diff --git a/packages/opencode/src/tool/task.ts b/packages/opencode/src/tool/task.ts
index ac2d9fa0812..74aabd7598a 100644
--- a/packages/opencode/src/tool/task.ts
+++ b/packages/opencode/src/tool/task.ts
@@ -211,8 +211,12 @@ export const TaskTool = Tool.define(
           parts,
         })
         if (result.info.role === "assistant" && result.info.error) {
+          const message =
+            "message" in result.info.error.data && typeof result.info.error.data.message === "string"
+              ? result.info.error.data.message
+              : result.info.error.name
           return yield* Effect.fail(
-            new Error(`Subagent failed (task_id: ${nextSession.id}): ${result.info.error.data.message}`),
+            new Error(`Subagent failed (task_id: ${nextSession.id}): ${message}`),
           )
         }
         return result.parts.findLast((item) => item.type === "text")?.text ?? ""
diff --git a/packages/opencode/test/tool/task.test.ts b/packages/opencode/test/tool/task.test.ts
index d82b7aa33ca..967dd046a42 100644
--- a/packages/opencode/test/tool/task.test.ts
+++ b/packages/opencode/test/tool/task.test.ts
@@ -300,9 +300,10 @@ describe("tool.task", () => {
       if (Exit.isSuccess(exit)) throw new Error("expected task failure")
       const child = (yield* sessions.children(chat.id))[0]
       expect(child).toBeDefined()
-      expect(Cause.squash(exit.cause).message).toBe(
-        `Subagent failed (task_id: ${child?.id}): Network connection lost`,
-      )
+      const failure = Cause.squash(exit.cause)
+      expect(failure).toBeInstanceOf(Error)
+      if (!(failure instanceof Error)) throw new Error("expected Error defect")
+      expect(failure.message).toBe(`Subagent failed (task_id: ${child?.id}): Network connection lost`)
     }),
   )