Hans-Peter Frei

Full Stack · Databases · AI

I build the tools I want to use. 25 years of shipping code — from Swiss banking systems to my own AI workflow.

Hans-Peter Frei — Full Stack Developer and Database Expert

Open Source

Things I built for myself and put out there.

VistaClair — Expose Your Home PC, Agent Inspector for Claude Code

Expose your home PC. Develop from everywhere. Claude Code tabs in the browser. A deep inspector that shows every LLM interaction, tool calls, hooks, and subagent parallelism. Ctrl-V paste and file drop into CLI sessions. Route to any LLM API.

Features: Home PC Automation, Claude Code Tabs, Deep LLM Inspector, Paste & Drop, Provider Routing (OpenAI, Gemini, DeepSeek, Kimi, Ollama), Rules, MCP Server, File Manager.

  • Home PC Automation
  • Claude Code Tabs
  • Deep LLM Inspector
  • Paste & Drop
  • Provider Routing

Explore VistaClair

Install: npx vistaclair | View on npm | View on GitHub

3D Human Anatomy Explorer

Built this to learn Three.js properly. Interactive 3D anatomy you can navigate in the browser — no plugins, pure WebGL.

  • Three.js
  • WebGL
  • JavaScript

Projects

Client work and in-house tools — not (yet) open source.

Latest from the Blog

Anatomy of a Claude Code Session: Prompts, Tools, and Token Economics

I intercepted 307 files from a Claude Code session to reverse-engineer its system prompt, tool definitions, subagent architecture, and caching strategy. Tool schemas alone consume 56% of input tokens, prompt caching saves 90% of costs, and about 19% of the tool payload could be trimmed.

May 24, 2026 · 20 min read

  • claude-code
  • system-prompt
  • prompt-engineering
  • ai-tools
  • prompt-caching
  • llm-architecture
  • anthropic
  • token-economics

19,000 Tokens Before You Type: Claude Code's Hidden Cost of a Simple Hello

I intercepted every API call Claude Code makes and compared two sessions: a simple greeting (8 calls, 22 output tokens) vs. a full security review (81 calls, multi-agent orchestration). The same 19K-token system prompt powers both. Here's what I found about routing, caching, subagents, and the real cost of AI-powered development tools.

May 22, 2026 · 14 min read

  • claude-code
  • llm
  • api-analysis
  • prompt-engineering
  • caching
  • developer-tools
  • anthropic
  • ai-agents

Claude Code's Two Planning Mechanisms: Plan Mode vs Plan Subagent

An analysis of Claude Code's two-layer planning system — plan mode and the Plan subagent — based on intercepted API calls, system instructions, and real session data from my inspector tool.

May 21, 2026 · 14 min read

  • claude-code
  • ai-tools
  • prompt-engineering
  • developer-tools
  • planning
  • llm-internals

All posts

About

From Bern, studied CS in Biel, living in Zurich. Spent 25 years in Swiss banking, now I build my own things full-time. Schwitzerdütsch and English.

When I'm not coding: family with two kids, mountain bike, ski, hike, gym.

Databases

Oracle is where I spent most of my career. PL/SQL, performance tuning, the whole stack.

Full Stack

Node.js is my go-to. I run everything on Linux with Nginx and PM2.

AI Integration

I wire up LLMs into everything now. Multiple providers, voice, images.

Financial Services

25 years of regulatory reporting and Avaloq in Swiss banking.

Get in Touch

Interested in working together? Let's talk.

Email: hp@hpfreilabs.com

Location: Zurich, Switzerland

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