Hey Product Hunt 👋 Four Line started because I was tired of asking the same question to four different AIs in four different tabs. Every morning: open ChatGPT, Claude, Gemini, Grok → paste the same prompt into each one → Cmd+Tab between them comparing answers. After the hundredth time, I figured the workflow itself should be the product. So Four Line replaces your new-tab page with a side-by-side workspace. Up to nine AI providers (ChatGPT, Claude, Gemini, Grok, Kimi, DeepSeek, Mistral, Z.ai/GLM, Google AI Studio) in any combination — resizable panes, a shared notes + prompt library, and a "broadcast" button that types your prompt into every visible AI's composer and submits for real. Four answers from one keystroke. The hardest part wasn't the UI — it was making broadcast actually land. Every provider uses a different rich-text editor (ProseMirror, Tiptap, Quill, plain textareas) and they all reject synthetic paste events that aren't shaped exactly right. Getting that to work across eight providers took longer than the rest of the product combined. A few opinionated bets I made early and never regretted: → Local-first. Your tabs, groups, prompts, and notes all live in your browser's storage. The only Four Line server in the loop is Firebase Auth for the Pro license check. Your conversations are between you and each AI, exactly the same as if you opened them in normal tabs. → Per-workspace AI sessions. Most multi-AI extensions reparent one ChatGPT iframe across groups, so switching loses your scroll, your chat, sometimes your login. Four Line gives every (group, AI) pair its own session — your "Code review" workspace's ChatGPT and your "Writing" workspace's ChatGPT remember completely different conversations. → Honest free tier. Four AI providers (ChatGPT, Claude, Gemini, Grok), two workspaces, real notes + prompts library — free forever. Pro is $9.99/mo for unlimited everything plus the rest of the providers, multi-image broadcast, and workspace export. I'd love feedback — especially on the broadcast flow, since that's the riskiest single thing in the product. If your favorite AI isn't supported yet, tell me; the limit is iframe-embedding policies, not taste. And a real thanks to everyone who poked at the beta and told me ChatGPT iframes were broken in specific weird ways. Worst feedback to receive, best feedback to act on 🙏

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1mo ago

Being able to pin specific chats so they stay open across browser sessions would save me a ton of time when I'm bouncing between long-running research threads.

12h ago

Love having all my AI tabs in one place, honestly saves me so much tab switching. One thing that would be amazing is if you could add a quick prompt sharing feature, basically like being able to save and sync prompt templates across the different models. Would make repeating workflows way smoother.

9h ago

Splitting four chats side-by-side actually changed how I compare model outputs. The drag-to-resize panes feel surprisingly snappy.

4h ago

FourLine

Chat with every AI at once, from one window.

Chat with every AI at once, from one window.