[BUG] "Buy credits" button permanently disabled - Free tier account incorrectly shows $500 limit, HTTP 429 errors on billing page

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

The "Buy credits" button on the Anthropic Console billing modal
(console.anthropic.com / platform.claude.com) is permanently disabled,
preventing me from purchasing API credits. I cannot use the Claude API
or Claude Code with API key authentication as a result.

Note: This is reported here because I've been unable to get a resolution
through the support channel (received only AI-generated responses
suggesting generic troubleshooting that did not resolve the issue).
The support team has confirmed the account configuration appears
inconsistent but stated they cannot inspect or modify backend state.

Account anomaly identified:

• Account status: Free tier (no successful credit purchases ever made)
• Credit balance: $0.00
• Yet monthly spend limit displays as $500 (which should correspond to Tier 2)

This inconsistency was acknowledged three times by support but not resolved.

What Should Happen?

The "Buy credits" button should be enabled when all required fields are
correctly filled, allowing me to purchase API credits successfully.
The displayed tier and spend limit should be consistent with the actual
account state.

Error Messages/Logs

Browser console errors on the billing page:

Failed to load resource: the server responded with a status of 429 ()
  sentry?o=1158394&p=4506240373030912:1

(Multiple repeated 429 Too Many Requests errors during billing page load)

UI symptom:
- "Buy credits" button rendered with disabled state (greyed out)
- Estimated tax and total amount calculate correctly (USD 22.00 for USD 20 credits)
- All form fields validate successfully
- No visible error message shown to the user

Account state mismatch:
- Settings → Limits shows "Free tier"  
- Dashboard shows "$500 monthly limit"
- Credit balance: $0.00
- No prior successful payments

Steps to Reproduce

1. Log in to console.anthropic.com (or platform.claude.com)
2. Navigate to billing / "Buy credits"
3. Select any credit amount (tested $5, $20)
4. Enter complete billing address (Korea, valid postal code)
5. Select registered Visa credit card

(same card works fine for active Claude Max subscription)

1. Leave Business Registration Number empty (individual user)
2. Verify estimated tax and total amount calculate correctly
3. Observe: "Buy credits" button remains disabled (greyed out)
4. Open browser DevTools → Console: HTTP 429 errors visible

Troubleshooting already attempted (all unsuccessful):

• Cleared browser cache and cookies
• Tested in incognito mode with all extensions disabled
• Tested in multiple browsers (Chrome, Edge)
• Logged out completely and logged back in
• Accessed billing page via direct URL

(platform.claude.com/settings/billing)

• Tried minimum credit amount ($5)
• No VPN, no IP masking, no firewall restrictions
• Verified no pending account verification requirements
• Confirmed card is valid (works for Claude Max subscription billing)

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

N/A — This issue is not specific to Claude Code itself, but to the Anthropic Console billing system that prevents obtaining the API key credits required to use Claude Code with API authentication.

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

WSL (Windows Subsystem for Linux)

Additional Information

_No response_