diff --git a/server/packages/sandbox-agent/tests/support/docker.rs b/server/packages/sandbox-agent/tests/support/docker.rs
index af4d81c..3315e49 100644
--- a/server/packages/sandbox-agent/tests/support/docker.rs
+++ b/server/packages/sandbox-agent/tests/support/docker.rs
@@ -240,8 +240,11 @@ fn build_env(layout: &TestLayout, auth: &AuthConfig) -> BTreeMap<String, String>
         env.insert("SANDBOX_AGENT_TEST_AUTH_TOKEN".to_string(), token.clone());
     }
 
-    let custom_path_entries =
-        custom_path_entries(layout.install_dir.parent().expect("install base"));
+    let mut custom_path_entries = custom_path_entries(layout.install_dir.parent().expect("install base"));
+    custom_path_entries.extend(explicit_path_entries());
+    custom_path_entries.sort();
+    custom_path_entries.dedup();
+
     if custom_path_entries.is_empty() {
         env.insert("PATH".to_string(), DEFAULT_PATH.to_string());
     } else {
@@ -441,6 +444,18 @@ fn custom_path_entries(root: &Path) -> Vec<PathBuf> {
     entries
 }
 
+fn explicit_path_entries() -> Vec<PathBuf> {
+    let mut entries = Vec::new();
+    if let Some(value) = std::env::var_os("SANDBOX_AGENT_TEST_EXTRA_PATHS") {
+        for entry in std::env::split_paths(&value) {
+            if entry.is_absolute() && entry.exists() {
+                entries.push(entry);
+            }
+        }
+    }
+    entries
+}
+
 fn rewrite_localhost_url(key: &str, value: &str) -> String {
     if key.ends_with("_URL") || key.ends_with("_URI") {
         return value
diff --git a/server/packages/sandbox-agent/tests/v1_api/control_plane.rs b/server/packages/sandbox-agent/tests/v1_api/control_plane.rs
index d6e2129..a0dd74c 100644
--- a/server/packages/sandbox-agent/tests/v1_api/control_plane.rs
+++ b/server/packages/sandbox-agent/tests/v1_api/control_plane.rs
@@ -187,6 +187,8 @@ async fn lazy_install_runs_on_first_bootstrap() {
     paths.extend(std::env::split_paths(&original_path));
     let merged_path = std::env::join_paths(paths).expect("join PATH");
     let _path_guard = EnvVarGuard::set_os("PATH", merged_path.as_os_str());
+    let _extra_paths_guard =
+        EnvVarGuard::set_os("SANDBOX_AGENT_TEST_EXTRA_PATHS", helper_bin.as_os_str());
 
     let test_app = TestApp::with_setup(AuthConfig::disabled(), |install_path| {
         fs::create_dir_all(install_path.join("agent_processes"))