OpenAI: GPT-5 Chat

Processes both text and image inputs within a single conversation thread, maintaining full context across turns. The model uses a unified transformer architecture that encodes images through a vision encoder and text through a language model, merging representations at intermediate layers to enable cross-modal reasoning. This allows the model to reference visual elements in follow-up text queries and vice versa without losing conversation history.

Supports extended context windows (128K+ tokens) enabling multi-turn conversations with substantial document analysis, code review, or knowledge base integration. The model uses sliding window attention with KV-cache optimization to manage memory efficiently across long sequences, allowing developers to maintain conversation state without explicit summarization or context management overhead.

Generates responses constrained to user-defined JSON schemas, ensuring outputs conform to expected structure without post-processing. The model uses constrained decoding (token-level masking during generation) to enforce schema compliance at generation time, preventing invalid outputs and eliminating the need for retry loops or validation layers.

Enables the model to invoke external tools and APIs through a standardized function-calling interface. The model receives a list of available functions with parameter schemas, decides when to call them based on user intent, and returns structured function calls that applications can execute. This is implemented via a dedicated token stream for function calls, allowing parallel function invocation and native integration with OpenAI's function-calling API.

Adapts model behavior through examples provided in the conversation context without fine-tuning. The model uses in-context learning to recognize patterns from provided examples and apply them to new inputs, enabling rapid customization for domain-specific tasks, writing styles, or output formats. This is implemented through standard conversation turns where examples are provided as user-assistant pairs.

Generates step-by-step reasoning chains that break down complex problems into intermediate steps before arriving at conclusions. The model uses extended token generation to produce verbose reasoning traces, enabling transparency into decision-making and improving accuracy on multi-step logical problems. This is implemented through standard text generation with longer output sequences and explicit reasoning prompts.

Manages conversation state through system prompts that define model behavior and explicit context windows that control which previous turns are included in each request. The model uses a standard conversation format (system, user, assistant turns) where developers control context retention through explicit message history management, enabling stateless API design with client-side or external state management.

Applies content filtering to both input and output to detect and prevent harmful content. The model uses built-in safety classifiers that evaluate requests for policy violations (hate speech, violence, sexual content, etc.) and can refuse to engage with prohibited topics. This is implemented through pre-generation filtering of inputs and post-generation filtering of outputs, with configurable safety levels.

Enforces usage limits based on API tier and account configuration, managing request rates and token consumption. The model operates within OpenAI's tiered API system where different subscription levels have different rate limits (requests per minute, tokens per minute) and quota allocations. This is implemented through server-side request throttling and quota tracking.