cosskill
Practice difficult conversations with AI personas before the
I just shipped cosskill — a free tool that lets you rehearse difficult real-world conversations with AI personas before they happen.
The problem I kept seeing:
Every month, millions of people google things like "how to ask for a raise," "how to break up over text," or "how to confront a coworker." They find advice articles, but reading tips is fundamentally different from actually practicing the words.
I've been in that situation myself — staring at my phone drafting a message to an ex, rewriting it 15 times, wishing I could just practice first. Or sitting in bed the night before a salary negotiation, running the conversation in my head but never feeling prepared.
What cosskill does:
Instead of reading generic advice, you practice the actual conversation with an AI persona that pushes back, challenges your framing, and helps you refine your approach.
There are 6 personas, each built around a distinct communication method:
Ex Persona — boundaries, emotional pacing, clean endings
Coworker Persona — workplace conflict, handovers, ownership gaps
Musk Persona — first-principles challenges, speed, constraint-breaking
Jobs Persona — product pitches, taste, clarity
Trump Persona — high-pressure negotiation, confrontation
Buffett Persona — long-term decisions, patience, downside protection
These aren't character roleplay bots. Each persona follows a structured framework with heuristics and boundaries — it's closer to a communication coach than a chatbot.
The stack:
Next.js 16 (App Router, RSC, TypeScript)
Cloudflare Workers + D1 (SQLite)
AI via OpenRouter (free tier models)
SSE streaming for real-time responses
Zero data collection — sessions stored in browser only
What it costs:
Nothing. Free, no signup, no account, no credit card. I wanted the barrier to practicing to be zero.
Why I'm sharing:
I'm curious whether this resonates. I've been using it myself before tough conversations and it genuinely helps — not because the AI gives perfect advice, but because the act of articulating your thoughts out loud (even to a bot) forces clarity.
Would love any feedback on the product, the positioning, or the approach. Happy to answer questions about the build too.
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