fix: make AWS Bedrock authentication predictable

Anthropic's Bedrock SDK creates an AWS credential provider chain [1]
for each request it needs to sign. By doing so right before actually
having to sign the request, it can utilize any session created after
VSCode launched (i.e. outside of the process), and it can renew the
sessions every time necessary transparently for the user.

Cline, on the other hand, by transforming the provided AWS_PROFILE into
a key / secret / session, as part of client initialization, completely
short-circuits this, making it very difficult for users in companies where
sessions are short-lived. Furthermore, Cline would silently ignore the
provided AWS_PROFILE if there isn't a current/non-expired session at the time
of initialization, pass null keys to the Bedrock SDK, which would then
make use the default profile, which may not be configured or authorized
to use AWS Bedrock (as most AWS SSO hub accounts would). From the
perspective of the user, this would manifest itself as an "supported
country" error or unhelpful errors that are basically impossible to
debug without attaching a debugger to Cline.. and such developers may
end up reaching out to their DevOps/IT teams for help, which also could
turn into a waste of time.

This PR addresses the aforementioned issues by resolving the credentials on
every invocation.

1: https://github.com/anthropics/anthropic-sdk-typescript/blob/61b55599d50d9c93840e4736cb756cb3a62b0696/packages/bedrock-sdk/src/auth.ts#L19

Author: Quentin-M

.changeset/cold-shirts-deny.md

@@ -0,0 +1,5 @@
+---
+"claude-dev": patch
+---
+
+fix: make AWS Bedrock authentication predictable

src/api/providers/bedrock.ts

@@ -3,79 +3,25 @@ import { Anthropic } from "@anthropic-ai/sdk"
 import { ApiHandler } from "../"
 import { ApiHandlerOptions, bedrockDefaultModelId, BedrockModelId, bedrockModels, ModelInfo } from "../../shared/api"
 import { ApiStream } from "../transform/stream"
-import { fromIni } from "@aws-sdk/credential-providers"
+import { fromNodeProviderChain } from "@aws-sdk/credential-providers"
 
 // https://docs.anthropic.com/en/api/claude-on-amazon-bedrock
 export class AwsBedrockHandler implements ApiHandler {
 	private options: ApiHandlerOptions
-	private client: AnthropicBedrock | any
-	private initializationPromise: Promise<void>
 
 	constructor(options: ApiHandlerOptions) {
 		this.options = options
-		this.initializationPromise = this.initializeClient()
-	}
-
-	private async initializeClient() {
-		let clientConfig: any = {
-			awsRegion: this.options.awsRegion || "us-east-1",
-		}
-		try {
-			if (this.options.awsUseProfile) {
-				// Use profile-based credentials if enabled
-				// Use named profile, defaulting to 'default' if not specified
-				var credentials: any
-				if (this.options.awsProfile) {
-					credentials = await fromIni({
-						profile: this.options.awsProfile,
-						ignoreCache: true,
-					})()
-				} else {
-					credentials = await fromIni({
-						ignoreCache: true,
-					})()
-				}
-				clientConfig.awsAccessKey = credentials.accessKeyId
-				clientConfig.awsSecretKey = credentials.secretAccessKey
-				clientConfig.awsSessionToken = credentials.sessionToken
-			} else if (this.options.awsAccessKey && this.options.awsSecretKey) {
-				// Use direct credentials if provided
-				clientConfig.awsAccessKey = this.options.awsAccessKey
-				clientConfig.awsSecretKey = this.options.awsSecretKey
-				if (this.options.awsSessionToken) {
-					clientConfig.awsSessionToken = this.options.awsSessionToken
-				}
-			}
-		} catch (error) {
-			console.error("Failed to initialize Bedrock client:", error)
-			throw error
-		} finally {
-			this.client = new AnthropicBedrock(clientConfig)
-		}
 	}
 
 	async *createMessage(systemPrompt: string, messages: Anthropic.Messages.MessageParam[]): ApiStream {
 		// cross region inference requires prefixing the model id with the region
-		let modelId: string
-		if (this.options.awsUseCrossRegionInference) {
-			let regionPrefix = (this.options.awsRegion || "").slice(0, 3)
-			switch (regionPrefix) {
-				case "us-":
-					modelId = `us.${this.getModel().id}`
-					break
-				case "eu-":
-					modelId = `eu.${this.getModel().id}`
-					break
-				default:
-					// cross region inference is not supported in this region, falling back to default model
-					modelId = this.getModel().id
-					break
-			}
-		} else {
-			modelId = this.getModel().id
-		}
+		let modelId = await this.getModelId()
+
+		// create anthropic client, using sessions created or renewed after this handler's
+		// initialization, and allowing for session renewal if necessary as well
+		let client = await this.getClient()
 
-		const stream = await this.client.messages.create({
+		const stream = await client.messages.create({
 			model: modelId,
 			max_tokens: this.getModel().info.maxTokens || 8192,
 			temperature: 0,
@@ -142,4 +88,68 @@ export class AwsBedrockHandler implements ApiHandler {
 			info: bedrockModels[bedrockDefaultModelId],
 		}
 	}
+
+	private async getClient(): Promise<AnthropicBedrock> {
+		// Create AWS credentials by executing a an AWS provider chain exactly as the
+		// Anthropic SDK does it, by wrapping the default chain into a temporary process
+		// environment.
+		const providerChain = fromNodeProviderChain()
+		const credentials = await AwsBedrockHandler.withTempEnv(
+			() => {
+				AwsBedrockHandler.setEnv("AWS_REGION", this.options.awsRegion)
+				AwsBedrockHandler.setEnv("AWS_ACCESS_KEY_ID", this.options.awsAccessKey)
+				AwsBedrockHandler.setEnv("AWS_SECRET_ACCESS_KEY", this.options.awsSecretKey)
+				AwsBedrockHandler.setEnv("AWS_SESSION_TOKEN", this.options.awsSessionToken)
+				AwsBedrockHandler.setEnv("AWS_PROFILE", this.options.awsProfile)
+			},
+			() => providerChain(),
+		)
+
+		// Return an AnthropicBedrock client with the resolved/assumed credentials.
+		//
+		// When AnthropicBedrock creates its AWS client, the chain will execute very
+		// fast as the access/secret keys will already be already provided, and have
+		// a higher precedence than the profiles.
+		return new AnthropicBedrock({
+			awsAccessKey: credentials.accessKeyId,
+			awsSecretKey: credentials.secretAccessKey,
+			awsSessionToken: credentials.sessionToken,
+			awsRegion: this.options.awsRegion || "us-east-1",
+		})
+	}
+
+	private async getModelId(): Promise<string> {
+		if (this.options.awsUseCrossRegionInference) {
+			let regionPrefix = (this.options.awsRegion || "").slice(0, 3)
+			switch (regionPrefix) {
+				case "us-":
+					return `us.${this.getModel().id}`
+				case "eu-":
+					return `eu.${this.getModel().id}`
+					break
+				default:
+					// cross region inference is not supported in this region, falling back to default model
+					return this.getModel().id
+					break
+			}
+		}
+		return this.getModel().id
+	}
+
+	private static async withTempEnv<R>(updateEnv: () => void, fn: () => Promise<R>): Promise<R> {
+		const previousEnv = { ...process.env }
+
+		try {
+			updateEnv()
+			return await fn()
+		} finally {
+			process.env = previousEnv
+		}
+	}
+
+	private static async setEnv(key: string, value: string | undefined) {
+		if (key !== "" && value !== undefined) {
+			process.env[key] = value
+		}
+	}
 }