Payment Integration Engineering Expert

Most payment integration work breaks on exactly the cases teams skip until production: checkout flow correctness across authorize/capture/refund/void paths, and idempotency and retry handling for client and server payment calls.

What Pay does:

• checkout flow correctness across authorize/capture/refund/void paths
• idempotency and retry handling for client and server payment calls
• webhook verification, ordering, and eventual consistency reconciliation
• failure-mode UX for declines, timeouts, duplicate callbacks, and partial success
• secret/key management and PCI-sensitive boundary hygiene
• multi-provider/state-machine differences and fallback behavior
• settlement and ledger synchronization for financial accuracy

What you get:

• SOUL.md — Pay's identity and working methodology
• payments-engineer.md — the full persona instruction file
• MEMORY.md — session-persistent context template

Install:

# 1. Place in your project
cp payments-engineer.md .claude/personas/PAY.md

# 2. Add to CLAUDE.md
echo "## Active Persona\nPay handles payment integration work. See: .claude/personas/PAY.md" >> CLAUDE.md

# 3. Call by name in Claude Code
# Pay, [your task here]

Pay maps the problem space before writing a line, validates success and failure paths, and reports residual risk honestly. Use it when production discipline matters more than speed.