fix(ai): filter ambient auth markers in compat dispatch

packages/ai/src/api/bedrock-converse-stream.ts

@@ -101,7 +101,6 @@ export interface BedrockOptions extends StreamOptions {
 type Block = (TextContent | ThinkingContent | ToolCall) & { index?: number; partialJson?: string };
 
 const EMPTY_TEXT_PLACEHOLDER = "<empty>";
-const AMBIENT_AUTH_MARKER = "<authenticated>";
 
 export const stream: StreamFunction<"bedrock-converse-stream", BedrockOptions> = (
 	model: Model<"bedrock-converse-stream">,
@@ -154,7 +153,7 @@ export const stream: StreamFunction<"bedrock-converse-stream", BedrockOptions> =
 		const skipAuth = getProviderEnvValue("AWS_BEDROCK_SKIP_AUTH", options.env) === "1";
 		const bearerToken =
 			options.bearerToken ||
-			(options.apiKey !== AMBIENT_AUTH_MARKER ? options.apiKey : undefined) ||
+			options.apiKey ||
 			getProviderEnvValue("AWS_BEARER_TOKEN_BEDROCK", options.env) ||
 			undefined;
 		const useBearerToken = bearerToken !== undefined && !skipAuth;

packages/ai/src/compat.ts

@@ -206,6 +206,7 @@ export function resetApiProviders(): void {
 registerBuiltInApiProviders();
 
 const compatModels = builtinModels();
+const AMBIENT_AUTH_MARKER = "<authenticated>";
 
 function hasExplicitApiKey(apiKey: string | undefined): apiKey is string {
 	return typeof apiKey === "string" && apiKey.trim().length > 0;
@@ -217,7 +218,7 @@ function withEnvApiKey<TOptions extends StreamOptions>(
 ): TOptions | undefined {
 	if (hasExplicitApiKey(options?.apiKey)) return options;
 	const apiKey = getEnvApiKey(model.provider, options?.env);
-	if (!apiKey) return options;
+	if (!apiKey || apiKey === AMBIENT_AUTH_MARKER) return options;
 	return { ...options, apiKey } as TOptions;
 }
 

packages/ai/test/bedrock-endpoint-resolution.test.ts

@@ -44,8 +44,8 @@ vi.mock("@aws-sdk/client-bedrock-runtime", () => {
 	};
 });
 
-import { type BedrockOptions, stream as streamBedrock } from "../src/api/bedrock-converse-stream.ts";
-import { getModel } from "../src/compat.ts";
+import type { BedrockOptions } from "../src/api/bedrock-converse-stream.ts";
+import { getModel, stream as streamBedrock } from "../src/compat.ts";
 import type { Context, Model } from "../src/types.ts";
 
 const context: Context = {
@@ -182,6 +182,21 @@ describe("bedrock endpoint resolution", () => {
 		expect(config.region).toBe("us-gov-west-1");
 	});
 
+	it("preserves ambient AWS auth for custom model IDs through compat dispatch", async () => {
+		process.env.AWS_PROFILE = "bedrock-profile";
+		const baseModel = getModel("amazon-bedrock", "us.anthropic.claude-opus-4-8");
+		const model: Model<"bedrock-converse-stream"> = {
+			...baseModel,
+			id: "arn:aws:bedrock:us-east-1:123456789012:application-inference-profile/example",
+		};
+
+		const config = await captureClientConfig(model);
+
+		expect(config.profile).toBe("bedrock-profile");
+		expect(config.token).toBeUndefined();
+		expect(config.authSchemePreference).toBeUndefined();
+	});
+
 	it("uses the generic API key option as a Bedrock bearer token", async () => {
 		const model = getModel("amazon-bedrock", "us.anthropic.claude-opus-4-8");
 
@@ -190,13 +205,4 @@ describe("bedrock endpoint resolution", () => {
 		expect(config.token).toEqual({ token: "bedrock-api-key" });
 		expect(config.authSchemePreference).toEqual(["httpBearerAuth"]);
 	});
-
-	it("does not use the ambient AWS auth marker as a bearer token", async () => {
-		const model = getModel("amazon-bedrock", "us.anthropic.claude-opus-4-8");
-
-		const config = await captureClientConfig(model, { apiKey: "<authenticated>" });
-
-		expect(config.token).toBeUndefined();
-		expect(config.authSchemePreference).toBeUndefined();
-	});
 });