feat(vertex): add 1M context window beta support for Claude Sonnet 4

Author: hannesrudolph

packages/types/src/provider-settings.ts

@@ -237,6 +237,7 @@ const vertexSchema = apiModelIdProviderModelSchema.extend({
 	vertexRegion: z.string().optional(),
 	enableUrlContext: z.boolean().optional(),
 	enableGrounding: z.boolean().optional(),
+	vertex1MContext: z.boolean().optional(), // Enable 'context-1m-2025-08-07' beta for 1M context window.
 })
 
 const openAiSchema = baseProviderSettingsSchema.extend({

packages/types/src/providers/vertex.ts

@@ -517,6 +517,10 @@ export const vertexModels = {
 	},
 } as const satisfies Record<string, ModelInfo>
 
+// Vertex AI models that support 1M context window beta
+// Uses the same beta header 'context-1m-2025-08-07' as Anthropic and Bedrock
+export const VERTEX_1M_CONTEXT_MODEL_IDS = ["claude-sonnet-4@20250514", "claude-sonnet-4-5@20250929"] as const
+
 export const VERTEX_REGIONS = [
 	{ value: "global", label: "global" },
 	{ value: "us-central1", label: "us-central1" },

webview-ui/src/components/settings/providers/Vertex.tsx

@@ -2,7 +2,7 @@ import { useCallback } from "react"
 import { Checkbox } from "vscrui"
 import { VSCodeLink, VSCodeTextField } from "@vscode/webview-ui-toolkit/react"
 
-import { type ProviderSettings, VERTEX_REGIONS } from "@roo-code/types"
+import { type ProviderSettings, VERTEX_REGIONS, VERTEX_1M_CONTEXT_MODEL_IDS } from "@roo-code/types"
 
 import { useAppTranslation } from "@src/i18n/TranslationContext"
 import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from "@src/components/ui"
@@ -18,6 +18,13 @@ type VertexProps = {
 export const Vertex = ({ apiConfiguration, setApiConfigurationField, simplifySettings }: VertexProps) => {
 	const { t } = useAppTranslation()
 
+	// Check if the selected model supports 1M context (Claude Sonnet 4 / 4.5)
+	const supports1MContextBeta =
+		!!apiConfiguration?.apiModelId &&
+		VERTEX_1M_CONTEXT_MODEL_IDS.includes(
+			apiConfiguration.apiModelId as (typeof VERTEX_1M_CONTEXT_MODEL_IDS)[number],
+		)
+
 	const handleInputChange = useCallback(
 		<K extends keyof ProviderSettings, E>(
 			field: K,
@@ -94,6 +101,22 @@ export const Vertex = ({ apiConfiguration, setApiConfigurationField, simplifySet
 				</Select>
 			</div>
 
+			{supports1MContextBeta && (
+				<div>
+					<Checkbox
+						data-testid="checkbox-vertex-1m-context"
+						checked={apiConfiguration?.vertex1MContext ?? false}
+						onChange={(checked: boolean) => {
+							setApiConfigurationField("vertex1MContext", checked)
+						}}>
+						{t("settings:providers.vertex1MContextBetaLabel")}
+					</Checkbox>
+					<div className="text-sm text-vscode-descriptionForeground mt-1 ml-6">
+						{t("settings:providers.vertex1MContextBetaDescription")}
+					</div>
+				</div>
+			)}
+
 			{!simplifySettings && apiConfiguration.apiModelId?.startsWith("gemini") && (
 				<div className="mt-6">
 					<Checkbox

webview-ui/src/i18n/locales/ca/settings.json

@@ -310,6 +310,8 @@
 		"anthropic1MContextBetaDescription": "Extends context window to 1 million tokens for Claude Sonnet 4",
 		"awsBedrock1MContextBetaLabel": "Enable 1M context window (Beta)",
 		"awsBedrock1MContextBetaDescription": "Extends context window to 1 million tokens for Claude Sonnet 4",
+		"vertex1MContextBetaLabel": "Enable 1M context window (Beta)",
+		"vertex1MContextBetaDescription": "Extends context window to 1 million tokens for Claude Sonnet 4",
 		"basetenApiKey": "Baseten API Key",
 		"getBasetenApiKey": "Get Baseten API Key",
 		"cerebrasApiKey": "Cerebras API Key",