# AGENTS.md — Build guide for Sellfy

## Project scope
Create a small digital-file storefront using Stripe Checkout, verify payment webhooks and give buyers expiring download links. Add an operator view for resend and refund-status reconciliation.

Catalogue verdict: kinda. The core loop is buildable, but a dependable replacement becomes a real weekend or multi-day project. For Sellfy, sell digital files and simple subscriptions from a user-owned storefront. The hard boundary is payments, hosted delivery, email, print-on-demand, upsells, and support, plus payments, tax, distribution, and operations.
Use the implementation prompt below to define the deliverable. Complete each phase's acceptance checks before extending the scope.

## Working agreement
- Inspect the repository and its existing instructions before choosing paths, dependencies or commands. Keep one coherent stack and explain changes to the proposed architecture.
- Plan a vertical slice that accepts a real input and produces the useful output described below. Persist only the state the prompt calls for; respect memory-only and upstream-managed workflows. Use fixtures only when they are clearly labelled.
- After scaffolding, document the actual install, development, check and build commands in README and keep them synchronized with the package or project manifest. Do not report commands as successful unless they ran.
- Work in small steps. At handoff, list implemented flows, checks actually performed, remaining blockers, and any credentials or provider setup the owner must supply.
- Do not publish, spend money, contact customers, delete source data or run irreversible migrations without the project owner's authorization.

## Prerequisites
- A supported Node release, PostgreSQL, HTTPS for a shared deployment, and a backup destination. Begin with one workspace and explicit owner/member permissions. Stripe integration requires the account keys, verified webhook secret and public HTTPS endpoint; start with sandbox fixtures before live payments.
- Implementation components: Next.js App Router and TypeScript for server-rendered pages and validated mutations. PostgreSQL with Drizzle migrations; Better Auth sessions for a small private workspace.
- Scope boundary: Tax determination, print-on-demand and advanced subscription lifecycle rules are separate scope.

## Stack and architecture
- Next.js App Router and TypeScript for server-rendered pages and validated mutations.
- PostgreSQL with Drizzle migrations; Better Auth sessions for a small private workspace.
- Domain model: digital products, price snapshots, checkout sessions, orders, entitlements and download receipts

## Security and data integrity
- Authorize every record read and mutation on the server using its workspace membership; validate payloads, protect mutations against CSRF, and escape user-authored HTML.
- Correctness boundary: A successful redirect does not grant access; files remain private and repeated payment events do not create duplicate entitlements.
- Commit related database changes in one transaction. Use version checks for competing edits and an outbox for external notifications; retry delivery independently of saving the record.
- Export versioned JSON plus attachments and a readable CSV summary. Restore into a separate database and compare record IDs and attachment checksums before switching.

## Agent implementation rules
- Project rule — data model: digital products, price snapshots, checkout sessions, orders, entitlements and download receipts
- Project rule — preserve this invariant: A successful redirect does not grant access; files remain private and repeated payment events do not create duplicate entitlements.
- Project rule — acceptance evidence: Replay a paid webhook and deliver one order; a revoked entitlement cannot generate another signed download URL.

## Optional agent skills and references
- Optional external skill: [vercel-react-best-practices](https://github.com/vercel-labs/agent-skills/blob/main/skills/react-best-practices/SKILL.md) — Improve React and Next.js data fetching, rendering, bundle size and server performance. Review its instructions and compatibility before use; it does not grant deployment, data-access or publication permission.
- Optional external skill: [supabase-postgres-best-practices](https://github.com/supabase/agent-skills/blob/main/skills/supabase-postgres-best-practices/SKILL.md) — Review PostgreSQL schemas, queries, indexes, pooling, concurrency and row-level security. Review its instructions and compatibility before use; it does not grant deployment, data-access or publication permission.
- Optional external skill: [web-design-guidelines](https://github.com/vercel-labs/agent-skills/blob/main/skills/web-design-guidelines/SKILL.md) — Review web interfaces for accessibility, keyboard focus, forms, navigation and interaction quality. Review its instructions and compatibility before use; it does not grant deployment, data-access or publication permission.
- Optional external skill: [stripe-best-practices](https://github.com/stripe/ai/blob/main/skills/stripe-best-practices/SKILL.md) — Plan Stripe checkout, subscriptions, webhooks, platform payments and secure API integration. Review its instructions and compatibility before use; it does not grant deployment, data-access or publication permission.

Read the linked SKILL.md and its dependencies before adding a skill. Select only the skills matching this project's runtime and task; their documentation does not supply API access, credentials or approval to perform external actions. Pin the reviewed revision where the tool supports it. Follow the chosen agent's documented project-level installation mechanism.

## Distribution ideas
These are optional planning notes. Obtain the owner's approval before publishing or contacting anyone.
- Demonstrate the actual Sellfy-inspired workflow with owned or clearly labeled sample data: Create a small digital-file storefront using Stripe Checkout, verify payment webhooks and give buyers expiring download links. Add an operator view for resend and refund-status reconciliation.
- Publish a reproducible walkthrough with this observable result: Replay a paid webhook and deliver one order; a revoked entitlement cannot generate another signed download URL.
- Explain who can operate this scoped tool, its setup and ongoing costs, and these remaining product gaps: Tax determination, print-on-demand and advanced subscription lifecycle rules are separate scope. Avoid guaranteed savings, performance scores or implied endorsement.

## Engineering roadmap
1. Phase 1 — Scope and fixtures. Implement this bounded workflow: Create a small digital-file storefront using Stripe Checkout, verify payment webhooks and give buyers expiring download links. Add an operator view for resend and refund-status reconciliation. Record prerequisites, select representative user-owned fixtures and document the unsupported features: Tax determination, print-on-demand and advanced subscription lifecycle rules are separate scope.
2. Phase 2 — Durable model. Model digital products, price snapshots, checkout sessions, orders, entitlements and download receipts Add migrations or a versioned document format, explicit validation, stable IDs and a visible import-error report. Preserve this rule: A successful redirect does not grant access; files remain private and repeated payment events do not create duplicate entitlements.
3. Phase 3 — Complete the first useful path. Implement the workflow's input, review and output interface, with clear controls and explicit empty/error states. Commit related database changes in one transaction. Use version checks for competing edits and an outbox for external notifications; retry delivery independently of saving the record.
4. Phase 4 — Permissions and integration failure. Authorize every record read and mutation on the server using its workspace membership; validate payloads, protect mutations against CSRF, and escape user-authored HTML. Request integration credentials and permissions only for the enabled feature; show a disconnected state instead of mock results.
5. Phase 5 — Portable handoff. Export versioned JSON plus attachments and a readable CSV summary. Restore into a separate database and compare record IDs and attachment checksums before switching. Include setup, operating limits, fixture walkthrough and shutdown/restart instructions in the README.
6. Phase 6 — Acceptance scenarios. Replay a paid webhook and deliver one order; a revoked entitlement cannot generate another signed download URL. Repeat the workflow after restart and with a denied permission or unavailable dependency; show recoverable failure rather than a success placeholder.

## Paid-product capabilities outside this build
- payments, hosted delivery, email, print-on-demand, upsells, and support
- marketplace discovery
- tax remittance
- fraud operations
- advanced course and community tooling

## Implementation prompt
WORKING SLICE
Create a small digital-file storefront using Stripe Checkout, verify payment webhooks and give buyers expiring download links. Add an operator view for resend and refund-status reconciliation.

Build this scoped Sellfy-inspired workflow with a documented data model and visible failure states.

Architecture
- Next.js App Router and TypeScript for server-rendered pages and validated mutations.
- PostgreSQL with Drizzle migrations; Better Auth sessions for a small private workspace.

Prerequisites and limits
A supported Node release, PostgreSQL, HTTPS for a shared deployment, and a backup destination. Begin with one workspace and explicit owner/member permissions. Stripe integration requires the account keys, verified webhook secret and public HTTPS endpoint; start with sandbox fixtures before live payments.
Outside this release: Tax determination, print-on-demand and advanced subscription lifecycle rules are separate scope.

Data model and correctness
digital products, price snapshots, checkout sessions, orders, entitlements and download receipts
Invariant: A successful redirect does not grant access; files remain private and repeated payment events do not create duplicate entitlements.
Commit related database changes in one transaction. Use version checks for competing edits and an outbox for external notifications; retry delivery independently of saving the record.

Security and privacy
Authorize every record read and mutation on the server using its workspace membership; validate payloads, protect mutations against CSRF, and escape user-authored HTML.

Recovery and export
Export versioned JSON plus attachments and a readable CSV summary. Restore into a separate database and compare record IDs and attachment checksums before switching.

Implementation order
1. Phase 1 — Scope and fixtures. Implement this bounded workflow: Create a small digital-file storefront using Stripe Checkout, verify payment webhooks and give buyers expiring download links. Add an operator view for resend and refund-status reconciliation. Record prerequisites, select representative user-owned fixtures and document the unsupported features: Tax determination, print-on-demand and advanced subscription lifecycle rules are separate scope.
2. Phase 2 — Durable model. Model digital products, price snapshots, checkout sessions, orders, entitlements and download receipts Add migrations or a versioned document format, explicit validation, stable IDs and a visible import-error report. Preserve this rule: A successful redirect does not grant access; files remain private and repeated payment events do not create duplicate entitlements.
3. Phase 3 — Complete the first useful path. Implement the workflow's input, review and output interface, with clear controls and explicit empty/error states. Commit related database changes in one transaction. Use version checks for competing edits and an outbox for external notifications; retry delivery independently of saving the record.
4. Phase 4 — Permissions and integration failure. Authorize every record read and mutation on the server using its workspace membership; validate payloads, protect mutations against CSRF, and escape user-authored HTML. Request integration credentials and permissions only for the enabled feature; show a disconnected state instead of mock results.
5. Phase 5 — Portable handoff. Export versioned JSON plus attachments and a readable CSV summary. Restore into a separate database and compare record IDs and attachment checksums before switching. Include setup, operating limits, fixture walkthrough and shutdown/restart instructions in the README.
6. Phase 6 — Acceptance scenarios. Replay a paid webhook and deliver one order; a revoked entitlement cannot generate another signed download URL. Repeat the workflow after restart and with a denied permission or unavailable dependency; show recoverable failure rather than a success placeholder.

Acceptance
Replay a paid webhook and deliver one order; a revoked entitlement cannot generate another signed download URL.
Use real source data or clearly labeled fixtures. Explain unsupported input and provider failures; do not fabricate analytics, delivery receipts, accuracy claims or security guarantees.

Optional agent guidance
Optional external skill: [vercel-react-best-practices](https://github.com/vercel-labs/agent-skills/blob/main/skills/react-best-practices/SKILL.md) — Improve React and Next.js data fetching, rendering, bundle size and server performance. Review its instructions and compatibility before use; it does not grant deployment, data-access or publication permission.
Optional external skill: [supabase-postgres-best-practices](https://github.com/supabase/agent-skills/blob/main/skills/supabase-postgres-best-practices/SKILL.md) — Review PostgreSQL schemas, queries, indexes, pooling, concurrency and row-level security. Review its instructions and compatibility before use; it does not grant deployment, data-access or publication permission.
Optional external skill: [web-design-guidelines](https://github.com/vercel-labs/agent-skills/blob/main/skills/web-design-guidelines/SKILL.md) — Review web interfaces for accessibility, keyboard focus, forms, navigation and interaction quality. Review its instructions and compatibility before use; it does not grant deployment, data-access or publication permission.
Optional external skill: [stripe-best-practices](https://github.com/stripe/ai/blob/main/skills/stripe-best-practices/SKILL.md) — Plan Stripe checkout, subscriptions, webhooks, platform payments and secure API integration. Review its instructions and compatibility before use; it does not grant deployment, data-access or publication permission.
Project rule — data model: digital products, price snapshots, checkout sessions, orders, entitlements and download receipts
Project rule — preserve this invariant: A successful redirect does not grant access; files remain private and repeated payment events do not create duplicate entitlements.
Project rule — acceptance evidence: Replay a paid webhook and deliver one order; a revoked entitlement cannot generate another signed download URL.

## Completion evidence
Demonstrate the prompt's acceptance scenarios against the scoped workflow. Include setup from a clean checkout and failure recovery. Check persistence across restart and export/restore only for the state the prompt says to store; for memory-only tools, confirm that temporary content is discarded as specified. Record actual results and remaining limitations. A detailed plan alone does not establish a working replacement.