refactor: improve error response for non-available models (#298)

scripts/system-check.ts

@@ -58,6 +58,31 @@ function parseOptions(argv: string[]): CliOptions {
   return options
 }
 
+export function formatReachabilityFailureDetail(
+  endpoint: string,
+  status: number,
+  responseBody: string,
+  request: {
+    transport: string
+    requestedModel: string
+    resolvedModel: string
+  },
+): string {
+  const compactBody = responseBody.trim().replace(/\s+/g, ' ').slice(0, 240)
+  const base = `Unexpected status ${status} from ${endpoint}.`
+  const bodySuffix = compactBody ? ` Body: ${compactBody}` : ''
+
+  if (request.transport !== 'codex_responses' || status !== 400) {
+    return `${base}${bodySuffix}`
+  }
+
+  if (!/not supported.*chatgpt account/i.test(responseBody)) {
+    return `${base}${bodySuffix}`
+  }
+
+  return `${base}${bodySuffix} Hint: model alias "${request.requestedModel}" resolved to "${request.resolvedModel}", which this ChatGPT account does not currently allow. Try "codexplan" or another entitled Codex model.`
+}
+
 function checkNodeVersion(): CheckResult {
   const raw = process.versions.node
   const major = Number(raw.split('.')[0] ?? '0')
@@ -284,6 +309,7 @@ async function checkBaseUrlReachability(): Promise<CheckResult> {
         headers['chatgpt-account-id'] = credentials.accountId
       }
       headers['Content-Type'] = 'application/json'
+      headers.originator = 'openclaude'
       method = 'POST'
       body = JSON.stringify({
         model: request.resolvedModel,
@@ -315,7 +341,17 @@ async function checkBaseUrlReachability(): Promise<CheckResult> {
       return pass('Provider reachability', `Reached ${endpoint} (status ${response.status}).`)
     }
 
-    return fail('Provider reachability', `Unexpected status ${response.status} from ${endpoint}.`)
+    const responseBody = await response.text().catch(() => '')
+    const detail = formatReachabilityFailureDetail(
+      endpoint,
+      response.status,
+      responseBody,
+      request,
+    )
+    return fail(
+      'Provider reachability',
+      detail,
+    )
   } catch (error) {
     const message = error instanceof Error ? error.message : String(error)
     return fail('Provider reachability', `Failed to reach ${endpoint}: ${message}`)
@@ -504,6 +540,8 @@ async function main(): Promise<void> {
   }
 }
 
-await main()
+if (import.meta.main) {
+  await main()
+}
 
 export {}