Anthropic API Authentication Error: OAuth Not Supported

I'm using a corporate account. It's fully funded, and I've only just started using Claude Code with this account. There's no reason to think that it should have run out of quota.

Bug Description
I keep getting this error any time I ask claude code to do something:

⏺ Claude Opus limit reached, now using Sonnet 4
⎿  API Error: 401 {"type":"error","error":{"type":"authentication_error","message":"OAuth authentication is currently not supported."}}

/agents

Environment Info

• Platform: darwin
• Terminal: intellij
• Version: 1.0.83
• Feedback ID: 255549df-3dfe-43cd-a58c-acdc25faa3a0

Errors

[{"error":"Error: 401 {\"type\":\"error\",\"error\":{\"type\":\"authentication_error\",\"message\":\"OAuth authentication is currently not supported.\"}}\n    at D6.generate (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:942:2449)\n    at sP.makeStatusError (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:959:2101)\n    at sP.makeRequest (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:959:5315)\n    at process.processTicksAndRejections (node:internal/process/task_queues:105:5)\n    at async KSB.sG1.showErrors (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:1875:24578)\n    at async sG1 (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:1875:13705)\n    at async KSB (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:1875:24429)\n    at async file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:1875:19524\n    at async cN0 (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:1875:5164)\n    at async V01 (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:1875:19494)","timestamp":"2025-08-18T18:52:24.987Z"},{"error":"Error: 401 {\"type\":\"error\",\"error\":{\"type\":\"authentication_error\",\"message\":\"OAuth authentication is currently not supported.\"}}\n    at D6.generate (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:942:2449)\n    at sP.makeStatusError (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:959:2101)\n    at sP.makeRequest (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:959:5315)\n    at process.processTicksAndRejections (node:internal/process/task_queues:105:5)\n    at async KSB.sG1.showErrors (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:1875:24578)\n    at async sG1 (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:1875:13705)\n    at async KSB (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:1875:24429)\n    at async file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:1875:19524\n    at async cN0 (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:1875:5164)\n    at async V01 (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:1875:19494)","timestamp":"2025-08-18T18:58:06.516Z"},{"error":"Error: 400 {\"type\":\"error\",\"error\":{\"type\":\"invalid_request_error\",\"message\":\"Your credit balance is too low to access the Anthropic API. Please go to Plans & Billing to upgrade or purchase credits.\"}}\n    at D6.generate (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:942:2414)\n    at sP.makeStatusError (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:959:2101)\n    at sP.makeRequest (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:959:5315)\n    at process.processTicksAndRejections (node:internal/process/task_queues:105:5)\n    at async CSB.sG1.maxRetries (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:1875:17451)\n    at async sG1 (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:1875:13705)\n    at async CSB (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:1875:17320)\n    at async Object.onChangeAPIKey (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:3379:2483)","timestamp":"2025-08-18T19:13:27.796Z"},{"error":"Error: 401 {\"type\":\"error\",\"error\":{\"type\":\"authentication_error\",\"message\":\"OAuth authentication is currently not supported.\"}}\n    at D6.generate (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:942:2449)\n    at sP.makeStatusError (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:959:2101)\n    at sP.makeRequest (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:959:5315)\n    at process.processTicksAndRejections (node:internal/process/task_queues:105:5)\n    at async KSB.sG1.showErrors (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:1875:24578)\n    at async sG1 (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:1875:13705)\n    at async KSB (file:///opt/homebrew/lib/node_modules/@anthropic-ai/claude-code/cli.js:1875:24429)\n    at async file:///opt/homebrew/lib/no

Note: Error logs were truncated.