fix(bedrock): enable prompt caching for custom ARN and default to ON

src/api/providers/__tests__/bedrock.spec.ts

@@ -1287,4 +1287,67 @@ describe("AwsBedrockHandler", () => {
 			expect(mockCaptureException).toHaveBeenCalled()
 		})
 	})
+
+	describe("prompt cache default behavior", () => {
+		function setupMockStreamText() {
+			async function* mockFullStream() {
+				yield { type: "text-delta", text: "response" }
+			}
+			mockStreamText.mockReturnValue({
+				fullStream: mockFullStream(),
+				usage: Promise.resolve({ inputTokens: 10, outputTokens: 5 }),
+				providerMetadata: Promise.resolve({}),
+			})
+		}
+
+		const messages: Anthropic.Messages.MessageParam[] = [{ role: "user", content: "Hello" }]
+
+		it("should enable prompt caching by default when awsUsePromptCache is undefined", async () => {
+			setupMockStreamText()
+
+			const defaultHandler = new AwsBedrockHandler({
+				apiModelId: "anthropic.claude-3-5-sonnet-20241022-v2:0",
+				awsAccessKey: "test-access-key",
+				awsSecretKey: "test-secret-key",
+				awsRegion: "us-east-1",
+				// awsUsePromptCache is intentionally omitted (undefined)
+			})
+
+			const generator = defaultHandler.createMessage("You are a helpful assistant", messages)
+			for await (const _chunk of generator) {
+				// consume the stream
+			}
+
+			expect(mockStreamText).toHaveBeenCalledTimes(1)
+			const callArgs = mockStreamText.mock.calls[0][0]
+
+			// systemProviderOptions should include cachePoint since prompt caching defaults to ON
+			expect(callArgs.systemProviderOptions).toEqual({
+				bedrock: { cachePoint: { type: "default" } },
+			})
+		})
+
+		it("should disable prompt caching when awsUsePromptCache is explicitly false", async () => {
+			setupMockStreamText()
+
+			const disabledHandler = new AwsBedrockHandler({
+				apiModelId: "anthropic.claude-3-5-sonnet-20241022-v2:0",
+				awsAccessKey: "test-access-key",
+				awsSecretKey: "test-secret-key",
+				awsRegion: "us-east-1",
+				awsUsePromptCache: false,
+			})
+
+			const generator = disabledHandler.createMessage("You are a helpful assistant", messages)
+			for await (const _chunk of generator) {
+				// consume the stream
+			}
+
+			expect(mockStreamText).toHaveBeenCalledTimes(1)
+			const callArgs = mockStreamText.mock.calls[0][0]
+
+			// systemProviderOptions should NOT include cachePoint since caching is explicitly disabled
+			expect(callArgs.systemProviderOptions).toBeUndefined()
+		})
+	})
 })

src/api/providers/bedrock.ts

@@ -271,7 +271,9 @@ export class AwsBedrockHandler extends BaseProvider implements SingleCompletionH
 		// We identify targets in the ORIGINAL Anthropic messages (before AI SDK conversion)
 		// because convertToAiSdkMessages() splits user messages containing tool_results into
 		// separate "tool" + "user" role messages, which would skew naive counting.
-		const usePromptCache = Boolean(this.options.awsUsePromptCache && this.supportsAwsPromptCache(modelConfig))
+		const usePromptCache = Boolean(
+			(this.options.awsUsePromptCache ?? true) && this.supportsAwsPromptCache(modelConfig),
+		)
 
 		if (usePromptCache) {
 			const cachePointOption = { bedrock: { cachePoint: { type: "default" as const } } }

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

@@ -198,7 +198,7 @@ export const Bedrock = ({ apiConfiguration, setApiConfigurationField, selectedMo
 			{selectedModelInfo?.supportsPromptCache && (
 				<>
 					<Checkbox
-						checked={apiConfiguration?.awsUsePromptCache || false}
+						checked={apiConfiguration?.awsUsePromptCache ?? true}
 						onChange={handleInputChange("awsUsePromptCache", noTransform)}>
 						<div className="flex items-center gap-1">
 							<span>{t("settings:providers.enablePromptCaching")}</span>

webview-ui/src/components/ui/hooks/__tests__/useSelectedModel.spec.ts

@@ -464,6 +464,52 @@ describe("useSelectedModel", () => {
 		})
 	})
 
+	describe("bedrock provider with custom ARN", () => {
+		beforeEach(() => {
+			mockUseRouterModels.mockReturnValue({
+				data: {
+					openrouter: {},
+					requesty: {},
+					litellm: {},
+				},
+				isLoading: false,
+				isError: false,
+			} as any)
+
+			mockUseOpenRouterModelProviders.mockReturnValue({
+				data: {},
+				isLoading: false,
+				isError: false,
+			} as any)
+		})
+
+		it("should enable supportsPromptCache for custom-arn model", () => {
+			const apiConfiguration: ProviderSettings = {
+				apiProvider: "bedrock",
+				apiModelId: "custom-arn",
+			}
+
+			const wrapper = createWrapper()
+			const { result } = renderHook(() => useSelectedModel(apiConfiguration), { wrapper })
+
+			expect(result.current.id).toBe("custom-arn")
+			expect(result.current.info?.supportsPromptCache).toBe(true)
+		})
+
+		it("should enable supportsImages for custom-arn model", () => {
+			const apiConfiguration: ProviderSettings = {
+				apiProvider: "bedrock",
+				apiModelId: "custom-arn",
+			}
+
+			const wrapper = createWrapper()
+			const { result } = renderHook(() => useSelectedModel(apiConfiguration), { wrapper })
+
+			expect(result.current.id).toBe("custom-arn")
+			expect(result.current.info?.supportsImages).toBe(true)
+		})
+	})
+
 	describe("litellm provider", () => {
 		beforeEach(() => {
 			mockUseOpenRouterModelProviders.mockReturnValue({

webview-ui/src/components/ui/hooks/useSelectedModel.ts

@@ -183,7 +183,7 @@ function getSelectedModel({
 			if (id === "custom-arn") {
 				return {
 					id,
-					info: { maxTokens: 5000, contextWindow: 128_000, supportsPromptCache: false, supportsImages: true },
+					info: { maxTokens: 5000, contextWindow: 128_000, supportsPromptCache: true, supportsImages: true },
 				}
 			}