fix: show loading view with retry instead of grey screen when state not hydrated

Replace `return null` with a LoadingView component when the webview
has not yet received its initial state from the extension host. This
prevents users from seeing a blank grey panel (#11931).

The LoadingView shows a spinner while waiting, automatically retries
the webviewDidLaunch message up to 3 times (every 5 seconds), and
displays a manual "Retry Connection" button after all retries are
exhausted.

webview-ui/src/App.tsx

@@ -19,6 +19,7 @@ import { MarketplaceView } from "./components/marketplace/MarketplaceView"
 import { CheckpointRestoreDialog } from "./components/chat/CheckpointRestoreDialog"
 import { DeleteMessageDialog, EditMessageDialog } from "./components/chat/MessageModificationConfirmationDialog"
 import ErrorBoundary from "./components/ErrorBoundary"
+import LoadingView from "./components/LoadingView"
 import { CloudView } from "./components/cloud/CloudView"
 import { useAddNonInteractiveClickListener } from "./components/ui/hooks/useNonInteractiveClick"
 import { TooltipProvider } from "./components/ui/tooltip"
@@ -217,7 +218,7 @@ const App = () => {
 	}, [tab])
 
 	if (!didHydrateState) {
-		return null
+		return <LoadingView />
 	}
 
 	// Do not conditionally load ChatView, it's expensive and there's state we

webview-ui/src/components/LoadingView.tsx

@@ -0,0 +1,73 @@
+import React, { useEffect, useState, useCallback } from "react"
+import { useAppTranslation } from "../i18n/TranslationContext"
+import { vscode } from "../utils/vscode"
+
+const RETRY_INTERVAL_MS = 5_000
+const MAX_RETRIES = 3
+
+/**
+ * LoadingView is displayed while the webview waits for the extension host to
+ * send the initial state hydration message.  It replaces the previous
+ * `return null` which left users staring at a blank grey panel (see #11931).
+ *
+ * If the state message does not arrive within {@link RETRY_INTERVAL_MS} the
+ * component automatically re-sends the `webviewDidLaunch` message up to
+ * {@link MAX_RETRIES} times, after which a manual "Retry" button is shown.
+ */
+export default function LoadingView() {
+	const { t } = useAppTranslation()
+	const [retryCount, setRetryCount] = useState(0)
+	const [showRetryButton, setShowRetryButton] = useState(false)
+
+	const retry = useCallback(() => {
+		vscode.postMessage({ type: "webviewDidLaunch" })
+		setRetryCount((prev) => prev + 1)
+	}, [])
+
+	// Automatic retries on a timer
+	useEffect(() => {
+		if (showRetryButton) {
+			return // Stop auto-retrying once we're showing the manual button.
+		}
+
+		const timer = setTimeout(() => {
+			if (retryCount < MAX_RETRIES) {
+				retry()
+			} else {
+				setShowRetryButton(true)
+			}
+		}, RETRY_INTERVAL_MS)
+
+		return () => clearTimeout(timer)
+	}, [retryCount, showRetryButton, retry])
+
+	return (
+		<div className="absolute inset-0 flex flex-col bg-vscode-editor-background text-vscode-foreground">
+			<div className="flex-1 flex items-center justify-center px-6">
+				<div className="flex flex-col items-center gap-5 text-center">
+					{!showRetryButton ? (
+						<div className="flex items-center gap-2 text-sm text-vscode-descriptionForeground">
+							<span className="codicon codicon-loading codicon-modifier-spin text-base" />
+							<span>{t("common:ui.initializing")}</span>
+						</div>
+					) : (
+						<div className="flex flex-col items-center gap-3">
+							<p className="text-sm text-vscode-descriptionForeground">
+								{t("common:ui.connection_failed")}
+							</p>
+							<button
+								className="px-4 py-1.5 rounded text-sm font-medium bg-vscode-button-background text-vscode-button-foreground hover:bg-vscode-button-hoverBackground"
+								onClick={() => {
+									setRetryCount(0)
+									setShowRetryButton(false)
+									retry()
+								}}>
+								{t("common:ui.retry_connection")}
+							</button>
+						</div>
+					)}
+				</div>
+			</div>
+		</div>
+	)
+}

webview-ui/src/components/__tests__/LoadingView.spec.tsx

@@ -0,0 +1,100 @@
+// npx vitest run src/components/__tests__/LoadingView.spec.tsx
+
+import React from "react"
+import { render, screen, act } from "@testing-library/react"
+import LoadingView from "../LoadingView"
+
+vi.mock("@src/utils/vscode", () => ({
+	vscode: {
+		postMessage: vi.fn(),
+	},
+}))
+
+vi.mock("@src/i18n/TranslationContext", () => ({
+	useAppTranslation: () => ({
+		t: (key: string) => {
+			const translations: Record<string, string> = {
+				"common:ui.initializing": "Initializing...",
+				"common:ui.retry_connection": "Retry Connection",
+				"common:ui.connection_failed":
+					"Unable to connect to the extension host. Click the button below to retry.",
+			}
+			return translations[key] ?? key
+		},
+	}),
+}))
+
+describe("LoadingView", () => {
+	beforeEach(() => {
+		vi.clearAllMocks()
+		vi.useFakeTimers()
+	})
+
+	afterEach(() => {
+		vi.useRealTimers()
+	})
+
+	it("renders a spinner and initializing text", () => {
+		render(<LoadingView />)
+		expect(screen.getByText("Initializing...")).toBeInTheDocument()
+	})
+
+	it("does not show retry button initially", () => {
+		render(<LoadingView />)
+		expect(screen.queryByText("Retry Connection")).not.toBeInTheDocument()
+	})
+
+	it("retries webviewDidLaunch after timeout", async () => {
+		const { vscode } = await import("@src/utils/vscode")
+		render(<LoadingView />)
+
+		// Advance past the first retry interval (5s)
+		act(() => {
+			vi.advanceTimersByTime(5_000)
+		})
+
+		expect(vscode.postMessage).toHaveBeenCalledWith({ type: "webviewDidLaunch" })
+	})
+
+	it("shows retry button after max retries", async () => {
+		render(<LoadingView />)
+
+		// Advance through all 3 retries (5s each) + one more to trigger the button
+		for (let i = 0; i < 4; i++) {
+			act(() => {
+				vi.advanceTimersByTime(5_000)
+			})
+		}
+
+		expect(screen.getByText("Retry Connection")).toBeInTheDocument()
+		expect(
+			screen.getByText("Unable to connect to the extension host. Click the button below to retry."),
+		).toBeInTheDocument()
+	})
+
+	it("allows manual retry when button is clicked", async () => {
+		const { vscode } = await import("@src/utils/vscode")
+		render(<LoadingView />)
+
+		// Advance through all retries to show the button
+		for (let i = 0; i < 4; i++) {
+			act(() => {
+				vi.advanceTimersByTime(5_000)
+			})
+		}
+
+		const calls = (vscode.postMessage as ReturnType<typeof vi.fn>).mock.calls.length
+
+		const retryButton = screen.getByText("Retry Connection")
+		act(() => {
+			retryButton.click()
+		})
+
+		// Should have sent another webviewDidLaunch
+		expect((vscode.postMessage as ReturnType<typeof vi.fn>).mock.calls.length).toBeGreaterThan(calls)
+		expect(vscode.postMessage).toHaveBeenCalledWith({ type: "webviewDidLaunch" })
+
+		// Should go back to showing the spinner
+		expect(screen.getByText("Initializing...")).toBeInTheDocument()
+	})
+})

webview-ui/src/i18n/locales/en/common.json

@@ -21,7 +21,10 @@
 	},
 	"ui": {
 		"search_placeholder": "Search...",
-		"no_results": "No results found"
+		"no_results": "No results found",
+		"initializing": "Initializing...",
+		"retry_connection": "Retry Connection",
+		"connection_failed": "Unable to connect to the extension host. Click the button below to retry."
 	},
 	"mermaid": {
 		"loading": "Generating mermaid diagram...",