All packsSaaS Billing + Tax CoreSolve
stripe subscription schedule already exists error downgrade
One active schedule per subscription, and downgrades need one
Stripe allows exactly one active subscription schedule per subscription; a second downgrade throws unless the pack updates the existing schedule in place (D10).
This is one of the things SaaS Billing + Tax Core already handles. Charge per-seat subscriptions: upgrades, downgrades, failed cards, invoices and sales tax.
Is this you?
A downgrade is naturally modeled as a Stripe subscription schedule: keep the current plan until period end, then switch. Stripe allows exactly one active schedule per subscription, though -- a customer who downgrades twice, or upgrades after already scheduling a downgrade, hits a flat API error the second time a schedule gets created.
Why this one is easy to get wrong
subscriptionSchedules.create() doesn't warn about the one-schedule limit until a second call hits it, and the fix isn't a try/catch -- it's carrying whether a schedule already exists through the entire plan-change flow so the code updates it in place instead of creating a new one, which is a data-flow change, not an error-handling patch.
What you get instead
D10 has the plan-change route retrieve the live subscription first specifically to read its schedule field, thread existingScheduleId into planChangeAction(), and update an existing schedule in place rather than create a second one. Upgrades additionally release any pending downgrade schedule before applying, since Stripe errors if you touch items on a schedule-managed subscription directly.
Source: ARCHITECTURE.md D10 — checkable in the pack you receive
How you actually use this
You don’t install a library or wire up an SDK. Your own coding agent builds the code in your project, and you keep it — no runtime dependency on us.
Step 1
Download and unzip
You get a folder: the docs that tell an agent what to build, a starting skeleton, and the test suite that decides when it's done.
Step 2
Open it in Claude Code or Cursor
Point your coding agent at the folder. Nothing to install, no account with us, no API key.
Step 3
Paste one prompt
The pack contains the exact prompt. Paste it as your first message and leave it alone — it works through the build itself, choosing a cheaper or stronger model per task.
Step 4
Run ./verify.sh
One command. It prints a pass or fail for every check. Green means the build is done — the same script we ran to produce the receipt on this page.
Typical build: about 18 minutes of your agent working, mostly unattended. Then you integrate the working module into your app the way you would any code you’d written yourself.
Why you can believe this
3 of 3 runs passedWe ran this pack from an empty folder 3 times and published exactly what happened — every check, the model, the token cost, the wall time. Not a testimonial, and not our opinion: the same verify.sh you run yourself. Read the full receipt →