diff --git a/packages/opencode/src/tool/task.ts b/packages/opencode/src/tool/task.ts
index f87f46207b..fece68800b 100644
--- a/packages/opencode/src/tool/task.ts
+++ b/packages/opencode/src/tool/task.ts
@@ -24,6 +24,14 @@ export interface TaskPromptOps {
 }
 
 const id = "task"
+const BACKGROUND_DESCRIPTION = [
+  "",
+  "",
+  [
+    "Background mode: background=true launches the subagent asynchronously.",
+    "Use task_status(task_id=..., wait=false) to poll, or wait=true to block until done.",
+  ].join(" "),
+].join("\n")
 
 const BaseParameters = Schema.Struct({
   description: Schema.String.annotate({ description: "A short (3-5 words) description of the task" }),
@@ -327,7 +335,7 @@ export const TaskTool = Tool.define(
     })
 
     return {
-      description: DESCRIPTION,
+      description: flags.experimentalBackgroundSubagents ? DESCRIPTION + BACKGROUND_DESCRIPTION : DESCRIPTION,
       parameters: Parameters,
       jsonSchema: flags.experimentalBackgroundSubagents ? undefined : ToolJsonSchema.fromSchema(BaseParameters),
       execute: (params: Schema.Schema.Type<typeof Parameters>, ctx: Tool.Context) =>
diff --git a/packages/opencode/src/tool/task.txt b/packages/opencode/src/tool/task.txt
index 508dee97ac..e2ac605005 100644
--- a/packages/opencode/src/tool/task.txt
+++ b/packages/opencode/src/tool/task.txt
@@ -12,8 +12,7 @@ When NOT to use the Task tool:
 Usage notes:
 1. Launch multiple agents concurrently whenever possible, to maximize performance; to do that, use a single message with multiple tool uses
 2. When the agent is done, it will return a single message back to you. The result returned by the agent is not visible to the user. To show the user the result, you should send a text message back to the user with a concise summary of the result. The output includes a task_id you can reuse later to continue the same subagent session.
-3. If OPENCODE_EXPERIMENTAL_BACKGROUND_SUBAGENTS is enabled, background=true launches the subagent asynchronously. Use task_status(task_id=..., wait=false) to poll, or wait=true to block until done.
-4. Each agent invocation starts with a fresh context unless you provide task_id to resume the same subagent session (which continues with its previous messages and tool outputs). When starting fresh, your prompt should contain a highly detailed task description for the agent to perform autonomously and you should specify exactly what information the agent should return back to you in its final and only message to you.
-5. The agent's outputs should generally be trusted
-6. Clearly tell the agent whether you expect it to write code or just to do research (search, file reads, web fetches, etc.), since it is not aware of the user's intent. Tell it how to verify its work if possible (e.g., relevant test commands).
-7. If the agent description mentions that it should be used proactively, then you should try your best to use it without the user having to ask for it first. Use your judgement.
+3. Each agent invocation starts with a fresh context unless you provide task_id to resume the same subagent session (which continues with its previous messages and tool outputs). When starting fresh, your prompt should contain a highly detailed task description for the agent to perform autonomously and you should specify exactly what information the agent should return back to you in its final and only message to you.
+4. The agent's outputs should generally be trusted
+5. Clearly tell the agent whether you expect it to write code or just to do research (search, file reads, web fetches, etc.), since it is not aware of the user's intent. Tell it how to verify its work if possible (e.g., relevant test commands).
+6. If the agent description mentions that it should be used proactively, then you should try your best to use it without the user having to ask for it first. Use your judgement.