# AGENTS.md — Build guide for Zencal

## Project scope
Publish one host's booking page with event lengths and optional payment, then confirm only when capacity/calendar/payment conditions are satisfied.

Catalogue verdict: kinda. The core loop is buildable, but a dependable replacement becomes a real weekend or multi-day project. For Zencal, publish booking pages and collect optional payments through a simple workflow. The hard boundary is calendar connections, payments, reminders, team access, and hosted reliability, plus calendar integrations and reliability.
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- Do not publish, spend money, contact customers, delete source data or run irreversible migrations without the project owner's authorization.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
- Runtime and tools: TypeScript, React, Node and PostgreSQL with a single authorized calendar adapter.
- Before starting: One calendar account with documented OAuth scopes, HTTPS callbacks, the host timezone and an always-on worker for reminders.

## Stack and architecture
- TypeScript, React, Node and PostgreSQL with a single authorized calendar adapter
- Data design: Store EventType, SlotHold, Booking, PaymentEvent and CalendarReceipt; define cancellation/refund policy and handle late payment without silently confirming an expired slot.
- Setup: One calendar account with documented OAuth scopes, HTTPS callbacks, the host timezone and an always-on worker for reminders

## Security and data integrity
- Store UTC instants plus the host IANA timezone and local availability rules. Recheck external busy time before reserving; serialize overlapping local reservations, and reconcile external creation failures without silently confirming.
- Start with free bookings before adding a hosted payment flow. Use verified payment events and calendar reconciliation; reminders and redirects cannot prove the booking succeeded.
- Keep secrets outside client bundles and exported projects; document what leaves the device and make retention/deletion controls visible.

## Agent implementation rules
- Project rule — domain: Store EventType, SlotHold, Booking, PaymentEvent and CalendarReceipt; define cancellation/refund policy and handle late payment without silently confirming an expired slot.
- Project rule — scope and recovery: Start with free bookings before adding a hosted payment flow. Use verified payment events and calendar reconciliation; reminders and redirects cannot prove the booking succeeded.
- Project rule — acceptance: A checkout completes after its slot hold expires and another guest reserves the time; do not double-book, show the conflict and route payment to an explicit refund/reschedule decision.
- Project rule — delivery: document real setup commands and permissions; do not claim a build, accuracy level, performance result or security certification that has not been demonstrated.

## Optional agent skills and references
- Recommended skill: [supabase-postgres-best-practices](https://github.com/supabase/agent-skills/blob/main/skills/supabase-postgres-best-practices/SKILL.md) — review this PostgreSQL domain schema, uniqueness constraints, transaction boundaries and access-scoped queries; Supabase hosting is not required. Follow the maintainer's installation instructions and match its requirements to the chosen runtime.
- Recommended skill: [web-design-guidelines](https://github.com/vercel-labs/agent-skills/blob/main/skills/web-design-guidelines/SKILL.md) — review keyboard access, focus, validation, error recovery and the readable work/review interface or HTML report. Follow the maintainer's installation instructions and match its requirements to the chosen runtime.
- Recommended skill: [stripe-best-practices](https://github.com/stripe/ai/blob/main/skills/stripe-best-practices/SKILL.md) — design the optional hosted checkout, verified webhook and entitlement/refund state transitions using the current Stripe integration guidance. Follow the maintainer's installation instructions and match its requirements to the chosen runtime.

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 this working slice using synthetic or explicitly authorized non-sensitive examples: Publish one host's booking page with event lengths and optional payment, then confirm only when capacity/calendar/payment conditions are satisfied.
- Share a synthetic example export and the acceptance walkthrough; keep real customer, health, financial and source data private: A checkout completes after its slot hold expires and another guest reserves the time; do not double-book, show the conflict and route payment to an explicit refund/reschedule decision.
- State the limits before asking someone to replace their existing tool: Start with free bookings before adding a hosted payment flow. Use verified payment events and calendar reconciliation; reminders and redirects cannot prove the booking succeeded.

## Engineering roadmap
1. Phase 1 — Pin the working slice and create its example input: Publish one host's booking page with event lengths and optional payment, then confirm only when capacity/calendar/payment conditions are satisfied. Confirm setup: One calendar account with documented OAuth scopes, HTTPS callbacks, the host timezone and an always-on worker for reminders.
2. Phase 2 — Implement persistence and write-time invariants before decorating the UI: Store EventType, SlotHold, Booking, PaymentEvent and CalendarReceipt; define cancellation/refund policy and handle late payment without silently confirming an expired slot.
3. Phase 3 — Connect the working view to real saved state. Store UTC instants plus the host IANA timezone and local availability rules. Recheck external busy time before reserving; serialize overlapping local reservations, and reconcile external creation failures without silently confirming.
4. Phase 4 — Expose the app-specific limits and recovery path in context: Start with free bookings before adding a hosted payment flow. Use verified payment events and calendar reconciliation; reminders and redirects cannot prove the booking succeeded.
5. Phase 5 — Walk through this concrete acceptance case and preserve its exported evidence: A checkout completes after its slot hold expires and another guest reserves the time; do not double-book, show the conflict and route payment to an explicit refund/reschedule decision. Finish the README and backup/restore instructions; report unfinished capabilities explicitly.

## Paid-product capabilities outside this build
- calendar connections, payments, reminders, team access, and hosted reliability
- multiple calendar providers
- team routing and round-robin
- payments
- timezone edge-case maturity

## Implementation prompt
Build the following focused alternative to Zencal. This is a deliberately limited personal or small-team substitute, not parity with the paid service.

WORKING SLICE
Publish one host's booking page with event lengths and optional payment, then confirm only when capacity/calendar/payment conditions are satisfied.

SETUP AND ARCHITECTURE
Use TypeScript, React, Node and PostgreSQL with a single authorized calendar adapter. Prerequisites: One calendar account with documented OAuth scopes, HTTPS callbacks, the host timezone and an always-on worker for reminders. Before integrating anything, record actual versions and permissions, plus model files or provider limits only where used, in the README; make unavailable dependencies visible rather than simulating success.

DOMAIN MODEL AND INVARIANTS
Store EventType, SlotHold, Booking, PaymentEvent and CalendarReceipt; define cancellation/refund policy and handle late payment without silently confirming an expired slot.

IMPLEMENTATION CONTRACT
Store UTC instants plus the host IANA timezone and local availability rules. Recheck external busy time before reserving; serialize overlapping local reservations, and reconcile external creation failures without silently confirming. Provide an input/setup view, the main work view, and a review/export view appropriate to this workflow. Preserve the last saved state if a job or save fails. Include empty, loading, permission-denied, partial and retryable-error states. Log identifiers and error categories without secret values or unnecessary private content.

APP-SPECIFIC BOUNDARY AND RECOVERY
Start with free bookings before adding a hosted payment flow. Use verified payment events and calendar reconciliation; reminders and redirects cannot prove the booking succeeded.

ACCEPTANCE SCENARIO
A checkout completes after its slot hold expires and another guest reserves the time; do not double-book, show the conflict and route payment to an explicit refund/reschedule decision. Also reopen the app after an interrupted operation, confirm the saved record/export remains inspectable, and document the recovery action. These are implementation acceptance requirements, not a claim that this guide has been tested.

DELIVERY
Deliver a runnable repository with migrations or project-format versioning, a non-sensitive example, environment/permission setup, the exact manual acceptance steps, and a backup/export-and-restore walkthrough. Implement the working slice before optional integrations; list any deferred paid-product capabilities honestly. Do not add capabilities outside the working slice just to resemble the original product.

PROJECT RULES FOR AGENTS.md
Keep the domain invariants above executable at the write boundary. Propose scope changes before adding providers or permissions. Never fabricate source evidence, publish results, identity matches or successful delivery. Preserve user originals and require an explicit confirmation for destructive changes or external publication.

## 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.