fix: move anthropic_beta back to top level for AWS Bedrock 1M context

Fixes #7085 - "invalid beta flag" error when using 1M context with Claude Sonnet 4

The anthropic_beta parameter needs to be at the top level of the Bedrock payload,
not inside additionalModelRequestFields. This reverts the incorrect placement
introduced in PR #7056 while keeping the other improvements from that PR.

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

@@ -635,11 +635,10 @@ describe("AwsBedrockHandler", () => {
 			expect(mockConverseStreamCommand).toHaveBeenCalled()
 			const commandArg = mockConverseStreamCommand.mock.calls[0][0] as any
 
-			// Should include anthropic_beta in additionalModelRequestFields
-			expect(commandArg.additionalModelRequestFields).toBeDefined()
-			expect(commandArg.additionalModelRequestFields.anthropic_beta).toEqual(["context-1m-2025-08-07"])
+			// Should include anthropic_beta at top level of payload
+			expect(commandArg.anthropic_beta).toEqual(["context-1m-2025-08-07"])
 			// Should not include anthropic_version since thinking is not enabled
-			expect(commandArg.additionalModelRequestFields.anthropic_version).toBeUndefined()
+			expect(commandArg.anthropic_version).toBeUndefined()
 		})
 
 		it("should not include anthropic_beta parameter when 1M context is disabled", async () => {
@@ -665,7 +664,9 @@ describe("AwsBedrockHandler", () => {
 			expect(mockConverseStreamCommand).toHaveBeenCalled()
 			const commandArg = mockConverseStreamCommand.mock.calls[0][0] as any
 
-			// Should not include anthropic_beta in additionalModelRequestFields
+			// Should not include anthropic_beta at top level
+			expect(commandArg.anthropic_beta).toBeUndefined()
+			// Should not include additionalModelRequestFields when no thinking is enabled
 			expect(commandArg.additionalModelRequestFields).toBeUndefined()
 		})
 
@@ -693,6 +694,7 @@ describe("AwsBedrockHandler", () => {
 			const commandArg = mockConverseStreamCommand.mock.calls[0][0] as any
 
 			// Should not include anthropic_beta for non-Sonnet 4 models
+			expect(commandArg.anthropic_beta).toBeUndefined()
 			expect(commandArg.additionalModelRequestFields).toBeUndefined()
 		})
 
@@ -740,11 +742,10 @@ describe("AwsBedrockHandler", () => {
 				mockConverseStreamCommand.mock.calls.length - 1
 			][0] as any
 
-			// Should include anthropic_beta in additionalModelRequestFields
-			expect(commandArg.additionalModelRequestFields).toBeDefined()
-			expect(commandArg.additionalModelRequestFields.anthropic_beta).toEqual(["context-1m-2025-08-07"])
+			// Should include anthropic_beta at top level of payload
+			expect(commandArg.anthropic_beta).toEqual(["context-1m-2025-08-07"])
 			// Should not include anthropic_version since thinking is not enabled
-			expect(commandArg.additionalModelRequestFields.anthropic_version).toBeUndefined()
+			expect(commandArg.anthropic_version).toBeUndefined()
 			// Model ID should have cross-region prefix
 			expect(commandArg.modelId).toBe(`us.${BEDROCK_CLAUDE_SONNET_4_MODEL_ID}`)
 		})

src/api/providers/bedrock.ts

@@ -48,13 +48,12 @@ interface BedrockInferenceConfig {
 }
 
 // Define interface for Bedrock additional model request fields
-// This includes thinking configuration, 1M context beta, and other model-specific parameters
+// This includes thinking configuration and other model-specific parameters
 interface BedrockAdditionalModelFields {
 	thinking?: {
 		type: "enabled"
 		budget_tokens: number
 	}
-	anthropic_beta?: string[]
 	[key: string]: any // Add index signature to be compatible with DocumentType
 }
 
@@ -65,6 +64,7 @@ interface BedrockPayload {
 	system?: SystemContentBlock[]
 	inferenceConfig: BedrockInferenceConfig
 	anthropic_version?: string
+	anthropic_beta?: string[]
 	additionalModelRequestFields?: BedrockAdditionalModelFields
 }
 
@@ -383,14 +383,6 @@ export class AwsBedrockHandler extends BaseProvider implements SingleCompletionH
 		const baseModelId = this.parseBaseModelId(modelConfig.id)
 		const is1MContextEnabled = baseModelId === BEDROCK_CLAUDE_SONNET_4_MODEL_ID && this.options.awsBedrock1MContext
 
-		// Add anthropic_beta for 1M context to additionalModelRequestFields
-		if (is1MContextEnabled) {
-			if (!additionalModelRequestFields) {
-				additionalModelRequestFields = {} as BedrockAdditionalModelFields
-			}
-			additionalModelRequestFields.anthropic_beta = ["context-1m-2025-08-07"]
-		}
-
 		const payload: BedrockPayload = {
 			modelId: modelConfig.id,
 			messages: formatted.messages,
@@ -399,6 +391,8 @@ export class AwsBedrockHandler extends BaseProvider implements SingleCompletionH
 			...(additionalModelRequestFields && { additionalModelRequestFields }),
 			// Add anthropic_version at top level when using thinking features
 			...(thinkingEnabled && { anthropic_version: "bedrock-2023-05-31" }),
+			// Add anthropic_beta at top level when 1M context is enabled
+			...(is1MContextEnabled && { anthropic_beta: ["context-1m-2025-08-07"] }),
 		}
 
 		// Create AbortController with 10 minute timeout