fix: find and add missing variant in synthetic messages

lib/messages/inject.ts

@@ -3,7 +3,7 @@ import type { Logger } from "../logger"
 import type { PluginConfig } from "../config"
 import { loadPrompt } from "../prompts"
 import { extractParameterKey, buildToolIdList, createSyntheticUserMessage } from "./utils"
-import { getLastUserMessage } from "../shared-utils"
+import { getLastUserMessage, findUserVariant } from "../shared-utils"
 
 const getNudgeString = (config: PluginConfig): string => {
     const discardEnabled = config.tools.discard.enabled
@@ -125,5 +125,6 @@ export const insertPruneToolContext = (
     if (!lastUserMessage) {
         return
     }
-    messages.push(createSyntheticUserMessage(lastUserMessage, prunableToolsContent))
+    const variant = findUserVariant(messages)
+    messages.push(createSyntheticUserMessage(lastUserMessage, prunableToolsContent, variant))
 }

lib/messages/utils.ts

@@ -6,7 +6,7 @@ import type { UserMessage } from "@opencode-ai/sdk"
 const SYNTHETIC_MESSAGE_ID = "msg_01234567890123456789012345"
 const SYNTHETIC_PART_ID = "prt_01234567890123456789012345"
 
-export const createSyntheticUserMessage = (baseMessage: WithParts, content: string): WithParts => {
+export const createSyntheticUserMessage = (baseMessage: WithParts, content: string, variant?: string): WithParts => {
     const userInfo = baseMessage.info as UserMessage
     return {
         info: {
@@ -19,6 +19,8 @@ export const createSyntheticUserMessage = (baseMessage: WithParts, content: stri
                 providerID: userInfo.model.providerID,
                 modelID: userInfo.model.modelID,
             },
+            // @opencode-ai/sdk doesn't yet ship a variant type
+            ...(variant !== undefined && { variant }),
         },
         parts: [
             {

lib/shared-utils.ts

@@ -13,3 +13,16 @@ export const getLastUserMessage = (messages: WithParts[]): WithParts | null => {
     }
     return null
 }
+
+export const findUserVariant = (messages: WithParts[]): string | undefined => {
+    for (let i = messages.length - 1; i >= 0; i--) {
+        const msg = messages[i]
+        if (msg.info.role === "user") {
+            const variant = (msg.info as any).variant
+            if (variant !== undefined && variant !== null) {
+                return variant
+            }
+        }
+    }
+    return undefined
+}