Model Fallback Failure: Default Configuration Breaks Responsiveness

Bug Description
I am on the "max 200" plan, and have the model set to the default, which uses opus for a while then switches to sonnet. However, something is wrong. I have reduced the size of my claude.md and made sure the hooks were not abusing the api, but when model is set to default, claude code just stops responding altogether. Today I did not do much work, yet CC was unresponsive. I tried to switch to sonnet to force the issue, and this appears to have worked. CC is responding normally again. I get no warnings or messages like before, saying opus is used up, switching to sonnet, so it really feels like something is broken.

Also, I see below there's a password error, but I am not having any problems with auth in Claude Desktop for instance. It's been chugging along just fine on Sonnet. What does the below error even mean? Let me know if I'm meant to do something, and it would probably be good if CC's notifications were actually working like before.

Environment Info

• Platform: darwin
• Terminal: ghostty
• Version: 1.0.54
• Feedback ID: 131c88d3-707b-425e-b602-0217f01d51ab

Errors

[{"error":"Error: Command failed: security find-generic-password -a $USER -w -s \"Claude Code\"\nsecurity: SecKeychainSearchCopyNext: The specified item could not be found in the keychain.\n\n    at genericNodeError (node:internal/errors:983:15)\n    at wrappedFn (node:internal/errors:537:14)\n    at checkExecSyncError (node:child_process:924:11)\n    at execSync (node:child_process:996:15)\n    at DI (file:///Users/rcogley/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:730:2037)\n    at file:///Users/rcogley/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:640:41635\n    at Q (file:///Users/rcogley/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:542:14406)\n    at PF (file:///Users/rcogley/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:640:39420)\n    at $X (file:///Users/rcogley/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:640:38286)\n    at MB (file:///Users/rcogley/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:640:44255)","timestamp":"2025-07-17T04:51:54.818Z"}]