Merge pull request #5832 from stephanmck/fix/provider-error-body-passthrough-5763

fix(ai): surface provider HTTP error body instead of opaque SDK message

packages/ai/src/api/google-vertex.ts

@@ -24,6 +24,7 @@ import type {
 	ThinkingContent,
 	ToolCall,
 } from "../types.ts";
+import { formatProviderError, normalizeProviderError } from "../utils/error-body.ts";
 import { AssistantMessageEventStream } from "../utils/event-stream.ts";
 import { providerHeadersToRecord } from "../utils/headers.ts";
 import { getProviderEnvValue } from "../utils/provider-env.ts";
@@ -288,7 +289,7 @@ export const stream: StreamFunction<"google-vertex", GoogleVertexOptions> = (
 				}
 			}
 			output.stopReason = options?.signal?.aborted ? "aborted" : "error";
-			output.errorMessage = error instanceof Error ? error.message : JSON.stringify(error);
+			output.errorMessage = formatProviderError(normalizeProviderError(error));
 			stream.push({ type: "error", reason: output.stopReason, error: output });
 			stream.end();
 		}