Fix persisted agent defaults display

desktop/src/features/agents/ui/AgentConfigFields.tsx

@@ -200,8 +200,16 @@ export function AgentConfigFields({
     () => getGlobalModelFallback(bakedEnv, effectiveProvider, config.env_vars),
     [bakedEnv, config.env_vars, effectiveProvider],
   );
+  const modelField = fieldModel.fields.find(
+    (field) => field.kind === "model" && field.render === "control",
+  );
+  // CLI-login harnesses apply this setting through ACP rather than an env var
+  // and provide their own default when no model override is persisted.
+  const modelIsOptional = modelField?.targetApplication.kind === "acpNative";
   const modelIsValid =
-    (config.model?.trim().length ?? 0) > 0 || fallbackModel !== null;
+    modelIsOptional ||
+    (config.model?.trim().length ?? 0) > 0 ||
+    fallbackModel !== null;
   React.useEffect(() => {
     onValidityChange?.(modelIsValid);
   }, [modelIsValid, onValidityChange]);
@@ -653,6 +661,7 @@ export function AgentConfigFields({
           isCustomModelEditing={isCustomModelEditing}
           isRequired={
             showRequiredIndicators &&
+            !modelIsOptional &&
             fallbackModel === null &&
             !dependentFieldsDisabled
           }

desktop/src/features/agents/ui/AgentDefaultsEditor.tsx

@@ -20,6 +20,13 @@ import type { GlobalAgentConfig } from "@/shared/api/types";
 import { getBakedBuildEnv, type BakedEnvEntry } from "@/shared/api/tauri";
 import { globalAgentConfigQueryKey } from "@/features/agents/useGlobalAgentConfig";
 import { useAcpRuntimesQuery } from "@/features/agents/hooks";
+import {
+  formatRuntimeOptionLabel,
+  getDefaultPersonaRuntime,
+  resetConfigForHarnessChange,
+  sortPersonaRuntimes,
+} from "@/features/agents/ui/agentConfigOptions";
+import { AgentDropdownSelect } from "@/features/agents/ui/agentConfigControls";
 import {
   AgentConfigFields,
   EMPTY_GLOBAL_CONFIG,
@@ -105,17 +112,36 @@ export function AgentDefaultsEditor({
       });
   }, []);
 
-  // Resolve the buzz-agent runtime catalog entry for model discovery.
   const runtimesQuery = useAcpRuntimesQuery();
-  const buzzAgentRuntime = React.useMemo(
-    () => (runtimesQuery.data ?? []).find((r) => r.id === "buzz-agent"),
+  const sortedRuntimes = React.useMemo(
+    () => sortPersonaRuntimes(runtimesQuery.data ?? []),
     [runtimesQuery.data],
   );
+  // A missing/stale preference displays the same effective fallback the backend
+  // would use; it is persisted only after the user edits and saves this form.
+  // Keep persona ordering here so this shared editor matches agent dialogs.
+  const selectedRuntime = React.useMemo(
+    () =>
+      sortedRuntimes.find(
+        (runtime) => runtime.id === config.preferred_runtime,
+      ) ??
+      getDefaultPersonaRuntime(sortedRuntimes) ??
+      sortedRuntimes[0],
+    [config.preferred_runtime, sortedRuntimes],
+  );
+  const harnessOptions = React.useMemo(
+    () =>
+      sortedRuntimes.map((runtime) => ({
+        label: formatRuntimeOptionLabel(runtime),
+        value: runtime.id,
+      })),
+    [sortedRuntimes],
+  );
   const configSurfaceLoading = isLoading || runtimesQuery.isLoading;
   const configSurfaceError =
     loadError ||
     runtimesQuery.isError ||
-    (!configSurfaceLoading && buzzAgentRuntime === undefined);
+    (!configSurfaceLoading && selectedRuntime === undefined);
 
   function handleConfigChange(next: GlobalAgentConfig) {
     configRef.current = next;
@@ -125,6 +151,12 @@ export function AgentDefaultsEditor({
     setSaveError(null);
   }
 
+  function handleHarnessChange(runtimeId: string) {
+    handleConfigChange(resetConfigForHarnessChange(config, runtimeId));
+    setIsCustomModelEditing(false);
+    setIsCustomProvider(false);
+  }
+
   async function handleSave() {
     // Snapshot the config being submitted so we can detect edits that arrive
     // during the IPC round-trip and avoid clobbering the user's newer input.
@@ -183,18 +215,36 @@ export function AgentDefaultsEditor({
           Couldn't load agent defaults. Restart the app to try again.
         </div>
       ) : (
-        <AgentConfigFields
-          bakedEnv={bakedEnv}
-          selectedRuntime={buzzAgentRuntime}
-          config={config}
-          isCustomModelEditing={isCustomModelEditing}
-          isCustomProvider={isCustomProvider}
-          onConfigChange={handleConfigChange}
-          onCustomModelEditingChange={setIsCustomModelEditing}
-          onIsCustomProviderChange={setIsCustomProvider}
-          onValidityChange={setConfigIsValid}
-          useCustomSelect
-        />
+        <>
+          <div className="space-y-1.5">
+            <label
+              className="text-sm font-medium text-foreground"
+              htmlFor="global-agent-default-harness"
+            >
+              Default harness
+            </label>
+            <AgentDropdownSelect
+              id="global-agent-default-harness"
+              onValueChange={handleHarnessChange}
+              options={harnessOptions}
+              placeholder="Select a harness"
+              testId="global-agent-default-harness"
+              value={selectedRuntime?.id ?? ""}
+            />
+          </div>
+          <AgentConfigFields
+            bakedEnv={bakedEnv}
+            selectedRuntime={selectedRuntime}
+            config={config}
+            isCustomModelEditing={isCustomModelEditing}
+            isCustomProvider={isCustomProvider}
+            onConfigChange={handleConfigChange}
+            onCustomModelEditingChange={setIsCustomModelEditing}
+            onIsCustomProviderChange={setIsCustomProvider}
+            onValidityChange={setConfigIsValid}
+            useCustomSelect
+          />
+        </>
       )}
 
       {/* Save bar */}

desktop/src/features/agents/ui/agentConfigOptions.test.mjs

@@ -5,6 +5,7 @@ import {
   getDefaultPersonaRuntime,
   getPersonaModelOptions,
   getPersonaProviderOptions,
+  resetConfigForHarnessChange,
   runtimeSupportsLlmProviderSelection,
 } from "./agentConfigOptions.tsx";
 import { formatModelDiscoveryErrorStatus } from "./personaModelDiscoveryStatus.ts";
@@ -145,6 +146,49 @@ test("runtimeSupportsLlmProviderSelection is false for codex and claude", () =>
   assert.equal(runtimeSupportsLlmProviderSelection("claude"), false);
 });
 
+test("resetConfigForHarnessChange clears harness-specific values", () => {
+  const config = {
+    env_vars: { BUZZ_AGENT_THINKING_EFFORT: "high", KEEP_ME: "yes" },
+    model: "claude-opus",
+    preferred_runtime: "buzz-agent",
+    provider: "anthropic",
+  };
+
+  assert.deepEqual(resetConfigForHarnessChange(config, "claude"), {
+    env_vars: { KEEP_ME: "yes" },
+    model: null,
+    preferred_runtime: "claude",
+    provider: null,
+  });
+});
+
+test("resetConfigForHarnessChange preserves compatible provider selection", () => {
+  const config = {
+    env_vars: { KEEP_ME: "yes" },
+    model: "old-model",
+    preferred_runtime: "claude",
+    provider: "anthropic",
+  };
+
+  assert.deepEqual(resetConfigForHarnessChange(config, "goose"), {
+    env_vars: { KEEP_ME: "yes" },
+    model: null,
+    preferred_runtime: "goose",
+    provider: "anthropic",
+  });
+});
+
+test("resetConfigForHarnessChange does not carry relay mesh to Goose", () => {
+  const config = {
+    env_vars: {},
+    model: "auto",
+    preferred_runtime: "buzz-agent",
+    provider: "relay-mesh",
+  };
+
+  assert.equal(resetConfigForHarnessChange(config, "goose").provider, null);
+});
+
 // ── getPersonaModelOptions — codex/claude do not use global provider ──────────
 //
 // The discovery call in AgentDefinitionDialog passes

desktop/src/features/agents/ui/agentConfigOptions.tsx

@@ -1,4 +1,8 @@
-import type { AcpRuntimeCatalogEntry } from "@/shared/api/types";
+import type {
+  AcpRuntimeCatalogEntry,
+  GlobalAgentConfig,
+} from "@/shared/api/types";
+import { BUZZ_AGENT_THINKING_EFFORT } from "./buzzAgentConfig";
 import type { RuntimeFileConfigSubset } from "@/shared/api/tauri";
 // Dialogs import getDefaultPersonaRuntime via this re-export; lib code imports
 // directly from lib/resolvePersonaRuntime.
@@ -173,6 +177,27 @@ export function runtimeSupportsLlmProviderSelection(runtimeId: string) {
   return runtimeId === "buzz-agent" || runtimeId === "goose";
 }
 
+/** Clears values whose meaning or support changes with the selected harness. */
+export function resetConfigForHarnessChange(
+  config: GlobalAgentConfig,
+  runtimeId: string,
+): GlobalAgentConfig {
+  const nextEnvVars = { ...config.env_vars };
+  delete nextEnvVars[BUZZ_AGENT_THINKING_EFFORT];
+
+  return {
+    ...config,
+    env_vars: nextEnvVars,
+    model: null,
+    preferred_runtime: runtimeId || null,
+    provider:
+      runtimeSupportsLlmProviderSelection(runtimeId) &&
+      config.provider !== "relay-mesh"
+        ? config.provider
+        : null,
+  };
+}
+
 function effectiveModelProviderForOptions(
   runtimeId: string,
   providerId: string | null | undefined,

desktop/src/features/onboarding/ui/DefaultConfigStep.tsx

@@ -5,8 +5,7 @@ import {
   AgentConfigFields,
   EMPTY_GLOBAL_CONFIG,
 } from "@/features/agents/ui/AgentConfigFields";
-import { BUZZ_AGENT_THINKING_EFFORT } from "@/features/agents/ui/buzzAgentConfig";
-import { runtimeSupportsLlmProviderSelection } from "@/features/agents/ui/agentConfigOptions";
+import { resetConfigForHarnessChange } from "@/features/agents/ui/agentConfigOptions";
 import { AgentDropdownSelect } from "@/features/agents/ui/agentConfigControls";
 import { createSaveCoalescer } from "./saveCoalescer";
 import { getBakedBuildEnv, type BakedEnvEntry } from "@/shared/api/tauri";
@@ -26,6 +25,7 @@ import {
   type OnboardingTransitionDirection,
   OnboardingSlideTransition,
 } from "./OnboardingSlideTransition";
+import { ONBOARDING_RUNTIME_ORDER } from "./onboardingRuntimeSelection";
 import type { DefaultConfigStepActions } from "./types";
 
 type DefaultConfigStepProps = {
@@ -34,8 +34,6 @@ type DefaultConfigStepProps = {
   selectedRuntimeIds: readonly string[];
 };
 
-const RUNTIME_ORDER = ["claude", "codex", "goose", "buzz-agent"];
-
 function formatHarnessLabel(runtime: AcpRuntimeCatalogEntry | undefined) {
   if (!runtime) return "Select a harness";
   return runtime.id === "buzz-agent" ? "Buzz" : runtime.label;
@@ -49,11 +47,11 @@ function sortSelectedRuntimes(
   return runtimes
     .filter((runtime) => selectedRuntimeIdSet.has(runtime.id))
     .sort((left, right) => {
-      const leftIndex = RUNTIME_ORDER.indexOf(left.id);
-      const rightIndex = RUNTIME_ORDER.indexOf(right.id);
+      const leftIndex = ONBOARDING_RUNTIME_ORDER.indexOf(left.id);
+      const rightIndex = ONBOARDING_RUNTIME_ORDER.indexOf(right.id);
       return (
-        (leftIndex === -1 ? RUNTIME_ORDER.length : leftIndex) -
-        (rightIndex === -1 ? RUNTIME_ORDER.length : rightIndex)
+        (leftIndex === -1 ? ONBOARDING_RUNTIME_ORDER.length : leftIndex) -
+        (rightIndex === -1 ? ONBOARDING_RUNTIME_ORDER.length : rightIndex)
       );
     });
 }
@@ -146,20 +144,7 @@ function AgentDefaultsSection({
 
   const handleHarnessChange = React.useCallback(
     (runtimeId: string) => {
-      const nextEnvVars = { ...config.env_vars };
-      delete nextEnvVars[BUZZ_AGENT_THINKING_EFFORT];
-      const nextProvider =
-        runtimeSupportsLlmProviderSelection(runtimeId) &&
-        config.provider !== "relay-mesh"
-          ? config.provider
-          : null;
-      const next = {
-        ...config,
-        env_vars: nextEnvVars,
-        model: null,
-        preferred_runtime: runtimeId || null,
-        provider: nextProvider,
-      };
+      const next = resetConfigForHarnessChange(config, runtimeId);
       setIsCustomModelEditing(false);
       setIsCustomProvider(false);
       setConfig(next);

desktop/src/features/onboarding/ui/MachineOnboardingFlow.tsx

@@ -10,8 +10,7 @@ import {
   importIdentity,
   persistCurrentIdentity,
 } from "@/shared/api/tauriIdentity";
-import { runtimeSupportsLlmProviderSelection } from "@/features/agents/ui/agentConfigOptions";
-import { BUZZ_AGENT_THINKING_EFFORT } from "@/features/agents/ui/buzzAgentConfig";
+import { resetConfigForHarnessChange } from "@/features/agents/ui/agentConfigOptions";
 import { Button } from "@/shared/ui/button";
 import { StartupWindowDragRegion } from "@/shared/ui/StartupWindowDragRegion";
 import { BackupStep } from "./BackupStep";
@@ -94,20 +93,9 @@ export function MachineOnboardingFlow({
           return;
         }
 
-        const nextEnvVars = { ...current.env_vars };
-        delete nextEnvVars[BUZZ_AGENT_THINKING_EFFORT];
-        await setGlobalAgentConfig({
-          ...current,
-          env_vars: nextEnvVars,
-          model: null,
-          preferred_runtime: preferredRuntimeId,
-          provider:
-            preferredRuntimeId &&
-            runtimeSupportsLlmProviderSelection(preferredRuntimeId) &&
-            current.provider !== "relay-mesh"
-              ? current.provider
-              : null,
-        });
+        await setGlobalAgentConfig(
+          resetConfigForHarnessChange(current, preferredRuntimeId ?? ""),
+        );
       });
       runtimeSaveChain.current = save.then(
         () => undefined,

desktop/src/features/onboarding/ui/onboardingRuntimeSelection.test.mjs

@@ -101,14 +101,29 @@ test("provider-backed selections drive the default model config step", () => {
     getDefaultModelConfigRuntimeId(["claude", "codex", "goose", "buzz-agent"]),
     "buzz-agent",
   );
+});
+
+test("onboarding display order drives the preferred runtime", () => {
   assert.equal(
-    getPreferredRuntimeIdForSelection(["claude", "codex", "goose"]),
-    "goose",
+    getPreferredRuntimeIdForSelection([
+      "buzz-agent",
+      "goose",
+      "codex",
+      "claude",
+    ]),
+    "claude",
   );
   assert.equal(
-    getPreferredRuntimeIdForSelection(["claude", "codex"]),
-    "claude",
+    getPreferredRuntimeIdForSelection(["buzz-agent", "goose", "codex"]),
+    "codex",
+  );
+  assert.equal(
+    getPreferredRuntimeIdForSelection(["buzz-agent", "goose"]),
+    "goose",
   );
+  assert.equal(getPreferredRuntimeIdForSelection(["buzz-agent"]), "buzz-agent");
+  assert.equal(getPreferredRuntimeIdForSelection(["custom"]), "custom");
+  assert.equal(getPreferredRuntimeIdForSelection([]), null);
 });
 
 test("any harness selection drives the defaults step", () => {