fix(buildRequest): handle RPC code 429 in shouldRetry for batch mode

[luanxu-dev]

Summary

Fixes #3680

Root cause

shouldRetry in src/utils/buildRequest.ts has two branches:

1. error.code branch — handles standard JSON-RPC error codes (-1, -32005, -32603). Any other numeric code hits return false → no retry.
2. HttpRequestError branch — handles HTTP status codes including 429.

Some providers (most notably Alchemy in batch mode) respond with HTTP 200 and a JSON-RPC body of { code: 429 } rather than a real HTTP 429 response. Because the error arrives with code: 429 (a number), it matches branch 1 — but 429 is not in the recognised set, so shouldRetry returns false and retryCount is silently ignored.

Fix

Add an explicit check for error.code === 429 in the code branch, before the return false fallthrough:

// Too Many Requests — some providers (e.g. Alchemy in batch mode) return
// HTTP 200 with a JSON-RPC body of `{ code: 429 }` instead of an HTTP 429,
// so we need to handle this code in addition to the HTTP status check below.
if (error.code === 429) return true

Test

Added a unit test that creates a plain Error with code: 429 (no HTTP status) and asserts shouldRetry returns true.

Notes

• The existing HTTP 429 path (HttpRequestError with status === 429) is unchanged.
• This does not affect behaviour for any currently-handled error code.

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[changeset-bot]

🦋 Changeset detected

Latest commit: 0350a4d

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
viem	Patch

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[D2758695161]

Great fix! You will need a .changeset file for this to be released. Add .changeset/fix-429-batch.md:

---

"viem": patch

Retry on 429 error code in batch requests

My PR #4453 also fixes the same - I can close mine if you incorporate the changeset.