feat: add variants toggle (#6325)

Co-authored-by: Github Action <action@github.com>

packages/opencode/src/session/prompt.ts

@@ -90,6 +90,7 @@ export namespace SessionPrompt {
     noReply: z.boolean().optional(),
     tools: z.record(z.string(), z.boolean()).optional(),
     system: z.string().optional(),
+    variant: z.string().optional(),
     parts: z.array(
       z.discriminatedUnion("type", [
         MessageV2.TextPart.omit({
@@ -727,6 +728,7 @@ export namespace SessionPrompt {
       agent: agent.name,
       model: input.model ?? agent.model ?? (await lastModel(input.sessionID)),
       system: input.system,
+      variant: input.variant,
     }
 
     const parts = await Promise.all(
@@ -1267,6 +1269,7 @@ export namespace SessionPrompt {
     model: z.string().optional(),
     arguments: z.string(),
     command: z.string(),
+    variant: z.string().optional(),
   })
   export type CommandInput = z.infer<typeof CommandInput>
   const bashRegex = /!`([^`]+)`/g
@@ -1369,6 +1372,7 @@ export namespace SessionPrompt {
       model,
       agent: agentName,
       parts,
+      variant: input.variant,
     })) as MessageV2.WithParts
 
     Bus.publish(Command.Event.Executed, {