feat: inherit variant from parent session in subagent tasks

Author: mugnimaestra

packages/opencode/src/tool/task.ts

@@ -108,6 +108,10 @@ export const TaskTool = Tool.define("task", async (ctx) => {
         providerID: msg.info.providerID,
       }
 
+      // Inherit variant from parent user message when subagent has no explicit variant
+      const parentUser = await MessageV2.get({ sessionID: ctx.sessionID, messageID: msg.info.parentID })
+      const variant = !agent.variant && parentUser.info.role === "user" ? parentUser.info.variant : undefined
+
       ctx.metadata({
         title: params.description,
         metadata: {
@@ -133,6 +137,7 @@ export const TaskTool = Tool.define("task", async (ctx) => {
           providerID: model.providerID,
         },
         agent: agent.name,
+        variant,
         tools: {
           todowrite: false,
           todoread: false,

packages/opencode/test/session/prompt-variant.test.ts

@@ -57,4 +57,31 @@ describe("session.prompt agent variant", () => {
       },
     })
   })
+
+  test("explicit variant input takes effect without agent variant config", async () => {
+    await using tmp = await tmpdir({
+      git: true,
+      config: {},
+    })
+
+    await Instance.provide({
+      directory: tmp.path,
+      fn: async () => {
+        const session = await Session.create({})
+
+        // Simulates what task.ts does: passing parent's variant as explicit input
+        const msg = await SessionPrompt.prompt({
+          sessionID: session.id,
+          agent: "general",
+          variant: "high",
+          noReply: true,
+          parts: [{ type: "text", text: "hello" }],
+        })
+        if (msg.info.role !== "user") throw new Error("expected user message")
+        expect(msg.info.variant).toBe("high")
+
+        await Session.remove(session.id)
+      },
+    })
+  })
 })