Simon Willison released CORS Chat on 15th August 2026 as a browser-based tool for chatting directly with any OpenAI Responses-compatible API endpoint that supports CORS headers. The tool lets users configure endpoints with custom headers, save conversations locally, and manage multiple chat sessions with different models and reasoning settings.

Willison said he built CORS Chat today with GPT-5.6-Sol xhigh to test Qwen 3.8 27B running in LM Studio on both an M5 MacBook Pro and an NVIDIA DGX Spark. The web UI is designed to exercise an OpenAI-Responses-compatible chat endpoint, and he said he tried it against LM Studio with the --cors option and OpenRouter, with both working fine.

CORS Chat persists conversations in the browser and exports them as copy-pasted JSON. It also detects generated SVG images and progressively renders them in the chat while tokens are still streaming.

Simon Willison released CORS Chat on 15th August 2026 as a browser-based tool for chatting directly with any OpenAI Responses-compatible API endpoint that supports CORS headers. The tool lets users configure endpoints with custom headers, save conversations locally, and manage multiple chat sessions with different models and reasoning settings.

Willison said he built CORS Chat today with GPT-5.6-Sol xhigh to test Qwen 3.8 27B running in LM Studio on both an M5 MacBook Pro and an NVIDIA DGX Spark. The web UI is designed to exercise an OpenAI-Responses-compatible chat endpoint, and he said he tried it against LM Studio with the --cors option and OpenRouter, with both working fine.

CORS Chat persists conversations in the browser and exports them as copy-pasted JSON. It also detects generated SVG images and progressively renders them in the chat while tokens are still streaming.