[Bug] Vertex AI provider defaults to Claude 3.5 Sonnet 4.5 instead of latest 4.6

Bug Description
When I enter /model sonnet on vertex it sets it to Sonnet 4.5 and lists it as a custom model versus when I do the same on my Anthropic seat it sets it to Sonnet 4.6. I suspect something is not set correctly on Vertex version.

Environment Info

• Platform: darwin
• Terminal: Apple_Terminal
• Version: 2.1.78
• Feedback ID: d120ecfa-587b-416f-b654-500840588beb

Errors

[{"error":"Error: Failed to delete keychain entry\n    at Fa7 (/$bunfs/root/src/entrypoints/cli.js:4205:8197)\n    at async OY9 (/$bunfs/root/src/entrypoints/cli.js:7119:698)\n    at async MIq (/$bunfs/root/src/entrypoints/cli.js:7119:596)\n    at async oQ_ (/$bunfs/root/src/entrypoints/cli.js:2625:2201)\n    at async $A_ (/$bunfs/root/src/entrypoints/cli.js:2649:5381)\n    at async <anonymous> (/$bunfs/root/src/entrypoints/cli.js:2669:2729)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-03-18T15:42:03.615Z"}]