pass bedrock unhandled stop reasons to error message (#6598)

fixes #6485

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

@@ -260,7 +260,11 @@ export const stream: StreamFunction<"bedrock-converse-stream", BedrockOptions> =
 				} else if (item.contentBlockStop) {
 					handleContentBlockStop(item.contentBlockStop, blocks, output, stream);
 				} else if (item.messageStop) {
-					output.stopReason = mapStopReason(item.messageStop.stopReason);
+					const { stopReason, errorMessage } = mapStopReason(item.messageStop.stopReason);
+					output.stopReason = stopReason;
+					if (errorMessage) {
+						output.errorMessage = errorMessage;
+					}
 				} else if (item.metadata) {
 					handleMetadata(item.metadata, model, output);
 				} else if (item.internalServerException) {
@@ -281,7 +285,7 @@ export const stream: StreamFunction<"bedrock-converse-stream", BedrockOptions> =
 			}
 
 			if (output.stopReason === "error" || output.stopReason === "aborted") {
-				throw new Error("An unknown error occurred");
+				throw new Error(output.errorMessage || "An unknown error occurred");
 			}
 
 			stream.push({ type: "done", reason: output.stopReason, message: output });
@@ -932,18 +936,18 @@ function convertToolConfig(
 	return { tools: bedrockTools, toolChoice: bedrockToolChoice };
 }
 
-function mapStopReason(reason: string | undefined): StopReason {
+function mapStopReason(reason: string | undefined): { stopReason: StopReason; errorMessage?: string } {
 	switch (reason) {
 		case BedrockStopReason.END_TURN:
 		case BedrockStopReason.STOP_SEQUENCE:
-			return "stop";
+			return { stopReason: "stop" };
 		case BedrockStopReason.MAX_TOKENS:
 		case BedrockStopReason.MODEL_CONTEXT_WINDOW_EXCEEDED:
-			return "length";
+			return { stopReason: "length" };
 		case BedrockStopReason.TOOL_USE:
-			return "toolUse";
+			return { stopReason: "toolUse" };
 		default:
-			return "error";
+			return reason ? { stopReason: "error", errorMessage: reason } : { stopReason: "error" };
 	}
 }