The Arc — Private Coaching Web App for Reel Weight Loss
A bespoke daily coaching app built from the ground up for Stephanie Klein's weight-loss methodology.
Overview
The Arc is a private coaching web app built exclusively for Stephanie Klein's Reel Weight Loss membership clients. Every screen, interaction, data model, and email was designed and engineered from scratch to match Stephanie's proprietary methodology: daily food and habit planning, morning intention-setting, live check-ins, evening reflection, and consistent tracking over time. There is no off-the-shelf platform behind it — The Arc is a fully custom build, live at thearc.today.
The Problem
Stephanie's coaching methodology is structured and proprietary — generic apps like MyFitnessPal or Notion simply could not replicate it. Her clients needed a purpose-built daily practice tool: one that guided them through J-B-A-L-D-S meal planning each morning, captured live check-ins with hunger scores and alignment ratings, prompted evening reflection without judgement, and gave Stephanie a coach dashboard with full visibility into every client's progress. Nothing off the shelf came close.
The Solution
A fully custom Next.js web app built on PostgreSQL, deployed on Vercel, with a coach-and-client dual-role system. Every feature was designed to mirror Stephanie's coaching methodology step by step — from the rotating morning intention modules to the weekly lookback summary and XLSX data exports.
The app uses a custom brand design system: Brand Navy (#041E3A), Brand Yellow (#FAEB27), layered cream/ivory neutral backgrounds, and brand serif + script fonts for a cinematic, editorial feel. The mobile-first layout includes a slide-in nav drawer on small screens. The daily workflow is frictionless — plan in the morning, check in mid-day or evening, reflect at night. Rotating coaching modules keep the experience fresh so clients don't disengage over weeks.
Built on Next.js 15 (App Router) with TypeScript and Prisma ORM over PostgreSQL hosted on Hetzner Cloud. Auth.js v5 handles authentication with a secure token-based password reset flow (SHA-256 hashed, 1-hour expiry, single-use). All date logic is anchored to America/New_York regardless of server timezone. Audio files upload browser-direct to Hetzner S3-compatible Object Storage via presigned URLs, bypassing Vercel's 4.5 MB serverless body limit. Rotating coaching modules use a day-index algorithm with today's module locked on first save.
Our Process
Research
Worked directly with Stephanie to map her full coaching methodology before writing a line of code. Every data model — from the J-B-A-L-D-S structure to the urge tracker fields — was derived from her actual coaching process and the language she uses with clients.
Design
Built a custom brand design system from scratch using Stephanie's Arc identity: navy, yellow, cream, and editorial typography. Designed the daily workflow as a linear morning-to-evening arc so clients always know what step comes next.
Development
Sixteen-week build covering the full client-side daily practice, the coach dashboard, invite system, audio upload pipeline, XLSX export, password reset, and all transactional emails via Resend. Browser-direct S3 upload was engineered to work around Vercel's serverless body-size limit.
Testing
Tested all timezone edge cases for midnight rollover (UTC server vs. ET clients). Password reset tokens verified for single-use burn. XLSX export validated across all 8 sheet tabs with real client data. Audio upload tested on slow connections with live progress tracking.
Tech Stack
Results
Conclusion
The Arc is the rare kind of project where the brief was a methodology, not a feature list. Every decision — from the rotating module algorithm to the timezone anchoring — was made in service of Stephanie's coaching practice and her clients' daily experience. The result is a purpose-built tool that lives at thearc.today and cannot be replicated with any off-the-shelf product.
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