diff --git a/packages/app/e2e/browser/offline-draft.spec.ts b/packages/app/e2e/browser/offline-draft.spec.ts
new file mode 100644
index 0000000000..36ae726457
--- /dev/null
+++ b/packages/app/e2e/browser/offline-draft.spec.ts
@@ -0,0 +1,32 @@
+import { expect, test } from "../support/fixtures";
+import { expectComposerModel } from "../support/helpers/agent-profiles";
+import { installDaemonWebSocketGate } from "../support/helpers/daemon-websocket-gate";
+import { createAgentTabFromMenu } from "../support/helpers/workspace-tabs";
+import { submitMessage } from "../support/helpers/composer";
+
+async function restoreHostConnection(gate: Awaited<ReturnType<typeof installDaemonWebSocketGate>>) {
+  gate.holdNextServerMessage("status");
+  gate.restore();
+  await gate.waitForHeldServerMessage("status");
+  gate.releaseHeldServerMessage("status");
+}
+
+test("an offline workspace draft reports the disconnected host instead of loading models", async ({
+  page,
+  withWorkspace,
+}) => {
+  const gate = await installDaemonWebSocketGate(page);
+  const workspace = await withWorkspace();
+  await workspace.navigateTo();
+  await gate.drop();
+  await gate.waitForBlockedConnection();
+  await createAgentTabFromMenu(page);
+  await submitMessage(page, "hello");
+  await expect(page.getByRole("alert").filter({ hasText: "Host is not connected" })).toHaveText(
+    "Host is not connected",
+  );
+  await expect(page.getByText("Loading...", { exact: true })).toHaveCount(0);
+  await restoreHostConnection(gate);
+  await expectComposerModel(page, "Ten second stream");
+  await expect(page.getByRole("textbox", { name: "Message agent..." })).toHaveValue("hello");
+});
diff --git a/packages/app/src/composer/draft/workspace-tab-core.ts b/packages/app/src/composer/draft/workspace-tab-core.ts
index 30411aeb00..26bf548064 100644
--- a/packages/app/src/composer/draft/workspace-tab-core.ts
+++ b/packages/app/src/composer/draft/workspace-tab-core.ts
@@ -24,7 +24,7 @@ export function validateDraftSubmission(input: {
   };
   autoSubmitConfig: WorkspaceDraftAutoSubmitConfig | null;
   workspaceDirectory: string | null;
-  hasClient: boolean;
+  isConnected: boolean;
 }): string | null {
   const {
     text,
@@ -32,7 +32,7 @@ export function validateDraftSubmission(input: {
     composerState,
     autoSubmitConfig,
     workspaceDirectory,
-    hasClient,
+    isConnected,
   } = input;
   const readiness = resolveSubmissionReadiness({
     text,
@@ -46,7 +46,7 @@ export function validateDraftSubmission(input: {
     },
     autoSubmitConfig,
     workspaceDirectory,
-    hasClient,
+    isConnected,
   });
   return readiness.ok ? null : (readiness.reason ?? null);
 }
diff --git a/packages/app/src/composer/draft/workspace-tab.test.ts b/packages/app/src/composer/draft/workspace-tab.test.ts
index 5952083a62..1d7e2d4b2c 100644
--- a/packages/app/src/composer/draft/workspace-tab.test.ts
+++ b/packages/app/src/composer/draft/workspace-tab.test.ts
@@ -17,12 +17,26 @@ function validate(overrides = {}) {
     composerState: baseComposerState,
     autoSubmitConfig: null,
     workspaceDirectory: "/tmp/project",
-    hasClient: true,
+    isConnected: true,
     ...overrides,
   });
 }
 
 describe("workspace draft agent model validation", () => {
+  test("reports an offline host before an absent catalog or pending model defaults", () => {
+    expect(
+      validate({
+        isConnected: false,
+        composerState: {
+          ...baseComposerState,
+          providerDefinitions: [],
+          selectedProvider: null,
+          isModelLoading: true,
+        },
+      }),
+    ).toBe("Host is not connected");
+  });
+
   test("allows a ready provider with no models to submit without a selected model", () => {
     expect(validate({})).toBeNull();
   });
diff --git a/packages/app/src/composer/draft/workspace-tab.tsx b/packages/app/src/composer/draft/workspace-tab.tsx
index b54b344a36..27ca8b8af8 100644
--- a/packages/app/src/composer/draft/workspace-tab.tsx
+++ b/packages/app/src/composer/draft/workspace-tab.tsx
@@ -16,7 +16,7 @@ import { useAgentInputDraft } from "@/composer/draft/input-draft";
 import type { CreateAgentInitialValues } from "@/hooks/use-agent-form-state";
 import { useDraftAgentCreateFlow, type DraftCreateAttempt } from "@/composer/draft/create-flow";
 import { resolveTurnPresentation, TURN_LIVENESS_IDLE } from "@/timeline/turn-liveness";
-import { useHostRuntimeClient } from "@/runtime/host-runtime";
+import { useHostRuntimeClient, useHostRuntimeIsConnected } from "@/runtime/host-runtime";
 import { buildWorkspaceDraftAgentConfig } from "@/screens/workspace/workspace-draft-agent-config";
 import { buildDraftStoreKey } from "@/stores/draft-keys";
 import { useCreateFlowStore } from "@/stores/create-flow-store";
@@ -305,6 +305,7 @@ export function WorkspaceDraftAgentTab({
 }: WorkspaceDraftAgentTabProps) {
   const { t } = useTranslation();
   const client = useHostRuntimeClient(serverId);
+  const isConnected = useHostRuntimeIsConnected(serverId);
   const workspaceFields = useWorkspaceFields(serverId, workspaceId, (w) => ({
     workspaceDirectory: w.workspaceDirectory,
     id: w.id,
@@ -445,7 +446,7 @@ export function WorkspaceDraftAgentTab({
         composerState,
         autoSubmitConfig,
         workspaceDirectory: draftWorkingDirectory,
-        hasClient: Boolean(client),
+        isConnected,
       });
     },
     onBeforeSubmit: async () => {
diff --git a/packages/app/src/hooks/use-agent-form-state.ts b/packages/app/src/hooks/use-agent-form-state.ts
index 26908bd6a0..1522ce082e 100644
--- a/packages/app/src/hooks/use-agent-form-state.ts
+++ b/packages/app/src/hooks/use-agent-form-state.ts
@@ -36,6 +36,7 @@ import {
   type FormState,
   type ProviderModelsByProvider,
 } from "@/provider-selection/resolve-agent-form";
+import { useHostRuntimeIsConnected } from "@/runtime/host-runtime";
 import type { MaterializedAgentProfile } from "@/agent-profiles";
 
 export type { FormInitialValues } from "@/provider-selection/resolve-agent-form";
@@ -186,6 +187,8 @@ export function useAgentFormState(options: UseAgentFormStateOptions): UseAgentFo
     refetchIfStale: refetchSnapshotIfStale,
   } = useProvidersSnapshot(serverId, { cwd: workingDir });
 
+  const isConnected = useHostRuntimeIsConnected(serverId ?? "");
+
   const allProviderEntries = useMemo(() => snapshotEntries ?? [], [snapshotEntries]);
   const snapshotProviderDefinitions = useMemo(
     () => buildProviderDefinitions(snapshotEntries),
@@ -220,8 +223,8 @@ export function useAgentFormState(options: UseAgentFormStateOptions): UseAgentFo
     [snapshotEntries],
   );
   const snapshotModelSelectorProviders = useMemo(
-    () => buildSelectableProviderSelectorProviders(snapshotEntries),
-    [snapshotEntries],
+    () => buildSelectableProviderSelectorProviders(snapshotEntries, isConnected),
+    [snapshotEntries, isConnected],
   );
   const snapshotSelectedEntry = useMemo(
     () =>
@@ -247,7 +250,8 @@ export function useAgentFormState(options: UseAgentFormStateOptions): UseAgentFo
   const availableModels = snapshotSelectedProviderModels;
   const modeOptions = snapshotSelectedProviderModes;
   const isModelSelectionLoading =
-    resolution.status === "pending" || snapshotIsLoading || selectedProviderIsLoading;
+    isConnected &&
+    (resolution.status === "pending" || snapshotIsLoading || selectedProviderIsLoading);
   const isAllModelsLoading = isModelSelectionLoading;
 
   useEffect(() => {
diff --git a/packages/app/src/provider-selection/provider-selection.test.ts b/packages/app/src/provider-selection/provider-selection.test.ts
index 6c13ad3d83..1c04c0b154 100644
--- a/packages/app/src/provider-selection/provider-selection.test.ts
+++ b/packages/app/src/provider-selection/provider-selection.test.ts
@@ -15,6 +15,21 @@ import {
 } from "./provider-selection";
 
 describe("combined model selector data", () => {
+  it("shows a disconnected error for unfinished catalogs while keeping known models", () => {
+    const providers = buildSelectableProviderSelectorProviders(
+      [
+        snapshotEntry({ provider: "waiting", status: "loading", models: [] }),
+        snapshotEntry({ provider: "codex", status: "ready", models: [codexModel] }),
+      ],
+      false,
+    );
+    expect(providers[0].modelSelection).toEqual({
+      kind: "error",
+      message: "Host is not connected",
+    });
+    expect(providers[1].modelSelection.kind).toBe("models");
+  });
+
   const codexModel: AgentModelDefinition = {
     provider: "codex",
     id: "gpt-5.4",
@@ -367,7 +382,7 @@ describe("combined model selector data", () => {
         },
         autoSubmitConfig: null,
         workspaceDirectory: "/repo",
-        hasClient: true,
+        isConnected: true,
       }),
     ).toEqual({
       ok: false,
@@ -387,7 +402,7 @@ describe("combined model selector data", () => {
         },
         autoSubmitConfig: null,
         workspaceDirectory: "/repo",
-        hasClient: true,
+        isConnected: true,
       }),
     ).toEqual({ ok: true });
   });
@@ -426,7 +441,7 @@ describe("combined model selector data", () => {
           },
           autoSubmitConfig: null,
           workspaceDirectory: "/repo",
-          hasClient: true,
+          isConnected: true,
         }),
       ).toEqual({ ok: false, reason: "初始 prompt 必填" });
     } finally {
diff --git a/packages/app/src/provider-selection/provider-selection.ts b/packages/app/src/provider-selection/provider-selection.ts
index f66a1b1476..e0313c6623 100644
--- a/packages/app/src/provider-selection/provider-selection.ts
+++ b/packages/app/src/provider-selection/provider-selection.ts
@@ -103,6 +103,7 @@ function buildModelSelection(
 function buildEntryModelSelection(
   entry: ProviderSnapshotEntry,
   label: string,
+  isConnected: boolean,
 ): ProviderModelSelection {
   if ((entry.models?.length ?? 0) > 0) {
     return buildModelSelection(entry.provider, label, entry.models ?? null);
@@ -111,7 +112,9 @@ function buildEntryModelSelection(
     return buildModelSelection(entry.provider, label, entry.models ?? null);
   }
   if (entry.status === "loading") {
-    return { kind: "loading" };
+    return isConnected
+      ? { kind: "loading" }
+      : { kind: "error", message: i18n.t("providerSelection.readiness.hostDisconnected") };
   }
   return {
     kind: "error",
@@ -142,6 +145,7 @@ export function buildProviderSelectorProviders(input: {
 
 export function buildSelectableProviderSelectorProviders(
   entries: ProviderSnapshotEntry[] | undefined,
+  isConnected = true,
 ): ProviderSelectorProvider[] {
   return (entries ?? [])
     .filter((entry) => entry.enabled)
@@ -150,7 +154,7 @@ export function buildSelectableProviderSelectorProviders(
       return {
         id: entry.provider,
         label,
-        modelSelection: buildEntryModelSelection(entry, label),
+        modelSelection: buildEntryModelSelection(entry, label, isConnected),
       };
     });
 }
@@ -345,11 +349,14 @@ export function resolveSubmissionReadiness(input: {
   };
   autoSubmitConfig: { provider: string; model: string | null } | null;
   workspaceDirectory: string | null;
-  hasClient: boolean;
+  isConnected: boolean;
 }): ProviderSelectionReadiness {
   if (!input.allowsEmptyAutoSubmit && !input.text.trim()) {
     return { ok: false, reason: i18n.t("providerSelection.readiness.initialPromptRequired") };
   }
+  if (!input.isConnected) {
+    return { ok: false, reason: i18n.t("providerSelection.readiness.hostDisconnected") };
+  }
   if (input.providerCount === 0) {
     return { ok: false, reason: i18n.t("providerSelection.readiness.noProviders") };
   }
@@ -366,8 +373,5 @@ export function resolveSubmissionReadiness(input: {
   if (!input.workspaceDirectory) {
     return { ok: false, reason: i18n.t("providerSelection.readiness.workspaceDirectoryNotFound") };
   }
-  if (!input.hasClient) {
-    return { ok: false, reason: i18n.t("providerSelection.readiness.hostDisconnected") };
-  }
   return { ok: true };
 }