diff --git a/packages/types/src/providers/bedrock.ts b/packages/types/src/providers/bedrock.ts
index 9ea52bced8..d9571da5bd 100644
--- a/packages/types/src/providers/bedrock.ts
+++ b/packages/types/src/providers/bedrock.ts
@@ -520,6 +520,16 @@ export const BEDROCK_REGIONS = [
 	{ value: "us-gov-west-1", label: "us-gov-west-1" },
 ].sort((a, b) => a.value.localeCompare(b.value))
 
+// Older Claude 3 models on Bedrock that do NOT support the fine-grained-tool-streaming beta.
+// Sending this beta flag to these models causes Bedrock to reject the request with
+// "invalid beta flag". See: https://github.com/RooCodeInc/Roo-Code/issues/11715
+export const BEDROCK_FINE_GRAINED_STREAMING_UNSUPPORTED_IDS = [
+	"anthropic.claude-3-haiku-20240307-v1:0",
+	"anthropic.claude-3-opus-20240229-v1:0",
+	"anthropic.claude-3-sonnet-20240229-v1:0",
+	"anthropic.claude-3-5-sonnet-20240620-v1:0",
+] as const
+
 export const BEDROCK_1M_CONTEXT_MODEL_IDS = [
 	"anthropic.claude-sonnet-4-20250514-v1:0",
 	"anthropic.claude-sonnet-4-5-20250929-v1:0",
diff --git a/src/api/providers/__tests__/bedrock.spec.ts b/src/api/providers/__tests__/bedrock.spec.ts
index 975e38af12..ce53bfb737 100644
--- a/src/api/providers/__tests__/bedrock.spec.ts
+++ b/src/api/providers/__tests__/bedrock.spec.ts
@@ -38,6 +38,7 @@ import { AwsBedrockHandler } from "../bedrock"
 import { ConverseStreamCommand, BedrockRuntimeClient, ConverseCommand } from "@aws-sdk/client-bedrock-runtime"
 import {
 	BEDROCK_1M_CONTEXT_MODEL_IDS,
+	BEDROCK_FINE_GRAINED_STREAMING_UNSUPPORTED_IDS,
 	BEDROCK_SERVICE_TIER_MODEL_IDS,
 	bedrockModels,
 	ApiProviderError,
@@ -843,6 +844,68 @@ describe("AwsBedrockHandler", () => {
 			expect(commandArg.additionalModelRequestFields.anthropic_beta).not.toContain("context-1m-2025-08-07")
 		})
 
+		it("should NOT include fine-grained-tool-streaming beta for older Claude 3 models", async () => {
+			// Test with Claude 3 Haiku - the model from the original bug report
+			for (const unsupportedModelId of BEDROCK_FINE_GRAINED_STREAMING_UNSUPPORTED_IDS) {
+				const handler = new AwsBedrockHandler({
+					apiModelId: unsupportedModelId,
+					awsAccessKey: "test",
+					awsSecretKey: "test",
+					awsRegion: "us-east-1",
+				})
+
+				const messages: Anthropic.Messages.MessageParam[] = [
+					{
+						role: "user",
+						content: "Test message",
+					},
+				]
+
+				mockConverseStreamCommand.mockClear()
+
+				const generator = handler.createMessage("", messages)
+				await generator.next()
+
+				expect(mockConverseStreamCommand).toHaveBeenCalled()
+				const commandArg = mockConverseStreamCommand.mock.calls[0][0] as any
+
+				// Older Claude 3 models should NOT have fine-grained-tool-streaming beta
+				if (commandArg.additionalModelRequestFields?.anthropic_beta) {
+					expect(commandArg.additionalModelRequestFields.anthropic_beta).not.toContain(
+						"fine-grained-tool-streaming-2025-05-14",
+					)
+				}
+			}
+		})
+
+		it("should still include fine-grained-tool-streaming beta for newer Claude models", async () => {
+			const handler = new AwsBedrockHandler({
+				apiModelId: "anthropic.claude-3-5-sonnet-20241022-v2:0",
+				awsAccessKey: "test",
+				awsSecretKey: "test",
+				awsRegion: "us-east-1",
+			})
+
+			const messages: Anthropic.Messages.MessageParam[] = [
+				{
+					role: "user",
+					content: "Test message",
+				},
+			]
+
+			const generator = handler.createMessage("", messages)
+			await generator.next()
+
+			expect(mockConverseStreamCommand).toHaveBeenCalled()
+			const commandArg = mockConverseStreamCommand.mock.calls[0][0] as any
+
+			// Newer Claude models should still have the beta
+			expect(commandArg.additionalModelRequestFields).toBeDefined()
+			expect(commandArg.additionalModelRequestFields.anthropic_beta).toContain(
+				"fine-grained-tool-streaming-2025-05-14",
+			)
+		})
+
 		it("should enable 1M context window with cross-region inference for Claude Sonnet 4", () => {
 			const handler = new AwsBedrockHandler({
 				apiModelId: BEDROCK_1M_CONTEXT_MODEL_IDS[0],
diff --git a/src/api/providers/bedrock.ts b/src/api/providers/bedrock.ts
index 3ceb251003..94e0ebb19c 100644
--- a/src/api/providers/bedrock.ts
+++ b/src/api/providers/bedrock.ts
@@ -27,6 +27,7 @@ import {
 	BEDROCK_DEFAULT_CONTEXT,
 	AWS_INFERENCE_PROFILE_MAPPING,
 	BEDROCK_1M_CONTEXT_MODEL_IDS,
+	BEDROCK_FINE_GRAINED_STREAMING_UNSUPPORTED_IDS,
 	BEDROCK_GLOBAL_INFERENCE_MODEL_IDS,
 	BEDROCK_SERVICE_TIER_MODEL_IDS,
 	BEDROCK_SERVICE_TIER_PRICING,
@@ -436,9 +437,14 @@ export class AwsBedrockHandler extends BaseProvider implements SingleCompletionH
 			anthropicBetas.push("context-1m-2025-08-07")
 		}
 
-		// Add fine-grained tool streaming beta for Claude models
-		// This enables proper tool use streaming for Anthropic models on Bedrock
-		if (baseModelId.includes("claude")) {
+		// Add fine-grained tool streaming beta for Claude models that support it.
+		// Older Claude 3 models (Haiku, Opus, Sonnet, and original 3.5 Sonnet) do not
+		// support this beta flag and Bedrock rejects the request with "invalid beta flag".
+		// See: https://github.com/RooCodeInc/Roo-Code/issues/11715
+		if (
+			baseModelId.includes("claude") &&
+			!BEDROCK_FINE_GRAINED_STREAMING_UNSUPPORTED_IDS.includes(baseModelId as any)
+		) {
 			anthropicBetas.push("fine-grained-tool-streaming-2025-05-14")
 		}