fix(opencode): keep user message variants scoped to model (#21332)

packages/app/src/components/prompt-input/submit.test.ts

@@ -146,7 +146,7 @@ beforeAll(async () => {
           add: (value: {
             directory?: string
             sessionID?: string
-            message: { agent: string; model: { providerID: string; modelID: string }; variant?: string }
+            message: { agent: string; model: { providerID: string; modelID: string; variant?: string } }
           }) => {
             optimistic.push(value)
             optimisticSeeded.push(
@@ -310,8 +310,7 @@ describe("prompt submit worktree selection", () => {
     expect(optimistic[0]).toMatchObject({
       message: {
         agent: "agent",
-        model: { providerID: "provider", modelID: "model" },
-        variant: "high",
+        model: { providerID: "provider", modelID: "model", variant: "high" },
       },
     })
   })

packages/app/src/components/prompt-input/submit.ts

@@ -121,8 +121,7 @@ export async function sendFollowupDraft(input: FollowupSendInput) {
     role: "user",
     time: { created: Date.now() },
     agent: input.draft.agent,
-    model: input.draft.model,
-    variant: input.draft.variant,
+    model: { ...input.draft.model, variant: input.draft.variant },
   }
 
   const add = () =>