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Integration Medium by Agent Buildprint
Stripe Billing Extension
Add SaaS billing to an existing product without missing webhook signatures, entitlement checks, or subscription lifecycle states.
methodology
agent-ready 01 Contract spine
02 Implementation phases
03 Validation gates
04 Prompt handoff
Executable packet spine
The files or runtime artifacts a fresh agent must read or produce before claiming progress.
- BUILDPRINT.md
- CONTRACTS.md
- README.md
- SPEC.md
- TARGET_STACK_ADAPTERS.md
- TEST_MATRIX.md
- proof/dist/src/billing/entitlements.js
- PLAN.md
- VALIDATION_TEMPLATE.md
- checks/acceptance.md
Proof gates
Checks that prevent a vague implementation from being reported as complete.
- ✓Webhook signatures are verified
- ✓Portal access requires auth
- ✓Entitlements check server state
- ✓Lifecycle tests cover updates/cancellations
Risks covered
Failure modes the Buildprint makes visible before an agent can hide them in “done”.
- ⚠Webhook replay bugs
- ⚠Payment state drift
- ⚠Premium access without active subscription
What this ships
01
Checkout sessions
02
Customer portal
03
Webhook verification
04
Subscription state
05
Entitlement guards
Validation evidence
For newer phase-flow Buildprints, this names replay or outcome evidence. For older registry entries, it lists the included validation checks.
- Webhook signatures are verified
- Portal access requires auth
- Entitlements check server state
- Lifecycle tests cover updates/cancellations
Copyable agent prompt
Use the Agent Buildprint: Stripe Billing Extension.
Bootstrap it with `agb start https://agent-buildprint.com/buildprints/stripe-billing-extension/package.json ./my-build` or inspect the GitHub folder. Follow BUILDPRINT.md as the authority spine, read the supporting contracts/checks before implementation, preserve the stated non-goals and safety gates, and do not claim completion until the included validation checks pass.