Gryter: AI Team Skill Files

See how a solo builder's AI harness, with specialized agents and skill files, achieved team-level output, demonstrated through a fitness app and real-world file examples.

Claude Opus 4 Claude Code MCP connectors Flutter Firebase

Overview

Gryter is an AI fitness coach I built solo.
The first ~90 seconds is the app running (onboarding through a generated workout). The rest is the AI harness behind it: The 12 Gryter skill files (product-lead, fitness-coach, security-engineer, gryter-design-system, and 8 more), the specialized subagents, the need for CLAUDE.md, and the MCP connectors that let the agents talk to my actual Firebase project, run Flutter tests, and drive the app on a real device. I’ll walk through the orchestration with real files and diffs from a recent feature ship. The app is the proof; the AI harness is the demo.

Links

https://gryter.com/
Gryter provides periodized, adaptive strength programming via AI-driven recovery analysis.

Tech stack

Claude Opus 4

Claude 4 Opus is Anthropic’s next-generation frontier model designed for high-stakes reasoning and complex multi-step orchestration.

Claude 4 Opus represents the peak of the Claude 4 family, delivering significant gains in coding proficiency and nuanced linguistic understanding. It handles massive 200k-token contexts with near-perfect recall (99% accuracy) and excels at autonomous task execution. Built on updated Constitutional AI frameworks, Opus 4 provides enterprise-grade reliability for quantitative analysis and creative synthesis while maintaining a near-zero hallucination rate in technical documentation.

https://www.anthropic.com/claude

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Claude Code

Anthropic's agentic coding tool: Unleash Claude's raw power directly in your terminal or IDE to turn complex, hours-long workflows into a single command.

Claude Code is Anthropic’s powerful agentic coding assistant, designed for high-velocity development. It operates natively within your terminal, IDE (VS Code, JetBrains), or via a web interface, allowing you to delegate complex tasks like feature building, bug fixing, and codebase navigation. The agent plans, edits files, executes commands, and creates commits, maintaining awareness of your entire project structure. Internally, Anthropic engineers using Claude Code reported a 67% increase in productivity, demonstrating its capacity to deliver significant gains for Pro and Max plan users.

https://claude.com/code

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MCP connectors

MCP connectors are standardized interfaces that link AI models to local data sources and third-party software tools.

The Model Context Protocol (MCP) replaces fragmented integrations with a universal standard for AI connectivity. These connectors allow Large Language Models (LLMs) to securely query local databases like PostgreSQL, interact with GitHub repositories, or pull live data from Slack and Google Drive. By decoupling the data source from the model interface, developers use a single protocol to swap between providers like Anthropic, OpenAI, or local instances without rewriting integration logic. It is a production-ready framework (built on JSON-RPC 2.0) that gives agents direct, governed access to the specific files and tools they need to execute complex workflows.

https://modelcontextprotocol.io

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Flutter

Flutter is Google's UI toolkit: build, test, and deploy natively compiled applications for mobile, web, and desktop from one codebase.

Flutter is Google’s open-source UI software development kit (SDK), designed for crafting beautiful, high-performance applications across six platforms (iOS, Android, web, Windows, macOS, and Linux) from a single codebase. It uses the Dart programming language and leverages a reactive, widget-based architecture for its UI. The key productivity feature is Hot Reload, which allows developers to see code changes reflected in the running app in milliseconds, without losing application state. This efficiency, combined with its native compilation to ARM or Intel machine code, ensures fast performance and a consistent, pixel-perfect user experience on every screen.

https://flutter.dev

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Firebase

Firebase is Google's mobile and web app development platform: a comprehensive, serverless Backend-as-a-Service (BaaS) for building, improving, and scaling applications.

Firebase is a powerful, integrated platform from Google, offering a suite of nearly 20 products for developers targeting iOS, Android, web, and Unity. It eliminates backend complexity: services like Cloud Firestore (a NoSQL database) and Firebase Authentication (supporting providers like Google, Facebook, and Apple) handle infrastructure automatically. Developers use Firebase Hosting for global Content Delivery Network (CDN) deployment and Cloud Functions for running serverless backend logic. Post-launch, tools like Crashlytics and Google Analytics for Firebase provide crucial performance monitoring and user behavior data, ensuring the app scales reliably and efficiently.

https://firebase.google.com/

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