Building a Shopify bundles app for stores with real fulfillment: here's the wedge

Every big bundle app is a conversion widget: great product page, then the order says "Bundle" and your 3PL has no idea what to pick. The one app that fixes it does so by editing orders after creation, and that races the 3PL's order import.

I'm building Solid Bundles on Shopify's Cart Transform API instead: components with real SKUs land in the order at checkout time, by construction. The cleanest frame I've found while building this: bundle setups are either analytics-clean (the bundle is its own product, tidy reporting, sync jobs forever) or ops-clean (the order carries real components, warehouses just work). Almost every app picks analytics. I picked ops.

Then the category made my argument for me. Two of the big bundle apps vanished from the App Store within two weeks of each other: one after a security incident that got it deactivated on thousands of stores overnight, the other with no explanation at all. Every migration thread asks the same two questions: what did the app leave behind in my orders and inventory, and how do I make sure the next one fails safe. Nobody asks about the product page widget.

This week a Shopify theme dev who has installed bundle apps across hundreds of client stores gave me his support-side ranking of what actually breaks after install: price display first (discount shows at cart, product page shows list price, merchants file "app is broken" tickets by day two), custom AJAX cart drawers second, discount stacking rules third, bundle-parent inventory confusion fourth. I spent a day checking my codebase against all four. Two were already safe by architecture (the parent product carries the real bundle price; stacking rules are explicit, not accidental), one was half-built and just got promoted to next ship (savings note on the product page), and one became my beta test matrix (Impulse, Prestige and Flex cart drawers).

Flat $29/mo, no revenue caps. The category's usage-based pricing is its most-hated feature: the current top 1-star review on the market leader calls it "a tax based on how much we sell."

Status update while drafting this: the approval email arrived this morning. Solid Bundles is now listed on the App Store, nine days after submission. About 20 build hours and $19 spent, $0 MRR, and the 60-day kill threshold starts ticking when I flip the listing to full visibility this week. This week I also shipped migration guides for stores hit by the delistings, and a feature that adopts an orphaned bundle product in place so a migrating merchant keeps their product URLs and SEO. Looking for beta merchants with 3PL or warehouse setups: free lifetime plan, personal onboarding, your feedback steers the roadmap. Comment or DM if that's your stack.