Shopify Developer - Custom Discount Logic (Shopify Functions) + Cart Auto-Add Feature

JOB DESCRIPTION: I run an established luxury furniture e-commerce store on Shopify (Grow plan) doing consistent 6-figure annual volume. I need an experienced Shopify developer to build a membership pricing system with custom cart and discount logic. This is a defined-scope project with clear specs, and strong potential for ongoing work if it goes well. WHAT YOU'LL BUILD 1. Cart auto-add feature (theme level) - When a cart's eligible subtotal crosses a defined threshold, a $200/year membership product is automatically added to the cart as a visible, removable line item - A dynamic savings line displays in real time ("You're saving $X on this order as a member") - One-click remove: removing the membership reverts all prices to retail and prevents re-adding for that session - Must work in the cart drawer and cart page, styled to match the existing theme exactly (fonts, spacing, colors - it must look native, not like a widget) 2. Custom discount logic (Shopify Functions) - If the membership product is in the cart: apply 30% off eligible items in that same order - Separate existing logic: customers tagged as members (via Appstle Memberships) get 30% off automatically on all future orders - Both discounts respect a collection exclusion list - Strict no-stacking rules: member discount and sale discounts are mutually exclusive, best price wins, never combined - including manual discount codes - The in-cart discount and the tag-based discount must never both apply to one order - Deployed as a custom app via your own Shopify Partners account (you handle deployment) 3. Edge cases (full list provided on hire) Includes: membership removal behavior, cart dropping below threshold, excluded-collection-only carts, already-tagged members, refund handling, and a global toggle that disables the entire mechanic during sale events REQUIRED SKILLS - PLEASE DO NOT APPLY WITHOUT THESE - Shopify Functions (discount functions specifically) - you must have shipped at least one to production. Describe it in your application - Shopify theme development (Liquid, JS, cart AJAX API) - Shopify Partners account and experience deploying custom apps to client stores - Experience with Appstle Memberships or comparable membership/subscription apps - Experience with automatic discounts and discount combination settings WORKING STYLE - All work happens on a duplicate/preview theme first - nothing touches the live theme until I approve - You'll get collaborator access with limited permissions (request via collaborator code) - I test everything personally on mobile and desktop before launch, against a written checklist - Clear communication and flagging risks early matters more to me than speed TO APPLY 1. Describe a Shopify Functions discount you've shipped to production and what it did 2. Confirm you can deploy custom apps through your own Partners account 3. Estimated timeline and fixed quote for the scope above 4. Start with the word CEDAR so I know you read the full post DO NOT CONTACT VIA EMAIL OR SOCIAL MEDIA WILL ONLY ACCEPT UPWORK APPLICATIONS