diff --git a/content/manuals/ai/sandboxes/customize/kit-examples.md b/content/manuals/ai/sandboxes/customize/kit-examples.md
index 615b9108704..248ee10d3bf 100644
--- a/content/manuals/ai/sandboxes/customize/kit-examples.md
+++ b/content/manuals/ai/sandboxes/customize/kit-examples.md
@@ -411,8 +411,6 @@ for the complete order.
 Agent settings mechanisms differ. If an agent doesn't support an additional
 config file, launch option, or environment variable for the setting, kits can't
 replace the sandbox-managed user settings before the agent launches.
-`setup.startup` doesn't gate the agent entrypoint, so don't use it for settings
-the agent must read during initialization.
 
 ## Fork an existing agent
 
diff --git a/content/manuals/ai/sandboxes/customize/kit-reference.md b/content/manuals/ai/sandboxes/customize/kit-reference.md
index 42408a8bd38..a196c9df62a 100644
--- a/content/manuals/ai/sandboxes/customize/kit-reference.md
+++ b/content/manuals/ai/sandboxes/customize/kit-reference.md
@@ -498,7 +498,7 @@ Runs at every sandbox start. String array, not interpreted by a shell.
 | ------------- | -------- | ----------------------------------- |
 | `command`     | —        | Command and args as a string array. |
 | `user`        | `"1000"` | User to run as. `"1000"` = agent.   |
-| `background`  | `false`  | Block later startup commands until this command finishes. Set to `true` to let later commands run without waiting. |
+| `background`  | `false`  | Run this command in the background. When `false`, the startup dispatcher waits for this command to finish before running the next startup command. When `true`, the dispatcher continues immediately. Neither setting delays the agent entrypoint. |
 | `description` | —        | Human-readable description.         |
 
 Startup commands are non-interactive. They run before the agent