diff --git a/docs/public/workflows/stages-and-nodes.mdx b/docs/public/workflows/stages-and-nodes.mdx
index 79ae0b00f..59f48df69 100644
--- a/docs/public/workflows/stages-and-nodes.mdx
+++ b/docs/public/workflows/stages-and-nodes.mdx
@@ -117,7 +117,7 @@ When a node has no explicit `shape` or `type`, the presence of `script` makes it
 
 For `stdin_source`, strings are passed unchanged. Other JSON values use compact
 JSON. Fabro does not add a newline. A missing source, or a value larger than
-10 MiB, fails before the command starts.
+30 MiB, fails before the command starts.
 
 ### Human
 
diff --git a/lib/components/fabro-workflow/src/handler/command.rs b/lib/components/fabro-workflow/src/handler/command.rs
index 0de483869..6cf7d5741 100644
--- a/lib/components/fabro-workflow/src/handler/command.rs
+++ b/lib/components/fabro-workflow/src/handler/command.rs
@@ -220,8 +220,10 @@ impl Handler for CommandHandler {
 /// Ceiling on encoded stdin bytes. `stdin_source` values are runtime data —
 /// often model-produced — so their size is not something a workflow author
 /// reviewed; this bounds peak memory and remote uploads the same way
-/// `MAX_FOR_EACH_ITEMS` bounds `for_each` fan-out.
-const MAX_STDIN_BYTES: usize = 10 * 1024 * 1024;
+/// `MAX_FOR_EACH_ITEMS` bounds `for_each` fan-out. Sized for wide fan-in:
+/// a `context.parallel.results` batch from a large `for_each` round easily
+/// carries tens of structured agent outputs.
+const MAX_STDIN_BYTES: usize = 30 * 1024 * 1024;
 
 fn validated_stdin_source(node: &Node) -> Result<Option<&str>, String> {
     match node.context_key_attr("stdin_source") {