• Knowledge cut-off of Sep 30 2024 ensures familiarity with recent tools and frameworks.

4. Reasoning Token Support

• Provides explicit support for reasoning tokens, enabling developers to fine-tune the balance between reasoning depth and speed.

1. Smartest non-reasoning model

• Highest intelligence among models without a reasoning step.
• Great for tasks where speed + accuracy matter without deep chain-of-thought.

2. Excellent instruction following

• Very strong at structured tasks, formatting, and precise execution.
• Ideal for productized workflows and deterministic outputs.

3. Reliable tool calling

• Works smoothly with Web Search, File Search, Image Generation, and Code Interpreter.
• Supports MCP and advanced tool-enabled API flows.

4. Large 1M-token context window

• Allows extremely long conversations, large documents, and multi-file use cases.
• Handles context-heavy tasks without requiring chunking.

5. Low latency (no reasoning step)

• Faster responses than GPT-5 family when reasoning mode isn't required.
• More predictable timing for production use.

6. Multimodal input

• Accepts text + image.
• Output is text only.

7. Supports fine-tuning

• Can be fine-tuned for specialized tasks.
• Also supports distillation for smaller custom models.