[Bug] "Ultrathink" keyword mistaken for feature request instead of literal string

Bug Description
I used the special keyword "Ultrathink" and agent confused it with an ultrathinking feature that I want it to build.

Environment Info

• Platform: darwin
• Terminal: iTerm.app
• Version: 2.0.36
• Feedback ID: ed58e26f-354f-4612-9aa8-a380597c1b58

Errors

[{"error":"Error\n    at Zw (/$bunfs/root/claude:54:1142)\n    at <anonymous> (/$bunfs/root/claude:59:10074)\n    at emit (node:events:92:22)\n    at endReadableNT (internal:streams/readable:861:50)\n    at processTicksAndRejections (native:7:39)\n    at request (/$bunfs/root/claude:61:2146)\n    at processTicksAndRejections (native:7:39)","timestamp":"2025-11-08T15:27:52.856Z"},{"error":"Error: Lock file is already being held\n    at <anonymous> (/$bunfs/root/claude:82:11838)\n    at O (/$bunfs/root/claude:81:5167)\n    at <anonymous> (node:fs:243:13)\n    at processTicksAndRejections (native:7:39)","timestamp":"2025-11-08T15:28:01.155Z"},{"error":"Error: Lock file is already being held\n    at <anonymous> (/$bunfs/root/claude:82:11838)\n    at O (/$bunfs/root/claude:81:5167)\n    at <anonymous> (node:fs:243:13)\n    at processTicksAndRejections (native:7:39)","timestamp":"2025-11-08T15:29:51.861Z"},{"error":"Error: Language not supported while highlighting code, falling back to markdown: \n    at oJ (/$bunfs/root/claude:1003:4395)\n    at <anonymous> (/$bunfs/root/claude:1003:4117)\n    at map (native:1:11)\n    at CI (/$bunfs/root/claude:1003:4109)\n    at fQB (/$bunfs/root/claude:1687:6605)\n    at B7 (/$bunfs/root/claude:101:19663)\n    at T2 (/$bunfs/root/claude:103:42806)\n    at rF (/$bunfs/root/claude:103:38344)\n    at c1 (/$bunfs/root/claude:103:38272)\n    at ZJ (/$bunfs/root/claude:103:38126)","timestamp":"2025-11-08T15:33:51.785Z"},{"error":"Error: Lock file is already being held\n    at <anonymous> (/$bunfs/root/claude:82:11838)\n    at O (/$bunfs/root/claude:81:5167)\n    at <anonymous> (node:fs:243:13)\n    at processTicksAndRejections (native:7:39)","timestamp":"2025-11-08T15:33:56.275Z"}]