[Bug] Model fallback to claude-3-5-sonnet when requested model unavailable

Bug Description
"struggling once again with model selection. I told it to use gemini 3.0 and it fell back to unacceptable 2.5."

Environment Info

• Platform: darwin
• Terminal: zed
• Version: 2.1.20
• Feedback ID: 411b25af-df29-40f2-86e1-f9eb7a749134

Errors

[{"error":"Error: ENOENT: no such file or directory, scandir '/Library/Application Support/ClaudeCode/.claude/skills'\n    at readdirSync (unknown)\n    at <anonymous> (/$bunfs/root/claude:12:2063)\n    at oW (/$bunfs/root/claude:11:35584)\n    at readdirSync (/$bunfs/root/claude:12:2024)\n    at MIR (/$bunfs/root/claude:1758:380)\n    at MIR (/$bunfs/root/claude:1758:1350)\n    at <anonymous> (/$bunfs/root/claude:1758:4670)\n    at <anonymous> (/$bunfs/root/claude:1758:5401)\n    at A (/$bunfs/root/claude:11:7259)\n    at fw8 (/$bunfs/root/claude:4826:4342)","timestamp":"2026-01-27T05:03:33.864Z"},{"error":"Error: NON-FATAL: Lock acquisition failed for /Users/fred/.local/share/claude/versions/2.1.20 (expected in multi-process scenarios)\n    at mFR (/$bunfs/root/claude:3973:2091)\n    at sMA (/$bunfs/root/claude:3973:1202)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-01-27T05:03:33.893Z"},{"error":"Error: Plugin MCP server error - mcp-config-invalid: MCP server greptile invalid: Missing environment variables: GREPTILE_API_KEY\n    at YJT (/$bunfs/root/claude:1540:27820)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-01-27T05:03:33.954Z"},{"error":"Error: Plugin MCP server error - mcp-config-invalid: MCP server greptile invalid: Missing environment variables: GREPTILE_API_KEY\n    at YJT (/$bunfs/root/claude:1540:27820)\n    at async W (/$bunfs/root/claude:4197:13647)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-01-27T05:03:35.294Z"},{"error":"Error: Plugin MCP server error - mcp-config-invalid: MCP server greptile invalid: Missing environment variables: GREPTILE_API_KEY\n    at YJT (/$bunfs/root/claude:1540:27820)\n    at async J (/$bunfs/root/claude:4197:14163)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-01-27T05:03:35.294Z"},{"error":"Error: 400 {\"type\":\"error\",\"error\":{\"type\":\"invalid_request_error\",\"message\":\"output_config: Extra inputs are not permitted\"},\"request_id\":\"req_011CXXJEhHEtrKuXzvMcmQYi\"}\n    at generate (/$bunfs/root/claude:145:37631)\n    at makeRequest (/$bunfs/root/claude:162:5435)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-01-27T05:03:35.626Z"},{"error":"SyntaxError: JSON Parse error: Unexpected identifier \"API\"\n    at <parse> (:0)\n    at parse (unknown)\n    at <anonymous> (/$bunfs/root/claude:70:855)\n    at A (/$bunfs/root/claude:11:7259)\n    at Wt_ (/$bunfs/root/claude:1540:40110)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-01-27T05:03:35.627Z"},{"error":"Error: Command failed: /Users/fred/.local/share/claude/versions/2.1.20 --ripgrep --hidden --glob !.git --glob !.svn --glob !.hg --glob !.bzr --max-columns 500 -i -l RKHS|reproducing kernel --glob *.md /Users/fred\nrg: /Users/fred/Library/Caches/com.apple.ap.adprivacyd: Operation not permitted (os error 1)\nrg: /Users/fred/Library/Trial: Operation not permitted (os error 1)\nrg: /Users/fred/Library/Mail: Operation not permitted (os error 1)\nrg: /Users/fred/Library/com.apple.aiml.instrumentation: Operation not permitted (os error 1)\nrg: /Users/fred/Library/Sharing: Operation not permitted (os error 1)\nrg: /Users/fred/Library/HomeKit: Operation not permitted (os error 1)\nrg: /Users/fred/Library/Messages: Operation not permitted (os error 1)\nrg: /Users/fred/Library/Calendars: Operation not permitted (os error 1)\nrg: /Users/fred/Library/Biome: Operation not permitted (os error 1)\nrg: /Users/fred/Library/Safari: Operation not permitted (os error 1)\nrg: /Users/fred/Library/Accounts: Operation not permitted (os error 1)\nrg: /Users/fred/Library/Caches/com.apple.homed: Operation not permitted (os error 1)\nrg: /Users/fred/Library/Autosave Information: Operation not permitted (os error 1)\nrg: /Users/fred/Library/Daemon Containers: Operation not permitted (os error 1)\nrg: /Users/fred/Library/Assistant/SiriVocabulary: Operation not permitted (os error 1)\nrg: /Users/fred/Library/DuetExpertCenter: Operation not permitted (os error 1)\nrg: /Users/fred/Library/AppleMediaServices: Operation not permitted (os error 1)\nrg: /Users/fred/Library/Caches/FamilyCircle: Operation not permitted (os error 1)\nrg: /Users/fred/Library/Cookies: Operation not permitted (os error 1)\nrg: /Users/fred/Library/Metadata/com.apple.IntelligentSuggestions: Operation not permitted (os error 1)\nrg: /Users/fred/Library/Metadata/CoreSpotlight: Operation not permitted (os error 1)\nrg: /Users/fred/Library/Application Support/CallHistoryDB: Operation not permitted (os error 1)\nrg: /Users/fred…

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