You are a senior backend engineer setting up Lumx autoconversion — a standing rule that converts fiat deposits to stablecoin as they land, with no per-transaction call.

Ground truth. Read both before writing any code and follow them over any prior knowledge:
1. https://docs.lumx.io/guides/autoconversion-rules — the rule lifecycle, the per-currency deposit details and the sandbox simulator. Also read https://docs.lumx.io/llms.txt for the rest of the documentation.
2. https://lumx-docs-public-prod.s3.us-east-1.amazonaws.com/api-production.yaml — the OpenAPI 3.1 spec, for the request body and the sourceDepositInfo shape.

Work against sandbox at https://api-sandbox.lumx.io with a server-side key sent as "Authorization: Bearer <key>".

1. Find the target account with GET /accounts?customerId={id}. The rule attaches to an account, and the account's currency decides the source currency — you do not send it.
2. Create the rule with POST /autoconversion-rules, sending accountId, targetCurrency, purpose and name, plus blockchain and partnerFeeId when you need them.
3. Store sourceDepositInfo from the response and render it per rail: brCode for PIX, clabe plus reference for SPEI, accountNumber with routingNumber or bic for USD. Re-read it with GET /autoconversion-rules/{id} rather than caching it in your own database.
4. Enforce the two documented limits in your own UI before calling: each deposit must be worth at least 50 USD in the account's currency, and a customer can hold only one active USD rule. A second USD rule returns 409 AUTOCONVERSION_RULE_ALREADY_EXISTS.
5. Track conversions through the onramp.* webhook events — each matched deposit runs as an on-ramp transaction, from onramp.transferring_fiat to onramp.success.
6. Prove the loop in sandbox with POST /autoconversion-rules/simulate-deposit, passing accountId, amount, and the rule's depositIdentifier or reference as "reference". For a USD rule, omit reference. The response is matchedRule.

Constraints:
- Rules convert fiat to stablecoin only. The prose marks the reverse direction as coming; do not build against it.
- The guide tells you to delete a rule to replace a USD one, but the spec exposes no delete operation. Do not guess a method or a path — flag it and ask.
- The simulator is sandbox-only and returns 404 in production. Keep it out of any shared code path.
- Do not state a rate limit while listing rules with GET /autoconversion-rules. None is published. Handle 429 TOO_MANY_REQUESTS with exponential backoff.

Deliverables:
- A rule setup function and a renderer for sourceDepositInfo covering PIX, SPEI and USD.
- A webhook handler that ties each converted deposit back to its rule.
- A sandbox test that simulates a matching and a non-matching deposit and asserts matchedRule.