Preserve existing environment overrides

Keep saved non-local overrides visible even when they are not runnable so operators can inspect or clear stale environment selections.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

ui/src/components/AgentConfigForm.render.test.tsx

@@ -155,7 +155,7 @@ function makeEnvironment(overrides: Partial<Environment>): Environment {
   };
 }
 
-async function renderForm(environments: Environment[]) {
+async function renderForm(environments: Environment[], agentOverrides: Partial<Agent> = {}) {
   mockEnvironmentsApi.list.mockResolvedValue(environments);
 
   const container = document.createElement("div");
@@ -174,7 +174,7 @@ async function renderForm(environments: Environment[]) {
         <TooltipProvider>
           <AgentConfigForm
             mode="edit"
-            agent={makeAgent()}
+            agent={makeAgent(agentOverrides)}
             onSave={vi.fn()}
             hidePromptTemplate
             showAdapterTypeField={false}
@@ -246,4 +246,27 @@ describe("AgentConfigForm environment selector", () => {
     expect(text).not.toContain("Leave this unset to inherit the instance default");
     expect(text).not.toContain("Inherit instance default");
   });
+
+  it("keeps an existing non-runnable override visible so it can be cleared", async () => {
+    const result = await renderForm(
+      [
+        makeEnvironment({ id: "local-1", name: "Local", driver: "local" }),
+        makeEnvironment({
+          id: "fake-sandbox-1",
+          name: "Fake Sandbox",
+          driver: "sandbox",
+          config: { provider: "fake" },
+        }),
+      ],
+      { defaultEnvironmentId: "fake-sandbox-1" },
+    );
+    roots.push(result.root);
+
+    const text = result.container.textContent ?? "";
+    const selector = result.container.querySelector("select");
+
+    expect(text).toContain("Environment override");
+    expect(selector?.textContent).toContain("Default: Local");
+    expect(selector?.textContent).toContain("Fake Sandbox · sandbox");
+  });
 });

ui/src/components/AgentConfigForm.tsx

@@ -400,11 +400,19 @@ export function AgentConfigForm(props: AgentConfigFormProps) {
     }),
     [environments, supportedEnvironmentDrivers],
   );
+  const environmentOptions = useMemo(() => {
+    if (!currentDefaultEnvironment) return runnableEnvironments;
+    if (runnableEnvironments.some((environment) => environment.id === currentDefaultEnvironment.id)) {
+      return runnableEnvironments;
+    }
+    return [...runnableEnvironments, currentDefaultEnvironment];
+  }, [currentDefaultEnvironment, runnableEnvironments]);
   // `runnableEnvironments` excludes the always-available Local environment, so a
   // single entry already means the user has more than one environment configured
   // (Local + that environment) and the override selector is meaningful.
   const showEnvironmentOverrideControl = environmentsEnabled && (
     forcedKubernetes ||
+    currentDefaultEnvironmentId.length > 0 ||
     runnableEnvironments.length >= 1
   );
   const inheritedEnvironmentLabel = instanceDefaultEnvironment
@@ -929,7 +937,7 @@ export function AgentConfigForm(props: AgentConfigFormProps) {
                   }}
                 >
                   <option value="">Default: {inheritedEnvironmentLabel}</option>
-                  {runnableEnvironments.map((environment) => (
+                  {environmentOptions.map((environment) => (
                     <option key={environment.id} value={environment.id}>
                       {environment.name} · {environment.driver}
                     </option>