feat: flag 403 as non-deterministic error for fallback Transport

.changeset/warm-apes-reply.md

@@ -0,0 +1,5 @@
+---
+"viem": patch
+---
+
+Flagged 403 as non-deterministic error for `fallback` Transport.

src/utils/buildRequest.test.ts

@@ -646,6 +646,31 @@ describe('behavior', () => {
       expect(retryCount).toBe(3)
     })
 
+    test('non-deterministic HttpRequestError (403)', async () => {
+      let retryCount = -1
+      const server = await createHttpServer((_req, res) => {
+        retryCount++
+        res.writeHead(403, {
+          'Content-Type': 'application/json',
+        })
+        res.end(JSON.stringify({}))
+      })
+
+      await expect(() =>
+        buildRequest(request(server.url))({ method: 'eth_blockNumber' }),
+      ).rejects.toThrowErrorMatchingInlineSnapshot(`
+        "HTTP request failed.
+
+        Status: 403
+        URL: http://localhost
+        Request body: {\\"method\\":\\"eth_blockNumber\\"}
+
+        Details: Forbidden
+        Version: viem@1.0.2"
+      `)
+      expect(retryCount).toBe(3)
+    })
+
     test('non-deterministic HttpRequestError (408)', async () => {
       let retryCount = -1
       const server = await createHttpServer((_req, res) => {
@@ -814,6 +839,14 @@ describe('isDeterministicError', () => {
     ).toBe(false)
   })
 
+  test('HttpRequestError (403)', () => {
+    expect(
+      isDeterministicError(
+        new HttpRequestError({ body: {}, details: '', status: 403, url: '' }),
+      ),
+    ).toBe(false)
+  })
+
   test('HttpRequestError (408)', () => {
     expect(
       isDeterministicError(

src/utils/buildRequest.ts

@@ -37,6 +37,7 @@ export const isDeterministicError = (error: Error) => {
     )
   if (error instanceof HttpRequestError && error.status)
     return (
+      error.status !== 403 &&
       error.status !== 408 &&
       error.status !== 413 &&
       error.status !== 429 &&