fix: default resolveChain to mainnet, add resolveRpcUrl helper

- Add resolveRpcUrl() that consolidates RPC URL resolution:
  explicit flag → MPPX_RPC_URL env → RPC_URL env → undefined.
  Replaces 5 scattered inline patterns across cli.ts, tempo.ts,
  and utils.ts.

- resolveChain() now uses resolveRpcUrl() internally, so env vars
  are always respected. Default is tempoMainnet (not testnet).

- Add tests for both resolveRpcUrl and resolveChain defaults.

Author: brendanjryan

src/cli/cli.ts

@@ -32,6 +32,7 @@ import {
   printResponseHeaders,
   prompt,
   resolveChain,
+  resolveRpcUrl,
 } from './utils.js'
 
 const packageJson = createRequire(import.meta.url)('../../package.json') as {
@@ -516,8 +517,9 @@ const account = Cli.create('account', {
         ? link(`${explorerUrl}/address/${acct.address}`, acct.address)
         : acct.address
       console.log(pc.dim(`Address ${addrDisplay}`))
-      resolveChain(c.options)
-        .then((chain) => createClient({ chain, transport: http(c.options.rpcUrl) }))
+      const rpcUrl = resolveRpcUrl(c.options.rpcUrl)
+      resolveChain({ rpcUrl })
+        .then((chain) => createClient({ chain, transport: http(rpcUrl) }))
         .then((client) =>
           import('viem/tempo').then(({ Actions }) =>
             Actions.faucet.fund(client, { account: acct }).catch(() => {}),
@@ -629,8 +631,9 @@ const account = Cli.create('account', {
           return c.error({ code: 'ACCOUNT_NOT_FOUND', message: 'No account found.', exitCode: 69 })
       }
       const acct = privateKeyToAccount(key as `0x${string}`)
-      const chain = await resolveChain(c.options)
-      const client = createClient({ chain, transport: http(c.options.rpcUrl) })
+      const rpcUrl = resolveRpcUrl(c.options.rpcUrl)
+      const chain = await resolveChain({ rpcUrl })
+      const client = createClient({ chain, transport: http(rpcUrl) })
       console.log(`Funding "${accountName}" on ${chainName(chain)}`)
       try {
         const { Actions } = await import('viem/tempo')
@@ -711,8 +714,8 @@ const account = Cli.create('account', {
           })
         }
         const address = tempoEntry.wallet_address as Address
-        const rpcUrl = c.options.rpcUrl ?? (process.env.MPPX_RPC_URL || undefined)
-        const chain = rpcUrl ? await resolveChain({ rpcUrl }) : tempoMainnet
+        const rpcUrl = resolveRpcUrl(c.options.rpcUrl)
+        const chain = await resolveChain({ rpcUrl })
         const explorerUrl = chain.blockExplorers?.default?.url
         const addrDisplay = explorerUrl
           ? link(`${explorerUrl}/address/${address}`, address)
@@ -744,8 +747,8 @@ const account = Cli.create('account', {
           return c.error({ code: 'ACCOUNT_NOT_FOUND', message: 'No account found.', exitCode: 69 })
       }
       const acct = privateKeyToAccount(key as `0x${string}`)
-      const rpcUrl = c.options.rpcUrl ?? (process.env.MPPX_RPC_URL || undefined)
-      const chain = rpcUrl ? await resolveChain({ rpcUrl }) : tempoMainnet
+      const rpcUrl = resolveRpcUrl(c.options.rpcUrl)
+      const chain = await resolveChain({ rpcUrl })
       const explorerUrl = chain.blockExplorers?.default?.url
       const addrDisplay = explorerUrl
         ? link(`${explorerUrl}/address/${acct.address}`, acct.address)

src/cli/plugins/tempo.ts

@@ -24,6 +24,7 @@ import {
   link,
   pc,
   resolveChain,
+  resolveRpcUrl,
 } from '../utils.js'
 import { createPlugin, type Plugin } from './plugin.js'
 
@@ -67,7 +68,7 @@ export function tempo() {
         useTempoCliSign = true
         const tempoEntry = resolveTempoAccount(accountName)
         if (tempoEntry) {
-          const rpcUrl = options.rpcUrl ?? process.env.RPC_URL
+          const rpcUrl = resolveRpcUrl(options.rpcUrl)
           client = createClient({
             chain: await resolveChain({ rpcUrl }),
             transport: http(rpcUrl),
@@ -107,7 +108,7 @@ export function tempo() {
       } else account = privateKeyToAccount(privateKey as `0x${string}`)
 
       if (!useTempoCliSign && account) {
-        const rpcUrl = options.rpcUrl ?? process.env.RPC_URL
+        const rpcUrl = resolveRpcUrl(options.rpcUrl)
         client = createClient({
           chain: await resolveChain({ rpcUrl }),
           transport: http(rpcUrl),

src/cli/utils.test.ts

@@ -0,0 +1,64 @@
+import { tempo as tempoMainnet, tempoModerato } from 'viem/chains'
+import { afterEach, describe, expect, test, vi } from 'vp/test'
+
+import { resolveChain, resolveRpcUrl } from './utils.js'
+
+describe('resolveRpcUrl', () => {
+  afterEach(() => {
+    delete process.env.MPPX_RPC_URL
+    delete process.env.RPC_URL
+  })
+
+  test('returns explicit value when provided', () => {
+    process.env.MPPX_RPC_URL = 'https://env.example.com'
+    expect(resolveRpcUrl('https://explicit.example.com')).toBe('https://explicit.example.com')
+  })
+
+  test('falls back to MPPX_RPC_URL env var', () => {
+    process.env.MPPX_RPC_URL = 'https://mppx.example.com'
+    process.env.RPC_URL = 'https://rpc.example.com'
+    expect(resolveRpcUrl()).toBe('https://mppx.example.com')
+  })
+
+  test('falls back to RPC_URL env var when MPPX_RPC_URL is not set', () => {
+    process.env.RPC_URL = 'https://rpc.example.com'
+    expect(resolveRpcUrl()).toBe('https://rpc.example.com')
+  })
+
+  test('returns undefined when nothing is set', () => {
+    expect(resolveRpcUrl()).toBeUndefined()
+  })
+
+  test('trims whitespace from env vars', () => {
+    process.env.MPPX_RPC_URL = '  https://mppx.example.com  '
+    expect(resolveRpcUrl()).toBe('https://mppx.example.com')
+  })
+
+  test('skips empty MPPX_RPC_URL and falls back to RPC_URL', () => {
+    process.env.MPPX_RPC_URL = '  '
+    process.env.RPC_URL = 'https://rpc.example.com'
+    expect(resolveRpcUrl()).toBe('https://rpc.example.com')
+  })
+})
+
+describe('resolveChain', () => {
+  afterEach(() => {
+    delete process.env.MPPX_RPC_URL
+    delete process.env.RPC_URL
+  })
+
+  test('defaults to tempo mainnet when no rpcUrl is provided', async () => {
+    const chain = await resolveChain()
+    expect(chain.id).toBe(tempoMainnet.id)
+  })
+
+  test('defaults to tempo mainnet when rpcUrl is undefined', async () => {
+    const chain = await resolveChain({ rpcUrl: undefined })
+    expect(chain.id).toBe(tempoMainnet.id)
+  })
+
+  test('does not default to testnet', async () => {
+    const chain = await resolveChain()
+    expect(chain.id).not.toBe(tempoModerato.id)
+  })
+})

src/cli/utils.ts

@@ -221,17 +221,23 @@ export function fmtBalance(
   return `${dec ? `${formatted}.${dec}` : formatted} ${sym}`
 }
 
+/** Resolve RPC URL from explicit option, then MPPX_RPC_URL, then RPC_URL env vars. */
+export function resolveRpcUrl(explicit?: string | undefined): string | undefined {
+  return explicit ?? (process.env.MPPX_RPC_URL?.trim() || process.env.RPC_URL?.trim() || undefined)
+}
+
 export async function resolveChain(opts: { rpcUrl?: string | undefined } = {}): Promise<Chain> {
-  if (!opts.rpcUrl) return tempoModerato
+  const rpcUrl = resolveRpcUrl(opts.rpcUrl)
+  if (!rpcUrl) return tempoMainnet
   const { getChainId } = await import('viem/actions')
-  const chainId = await getChainId(createClient({ transport: http(opts.rpcUrl) }))
+  const chainId = await getChainId(createClient({ transport: http(rpcUrl) }))
   const allExports = Object.values(await import('viem/chains')) as unknown[]
   const candidates = allExports.filter(
     (c): c is Chain =>
       typeof c === 'object' && c !== null && 'id' in c && (c as Chain).id === chainId,
   )
   const found = candidates.find((c) => 'serializers' in c && c.serializers) ?? candidates[0]
-  if (!found) throw new Error(`Unknown chain ID ${chainId} from RPC ${opts.rpcUrl}`)
+  if (!found) throw new Error(`Unknown chain ID ${chainId} from RPC ${rpcUrl}`)
   return found
 }
 
@@ -306,7 +312,7 @@ export async function fetchBalanceLines(
 
   const mainnetClient = createClient({
     chain: tempoMainnet,
-    transport: http(process.env.MPPX_RPC_URL || undefined),
+    transport: http(resolveRpcUrl()),
   })
   const mainnetExplorerUrl = tempoMainnet.blockExplorers?.default?.url
   const mainnetResults = await Promise.all(