diff --git a/packages/opencode/test/tool/__snapshots__/parameters.test.ts.snap b/packages/opencode/test/tool/__snapshots__/parameters.test.ts.snap
index eb3fe6cce4..ffb1b9f55f 100644
--- a/packages/opencode/test/tool/__snapshots__/parameters.test.ts.snap
+++ b/packages/opencode/test/tool/__snapshots__/parameters.test.ts.snap
@@ -334,6 +334,10 @@ exports[`tool parameters JSON Schema (wire shape) task 1`] = `
 {
   "$schema": "https://json-schema.org/draft/2020-12/schema",
   "properties": {
+    "background": {
+      "description": "When true, launch the subagent in the background and return immediately",
+      "type": "boolean",
+    },
     "command": {
       "description": "The command that triggered this task",
       "type": "string",
@@ -352,6 +356,7 @@ exports[`tool parameters JSON Schema (wire shape) task 1`] = `
     },
     "task_id": {
       "description": "This should only be set if you mean to resume a previous task (you can pass a prior task_id and the task will continue the same subagent session as before instead of creating a fresh one)",
+      "pattern": "^ses.*",
       "type": "string",
     },
   },
diff --git a/packages/opencode/test/tool/parameters.test.ts b/packages/opencode/test/tool/parameters.test.ts
index 8ea008a457..487e6faa17 100644
--- a/packages/opencode/test/tool/parameters.test.ts
+++ b/packages/opencode/test/tool/parameters.test.ts
@@ -220,6 +220,19 @@ describe("tool parameters", () => {
       const parsed = parse(Task, { description: "d", prompt: "p", subagent_type: "general" })
       expect(parsed.subagent_type).toBe("general")
     })
+    test("accepts optional task_id + command + background", () => {
+      const parsed = parse(Task, {
+        description: "d",
+        prompt: "p",
+        subagent_type: "general",
+        task_id: "ses_test",
+        command: "/cmd",
+        background: true,
+      })
+      expect(parsed.task_id).toBe("ses_test")
+      expect(parsed.command).toBe("/cmd")
+      expect(parsed.background).toBe(true)
+    })
     test("rejects missing prompt", () => {
       expect(accepts(Task, { description: "d", subagent_type: "general" })).toBe(false)
     })