From f3319dd11102bfd52e1ec3065a4d9272a03075ec Mon Sep 17 00:00:00 2001
From: Will Pfleger <pfleger.will@gmail.com>
Date: Sun, 12 Jul 2026 18:23:27 -0400
Subject: [PATCH] fix(desktop): correct provider and model handling in agent
 config dialogs (#1764)

---
 desktop/playwright.config.ts                  |   1 +
 desktop/scripts/check-file-sizes.mjs          |   9 +-
 desktop/src/features/agents/hooks.ts          |  38 ----
 .../lib/instanceInputForDefinition.test.mjs   |  45 ++++
 .../agents/lib/instanceInputForDefinition.ts  |   6 +-
 .../agents/lib/resolvePersonaRuntime.ts       |  26 ++-
 .../agents/ui/AddTeamToChannelDialog.tsx      |  13 +-
 .../agents/ui/AgentDefinitionDialog.tsx       |  92 ++++++---
 .../agents/ui/AgentInstanceEditDialog.tsx     |  17 +-
 .../features/agents/ui/EnvVarsEditor.test.mjs |   4 +-
 .../ui/agentDefinitionSubmitPayload.test.mjs  |  88 ++++++++
 .../agents/ui/agentDefinitionSubmitPayload.ts |  75 +++++++
 .../agents/ui/buzzAgentModelTuningFields.tsx  |   8 +-
 .../ui/editAgentProviderDiscovery.test.mjs    |  58 ++++--
 .../agents/ui/personaDialogPickers.test.mjs   | 187 +++++++++++++++++
 .../agents/ui/personaDialogPickers.tsx        |  53 +++--
 .../agents/ui/usePersonaModelDiscovery.ts     |  26 ++-
 .../ui/GlobalAgentConfigSettingsCard.tsx      |  22 ++
 desktop/src/testing/e2eBridge.ts              |   6 +
 .../e2e/agent-provider-dropdowns.spec.ts      | 194 ++++++++++++++++++
 20 files changed, 856 insertions(+), 112 deletions(-)
 create mode 100644 desktop/src/features/agents/ui/agentDefinitionSubmitPayload.test.mjs
 create mode 100644 desktop/src/features/agents/ui/agentDefinitionSubmitPayload.ts
 create mode 100644 desktop/src/features/agents/ui/personaDialogPickers.test.mjs
 create mode 100644 desktop/tests/e2e/agent-provider-dropdowns.spec.ts

diff --git a/desktop/playwright.config.ts b/desktop/playwright.config.ts
index 441c2b650..3570864a6 100644
--- a/desktop/playwright.config.ts
+++ b/desktop/playwright.config.ts
@@ -93,6 +93,7 @@ export default defineConfig({
         "**/global-agent-config-screenshots.spec.ts",
         "**/doctor-states.spec.ts",
         "**/agent-lifecycle-feedback.spec.ts",
+        "**/agent-provider-dropdowns.spec.ts",
       ],
       use: {
         ...devices["Desktop Chrome"],
diff --git a/desktop/scripts/check-file-sizes.mjs b/desktop/scripts/check-file-sizes.mjs
index 184caab6b..40a9cc4e0 100644
--- a/desktop/scripts/check-file-sizes.mjs
+++ b/desktop/scripts/check-file-sizes.mjs
@@ -403,7 +403,14 @@ const overrides = new Map([
   // +23 rebase onto #1667: behavioral quad fields (respond_to/parallelism/toolsets)
   // plumbed through AgentInstanceEditDialog from PersonaAdvancedFields.
   // +2 provider-aware effort: model/provider props threaded to BuzzAgentModelTuningFields.
-  ["src/features/agents/ui/AgentInstanceEditDialog.tsx", 1165],
+  // +15 provider/model dropdown fixes: useBakedBuildEnvKeysQuery + hideProviderIds
+  // for Databricks v1 gate; prospectiveRuntimeId default fallback for builtins.
+  ["src/features/agents/ui/AgentInstanceEditDialog.tsx", 1180],
+  // AgentDefinitionDialog grew past 1000 with the following load-bearing fixes:
+  // isRuntimeAutoSeededRef tracking for edit-mode seeding (Fizz shows models);
+  // runtimeSupportsLlmProviderSelection guard on discovery provider (codex fix);
+  // hideProviderIds computation for Databricks v1 gate. Queued to split.
+  ["src/features/agents/ui/AgentDefinitionDialog.tsx", 1035],
 ]);
 
 await runFileSizeCheck({
diff --git a/desktop/src/features/agents/hooks.ts b/desktop/src/features/agents/hooks.ts
index b89841ffd..9423bfb45 100644
--- a/desktop/src/features/agents/hooks.ts
+++ b/desktop/src/features/agents/hooks.ts
@@ -57,7 +57,6 @@ import type {
 } from "@/shared/api/types";
 import type {
   AttachManagedAgentToChannelInput,
-  AttachManagedAgentToChannelResult,
   CreateChannelManagedAgentInput,
   CreateChannelManagedAgentsResult,
   CreateChannelManagedAgentResult,
@@ -84,10 +83,6 @@ export const acpRuntimesQueryKey = ["acp-runtimes"] as const;
 export const managedAgentPrereqsQueryKey = ["managed-agent-prereqs"] as const;
 export const backendProvidersQueryKey = ["backend-providers"] as const;
 
-export type EnsureGooseInChannelResult = AttachManagedAgentToChannelResult & {
-  created: boolean;
-};
-
 async function invalidateAgentQueries(
   queryClient: ReturnType<typeof useQueryClient>,
   channelId: string | null,
@@ -590,39 +585,6 @@ export function useCreateChannelManagedAgentsMutation(
   });
 }
 
-export function useEnsureGooseInChannelMutation(channelId: string | null) {
-  const queryClient = useQueryClient();
-
-  return useMutation({
-    mutationFn: async (): Promise<EnsureGooseInChannelResult> => {
-      if (!channelId) {
-        throw new Error("No channel selected.");
-      }
-
-      const attached = await ensureChannelAgentPresetInChannel(channelId, {
-        runtime: {
-          id: "goose",
-          label: "Goose",
-          command: "goose",
-          defaultArgs: ["acp"],
-          mcpCommand: null,
-        },
-        role: "bot",
-      });
-
-      return {
-        agent: attached.agent,
-        membershipAdded: attached.membershipAdded,
-        started: attached.started,
-        created: attached.created,
-      };
-    },
-    onSettled: () => {
-      invalidateAgentQueriesInBackground(queryClient, channelId);
-    },
-  });
-}
-
 export function useExportPersonaJsonMutation() {
   return useMutation({
     mutationFn: (id: string) => exportPersonaToJson(id),
diff --git a/desktop/src/features/agents/lib/instanceInputForDefinition.test.mjs b/desktop/src/features/agents/lib/instanceInputForDefinition.test.mjs
index dfd287ad2..92b3dd467 100644
--- a/desktop/src/features/agents/lib/instanceInputForDefinition.test.mjs
+++ b/desktop/src/features/agents/lib/instanceInputForDefinition.test.mjs
@@ -42,6 +42,14 @@ const claudeRuntime = {
   mcpCommand: null,
 };
 
+const buzzAgentRuntime = {
+  ...gooseRuntime,
+  id: "buzz-agent",
+  label: "Buzz Agent",
+  command: "buzz-agent-cmd",
+  mcpCommand: null,
+};
+
 function persona(overrides = {}) {
   return {
     id: "p-1",
@@ -346,3 +354,40 @@ test("row 6: unfetched query refetches instead of resolving empty", async () =>
     "an unfetched query must fetch, not spuriously report no runtimes",
   );
 });
+
+// ── item-13 regression: buzz-agent-first default runtime ─────────────────────
+//
+// Before this fix, resolveStartRuntimeForDefinition used runtimes[0] (catalog
+// order: goose, claude, codex, buzz-agent), so an installed goose would beat
+// the bundled buzz-agent sidecar as the default for runtime-less personas.
+// The fix applies the preference order: buzz-agent → goose → first available.
+
+test("item-13: goose+buzz-agent both available — persona with no runtime resolves buzz-agent", () => {
+  const { runtime, warnings } = resolveStartRuntimeForDefinition(
+    persona({ runtime: undefined }),
+    [gooseRuntime, claudeRuntime, buzzAgentRuntime],
+  );
+  assert.equal(
+    runtime.id,
+    "buzz-agent",
+    "buzz-agent must win over catalog-first goose for runtime-less personas",
+  );
+  assert.deepEqual(warnings, []);
+});
+
+test("item-13: goose-only available — persona with no runtime resolves goose", () => {
+  const { runtime, warnings } = resolveStartRuntimeForDefinition(
+    persona({ runtime: undefined }),
+    [gooseRuntime, claudeRuntime],
+  );
+  assert.equal(runtime.id, "goose");
+  assert.deepEqual(warnings, []);
+});
+
+test("item-13: no runtimes available — refuses with actionable error", () => {
+  assert.throws(
+    () => resolveStartRuntimeForDefinition(persona({ runtime: undefined }), []),
+    /No available runtime/,
+    "empty runtime list must throw, not silently return null",
+  );
+});
diff --git a/desktop/src/features/agents/lib/instanceInputForDefinition.ts b/desktop/src/features/agents/lib/instanceInputForDefinition.ts
index 3faa5318f..408ea5ca1 100644
--- a/desktop/src/features/agents/lib/instanceInputForDefinition.ts
+++ b/desktop/src/features/agents/lib/instanceInputForDefinition.ts
@@ -7,6 +7,7 @@ import type {
 import type { MeshAgentPresetPatch } from "@/features/mesh-compute/applyMeshAgentPreset";
 import type { MeshServeTarget } from "@/shared/api/tauriMesh";
 import {
+  getDefaultPersonaRuntime,
   resolvePersonaRuntime,
   type ResolvePersonaRuntimeResult,
 } from "./resolvePersonaRuntime";
@@ -47,7 +48,10 @@ export function resolveStartRuntimeForDefinition(
   persona: AgentPersona,
   runtimes: readonly AcpRuntime[],
 ): { runtime: AcpRuntime; warnings: string[] } {
-  const defaultRuntime = runtimes[0] ?? null;
+  // Use the buzz-agent-first preference (buzz-agent → goose → first available)
+  // so a freshly installed goose never beats the bundled buzz-agent sidecar
+  // for runtime-less personas (item 13 regression guard).
+  const defaultRuntime = getDefaultPersonaRuntime(runtimes);
   const { runtime, warnings, isOverridden }: ResolvePersonaRuntimeResult =
     resolvePersonaRuntime(persona.runtime, runtimes, defaultRuntime);
 
diff --git a/desktop/src/features/agents/lib/resolvePersonaRuntime.ts b/desktop/src/features/agents/lib/resolvePersonaRuntime.ts
index f59f963ab..e425ecb75 100644
--- a/desktop/src/features/agents/lib/resolvePersonaRuntime.ts
+++ b/desktop/src/features/agents/lib/resolvePersonaRuntime.ts
@@ -1,4 +1,28 @@
-import type { AcpRuntime } from "@/shared/api/types";
+import type { AcpRuntime, AcpRuntimeCatalogEntry } from "@/shared/api/types";
+
+/**
+ * Select the best default runtime from a catalog, using the same preference
+ * order as the UI picker: buzz-agent first (bundled sidecar), then goose,
+ * then the first available entry, then null when nothing is available.
+ *
+ * Generic so that passing AcpRuntime[] (the already-filtered start-path
+ * list) returns AcpRuntime | null while passing AcpRuntimeCatalogEntry[]
+ * (the full catalog) returns AcpRuntimeCatalogEntry | null.  Both call sites
+ * share one preference-order implementation.
+ */
+export function getDefaultPersonaRuntime<T extends AcpRuntimeCatalogEntry>(
+  runtimes: readonly T[],
+): T | null {
+  const available = runtimes.filter(
+    (runtime) => runtime.availability === "available",
+  );
+  return (
+    available.find((runtime) => runtime.id === "buzz-agent") ??
+    available.find((runtime) => runtime.id === "goose") ??
+    available[0] ??
+    null
+  );
+}
 
 /**
  * Result of resolving a persona's preferred runtime against the set of
diff --git a/desktop/src/features/agents/ui/AddTeamToChannelDialog.tsx b/desktop/src/features/agents/ui/AddTeamToChannelDialog.tsx
index 2f9c13eb0..454df09e5 100644
--- a/desktop/src/features/agents/ui/AddTeamToChannelDialog.tsx
+++ b/desktop/src/features/agents/ui/AddTeamToChannelDialog.tsx
@@ -12,6 +12,7 @@ import {
 } from "@/features/agents/lib/teamPersonas";
 import {
   collectRuntimeWarnings,
+  getDefaultPersonaRuntime,
   resolvePersonaRuntime,
 } from "@/features/agents/lib/resolvePersonaRuntime";
 import { useChannelsQuery } from "@/features/channels/hooks";
@@ -65,8 +66,10 @@ export function AddTeamToChannelDialog({
     [channelsQuery.data],
   );
 
-  const providers = providersQuery.data ?? [];
-  const defaultProvider = providers[0] ?? null;
+  const runtimes = providersQuery.data ?? [];
+  // Use the buzz-agent-first preference so the team-deploy fallback mirrors the
+  // single-agent start path (buzz-agent → goose → first available).
+  const defaultProvider = getDefaultPersonaRuntime(runtimes);
 
   const teamPersonaResolution = React.useMemo(
     () =>
@@ -80,8 +83,8 @@ export function AddTeamToChannelDialog({
   // This dialog has no runtime selector, so the fallback is always
   // `defaultProvider` (the first available runtime).
   const runtimeWarnings = React.useMemo(
-    () => collectRuntimeWarnings(resolved, providers, defaultProvider),
-    [resolved, providers, defaultProvider],
+    () => collectRuntimeWarnings(resolved, runtimes, defaultProvider),
+    [resolved, runtimes, defaultProvider],
   );
 
   function reset() {
@@ -122,7 +125,7 @@ export function AddTeamToChannelDialog({
       const inputs = resolved.map((persona) => {
         const { runtime: personaRuntime } = resolvePersonaRuntime(
           persona.runtime,
-          providers,
+          runtimes,
           defaultProvider,
         );
         const runtimeToUse = personaRuntime ?? defaultProvider;
diff --git a/desktop/src/features/agents/ui/AgentDefinitionDialog.tsx b/desktop/src/features/agents/ui/AgentDefinitionDialog.tsx
index e4f1dfcac..a2fdde482 100644
--- a/desktop/src/features/agents/ui/AgentDefinitionDialog.tsx
+++ b/desktop/src/features/agents/ui/AgentDefinitionDialog.tsx
@@ -40,6 +40,7 @@ import {
 } from "./personaBehaviorDraft";
 import {
   AUTO_PROVIDER_DROPDOWN_VALUE,
+  BLOCK_BUILD_HIDDEN_PROVIDER_IDS,
   buildTemplateModelDropdownOptions,
   CUSTOM_MODEL_DROPDOWN_VALUE,
   CUSTOM_PROVIDER_DROPDOWN_VALUE,
@@ -76,6 +77,7 @@ import {
 import { useBakedBuildEnvKeysQuery, useRuntimeFileConfigQuery } from "../hooks";
 import { useGlobalAgentConfig } from "../useGlobalAgentConfig";
 import { isBuzzAgentRuntime } from "./buzzAgentConfig";
+import { buildRuntimeModelProviderPayload } from "./agentDefinitionSubmitPayload";
 
 type AgentDefinitionDialogProps = {
   open: boolean;
@@ -154,6 +156,16 @@ export function AgentDefinitionDialog({
   // The seed the draft is diffed against at submit: an untouched quad
   // submits no behavior group, keeping unrelated edits hash-quiet.
   const behaviorSeedRef = React.useRef(emptyPersonaBehaviorDraft);
+  // Tracks when the runtime was auto-seeded by the default-runtime effect in
+  // edit mode (i.e. the user never explicitly chose a runtime). Used to omit
+  // the seeded runtime from the submit payload for builtin definitions whose
+  // canonical runtime is null — the sync would revert it anyway.
+  const isRuntimeAutoSeededRef = React.useRef(false);
+  // Guards the seeding effect so it fires at most once per dialog-open.
+  // Without this, clearing runtime back to "" via "No preference" would re-
+  // trigger the effect (the `runtime` dep would pass the length guard) and
+  // snap the dropdown back to the default — an edit-mode regression.
+  const hasSeededForOpenRef = React.useRef(false);
   const [showAdvancedFields, setShowAdvancedFields] = React.useState(false);
   const [isAvatarUploadPending, setIsAvatarUploadPending] =
     React.useState(false);
@@ -214,22 +226,32 @@ export function AgentDefinitionDialog({
     setIsAvatarUploadPending(false);
     setImportErrorMessage(null);
     setIsImportingUpdate(false);
+    isRuntimeAutoSeededRef.current = false;
+    hasSeededForOpenRef.current = false;
   }, [initialValues, open]);
 
   React.useEffect(() => {
     if (
       !open ||
       !initialValues ||
-      "id" in initialValues ||
       initialValues.runtime?.trim() ||
       runtimesLoading ||
       runtime.trim().length > 0 ||
-      defaultRuntime === null
+      defaultRuntime === null ||
+      hasSeededForOpenRef.current
     ) {
       return;
     }
 
     setRuntime(defaultRuntime.id);
+    hasSeededForOpenRef.current = true;
+    if ("id" in initialValues) {
+      // Edit mode: record that this runtime was auto-seeded so the submit path
+      // can omit it from the payload for builtin definitions (canonical runtime
+      // null; sync would revert the value anyway). Explicit user changes via
+      // the dropdown clear this flag.
+      isRuntimeAutoSeededRef.current = true;
+    }
   }, [defaultRuntime, initialValues, open, runtime, runtimesLoading]);
 
   const isWindowFileDragOver = useWindowFileDragOver(
@@ -299,6 +321,8 @@ export function AgentDefinitionDialog({
       setIsAvatarUploadPending(false);
       setImportErrorMessage(null);
       setIsImportingUpdate(false);
+      // isRuntimeAutoSeededRef and hasSeededForOpenRef are NOT reset here — the
+      // [initialValues, open] effect resets both when the dialog re-opens.
     }
 
     onOpenChange(next);
@@ -313,19 +337,21 @@ export function AgentDefinitionDialog({
       return;
     }
 
-    const trimmedRuntime = runtime.trim();
-    const previousRuntime = initialValues.runtime?.trim() ?? "";
-    const modelProviderEditableWithoutRuntime =
-      initialModelProviderEditableWithoutRuntime && trimmedRuntime.length === 0;
-    const llmProviderVisibleForSubmit =
-      (trimmedRuntime.length > 0 &&
-        runtimeSupportsLlmProviderSelection(trimmedRuntime)) ||
-      modelProviderEditableWithoutRuntime;
-    const shouldPreserveHiddenModelProvider =
-      "id" in initialValues &&
-      previousRuntime.length === 0 &&
-      trimmedRuntime.length === 0 &&
-      !modelProviderEditableWithoutRuntime;
+    const {
+      runtime: runtimeForSubmit,
+      model: modelForSubmit,
+      provider: providerForSubmit,
+    } = buildRuntimeModelProviderPayload({
+      runtime,
+      model,
+      provider,
+      isEditMode: "id" in initialValues,
+      isAutoSeeded: isRuntimeAutoSeededRef.current,
+      initialPreviousRuntime: initialValues.runtime?.trim() ?? "",
+      initialModel: initialValues.model,
+      initialProvider: initialValues.provider,
+      initialModelProviderEditableWithoutRuntime,
+    });
     const namePool = parsePersonaNamePoolText(namePoolText);
     const namePoolInput =
       namePool.length > 0
@@ -337,18 +363,9 @@ export function AgentDefinitionDialog({
       displayName: displayName.trim(),
       avatarUrl: avatarUrl.trim() || undefined,
       systemPrompt: systemPrompt,
-      runtime: trimmedRuntime || undefined,
-      model:
-        trimmedRuntime || modelProviderEditableWithoutRuntime
-          ? model.trim() || undefined
-          : shouldPreserveHiddenModelProvider
-            ? initialValues.model
-            : undefined,
-      provider: llmProviderVisibleForSubmit
-        ? provider.trim() || undefined
-        : shouldPreserveHiddenModelProvider
-          ? initialValues.provider
-          : undefined,
+      runtime: runtimeForSubmit,
+      model: modelForSubmit,
+      provider: providerForSubmit,
       namePool: namePoolInput,
       envVars,
       behavior: behaviorForSubmit(
@@ -515,7 +532,12 @@ export function AgentDefinitionDialog({
     isCustomProviderEditing,
     modelFieldVisible,
     open,
-    provider: effectiveProvider,
+    // Gate provider by runtime: runtimes that don't support LLM provider
+    // selection (codex, claude) must not inherit the global provider — doing
+    // so causes them to discover models from the wrong provider.
+    provider: runtimeSupportsLlmProviderSelection(runtime)
+      ? effectiveProvider
+      : "",
     selectedRuntime,
   });
   const staticModelOptions = getPersonaModelOptions(runtime, effectiveProvider);
@@ -532,10 +554,22 @@ export function AgentDefinitionDialog({
   });
   const showCustomModelInput =
     modelFieldVisible && (isCustomModelEditing || isModelCustom);
+  // On internal Block builds, BUZZ_AGENT_PROVIDER is baked in and a boot
+  // migration rewrites any persisted Databricks v1 values → v2. Hide the v1
+  // option there so it is not offered for new selections. OSS builds have no
+  // baked provider, so v1 remains visible.
+  const hideProviderIds = React.useMemo(
+    () =>
+      (bakedEnvKeys ?? []).includes("BUZZ_AGENT_PROVIDER")
+        ? BLOCK_BUILD_HIDDEN_PROVIDER_IDS
+        : new Set<string>(),
+    [bakedEnvKeys],
+  );
   const providerOptions = getPersonaProviderOptions(
     trimmedProvider,
     runtime,
     globalConfig.provider ?? "",
+    hideProviderIds,
   );
   const defaultLlmProviderLabel = getDefaultLlmProviderLabel(
     runtime,
@@ -668,6 +702,8 @@ export function AgentDefinitionDialog({
   function handleRuntimeDropdownChange(nextValue: string) {
     const nextRuntime =
       nextValue === NO_RUNTIME_DROPDOWN_VALUE ? "" : nextValue;
+    // The user made an explicit choice — no longer auto-seeded.
+    isRuntimeAutoSeededRef.current = false;
     setRuntime(nextRuntime);
     applySelection(
       selectionOnRuntimeChange(selection, {
diff --git a/desktop/src/features/agents/ui/AgentInstanceEditDialog.tsx b/desktop/src/features/agents/ui/AgentInstanceEditDialog.tsx
index 7ba254ff7..dbf226bb7 100644
--- a/desktop/src/features/agents/ui/AgentInstanceEditDialog.tsx
+++ b/desktop/src/features/agents/ui/AgentInstanceEditDialog.tsx
@@ -7,6 +7,7 @@ import { toast } from "sonner";
 import {
   useAcpRuntimesQuery,
   useAgentConfigSurface,
+  useBakedBuildEnvKeysQuery,
   usePersonasQuery,
   useStartManagedAgentMutation,
   useUpdateManagedAgentMutation,
@@ -28,10 +29,12 @@ import { EditAgentAdvancedFields } from "./EditAgentAdvancedFields";
 import {
   AUTO_MODEL_DROPDOWN_VALUE,
   AUTO_PROVIDER_DROPDOWN_VALUE,
+  BLOCK_BUILD_HIDDEN_PROVIDER_IDS,
   CUSTOM_MODEL_DROPDOWN_VALUE,
   CUSTOM_PROVIDER_DROPDOWN_VALUE,
   formatRuntimeOptionLabel,
   getDefaultLlmModelLabel,
+  getDefaultPersonaRuntime,
   getModelSelectValue,
   getPersonaProviderOptions,
   hasPersonaModelOption,
@@ -328,6 +331,9 @@ export function AgentInstanceEditDialog({
       runtimes.find((r) => r.command?.trim() === agent.agentCommand.trim())
         ?.id ??
       runtimes.find((r) => r.id === agent.agentCommand.trim())?.id ??
+      // Fall back to the app default runtime so discovery can run for agents
+      // whose persona has no runtime set (e.g. freshly-added catalog builtins).
+      getDefaultPersonaRuntime(runtimes)?.id ??
       ""
     );
   }, [
@@ -387,6 +393,8 @@ export function AgentInstanceEditDialog({
       setShowAdvancedFields,
     });
 
+  const { data: bakedEnvKeys } = useBakedBuildEnvKeysQuery({ enabled: open });
+
   // Merge global env as the base layer so credential keys satisfied via global
   // config (e.g. ANTHROPIC_API_KEY) are available to model discovery. Use
   // `inheritedSubmission.envVars` (the same snapshot the credential gate
@@ -773,10 +781,18 @@ export function AgentInstanceEditDialog({
 
   // Provider field derived state
   const trimmedProvider = provider.trim();
+  const hideProviderIds = React.useMemo(
+    () =>
+      (bakedEnvKeys ?? []).includes("BUZZ_AGENT_PROVIDER")
+        ? BLOCK_BUILD_HIDDEN_PROVIDER_IDS
+        : new Set<string>(),
+    [bakedEnvKeys],
+  );
   const providerOptions = getPersonaProviderOptions(
     trimmedProvider,
     selectedRuntime?.id ?? "",
     globalConfig.provider ?? "",
+    hideProviderIds,
   );
   const providerSelectValue = isCustomProviderEditing
     ? CUSTOM_PROVIDER_DROPDOWN_VALUE
@@ -923,7 +939,6 @@ export function AgentInstanceEditDialog({
                 </p>
               ) : null}
             </div>
-
             {/* LLM provider */}
             {llmProviderFieldVisible ? (
               <div className="space-y-1.5">
diff --git a/desktop/src/features/agents/ui/EnvVarsEditor.test.mjs b/desktop/src/features/agents/ui/EnvVarsEditor.test.mjs
index 567195026..318247e1a 100644
--- a/desktop/src/features/agents/ui/EnvVarsEditor.test.mjs
+++ b/desktop/src/features/agents/ui/EnvVarsEditor.test.mjs
@@ -483,13 +483,13 @@ test("inheritedRows_structured_keys_excluded_from_generic_rows", () => {
 test("getBakedProviderInheritLabel_known_provider_returns_friendly_name", () => {
   const options = [
     { id: "anthropic", label: "Anthropic" },
-    { id: "databricks_v2", label: "Databricks v2 (AI Gateway)" },
+    { id: "databricks_v2", label: "Databricks v2" },
     { id: "openai", label: "OpenAI" },
   ];
   const label = getBakedProviderInheritLabel("databricks_v2", options);
   assert.equal(
     label,
-    "Databricks v2 (AI Gateway) (inherited from build)",
+    "Databricks v2 (inherited from build)",
     "known provider id must resolve to friendly label",
   );
 });
diff --git a/desktop/src/features/agents/ui/agentDefinitionSubmitPayload.test.mjs b/desktop/src/features/agents/ui/agentDefinitionSubmitPayload.test.mjs
new file mode 100644
index 000000000..9cf465465
--- /dev/null
+++ b/desktop/src/features/agents/ui/agentDefinitionSubmitPayload.test.mjs
@@ -0,0 +1,88 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+
+import { buildRuntimeModelProviderPayload } from "./agentDefinitionSubmitPayload.ts";
+
+// Shared fixture for a builtin edit: previous runtime null, no saved model/provider.
+const BUILTIN_EDIT_BASE = {
+  isEditMode: true,
+  initialPreviousRuntime: "",
+  initialModel: null,
+  initialProvider: null,
+  initialModelProviderEditableWithoutRuntime: false,
+};
+
+// ── edit-untouched ─────────────────────────────────────────────────────────────
+//
+// User opens a null-runtime builtin, doesn't change model or provider, submits.
+// Runtime was auto-seeded (isAutoSeeded=true), model/provider still empty strings.
+// Expected: runtime and model and provider all omitted (undefined).
+
+test("edit-untouched: model and provider omitted when user changes nothing on auto-seeded builtin", () => {
+  const result = buildRuntimeModelProviderPayload({
+    ...BUILTIN_EDIT_BASE,
+    runtime: "",
+    model: "",
+    provider: "",
+    isAutoSeeded: true,
+  });
+  assert.equal(result.runtime, undefined, "runtime must be omitted");
+  assert.equal(result.model, undefined, "model must be omitted");
+  assert.equal(result.provider, undefined, "provider must be omitted");
+});
+
+// ── edit-model-only ────────────────────────────────────────────────────────────
+//
+// User opens a null-runtime builtin with auto-seed and picks a model.
+// Expected: model persisted, runtime omitted (auto-seeded, not explicit).
+
+test("edit-model-only: chosen model persists, runtime omitted on auto-seeded builtin", () => {
+  const result = buildRuntimeModelProviderPayload({
+    ...BUILTIN_EDIT_BASE,
+    runtime: "",
+    model: "claude-opus-4-8",
+    provider: "",
+    isAutoSeeded: true,
+  });
+  assert.equal(result.runtime, undefined, "runtime must be omitted");
+  assert.equal(result.model, "claude-opus-4-8", "model must be persisted");
+  assert.equal(result.provider, undefined, "provider must be omitted");
+});
+
+// ── edit-provider-only ─────────────────────────────────────────────────────────
+//
+// User opens a null-runtime builtin with auto-seed and picks a provider.
+// Expected: provider persisted, model and runtime omitted.
+
+test("edit-provider-only: chosen provider persists, runtime omitted on auto-seeded builtin", () => {
+  const result = buildRuntimeModelProviderPayload({
+    ...BUILTIN_EDIT_BASE,
+    runtime: "",
+    model: "",
+    provider: "anthropic",
+    isAutoSeeded: true,
+  });
+  assert.equal(result.runtime, undefined, "runtime must be omitted");
+  assert.equal(result.model, undefined, "model must be omitted");
+  assert.equal(result.provider, "anthropic", "provider must be persisted");
+});
+
+// ── explicit-runtime-chosen ────────────────────────────────────────────────────
+//
+// User opens a null-runtime builtin, the seeded default is shown, then the user
+// explicitly re-selects the same (or a different) runtime via the dropdown.
+// handleRuntimeDropdownChange clears isAutoSeeded=false so the runtime is no
+// longer treated as auto-seeded and MUST appear in the payload.
+
+test("explicit-runtime-chosen: runtime and model both persisted when user explicitly selects runtime", () => {
+  const result = buildRuntimeModelProviderPayload({
+    ...BUILTIN_EDIT_BASE,
+    runtime: "buzz-agent",
+    model: "claude-opus-4-8",
+    provider: "",
+    isAutoSeeded: false, // user made an explicit choice
+  });
+  assert.equal(result.runtime, "buzz-agent", "runtime must be persisted");
+  assert.equal(result.model, "claude-opus-4-8", "model must be persisted");
+  assert.equal(result.provider, undefined, "empty provider must be omitted");
+});
diff --git a/desktop/src/features/agents/ui/agentDefinitionSubmitPayload.ts b/desktop/src/features/agents/ui/agentDefinitionSubmitPayload.ts
new file mode 100644
index 000000000..56f623ecb
--- /dev/null
+++ b/desktop/src/features/agents/ui/agentDefinitionSubmitPayload.ts
@@ -0,0 +1,75 @@
+import { runtimeSupportsLlmProviderSelection } from "./personaDialogPickers";
+
+/**
+ * Pure helper extracted from the `handleSubmit` path of `AgentDefinitionDialog`
+ * so the payload logic can be unit-tested without rendering the component.
+ *
+ * Computes the `runtime`, `model`, and `provider` fields for the definition
+ * submit payload, resolving auto-seeded builtin-edit semantics: when the
+ * runtime was auto-seeded (the user never explicitly chose one), it is omitted
+ * from the payload, and model/provider edits are still persisted via the
+ * `modelProviderEditableWithoutRuntime` path.
+ */
+export function buildRuntimeModelProviderPayload({
+  runtime,
+  model,
+  provider,
+  isEditMode,
+  isAutoSeeded,
+  initialPreviousRuntime,
+  initialModel,
+  initialProvider,
+  initialModelProviderEditableWithoutRuntime,
+}: {
+  runtime: string;
+  model: string;
+  provider: string;
+  isEditMode: boolean;
+  isAutoSeeded: boolean;
+  initialPreviousRuntime: string;
+  initialModel: string | null | undefined;
+  initialProvider: string | null | undefined;
+  initialModelProviderEditableWithoutRuntime: boolean;
+}): {
+  runtime: string | undefined;
+  model: string | undefined;
+  provider: string | undefined;
+} {
+  const trimmedRuntime = runtime.trim();
+  const previousRuntime = initialPreviousRuntime;
+  const isAutoSeededRuntimeForBuiltinEdit =
+    isEditMode && previousRuntime.length === 0 && isAutoSeeded;
+  const runtimeForSubmit = isAutoSeededRuntimeForBuiltinEdit
+    ? ""
+    : trimmedRuntime;
+  // An auto-seeded builtin edit is treated the same as an existing builtin with
+  // a saved model/provider: the field is editable without a runtime, and the
+  // user's model/provider choice is persisted in the payload.
+  const modelProviderEditableWithoutRuntime =
+    (initialModelProviderEditableWithoutRuntime ||
+      isAutoSeededRuntimeForBuiltinEdit) &&
+    runtimeForSubmit.length === 0;
+  const llmProviderVisibleForSubmit =
+    (runtimeForSubmit.length > 0 &&
+      runtimeSupportsLlmProviderSelection(runtimeForSubmit)) ||
+    modelProviderEditableWithoutRuntime;
+  const shouldPreserveHiddenModelProvider =
+    isEditMode &&
+    previousRuntime.length === 0 &&
+    runtimeForSubmit.length === 0 &&
+    !modelProviderEditableWithoutRuntime;
+  return {
+    runtime: runtimeForSubmit || undefined,
+    model:
+      runtimeForSubmit || modelProviderEditableWithoutRuntime
+        ? model.trim() || undefined
+        : shouldPreserveHiddenModelProvider
+          ? (initialModel ?? undefined)
+          : undefined,
+    provider: llmProviderVisibleForSubmit
+      ? provider.trim() || undefined
+      : shouldPreserveHiddenModelProvider
+        ? (initialProvider ?? undefined)
+        : undefined,
+  };
+}
diff --git a/desktop/src/features/agents/ui/buzzAgentModelTuningFields.tsx b/desktop/src/features/agents/ui/buzzAgentModelTuningFields.tsx
index 98c6faebb..dc8d90c1c 100644
--- a/desktop/src/features/agents/ui/buzzAgentModelTuningFields.tsx
+++ b/desktop/src/features/agents/ui/buzzAgentModelTuningFields.tsx
@@ -55,8 +55,14 @@ export function EffortSelectField({
    * Label for the "Inherit" option when no inherited effort is set and the model
    * has a semantic default (i.e. `effortDefault !== null`).
    *
-   * Defaults to `"Inherit"`. Per-agent callers may pass `"Inherit (agent default)"`
+   * Defaults to `"Inherit"`.
+   *
+   * Per-agent callers (BuzzAgentModelTuningFields) pass `"Inherit (agent default)"`
    * to preserve the label that appeared before this component was extracted.
+   *
+   * The global-defaults card (GlobalAgentConfigSettingsCard) passes
+   * `"Default (<effort>)"` when a semantic default exists and nothing is baked
+   * in — so OSS users see "Default (medium)" rather than bare "Inherit".
    */
   inheritFallbackLabel?: string;
   /** Label text for the dropdown. */
diff --git a/desktop/src/features/agents/ui/editAgentProviderDiscovery.test.mjs b/desktop/src/features/agents/ui/editAgentProviderDiscovery.test.mjs
index 16278a49c..759e9a605 100644
--- a/desktop/src/features/agents/ui/editAgentProviderDiscovery.test.mjs
+++ b/desktop/src/features/agents/ui/editAgentProviderDiscovery.test.mjs
@@ -56,30 +56,54 @@ test("editAgent_providerFieldHidden_forBlankRuntime", () => {
 // ── Provider dropdown options for EditAgentProviderField ────────────────────
 //
 // The provider dropdown contains the well-known providers
-// (databricks_v2, anthropic, openai, openai-compat) plus a default-provider
-// fallback entry so users can clear a saved provider.
-// Note: bare "databricks" (V1 / Model Serving) is no longer offered as a
-// fresh choice in the default picker — Block builds migrate it to V2 at boot
-// and the picker would silently undo any intentional V1 selection.
+// (databricks, databricks_v2, anthropic, openai, openai-compat) plus a
+// default-provider fallback entry so users can clear a saved provider.
+//
+// On OSS builds, Databricks v1 ("databricks") is shown alongside v2 so OSS
+// users who were previously on v1 can select it. On internal Block builds,
+// callers pass hideProviderIds=new Set(["databricks"]) to suppress v1 — the
+// boot migration rewrites any persisted v1 value to v2, so offering v1 there
+// would silently undo the migration.
 
-test("editAgent_providerOptions_includesDatabricksV2Provider", () => {
+test("editAgent_providerOptions_includesDatabricksV2AndV1OnOSS", () => {
+  // OSS builds: no hideProviderIds → both v1 and v2 appear.
   const options = getPersonaProviderOptions("", "buzz-agent");
   const ids = options.map((o) => o.id);
+  assert.ok(ids.includes("databricks_v2"), "databricks_v2 must be present");
   assert.ok(
-    ids.includes("databricks_v2"),
-    "databricks_v2 must be a provider option",
-  );
-  assert.ok(
-    !ids.includes("databricks"),
-    "bare databricks (V1) must NOT be in the default provider list",
+    ids.includes("databricks"),
+    "bare databricks (V1) must be present on OSS builds",
   );
 });
 
-test("editAgent_providerOptions_includesDatabricksV1AsCurrentIfSaved", () => {
-  // A record that already has provider="databricks" (OSS / pre-migration)
-  // must still show it in the dropdown as the current selection so it
-  // remains visible without offering it as a fresh default choice.
-  const options = getPersonaProviderOptions("databricks", "buzz-agent");
+test("editAgent_providerOptions_hidesDatabricksV1OnInternalBuild", () => {
+  // Internal Block builds: pass hideProviderIds to suppress v1.
+  const options = getPersonaProviderOptions(
+    "",
+    "buzz-agent",
+    "",
+    new Set(["databricks"]),
+  );
+  const ids = options.map((o) => o.id);
+  assert.ok(
+    ids.includes("databricks_v2"),
+    "databricks_v2 must still be present",
+  );
+  assert.ok(
+    !ids.includes("databricks"),
+    "bare databricks (V1) must be hidden on internal builds",
+  );
+});
+
+test("editAgent_providerOptions_includesDatabricksV1AsCurrentEvenWhenHidden", () => {
+  // A record already persisted with provider="databricks" must show it as the
+  // current value even when hideProviderIds hides it from fresh selection.
+  const options = getPersonaProviderOptions(
+    "databricks",
+    "buzz-agent",
+    "",
+    new Set(["databricks"]),
+  );
   const ids = options.map((o) => o.id);
   assert.ok(
     ids.includes("databricks"),
diff --git a/desktop/src/features/agents/ui/personaDialogPickers.test.mjs b/desktop/src/features/agents/ui/personaDialogPickers.test.mjs
new file mode 100644
index 000000000..5cc49a989
--- /dev/null
+++ b/desktop/src/features/agents/ui/personaDialogPickers.test.mjs
@@ -0,0 +1,187 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+
+import {
+  getDefaultPersonaRuntime,
+  getPersonaModelOptions,
+  getPersonaProviderOptions,
+  runtimeSupportsLlmProviderSelection,
+} from "./personaDialogPickers.tsx";
+import { formatModelDiscoveryErrorStatus } from "./personaModelDiscoveryStatus.ts";
+
+// ── helpers ──────────────────────────────────────────────────────────────────
+
+function makeRuntime(id, availability = "available") {
+  return {
+    id,
+    label: id,
+    command: id,
+    defaultArgs: [],
+    mcpCommand: null,
+    availability,
+  };
+}
+
+// ── getPersonaProviderOptions — hideProviderIds ───────────────────────────────
+
+test("getPersonaProviderOptions returns databricks v1 and v2 when hideProviderIds is empty", () => {
+  const options = getPersonaProviderOptions("", "buzz-agent", "", new Set());
+  const ids = options.map((o) => o.id);
+  assert.ok(ids.includes("databricks"), "databricks v1 present");
+  assert.ok(ids.includes("databricks_v2"), "databricks v2 present");
+});
+
+test("getPersonaProviderOptions hides databricks v1 when it is in hideProviderIds", () => {
+  const options = getPersonaProviderOptions(
+    "",
+    "buzz-agent",
+    "",
+    new Set(["databricks"]),
+  );
+  const ids = options.map((o) => o.id);
+  assert.ok(!ids.includes("databricks"), "databricks v1 hidden");
+  assert.ok(ids.includes("databricks_v2"), "databricks v2 still present");
+});
+
+test("getPersonaProviderOptions appends (current) tail for a saved databricks v1 value even when hidden", () => {
+  // An agent already persisted with v1 must still render its saved value.
+  const options = getPersonaProviderOptions(
+    "databricks",
+    "buzz-agent",
+    "",
+    new Set(["databricks"]),
+  );
+  const tail = options.at(-1);
+  assert.equal(tail?.id, "databricks");
+  assert.equal(tail?.label, "databricks (current)");
+});
+
+test("getPersonaProviderOptions with no hideProviderIds omits the tail for a known provider", () => {
+  const options = getPersonaProviderOptions("anthropic", "buzz-agent");
+  const tail = options.at(-1);
+  // "anthropic" is a known id — no (current) tail appended
+  assert.ok(
+    tail?.id !== "anthropic" || tail?.label === "Anthropic",
+    "no duplicate tail for known provider",
+  );
+});
+
+test("getPersonaProviderOptions appends (current) tail for an unknown saved provider", () => {
+  const options = getPersonaProviderOptions("my-custom-llm", "buzz-agent");
+  const tail = options.at(-1);
+  assert.equal(tail?.id, "my-custom-llm");
+  assert.equal(tail?.label, "my-custom-llm (current)");
+});
+
+// ── getDefaultPersonaRuntime — buzz-agent first ───────────────────────────────
+
+test("getDefaultPersonaRuntime returns buzz-agent over goose when both are available", () => {
+  const runtimes = [
+    makeRuntime("goose"),
+    makeRuntime("buzz-agent"),
+    makeRuntime("claude"),
+  ];
+  const result = getDefaultPersonaRuntime(runtimes);
+  assert.equal(result?.id, "buzz-agent");
+});
+
+test("getDefaultPersonaRuntime falls back to goose when buzz-agent is unavailable", () => {
+  const runtimes = [
+    makeRuntime("buzz-agent", "not_installed"),
+    makeRuntime("goose"),
+  ];
+  const result = getDefaultPersonaRuntime(runtimes);
+  assert.equal(result?.id, "goose");
+});
+
+test("getDefaultPersonaRuntime returns first available when neither buzz-agent nor goose is available", () => {
+  const runtimes = [
+    makeRuntime("buzz-agent", "adapter_missing"),
+    makeRuntime("goose", "cli_missing"),
+    makeRuntime("claude"),
+  ];
+  const result = getDefaultPersonaRuntime(runtimes);
+  assert.equal(result?.id, "claude");
+});
+
+test("getDefaultPersonaRuntime returns null for an empty list", () => {
+  assert.equal(getDefaultPersonaRuntime([]), null);
+});
+
+test("getDefaultPersonaRuntime returns null when no runtime is available", () => {
+  const runtimes = [
+    makeRuntime("buzz-agent", "not_installed"),
+    makeRuntime("goose", "cli_missing"),
+  ];
+  assert.equal(getDefaultPersonaRuntime(runtimes), null);
+});
+
+// ── runtimeSupportsLlmProviderSelection — provider gating ────────────────────
+
+test("runtimeSupportsLlmProviderSelection is true for buzz-agent and goose", () => {
+  assert.equal(runtimeSupportsLlmProviderSelection("buzz-agent"), true);
+  assert.equal(runtimeSupportsLlmProviderSelection("goose"), true);
+});
+
+test("runtimeSupportsLlmProviderSelection is false for codex and claude", () => {
+  assert.equal(runtimeSupportsLlmProviderSelection("codex"), false);
+  assert.equal(runtimeSupportsLlmProviderSelection("claude"), false);
+});
+
+// ── getPersonaModelOptions — codex/claude do not use global provider ──────────
+//
+// The discovery call in AgentDefinitionDialog passes
+// `runtimeSupportsLlmProviderSelection(runtime) ? effectiveProvider : ""`
+// so codex/claude never receive the global provider. These tests verify that
+// the static model options also stay provider-agnostic for those runtimes.
+
+test("getPersonaModelOptions for codex returns only default model regardless of provider", () => {
+  const withProvider = getPersonaModelOptions("codex", "anthropic");
+  const withoutProvider = getPersonaModelOptions("codex", "");
+  assert.deepEqual(withProvider, withoutProvider);
+  assert.equal(withProvider.length, 1);
+  assert.equal(withProvider[0]?.id, "");
+});
+
+test("getPersonaModelOptions for buzz-agent with anthropic filters out zero-value default", () => {
+  // anthropic requires explicit model — zero-value option is filtered out
+  const options = getPersonaModelOptions("buzz-agent", "anthropic");
+  const zeroValue = options.find((o) => o.id === "");
+  assert.equal(
+    zeroValue,
+    undefined,
+    "explicit-model provider must not allow zero-value selection",
+  );
+});
+
+test("getPersonaModelOptions for buzz-agent with no provider returns default model", () => {
+  const options = getPersonaModelOptions("buzz-agent", "");
+  assert.equal(options.length, 1);
+  assert.equal(options[0]?.id, "");
+});
+
+// ── formatModelDiscoveryErrorStatus — runtime unavailable ────────────────────
+//
+// When selectedRuntime.availability !== "available", AgentDefinitionDialog and
+// usePersonaModelDiscovery now call formatModelDiscoveryErrorStatus with a
+// synthetic "Runtime not available: <availability>" error. Verify the status
+// is non-null (so the UI surfaces the reason) for each unavailability reason.
+
+test("formatModelDiscoveryErrorStatus returns a non-null status for runtime unavailable errors", () => {
+  for (const availability of [
+    "adapter_missing",
+    "cli_missing",
+    "not_installed",
+  ]) {
+    const status = formatModelDiscoveryErrorStatus(
+      new Error(`Runtime not available: ${availability}`),
+      "anthropic",
+    );
+    assert.ok(
+      status !== null,
+      `should return a status for availability=${availability}`,
+    );
+    assert.ok(typeof status?.message === "string", "status has a message");
+    assert.ok(typeof status?.tone === "string", "status has a tone");
+  }
+});
diff --git a/desktop/src/features/agents/ui/personaDialogPickers.tsx b/desktop/src/features/agents/ui/personaDialogPickers.tsx
index f62866b37..f7d53213a 100644
--- a/desktop/src/features/agents/ui/personaDialogPickers.tsx
+++ b/desktop/src/features/agents/ui/personaDialogPickers.tsx
@@ -1,5 +1,23 @@
 import type { AcpRuntimeCatalogEntry } from "@/shared/api/types";
 import type { RuntimeFileConfigSubset } from "@/shared/api/tauri";
+// Dialogs import getDefaultPersonaRuntime via this re-export; lib code imports
+// directly from lib/resolvePersonaRuntime.
+export { getDefaultPersonaRuntime } from "../lib/resolvePersonaRuntime";
+
+/**
+ * Provider ids suppressed from the selection list on internal Block builds.
+ * Databricks v1 (`"databricks"`) is boot-migrated to v2 on those builds, so
+ * offering it for new selections would create a regression path.
+ * OSS builds pass an empty `Set` so v1 remains visible.
+ *
+ * All three dialog sites that show a provider picker import this constant —
+ * `AgentDefinitionDialog`, `AgentInstanceEditDialog`, and
+ * `GlobalAgentConfigSettingsCard` — making it the single source of truth for
+ * which provider ids to suppress on Block builds.
+ */
+export const BLOCK_BUILD_HIDDEN_PROVIDER_IDS: ReadonlySet<string> = new Set([
+  "databricks",
+]);
 
 export const PERSONA_FIELD_SHELL_CLASS =
   "rounded-xl border border-input bg-muted/40 transition-colors duration-150 ease-out hover:border-muted-foreground/40 focus-within:border-muted-foreground/50";
@@ -16,6 +34,7 @@ export const NO_RUNTIME_DROPDOWN_VALUE = "__no_runtime__";
 
 const KNOWN_LLM_PROVIDER_IDS = [
   "anthropic",
+  "databricks",
   "databricks_v2",
   "openai",
   "openai-compat",
@@ -97,7 +116,8 @@ const PERSONA_LLM_PROVIDER_OPTIONS: readonly PersonaModelOption[] = [
   { id: "anthropic", label: "Anthropic" },
   { id: "openai", label: "OpenAI" },
   { id: "openai-compat", label: "OpenAI-compatible" },
-  { id: "databricks_v2", label: "Databricks v2 (AI Gateway)" },
+  { id: "databricks", label: "Databricks" },
+  { id: "databricks_v2", label: "Databricks v2" },
 ];
 
 const PERSONA_MODEL_OPTIONS_BY_RUNTIME: Record<
@@ -294,16 +314,33 @@ export function buildTemplateModelDropdownOptions(
   }));
 }
 
+/**
+ * Build the provider dropdown options for a persona/instance dialog.
+ *
+ * `hideProviderIds` suppresses specific provider ids from the base list while
+ * still preserving the `(current)` tail-append for saved values that are in
+ * the hidden set — so an agent already persisted with a hidden provider
+ * continues to render its current value, while the hidden option is not
+ * offered for new selections.
+ *
+ * Internal Block builds pass `BLOCK_BUILD_HIDDEN_PROVIDER_IDS` to hide the
+ * legacy Databricks v1 option (the boot migration rewrites v1→v2 on those
+ * builds). OSS builds pass an empty Set so v1 remains visible.
+ */
 export function getPersonaProviderOptions(
   currentProvider: string,
   runtimeId: string,
   globalProvider?: string,
+  hideProviderIds?: ReadonlySet<string>,
 ): readonly PersonaModelOption[] {
   const trimmedProvider = currentProvider.trim();
   const defaultProviderOptions = [
     { id: "", label: getDefaultLlmProviderLabel(runtimeId, globalProvider) },
   ];
-  const options = [...defaultProviderOptions, ...PERSONA_LLM_PROVIDER_OPTIONS];
+  const filteredOptions = hideProviderIds?.size
+    ? PERSONA_LLM_PROVIDER_OPTIONS.filter((o) => !hideProviderIds.has(o.id))
+    : PERSONA_LLM_PROVIDER_OPTIONS;
+  const options = [...defaultProviderOptions, ...filteredOptions];
   if (
     trimmedProvider.length === 0 ||
     options.some((option) => option.id === trimmedProvider)
@@ -408,18 +445,6 @@ export function sortPersonaRuntimes(
   });
 }
 
-export function getDefaultPersonaRuntime(runtimes: AcpRuntimeCatalogEntry[]) {
-  const available = runtimes.filter(
-    (runtime) => runtime.availability === "available",
-  );
-  return (
-    available.find((runtime) => runtime.id === "buzz-agent") ??
-    available.find((runtime) => runtime.id === "goose") ??
-    available[0] ??
-    null
-  );
-}
-
 /**
  * Returns true when `key` is satisfied at the global layer AND the agent-local
  * `envVars` does NOT explicitly shadow it with an empty string.
diff --git a/desktop/src/features/agents/ui/usePersonaModelDiscovery.ts b/desktop/src/features/agents/ui/usePersonaModelDiscovery.ts
index e0d4cda98..626c1ef9f 100644
--- a/desktop/src/features/agents/ui/usePersonaModelDiscovery.ts
+++ b/desktop/src/features/agents/ui/usePersonaModelDiscovery.ts
@@ -85,6 +85,11 @@ export function usePersonaModelDiscovery({
   const discoveryAgentCommand = selectedRuntime?.command?.trim()
     ? selectedRuntime.command
     : null;
+  // Narrow to the individual fields the effect consumes so a new object
+  // reference from a React Query refetch (same data, unstable ref) does not
+  // abandon and re-issue an in-flight discovery IPC call.
+  const selectedRuntimeAvailability = selectedRuntime?.availability;
+  const selectedRuntimeDefaultArgs = selectedRuntime?.defaultArgs;
   const canDiscoverModelOptions =
     open &&
     modelFieldVisible &&
@@ -121,7 +126,21 @@ export function usePersonaModelDiscovery({
     if (modelDiscoveryKey === null || discoveryAgentCommand === null) {
       modelDiscoveryRequestRef.current += 1;
       setModelDiscoveryData(null);
-      setModelDiscoveryStatus(null);
+      // When the runtime exists but is not available, surface a status message
+      // so the model dropdown explains why no live models can be loaded.
+      if (
+        selectedRuntimeAvailability != null &&
+        selectedRuntimeAvailability !== "available"
+      ) {
+        setModelDiscoveryStatus(
+          formatModelDiscoveryErrorStatus(
+            new Error(`Runtime not available: ${selectedRuntimeAvailability}`),
+            trimmedProvider,
+          ),
+        );
+      } else {
+        setModelDiscoveryStatus(null);
+      }
       setModelDiscoveryLoading(false);
       return;
     }
@@ -144,7 +163,7 @@ export function usePersonaModelDiscovery({
     function runModelDiscovery() {
       void discoverAgentModels({
         agentCommand: activeAgentCommand,
-        agentArgs: selectedRuntime?.defaultArgs ?? [],
+        agentArgs: selectedRuntimeDefaultArgs ?? [],
         provider: trimmedProvider || undefined,
         envVars,
       })
@@ -193,7 +212,8 @@ export function usePersonaModelDiscovery({
     discoveryAgentCommand,
     envVars,
     modelDiscoveryKey,
-    selectedRuntime?.defaultArgs,
+    selectedRuntimeAvailability,
+    selectedRuntimeDefaultArgs,
     shouldDebounceModelDiscovery,
     trimmedProvider,
   ]);
diff --git a/desktop/src/features/settings/ui/GlobalAgentConfigSettingsCard.tsx b/desktop/src/features/settings/ui/GlobalAgentConfigSettingsCard.tsx
index b28e4e8f1..b0f79e255 100644
--- a/desktop/src/features/settings/ui/GlobalAgentConfigSettingsCard.tsx
+++ b/desktop/src/features/settings/ui/GlobalAgentConfigSettingsCard.tsx
@@ -25,6 +25,7 @@ import type { InheritedEnvRow } from "@/features/agents/ui/EnvVarsEditor";
 import { getBakedProviderInheritLabel } from "@/features/agents/ui/bakedEnvHelpers";
 import {
   AUTO_PROVIDER_DROPDOWN_VALUE,
+  BLOCK_BUILD_HIDDEN_PROVIDER_IDS,
   CUSTOM_PROVIDER_DROPDOWN_VALUE,
   getPersonaProviderOptions,
 } from "@/features/agents/ui/personaDialogPickers";
@@ -136,6 +137,10 @@ export function GlobalAgentConfigSettingsCard() {
     () => bakedEnv.filter((e) => !BAKED_STRUCTURED_KEYS.has(e.key)),
     [bakedEnv],
   );
+  const bakedEnvKeys = React.useMemo(
+    () => bakedEnv.map((e) => e.key),
+    [bakedEnv],
+  );
 
   // Resolve the buzz-agent runtime catalog entry for model discovery.
   // The card is always visible (open=true), so the query is always enabled.
@@ -257,9 +262,21 @@ export function GlobalAgentConfigSettingsCard() {
     }
   }
 
+  // On internal Block builds, BUZZ_AGENT_PROVIDER is baked in and a boot
+  // migration rewrites v1→v2. Hide the legacy v1 option so it is not offered
+  // for new selections; OSS builds show it.
+  const hideProviderIds = React.useMemo(
+    () =>
+      bakedEnvKeys.includes("BUZZ_AGENT_PROVIDER")
+        ? BLOCK_BUILD_HIDDEN_PROVIDER_IDS
+        : new Set<string>(),
+    [bakedEnvKeys],
+  );
   const providerOptions = getPersonaProviderOptions(
     providerValue,
     "buzz-agent",
+    undefined,
+    hideProviderIds,
   );
   const providerSelectValue = isCustomProvider
     ? CUSTOM_PROVIDER_DROPDOWN_VALUE
@@ -371,6 +388,11 @@ export function GlobalAgentConfigSettingsCard() {
                     effortValid={effortValid}
                     htmlFor="global-agent-thinking-effort"
                     inheritedEffort={bakedEffort ?? undefined}
+                    inheritFallbackLabel={
+                      effortDefault !== null
+                        ? `Default (${effortDefault})`
+                        : undefined
+                    }
                     label="Default thinking / effort"
                     onChange={(value) => {
                       setConfig((prev) => {
diff --git a/desktop/src/testing/e2eBridge.ts b/desktop/src/testing/e2eBridge.ts
index 196368ff4..77d1ff6ff 100644
--- a/desktop/src/testing/e2eBridge.ts
+++ b/desktop/src/testing/e2eBridge.ts
@@ -8808,6 +8808,12 @@ export function maybeInstallE2eTauriMocks() {
             config?.mock?.globalConfigFailedRestartCount ?? 0,
         };
       }
+      case "get_baked_build_env":
+        // Mock always returns an empty baked env (OSS build simulation).
+        return [];
+      case "get_baked_build_env_keys":
+        // Mock always returns no baked env key names (OSS build simulation).
+        return [];
       case "update_managed_agent":
         return handleUpdateManagedAgent(
           payload as Parameters<typeof handleUpdateManagedAgent>[0],
diff --git a/desktop/tests/e2e/agent-provider-dropdowns.spec.ts b/desktop/tests/e2e/agent-provider-dropdowns.spec.ts
new file mode 100644
index 000000000..68cc6b8d9
--- /dev/null
+++ b/desktop/tests/e2e/agent-provider-dropdowns.spec.ts
@@ -0,0 +1,194 @@
+/**
+ * Screenshot-regression spec for PR #1764: provider/model dropdown fixes.
+ *
+ * Three states that previously regressed on fresh OSS installs:
+ *
+ *  01 – Global agent config provider select renders both Databricks v1 and v2
+ *       options (they are always shown on OSS builds; the mock bridge returns an
+ *       empty baked env, simulating an OSS install with no BUZZ_AGENT_PROVIDER).
+ *
+ *  02 – Effort dropdown shows "Default (medium)" instead of bare "Inherit" when
+ *       no effort is baked and the provider uses a known default effort level.
+ *       (provider unset → effortDefault = "medium" → inheritFallbackLabel fires)
+ *
+ *  03 – Edit dialog for a definition with runtime null auto-seeds the app-default
+ *       runtime (buzz-agent) and model discovery runs → model combobox is non-empty.
+ *       Previously, the seeding effect bailed in edit mode, leaving the runtime
+ *       empty and the model dropdown silently blank.
+ */
+import { expect, test } from "@playwright/test";
+
+import { installMockBridge } from "../helpers/bridge";
+import { waitForAnimations } from "../helpers/animations";
+
+const SHOTS = "test-results/screenshots-dialogs";
+
+/**
+ * Navigate to the agents view and wait for the global agent config card to
+ * finish its async load (spinner gone, card content visible).
+ */
+async function openAgentsView(page: import("@playwright/test").Page) {
+  await page.goto("/");
+  await page.getByTestId("open-agents-view").click();
+  await expect(page.getByTestId("settings-global-agent-config")).toBeVisible({
+    timeout: 10_000,
+  });
+  // The card shows a spinner during the async load effect; wait for it to clear.
+  await expect(page.locator(".animate-spin").first()).not.toBeVisible({
+    timeout: 5_000,
+  });
+}
+
+test.describe("agent provider dropdown screenshots", () => {
+  test.use({ viewport: { width: 1280, height: 900 } });
+
+  test.beforeEach(async ({ page }) => {
+    page.on("pageerror", (err) => {
+      console.error(
+        "PAGE ERROR:",
+        err.message,
+        err.stack?.split("\n").slice(0, 5).join("\n"),
+      );
+    });
+  });
+
+  // Shot 01: OSS provider dropdown includes both Databricks v1 and v2.
+  //
+  // The mock bridge returns get_baked_build_env_keys = [] (OSS), so no
+  // BUZZ_AGENT_PROVIDER is baked and hideProviderIds is empty → v1 appears.
+  test("01-provider-dropdown-oss", async ({ page }) => {
+    await installMockBridge(page);
+    await openAgentsView(page);
+
+    const providerSelect = page.locator("#global-agent-provider");
+    await expect(providerSelect).toBeVisible({ timeout: 5_000 });
+
+    // Regression: both v1 and v2 must be present on OSS.
+    const optionTexts = await providerSelect.evaluate((el: HTMLSelectElement) =>
+      Array.from(el.options).map((o) => o.text.trim()),
+    );
+    expect(optionTexts).toContain("Databricks");
+    expect(optionTexts).toContain("Databricks v2");
+
+    await waitForAnimations(page);
+
+    // Screenshot the card — provider select is closed but the assertion above
+    // proves both Databricks options are present in the option list.
+    await page
+      .getByTestId("settings-global-agent-config")
+      .screenshot({ path: `${SHOTS}/01-provider-dropdown-oss.png` });
+  });
+
+  // Shot 02: Effort dropdown shows "Default (medium)" (no baked effort,
+  // provider=databricks_v2 with no model → effortDefault = "medium").
+  //
+  // getProviderEffortConfig("databricks_v2", "") hits the blank-model branch:
+  //   → { defaultValue: "medium" }
+  // inheritFallbackLabel = "Default (medium)", bakedEffort = null (OSS)
+  // → the zero-value option reads "Default (medium)" instead of bare "Inherit".
+  //
+  // Using databricks_v2 here (rather than no provider) makes this card
+  // visually distinct from shot 01 — the provider select shows "Databricks v2"
+  // as the selected value — so the two PNG hashes differ.
+  test("02-effort-default-label", async ({ page }) => {
+    await installMockBridge(page, {
+      globalAgentConfig: {
+        provider: "databricks_v2",
+        model: null,
+        env_vars: {},
+      },
+    });
+    await openAgentsView(page);
+
+    const effortSelect = page.locator("#global-agent-thinking-effort");
+    await expect(effortSelect).toBeVisible({ timeout: 5_000 });
+
+    // Regression: the zero-value option must show the provider's default
+    // effort rather than a bare "Inherit".
+    const zeroOptionText = await effortSelect.evaluate(
+      (el: HTMLSelectElement) =>
+        Array.from(el.options)
+          .find((o) => o.value === "")
+          ?.text.trim() ?? "",
+    );
+    expect(zeroOptionText).toBe("Default (medium)");
+
+    await waitForAnimations(page);
+
+    await page
+      .getByTestId("settings-global-agent-config")
+      .screenshot({ path: `${SHOTS}/02-effort-default-label.png` });
+  });
+
+  // Shot 03: Edit dialog for a definition with null runtime auto-seeds the
+  // default runtime (buzz-agent via getDefaultPersonaRuntime) and model
+  // discovery runs, producing a non-empty model combobox.
+  //
+  // Previously the seeding effect bailed in edit mode ("id" in initialValues),
+  // leaving runtime = "" → modelFieldVisible = false → discovery never ran →
+  // the model dropdown was silently empty.
+  test("03-builtin-edit-runtime-seeded", async ({ page }) => {
+    await installMockBridge(page, {
+      personas: [
+        {
+          displayName: "Null Runtime Agent",
+          systemPrompt: "An agent with no runtime configured.",
+          // runtime/provider/model not set → all null in the mock, so the
+          // edit dialog must auto-seed the app default runtime.
+        },
+      ],
+    });
+
+    await page.goto("/");
+    await page.getByTestId("open-agents-view").click();
+    await expect(page.getByTestId("agents-library-personas")).toBeVisible({
+      timeout: 10_000,
+    });
+
+    // Open the persona's actions menu (visible for non-builtin personas).
+    const actionsBtn = page.getByRole("button", {
+      name: "Open actions for Null Runtime Agent",
+    });
+    await expect(actionsBtn).toBeVisible({ timeout: 8_000 });
+    await actionsBtn.click();
+
+    await page.getByRole("menuitem", { name: "Edit" }).click();
+
+    const dialog = page.getByTestId("persona-dialog");
+    await expect(dialog).toBeVisible({ timeout: 10_000 });
+
+    // Regression: the runtime trigger must not be empty — the auto-seed effect
+    // must have run and selected the app default (buzz-agent in the mock catalog).
+    const runtimeTrigger = dialog.locator("#persona-runtime");
+    await expect(runtimeTrigger).toBeVisible({ timeout: 8_000 });
+    await expect(runtimeTrigger).not.toContainText("No preference", {
+      timeout: 8_000,
+    });
+
+    // Regression: the model combobox must appear (modelFieldVisible = true once
+    // runtime is non-empty) and model discovery must have run, populating it.
+    const modelCombobox = dialog.getByRole("combobox", { name: /model/i });
+    await expect(modelCombobox).toBeVisible({ timeout: 8_000 });
+
+    // Open the picker and assert that a known model from the mock discovery
+    // response is listed. The mock returns "Claude Opus 4.6" for all providers
+    // (see discover_agent_models in e2eBridge.ts). A zero-model discovery
+    // regression would leave the list empty and this assertion would fail.
+    // The picker is a searchable command popover portaled outside the dialog
+    // whose items render as buttons — query at page level.
+    await modelCombobox.click();
+    await expect(
+      page.getByRole("button", { name: /Claude Opus 4\.6/i }),
+    ).toBeVisible({ timeout: 5_000 });
+    // Close the popover so the screenshot captures the dialog's resting state.
+    await page.keyboard.press("Escape");
+    await expect(
+      page.getByRole("button", { name: /Claude Opus 4\.6/i }),
+    ).toBeHidden();
+
+    await waitForAnimations(page);
+    await dialog.screenshot({
+      path: `${SHOTS}/03-builtin-edit-runtime-seeded.png`,
+    });
+  });
+});