diff --git a/src/crates/assembly/core/src/product_runtime.rs b/src/crates/assembly/core/src/product_runtime.rs
index 18825c7f13..b8113d6cd2 100644
--- a/src/crates/assembly/core/src/product_runtime.rs
+++ b/src/crates/assembly/core/src/product_runtime.rs
@@ -611,6 +611,7 @@ impl LocalWorkspaceSnapshotPort for CoreLocalWorkspaceSnapshot {
 /// harnesses; plugin runtime bindings are deliberately not part of this API.
 pub struct CoreProductAgentRuntime;
 
+#[cfg(feature = "opencode-plugin-host")]
 pub(crate) async fn fork_session_for_plugin(
     workspace_path: PathBuf,
     source_session_id: String,