Show HN: PolyGPT – ChatGPT, Claude, Gemini, Perplexity responses side-by-side (polygpt.app)

PolyGPT is a free, open-source tool that mirrors a single user prompt to multiple AI chat services (ChatGPT, Claude, Gemini, Perplexity) and displays their responses side‑by‑side in real time. Instead of switching tabs or copying prompts between web UIs, you "type once" and PolyGPT broadcasts the input to each supported interface and shows synchronous outputs, enabling immediate comparison. The project emphasizes privacy and local control — it's advertised as open source and "100% free" — so users don't route prompts through a third-party server. For the AI/ML community this is a practical productivity and evaluation tool: prompt engineers, researchers, and product teams can rapidly prototype prompts, spot behavioral differences, and benchmark responses across models without manual juggling. Key technical implications include multi‑interface mirroring (supports 4+ models presently), live side‑by‑side visualization, and likely client‑side integration with provider web UIs or APIs to avoid external data handling. It accelerates qualitative comparison and debugging of hallucinations, style, safety behaviors and latency, though users should still manage provider authentication, rate limits, and terms‑of‑service considerations for each model.