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

packages/opencode/src/session/compaction.ts

@@ -228,7 +228,7 @@ When constructing the summary, try to stick to this template:
           sessionID: input.sessionID,
           mode: "compaction",
           agent: "compaction",
-          variant: userMessage.variant,
+          variant: userMessage.model.variant,
           summary: true,
           path: {
             cwd: ctx.directory,
@@ -295,7 +295,6 @@ When constructing the summary, try to stick to this template:
               format: original.format,
               tools: original.tools,
               system: original.system,
-              variant: original.variant,
             })
             for (const part of replay.parts) {
               if (part.type === "compaction") continue

packages/opencode/src/session/llm.ts

@@ -127,7 +127,9 @@ export namespace LLM {
     }
 
     const variant =
-      !input.small && input.model.variants && input.user.variant ? input.model.variants[input.user.variant] : {}
+      !input.small && input.model.variants && input.user.model.variant
+        ? input.model.variants[input.user.model.variant]
+        : {}
     const base = input.small
       ? ProviderTransform.smallOptions(input.model)
       : ProviderTransform.options({

packages/opencode/src/session/message-v2.ts

@@ -371,10 +371,10 @@ export namespace MessageV2 {
     model: z.object({
       providerID: ProviderID.zod,
       modelID: ModelID.zod,
+      variant: z.string().optional(),
     }),
     system: z.string().optional(),
     tools: z.record(z.string(), z.boolean()).optional(),
-    variant: z.string().optional(),
   }).meta({
     ref: "UserMessage",
   })

packages/opencode/src/session/prompt.ts

@@ -569,7 +569,7 @@ NOTE: At any point in time through this workflow you should feel free to ask the
           sessionID,
           mode: task.agent,
           agent: task.agent,
-          variant: lastUser.variant,
+          variant: lastUser.model.variant,
           path: { cwd: ctx.directory, root: ctx.worktree },
           cost: 0,
           tokens: { input: 0, output: 0, reasoning: 0, cache: { read: 0, write: 0 } },
@@ -967,17 +967,20 @@ NOTE: At any point in time through this workflow you should feel free to ask the
             : undefined
         const variant = input.variant ?? (ag.variant && full?.variants?.[ag.variant] ? ag.variant : undefined)
 
-        const info: MessageV2.Info = {
+        const info: MessageV2.User = {
           id: input.messageID ?? MessageID.ascending(),
           role: "user",
           sessionID: input.sessionID,
           time: { created: Date.now() },
           tools: input.tools,
           agent: ag.name,
-          model,
+          model: {
+            providerID: model.providerID,
+            modelID: model.modelID,
+            variant,
+          },
           system: input.system,
           format: input.format,
-          variant,
         }
 
         yield* Effect.addFinalizer(() =>
@@ -1436,7 +1439,7 @@ NOTE: At any point in time through this workflow you should feel free to ask the
               role: "assistant",
               mode: agent.name,
               agent: agent.name,
-              variant: lastUser.variant,
+              variant: lastUser.model.variant,
               path: { cwd: ctx.directory, root: ctx.worktree },
               cost: 0,
               tokens: { input: 0, output: 0, reasoning: 0, cache: { read: 0, write: 0 } },