Contrails - Preserve your coding agent trails

An agent tried the obvious fix, ran the tests, realized it didn't work, and self-corrected. All of that reasoning - including the wrong turns - is now part of the repo.

contrails/Fixing duplicate payment charges on retry.md

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Fixing duplicate payment charges on retry.md

node_modules

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tests

package.json

tsconfig.json

# Fixing duplicate payment charges on retry

- **Created:** 
- **Agent:** GitHub Copilot
- **Model:** claude-opus-4.6

---------------------------------------

## 🧑 User

Can you please fix the duplicate charge bug on payment retry?

**Attachments:** `charge.ts`, `stripe.ts`

---------------------------------------

## 🤖 Assistant

Let me look into this.

### Tool Calls
- **readFile**: `charge.ts`, `stripe.ts`, `Order.ts`
- **editFile**: `charge.ts` - added status check guard
- **runTerminal**: `npm test`

1 test failed - race condition: two concurrent requests
both read `pending` before either writes.

### Tool Calls
- **readFile**: `Order.ts`
- **editFile**: `charge.ts` - added DB-level lock
- **runTerminal**: `npm test`

1 test failed - same issue, lock doesn't cover the
webhook path.

### Tool Calls
- **readFile**: `stripe.ts`, `Order.ts`
- **editFile**: `charge.ts` - atomic status transition
- **editFile**: `stripe.ts` - skip already-processed
- **runTerminal**: `npm test`

✅ All tests pass.

**Summary:**
The duplicate charge happened because retry
created a second PaymentIntent while the first was still
in flight. A simple status check didn't work because both
requests read `pending` at the same time. The fix was an
atomic `pending → processing` transition so only one
request can proceed, plus an idempotency key so Stripe
deduplicates on their end.

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