fix(web): allow switching away from Ultrathink effort without manual prompt editing

When Ultrathink was active, the effort dropdown was fully disabled,
requiring the user to manually remove the "Ultrathink:" prefix from the
prompt. Now selecting a different effort level automatically strips the
prefix and applies the new effort.

Author: Marve10s

apps/web/src/components/chat/ClaudeTraitsPicker.browser.tsx

@@ -148,7 +148,7 @@ describe("ClaudeTraitsPicker", () => {
     }
   });
 
-  it("shows prompt-controlled Ultrathink state with disabled effort controls", async () => {
+  it("shows prompt-controlled Ultrathink state with selectable effort controls", async () => {
     const mounted = await mountPicker({
       effort: "high",
       model: "claude-opus-4-6",
@@ -166,8 +166,7 @@ describe("ClaudeTraitsPicker", () => {
       await vi.waitFor(() => {
         const text = document.body.textContent ?? "";
         expect(text).toContain("Effort");
-        expect(text).toContain("Remove Ultrathink from the prompt to change effort.");
-        expect(text).not.toContain("Fallback Effort");
+        expect(text).not.toContain("Remove Ultrathink from the prompt to change effort.");
       });
     } finally {
       await mounted.cleanup();

apps/web/src/components/chat/ClaudeTraitsPicker.tsx

@@ -107,7 +107,6 @@ export const ClaudeTraitsMenuContent = memo(function ClaudeTraitsMenuContentImpl
 
   const handleEffortChange = useCallback(
     (value: ClaudeCodeEffort) => {
-      if (ultrathinkPromptControlled) return;
       if (!value) return;
       const nextEffort = options.find((option) => option === value);
       if (!nextEffort) return;
@@ -119,6 +118,10 @@ export const ClaudeTraitsMenuContent = memo(function ClaudeTraitsMenuContentImpl
         onPromptChange(nextPrompt);
         return;
       }
+      if (ultrathinkPromptControlled) {
+        const stripped = prompt.replace(/\bultrathink\b:?\s*/i, "");
+        onPromptChange(stripped);
+      }
       setProviderModelOptions(
         threadId,
         PROVIDER,
@@ -151,14 +154,12 @@ export const ClaudeTraitsMenuContent = memo(function ClaudeTraitsMenuContentImpl
         <>
           <MenuGroup>
             <div className="px-2 pt-1.5 pb-1 font-medium text-muted-foreground text-xs">Effort</div>
-            {ultrathinkPromptControlled ? (
-              <div className="px-2 pb-1.5 text-muted-foreground/80 text-xs">
-                Remove Ultrathink from the prompt to change effort.
-              </div>
-            ) : null}
-            <MenuRadioGroup value={effort} onValueChange={handleEffortChange}>
+            <MenuRadioGroup
+              value={ultrathinkPromptControlled ? "ultrathink" : effort}
+              onValueChange={handleEffortChange}
+            >
               {options.map((option) => (
-                <MenuRadioItem key={option} value={option} disabled={ultrathinkPromptControlled}>
+                <MenuRadioItem key={option} value={option}>
                   {CLAUDE_EFFORT_LABELS[option]}
                   {option === defaultReasoningEffort ? " (default)" : ""}
                 </MenuRadioItem>

apps/web/src/components/chat/CompactComposerControlsMenu.browser.tsx

@@ -159,7 +159,7 @@ describe("CompactComposerControlsMenu", () => {
     }
   });
 
-  it("shows prompt-controlled Ultrathink messaging with disabled effort controls", async () => {
+  it("shows prompt-controlled Ultrathink state with selectable effort controls", async () => {
     const mounted = await mountMenu({
       model: "claude-opus-4-6",
       prompt: "Ultrathink:\nInvestigate this",
@@ -176,8 +176,7 @@ describe("CompactComposerControlsMenu", () => {
       await vi.waitFor(() => {
         const text = document.body.textContent ?? "";
         expect(text).toContain("Effort");
-        expect(text).toContain("Remove Ultrathink from the prompt to change effort.");
-        expect(text).not.toContain("Fallback Effort");
+        expect(text).not.toContain("Remove Ultrathink from the prompt to change effort.");
       });
     } finally {
       await mounted.cleanup();