[Bug] Unexpected Opus Model Usage Despite Sonnet Selection

Bug Description

After the latest Claude Code update, I see two selectable models: Sonnet 4.5 (default) and Opus 4.1. I always choose Sonnet 4.5, but after several back-and-forth prompts I get a warning: “Opus limit has been reached.”

Why is this happening? I’m not using Opus and don’t want my usage counted against the more expensive Opus limits. I’m also concerned the system might be calling Opus in the background, because responses are sometimes slower and the quality feels different even when Sonnet is selected. Please confirm that requests are not being routed to Opus and ensure my usage is billed only to Sonnet 4.5.

Environment Info

• Platform: linux
• Terminal: wsl-Ubuntu-24.04
• Version: 2.0.2
• Feedback ID:

Errors

[{"error":"Error: Request was aborted.\n    at yP.makeRequest (file:///home/ubuntuadmin/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:1025:3864)\n    at process.processTicksAndRejections (node:internal/process/task_queues:105:5)","timestamp":"2025-10-01T06:39:23.544Z"},{"error":"AxiosError: Request failed with status code 401\n    at gN (file:///home/ubuntuadmin/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:715:1077)\n    at IncomingMessage.V0 (file:///home/ubuntuadmin/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:716:9955)\n    at IncomingMessage.emit (node:events:530:35)\n    at IncomingMessage.emit (node:domain:489:12)\n    at endReadableNT (node:internal/streams/readable:1698:12)\n    at process.processTicksAndRejections (node:internal/process/task_queues:90:21)\n    at xQ1.request (file:///home/ubuntuadmin/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:718:2088)\n    at process.processTicksAndRejections (node:internal/process/task_queues:105:5)\n    at async QI6 (file:///home/ubuntuadmin/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:1371:478)\n    at async Promise.all (index 0)\n    at async file:///home/ubuntuadmin/.claude/local/node_modules/@anthropic-ai/claude-code/cli.js:1357:12885","timestamp":"2025-10-01T22:54:24.193Z"}]