Adds an inline system prompt editor & toggle to DeepSeek chat. The prompt is injected as a system message before every new chat.
Adds a System Prompt button directly into the DeepSeek chat interface — right next to the DeepThink and Search toggles — giving you full control over model behavior without touching the API.
prompt() dialogs.GM_getValue / GM_setValue.Ctrl+Enter to save, Escape to close the panel.The script intercepts outgoing API requests at the network level:
fetch — Patches window.fetch to intercept chat completion requests.XMLHttpRequest — Patches XHR.send for legacy request paths.WebSocket — Wraps outgoing send calls to inject the prompt into real-time messages.When a matching API request is detected, the script prepends a { role: "system", content: "..." } message to the messages[] array — the standard way system prompts work in the OpenAI/DeepSeek API.
No data leaves your browser. The script makes zero external network requests. Everything runs locally in your userscript manager.
chat.deepseek.com — not the API or mobile app.Inspired by DeepSeek System Prompt Injector by NoahTheGinger — which uses a similar network interception approach but with context-menu-based UI. This script reimplements the concept with a fully inline editor panel.
